Forced Induction for Dummies (Turbocharger, Supercharger, Nitrous)
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Updated from the First One

First note: This is the tip of a VERY VERY VERY VERY VERY big iceberg. If you are thinking of going FI, DO YOUR HOMEWORK! Laziness now can cost you an engine.

I just now really noticed that there is no easy to find thread that clearly and easily describes this mod in plain English for people who have no idea other than "make more power, me want". In the hope that this NEW thread becomes a sticky, I thought I would make one.

Terms you Should Know
General Gas Law – In any gas (liquid is a gas or gas is a liquid and they are both fluids; you pick), the combination of volume, pressure and temperature are related. A change in any one will affect a corresponding change in the others. Pressure and Volume are inversely related (volume up, pressure down), Volume and Temperature are inversely related (Volume Up, Temperature Down) and Pressure and Temperature are proportional (Pressure Up, Temperature Up).

Volumetric Efficiency – The amount of air the engine is ingesting divided by the amount of air the engine is capable of ingesting at Atmospheric Pressure (14.7 PSIA). More simply air volume ingested/engine displacement.

Engine Cycle – One power stroke / engine revolution. RPM is (Revolutions per Minute). This is when the piston / rotor moves from Top Dead Center to Bottom Dead Center and back to Top Dead Center. For each Engine Rotation (RPM), the rotor/ piston leaves Top Dead Center (TDC) and moves to Bottom Dead Center(BDC), this movement creates vacuum as the volume of the space increases, this vacuum causes the Atmospheric Pressure to push air from the intake track into the engine in order to equalize the pressure differential. The perfect volume of air ingested by the engine is equal to the volume of the engine (displacement). Once the air is ingested, it is compressed by the reduction of volume as the rotor / piston travels from BDC to TDC. Along with fuel, this compressed mixture is ignited by the spark plug(s) creating a pressure expansion which drives the rotor / piston from TDC back to BDC rotating the eccentric shaft / crankshaft. Then exhaust is forced out the engine by movement from BDC back to TDC and the whole thing starts over again. This cycle is not perfect as restrictions on the intake, overlapping valves, mixtures of the outgoing / incoming gases and time to equalize the pressure differential all affect how much air the engine actually gets. The driving force of engine air movement is pressure gradients, the difference in pressure.

Tuning – Engine Tuning is the process of specifying the proper amount of fuel and the proper time to induce ignition based on the specific spot your engine is currently in. The engines Brain (or aftermarket Brain; or both) read from the sensors what your engine is doing. Based on the air, temperature, RPM, pressure, air density, throttle position, RPM change…yada yada yada; put in this amount of fuel and ignite the spark at this time. There are so many specific tuning “things” to deal with and know about, for now just know that each engine is different and tuning for FI will almost always have to be done.

Flame Speed / Brisance – Fuel is an explosive (kinda) and an engine produces a controlled explosion (kinda). The term Brisance is used to reference the shattering effect of an explosion. This can also be thought of as the speed in which the potential energy is converted to kinetic energy. In demolitions, we convert Brisance into Relative Effectiveness (RE) of an explosive, with TNT = 1. So C4, RDX and other High Explosives have an RE greater than 1, and Ammonium Nitrate and other Low Explosives have an RE less than 1. Low Explosives PUSH and High Explosives SHATTER. While TNT has a detonation velocity of 6,940 Meters Per Second a Stoichiometric Air Fuel Mixture has a flame speed of .34 Meters Per Second or an RE less than .0001. So Fuel is a LOW LOW EXPLOSIVE which PUSHES. The point to this is the higher the oxygen content the faster the flame speed (more push), this is also why timing is retarded during FI applications.

Partial Pressure of Oxygen (PPO2) - The master of all things "power" in your engine. In the end, what really matters is the number of oxygen molecules in the combustion chamber (provided you have enough fuel to use it.) With an increase in pressure, the number of molecules goes up due to squeezing more air in a smaller space. The term Partial Pressure is in reference to the pressure of the Oxygen as a percentage of total volume. So, in air at sea level the Partial Pressure is .21 or 21% of total volume at 1 Atmosphere. If you boost to 14.7 PSI, or 2 Atmospheres, the partial pressure is going to double to .42, since you have twice as many oxygen molecules per volume. This "extra" oxygen is what provides the extra power and why Forced Induction can make a small engine perform like a much larger one. You see, you do not need extra PRESSURE to make more power, you need more PPO2. You can get it from pressurizing the intake, or from increasing the Oxygen content in the engine (vis a vis Nitrous). Remember the General Gas Law, since you will heat the mixture while you pressurize it, 14.7 PSI of boost is not exactly .42 PPO2 since it would heat up and become less dense. The fine details are more complicated, but the theory is - plan for, fuel for, tune for, EVERYTHING for PPO2, that is absolute unlike other strategies.

Pressure Gradient - Picture that old Jr. High Science Class Exp. No, not the girl who first let you touch her boob, focus! The one where you have two cups of liquid and a hose between them, lift one cup and the liquid will flow into the other (lower) cup. This is a good demonstration of a pressure gradient. Simply put, air is going to flow from the higher pressure, into the lower pressure. The higher the "high" pressure / the lower the "low" pressure are, affects the velocity of that air movement. So in your engine cycle, the intake pressure is higher which moves the air into the cylinder. After combustion the expanded exhaust gas pressure is higher than the pressure in the exhaust so the air moves into the exhaust. In boosted applications, this air is moving faster due to an increased pressure gradient.

Mixed Gas - Technically "Air" is the mixture of 21% oxygen, and 79% nitrogen (I know, but for simplicity). When you alter that ratio, it is no longer air; it is classified as a MIXED GAS. This applies to storage and handling requirements as well as HAZMAT classification (more oxygen the more flammable the gas). Plus this is an important distinction for divers. So While Turbo and Superchargers deal with air, Nitrous deals with a mixed gas.

Volumetric Efficiency - the amount of power the engine can produce based on the amount of air it can get for each engine cycle. Technically, volumetric efficiency only relates to air flow, however for the sake of simplicity assume; more air + more fuel = more power, therefore volumetric efficiency can be directly related to power. Called VE for short, the goal of most engine mods is to increase VE, with the rest being designed to reduce loss of power by drag, heat or other variables. At ambient air pressure VE can approach 100%, it can even be slightly over 100% in some highly designed racing engines; but for all intensive purposes the goal is a VE of (1 or 100%); and naturally aspirated motors can't get there. An engine with manifold pressures greater than atmospheric will put a larger amount of air into the chamber than what atmospheric pressure would do and, therefore, have volumetric efficiencies greater than 100%.

Forced Induction - this is the term that applies to adding pressurized *air to make it contain more oxygen molecules per space in the engine. This means you can burn more fuel. By adding more air and more fuel you raise the combustion pressure on the eccentric shaft/ crankshaft which makes it turn harder (torque) and makes more horsepower (torque * engine RPM). Since all engine modifications (mods for short) attempt to increase the volumetric efficiency of the engine; forced induction is attractive as it can achieve a VE in excess of 1 quite readily. The saying "there is no replacement for displacement" should be "there is no replacement for VE".

* Special note about nitrous, NO2, NOS, ZEX, whatever. It raises the partial pressure of O2 (higher oxygen content, not the pressure) so it is not technically air anymore. But they all do the same thing; allow more fuel to be burned.

Turbocharger / Turbo / Snail – this raises the pressure of the air (boost) by using the exhaust gases exiting the engine to power a compressor that pressurizes the incoming air.

Supercharger / Blower – this raises the pressure of the air (boost) by using the eccentric shaft / crankshaft to power a compressor that pressurizes the incoming air.

Nitrous / Spray / Bottle – this raises the oxygen CONTENT or partial pressure by injecting nitrous oxide into the incoming air. A partial pressure of oxygen (pp O2) of .42 or 42% would be equal to the partial pressure of oxygen in air at 2 ATA, or roughly 14.7 PSI of boost. Oxygen at sea level is pp O2 = .21 or 21% of the total volume of air.

Turbo Advantages: can be installed anywhere in the exhaust stream. Usually smaller than a supercharger. Uses energy that is already being wasted anyway; low parasitic loss. Modern turbos can be highly reliable and provide boost at a wide range of engine speed (RPM). Modular, you can build or buy some or all the parts to make your own system or get a kit. Boost can be increased to the system without mechanical changes.

Turbo Disadvantages: Can be difficult to install. Compressor is not linear meaning it does not provide a specific pressure at a certain RPM, may cause tuning difficulty. It is an obstruction in the exhaust stream lowering the flow of the exhaust gases and therefore lowering overall VE. Requires tuning of more than just EMS for maximum performance and reliability (boost controller, BOV, wastegate etc.)

Supercharger Advantages: Can provide pressurized air as soon as the engine is running. May also provide a linear increase in pressure due to it being tied to the engine RPM. Tuning may be easier than a turbo.

Supercharger Disadvantages: Limited location area since it is physically powered by the eccentric / crankshaft of the engine. Uses some engine power to power compressor causing parasitic loss. Typically not modular. Boost cannot be increased without mechanical changes. Often tied to higher intake temperatures over similarly powered turbo cars.

Nitrous Oxide Advantages: Inexpensive to purchase and easy to install. Does not cause any additional heat of the intake air (intake charge). Can be installed in numerous locations depending on the size of the bottle. Easier to maintain.

Nitrous Oxide Disadvantages: Must refill bottle. Typically only on during wide open throttle and or a button is pushed. To reach any significant power levels, some expense must be added for engine management.

Special note about temperature and air – when air is compressed regardless of how, it creates heat due to the friction of the air molecules being squished together. Intercoolers and other modifications have been invented to cool this charge air, but the reality is that 1 cubic foot of air compressed into ½ cubic foot area will become hotter, thus is the nature of gas. So both a supercharger and a turbo will create more heat than a naturally aspirated engine of the same size and design. This does not account for heating of the exhaust gas due higher fuel volume in the chamber, all FI will cause a hotter "burn", this is a good thing when properly managed. See General Gas Law ^^^

Special note about exhaust temperature- all FI systems will raise exhaust temperatures due to the increase of air and fuel being burned in the combustion chamber. In most cases this is not a great concern. If you get an EGT or exhaust gas temperature monitor you can monitor changes from normal (assuming you know what your normal EGT is). You can also use EGT as a tuning aid.

Special note about fuel systems- Once you go FI, your max ability to boost will likely be limited by your ability to deliver fuel. You must work your FI system and fuel system together. If your FI application requires 30 lb/hr of fuel but you can only deliver 25 lb/hr, you will run lean and cause engine damage. Our injectors are typically rated in cc/min or lb/hr. The time it takes to deliver the rated fuel (the injector is open) is called duration. If a .44 lb/min injector needs to deliver .44 lb/min of fuel, it will be at 100% Duty Cycle AKA Maxed Out. Based on RPM, the duration available will be shorter in high RPMs and longer in low RPMs, all of this affects the total volume of fuel you can flow.

Special note about tuning - your non-factory FI-ed engine is designed to provide fuel in a variety of engine situations, none of which cover forced induction. With all of the extra air the engines "brain" will not add enough fuel causing you to run lean and destroy your engine. Therefore aftermarket forced induction kits have or will need an aftermarket computer to address this shortcoming. Setting this aftermarket computer up and refining the air fuel mixtures and timing is called tuning. All forced induction systems need to be tuned to your engine.

Why go FI at all? Is a Rotary a good FI engine?
Rotary engines do have some FI advantages. For turboing, a rotary flows twice as much air as its reciprocating counterpart. This means your 1.3L engine will use turbo sizing like a 2.6L piston engine. That takes you from Geo Metro to Subaru territory. When a piston engine suffers pre-ignition; the explosion usually occurs before top dead center, causing the piston to want to reverse course. Piston rods are already highly loaded due simply to moving the piston up and down. This applies a huge compressive force to the piston and supporting rod. Often, one will give and you will have catastrophic engine failure. In a rotary, the counterforce won't be as high. Usually, it will be a seal that gives rather than the rotor. This will still cause engine failure, though it may not manifest for a long time. See Reliability Below.

Recommended Reading:
Street Turbocharging - Mark Warner
How to Tune and Modify Engine Management Systems - Jeff Hartmen
Turbocharging - Corky Bell.
Engine Management: Advanced Tuning - Greg Banish

I'll add to the list if anyone has others they have personally read, don't tell me you heard from so and so that this book was good.

Any omissions or errors will be corrected in the original thread. Keep It Simple, the point is to give people a good down and dirty on FI.

Last note: This is the tip of a VERY big iceberg. If you are thinking FI, DO YOUR HOMEWORK! Laziness now can cost you an engine.

Where to next:
http://www.rx8club.com/showthread.php?t=63023 - Specific Information on performance and prices.
http://www.rx8club.com/showthread.php?t=109820 - Nitrous Information
http://www.rx8club.com/forumdisplay.php?f=63 - Tuning Information

Brake Specific Fuel Consumption (BSFC) - This is a measure of how much horsepower-hours an engine generates per pound of fuel consumption. This indicates the general efficiency of the engine it self. An internal combustion engine only makes use of a fraction of the chemical energy that is released during combustion. Much of the energy escapes as hot exhaust gas, heat into the cooling system, vibrations, and noise. Much of these factors do not get altered much with modification. Most of the time, modifications work on burning more fuel to generate more power rather than trying to generate more power out of the fuel the engine burns. BSFC is an excellent factor in designing an engine from scratch. It is not as useful on an engine that already exists. It's a worthwhile concept to keep in mind.

Reliability of Forced Induction Intro - Any FI will place more heat and more pressure on an engine than its naturally aspirated twin. However, Rotary engines are as FI-able as piston engines, with some special considerations. All FI-ed engines need more maintenance than a NA engine, but with proper maintenance can provide many trouble free miles. Ultimately, FI will shorten the life of your engine to some degree.

Rotary Fragility with Detonation
Understanding the "fragility" of a rotary motor as compared to a piston motor is not a simple exercise. Though the inertial loading on the rods of a piston motor are extreme, the dynamics are known and very simple. Piston design is at a state where there are very few variables left to consider.

A rotary motor is under considerably more stress and that stress is highly dynamic, principally because of the engine's simplicity. Think about what an apex seal is being asked to do: it must support two phases of combustion simultaneously on opposite sides while constantly accelerating (and decelerating) along two axes of motion!

Though there are no rods to stress, detonation affects the dynamics of the rotary motor with forces that are exponentially more damaging than they are in a piston motor. (BTW - detonation is not pre-ignition and understanding the difference is pretty important.) The Renesis is FAR more fragile than any other motor in existence. It cannot take ANY overheating. It cannot survive any pre-ignition. It will not survive any oiling malfunctions. Though it might keep running, any failings in the fuel/water/oil will yield a damaged motor. A piston motor's typical failure mode will lower its operational efficiency by some fraction of its total output. A rotary motor - even with a minor failure - typically becomes completely unusable. Similarly, a Renesis is not really rebuildable after a failure. Under optimal conditions however, the Renesis may be the most robust motor in existence because of its simplicity.

Oil
First, rotaries live and die by their oil. They require oil for both cooling and lubrication. Oil is passively added to the intake to lubricate the apex seals. Rx-8s come with front mounted oil coolers (often 2). Changing the oil will give you basically 50% new oil unless you empty the coolers as well.

Heat
Secondly, when adding FI of any sort to any car, more attention is always paid to getting more power than removing more heat. If you make twice as much horsepower, why would you expect the engine NOT to emit twice as much heat. There are 3 main causes of premature failure in aftermarket FI-ed cars: detonation, pre-ignition and heat. The rotary is no exception.

Heat death: Short of overhauling your oil and radiator systems, few modifications will make their way into your cooling system. To compensate, you will need to monitor your coolant, exhaust and oil temperatures to ensure that under boost, you do not put too much heat into either. Your stock cooling systems will not handle boosting for extended periods of time. Keep these things maintained and keep an eye on them.

Detonation
Detonation death: Three things contribute strongly to detonation: intake charge temperature, timing and air fuel ratio. Intake charge temperatures rise if you are pushing your turbo passed reasonable limits, you have inadequate charge cooling (intercooler), or if your initial intake temps and engine bay temps are simply too high. Air fuel ratio comes almost directly from the health of your components and the strength of your tune. Injectors not flowing correctly or a fuel pump not delivering the correct pressure can lean you out. Predominantly, however, it is either a tuning issue or a malfunction that leads to detonation. The best way to avoid both is to have the kit installed correctly and properly tuned from the get go. There are additional considerations for Octane rating and Timing that are beyond the scope of this document for the time being.

An interesting article from Ben Strader - EFI University
Air/Fuel Ratio Management For Racers, A Three Part Series

When it comes to racing, there is never any shortage of hard work and chores to be done before the next event. Often, race teams are required to travel long distances during the week, prep the car, show up on the weekend ready to run, and then do it all over again the next week. This doesn’t leave much time for experimentation and trying out new concepts. That means most of the time, when racers find something that works okay they tend not to change it, even though there might be a better way. They simply can’t afford to risk missing an event or losing a race. Often times a discussion arises about the best Air to Fuel ratio to use for various tracks and atmospheric conditions. I want to try and address a few of these questions in this series. Here is a list of some common questions asked by racers and tuners:

1) What Air to Fuel Ratio gives the best power?
2) Does the Air to Fuel Ratio that produces the best power change as the altitude my car operates at changes?
3) Does the Air to Fuel Ratio that produces the best power change as the intake air temperature my car operates at changes?

To find answers to these questions I have spent years on the dynamometer testing various engine combinations, talking with other knowledgeable tuners, reading various publications on the subject, and even wrote a book about tuning Electronic Fuel Injected engines, but I found the most convincing answers to these questions in a document written in 1922 by Stanwood Sparrow of the “Bureau of Standards” for the “National Advisory Committee for Aeronautics” (NACA), called NACA Report #189 “Relation of Fuel-Air Ratios to Engine Performance”. In this report, a government agency set out to answer these and many other questions about the effect of Air Fuel Ratios on engine performance over a wide range of parameters, and the evidence proves out many of the answers I am about to present to you for the above questions in this three part series.

PART I

What Air to Fuel Ratio gives the best power? Many folks have tried to shed light on this subject based on single-case observations made in sloppily controlled test environments which show results of all sorts, and yet other, seemingly more knowledgeable sources, (such as the companies trying to sell Air-Fuel ratio meters) are constantly trying to convince us that while they cannot (for reasons of liability) tell us what the magic number is, we cannot possibly hope to achieve maximum engine performance without the help of one of their whiz-bang doo-hickeys!

Well, according to NACA report 189, a wide variety of engines were tested across a large range of Air/Fuel ratios and what they found was basically the following:

“In adjusting the carburetor to obtain maximum power, The following method was employed. First, the mixture was altered until approximately maximum power (for the chosen set of conditions) was obtained. As will be shown later, values of power within 1 percent of maximum are obtained over a wide range of fuel-air ratios. Hence, little difficulty was experienced in finding an Air/Fuel ratio to give approximately maximum power.”

The report goes on to state later that, “From the results to date it is concluded that ordinarily maximum power (at least in so far as aviation engines are concerned) is obtained with gasoline-air ratios of between 0.07 and 0.08 pounds of fuel per pound of air (12.5 to 14.5 pounds of air per pound of fuel).”

What all this means is that basically, if simply making lots of power is your only goal, nearly any Air/Fuel ratio can get you pretty close to the mark.

This corresponds quite closely to what my years’ of engine testing have show as well, and in fact, this is what we have been teaching at EFI University for almost four years, but what I find surprising is the number of supposedly “expert” tuners out there who are still arguing against this point, and pretending that what they do is a special brand of “Magic”.

My experience has been that typically the best engine tuners in the business are the first ones to say: “Ask me anything you like, I have nothing to hide.”

Recently, I spoke with Shane Tecklenburg of FAST Motorsports in Huntington Beach, California, who is widely regarded to be one of the finest engine tuners in the USA, and he had this to say: “Nothing I do is black magic. Everything is based on simple laws of physics that anyone can learn with a little effort, so there is no reason for me not to answer a racer’s question about engine tuning, even if he is a competitor.” I have also spoken to a number of other well known tuners who have had quite the opposite attitude and tried to make it seem as if they knew some special trick or held the golden nugget of knowledge that, if shared with others would seriously jeopardize their standing. Most of the time, when I find a tuner with this attitude, it means they don’t actually know the answers and fear they might reveal this ugly fact if they say too much.

The simple fact is, ten years ago, before the age of $300 wide bands for everyone, nobody even knew what their Air Fuel Ratios were. The rule of thumb was to change the jets one size for every one-thousand feet of elevation, and that was just the way it was. We looked down the tailpipes and at our spark plugs for various color patterns, and even that wasn’t an exact science.

Most racers would have been horrified if they actually saw what the A/F ratios were doing in their engines during a run, but because the engine still performed well, no one cared. What has changed the industry so dramatically in recent years is the advent of the low-cost wide-band Air/Fuel ratio meters. Suddenly, everyone could afford access to this tool to gain priceless insight into their engine’s performance, and then “numbers game” began.

It is not uncommon to go to the racetrack these days and find any number of racers with their laptops plugged into their cars trying to get that last tenth of an A/F point in line. I’ve heard guys say “yesterday she was running a 12.8 A/F ratio, and today it seems to be running about 12.7 and that’s just too rich!” I wonder if either their dyno, or their E.T.’s would support that. If what the NACA report says is true, then I suppose it begs the question, “What is to be gained by agonizing over minute changes in A/F ratios”? Isn’t there some other chassis or tire component that would be better served by spending this time tweaking them instead? What good is ultimate power if it can’t reach the ground?

I’m not suggesting that we abandon this great new technology and throw away our wide-bands just yet. I simply want to help folks get back to the reality of what it is we are trying to accomplish: Getting the maximum performance from the engine… not getting bogged down in the data. Let’s all take a step back, close our eyes, take a deep breath and remember, the only numbers that really matter are not the ones on the wide-band, but the ones that say the letters “E.T.” next to them! Good luck out there folks!

Coming up in Part II: Does the Air to Fuel Ratio that produces the best power change as the altitude that my car operates at changes? Tune in next time to find out!


Written By: Ben Strader

Adding Room3

Adding Room4

Adding Room5

Adding Room6 - Done

now this may be out of left field, but remember a while back some nascar drivers got fined for having a foreign substance in their airboxes...any idea what that substance was and if it is some sort of evaporating oxidizer where can i get some lol.

and just for posterity 'power adder' sounds like a really bitching 80s hair metal band name

I don't know what this means in your post:

Supercharger advantages: Typically easier to install than a turbo. Provides pressurized air as soon as the engine is running. Linear increase in pressure due to it being tied to the engine RPM. May be cooler air than a turbo.

How is SC air cooler than turbo air? Compressing the air generates heat in both applications.

The hot side of a turbo (exhaust) should remain hot, as it travels faster that way. Not really a disadvantage. The part was designed to work in the exhaust stream.



Also:

Turbo disadvantages: Can be difficult to install. Compressor is not linear meaning it does not provide a specific pressure at a certain RPM.

That is actually one of the biggest advantages of the turbo system over superchargers. It's NOT tied to rpm. So as long as your exhaust can spool up the turbo fast enough, you can get your peak boost almost anytime you want. Low rpm, high rpm, doesn't matter. With a SC you're tied to the rpm, so you have to design it for high rpm (See DNA SC dynos), or low rpm, this results with huge trade offs.

I agree, I will update that. The tuning side of the spool up is more in line with my intentions.

MM already called me out on the heat argument. I need to fix that also, I just wanted to get it moved before I lost the formatting.

now this may be out of left field, but remember a while back some nascar drivers got fined for having a foreign substance in their airboxes...any idea what that substance was and if it is some sort of evaporating oxidizer where can i get some lol.

Woah. I can think of what it MIGHT be...but anything that is an oxidizer is also a very low level explosive. So I am not saying anything.

now this may sound newbish but is there a reason that liquid oxygen is not used in the same fashion as nitrous oxide to increase VE?

The higher the Partial Pressure of O2, the more flammable the mixture. So 100% O2, especially under pressure is very flammable, a bur or microscopic metal shaving in the path of flow can cause a massive conflagration (big big fire).

Updated.

Need more advantages / disadvantages of SC and NO2... unless I got them right.

a disadvatange of an SC is its lack of scalability easily. A turbo u can control with a boost controller, whereas a supercharger is fixed boost unless u get new pulleys and belts etc....

Nitrous Oxide Disadvantages:
As the nitrous tank pressures vary based upon a multitude of variables, It is very difficult to control/predict the desired input/output of your system. This makes it difficult to maintain the proper AF, and consequently the ignition curve. To be more specific: The bottle pressure varies greatly from time to time depending on the ambient temperature, the amount of nitrous in the bottle and the duration of your pass/passes.
The higher the ambient temps, the higher the bottle pressure. Longer passes lower the bottle pressure dramatically.
Such volatility of pressure, inadvertently changes the volume on the Nitrous delivered into your engine, thus making it difficult to tune. In order to streamline the variations of the pressure, additional parts must be purchased (pressure regulators), and to my experience they are not hat common and not easy to find. While there are a couple on the market, their price is quite high. This contributes to the price of the implementation of a "complete" system.
Also, It is illegal to use nitrous oxide outside of the race track. I think the bottle must be empty while driving on the streets.

Added SC info, I am going to leave the NO2 of for now because I think it may be too complex to qualify for entry level info.

If people disagree then I will update it.

How is SC air cooler than turbo air? Compressing the air generates heat in both applications.

The hot side of a turbo (exhaust) should remain hot, as it travels faster that way. Not really a disadvantage. The part was designed to work in the exhaust stream.


Add an intercooler on either a turbo/supercharged app, and the intake temps will come down drastically - even on a 2 or 3 core Air to Air (A/A).

Add an intercooler on either a turbo/supercharged app, and the intake temps will come down drastically - even on a 2 or 3 core Air to Air (A/A).

Gee really? Maybe I should do that. :P

MySql101 was referring to the heat from compression, I assume.

yes, afterall, that's what FI does :)

now this may sound newbish but is there a reason that liquid oxygen is not used in the same fashion as nitrous oxide to increase VE?


LoX is no joke..

Well unless your freezing frogs that happen to be on the flightline. :rolleyes:

But like Kane said, 100% O2 is damn flammable. LoX itself also cant mix with greases, etc, cause it will cause a big boom. Too many hazards.

I have a question, I've been reading from different sources for fuel efficiency.

I have seen reports that adding a charger, turbo or super would increase fuel effiency. But i've also heard that adding such devices to increase engine power decreases fuel effiency. I'm guessing there's two type of Fuel Effiency being talked about, but I haven't read 1 source that has both types (if both exist) listed.

I'm interested in getting the highest MPG out of an RX8 as possible and if there's any aftermarket items that would increase the MPG to a more tollerable number - like a low 30s. I don't care about engine power, Im not racing and I don't have any interest in showing off. I'd rather leave a couple minutes eariler and ride without a care, then stress and zoom for that hot flash that'll come over me when I see a parked police car. Thankfully the car must've not noticed me >.>

+1 with CRH.

You will never hit 30's consistantly with a rotary. The only mod you could try is to retune with an eye to efficiency instead of power. That and driving for economy, lightening your car are about it. But then you would end up with carbon galore in the engine since it would not be burning as hot... so all of your gas savings would go into a new engine at some point potentially.

Pros : Supercharger is more reliable

Evidence - RX8club.com threads

heh - flame away turbo fanbois but thats what I'm reading here almost every day .

So there are dozens of SC-ed RX8s with 30-40K miles trouble free? If there are, then you are right...

If you are going to introduce an addendum, I think you need a more valid piece of evidence.

Pros : Supercharger is more reliable

Evidence - RX8club.com threads


You must be proud of your GED.

How many cars are SC'ed? How many are TC'ed? How many miles driven on each? There are many more trouble free TC cars than there are even SC cars. Even you cannot dispute this.


Ultimately, we all know more moving parts means more reliable, right? :)

Yes, it's a crap shoot.

The worse part is, I'm always second guessing things.

heh - ok sorry fellas . I was in the mood for an argument last night .
You are right mysql101 - there is not enough evidence yet .
If I was a betting man though I'd be putting money on SC's FTW reliability wise .

PS what's a GED ?

I fell asleep halfway through, i'll finish reading later :)

if it was such a remarkable beast, why is it most of us are getting engine change outs? even before 50k?

While there seems to be quite a few who have had issues, *most* of us don't have engine problems.


heh - ok sorry fellas . I was in the mood for an argument last night .

If I was a betting man though I'd be putting money on SC's FTW reliability wise .

PS what's a GED ?

I still disagree. What makes you say a SC is more reliable? Ultimately it boils down to adding more air and fuel. So the most important part is fuel management. If you put that aside, the SC has more moving parts ... so there's going to be more to break, and more to wear out. There's nothing in a TC that makes is more dangerous to use.

GED = http://en.wikipedia.org/wiki/GED

I admit i'm no expert - but then again being an expert can sometimes cloud your judgement anyway .

these are my opinions only - formed in the most part by observation and what I read right here .

1/Heat - turbos allow more heat to be collected close to the engine and dispersed in that area rather than out the exhaust . Heat = bad for reliability

2/Restriction of exhaust - Exhaust gases have to be pushed out rather than just let out with an unrestricted exhaust . This has to mean more heat build up in the exhaust ports . Again heat = bad . There was suggestion a while back that this was a factor in many turbo renesis engines blowing (Pettit racing thread ) although who really knows .

3/Extremely hot turbo impellor spinning at 100's of thousands of RPM and being lubricated by engine oil . You are probably going to argue that lots of turbos last a long time on factory cars . I would counter this by saying this is not a factory turbo that has had countless hours of testing to destruction . We are talking aftermarket - and we all know how much effort greddy put into the 8's system. Probably the turbo itself could last a long time if everything was perfect in its setup but in an aftermarket situation this is often not the case.

4/ Tuning : By its nature A SC is always going to be easier to tune because boost is linked to engine rpm. With a turbo there are more variables so its harder to tune. So I contend this is another factor that can contribute to poor reliability.

5/ Boost from a SC is more gradual . A turbo can be quite severe (especially a big one) which has to be harder on the drivetrain.

6/ Anecdotal evidence from all the blown turbos/engines I hear about on this forum that suggest there may be some truth in all the above.

I admit i'm no expert - but then again being an expert can sometimes cloud your judgement anyway .

I'm no expert either, but are you seriously saying that it's bad for someone to know what they're talking about? lol.



Heat - turbos allow more heat to be collected close to the engine and dispersed in that area rather than out the exhaust . Heat = bad for reliability

If you're really worried about heat, get everything coated. The area that the turbo sits is already hot because of the engine exhaust manifold. Most people will install heat wrap on the pipes, so the heat continues out, without raising temps in the area.


Extremely hot turbo impellor spinning at 100's of thousands of RPM and being lubricated by engine oil . You are probably going to argue that lots of turbos last a long time on factory cars

That is not the argument I'd make. While it's true the engine oil is shared with the turbo, but it's not as bad as you make it out to be. Use a good synthetic oil and it's fine. I monitor oil temps (racing beat pod), and I rarely go over 180F. This is not an issue. Remember, only a tiny drip of oil goes into the turbo. It's not like it's located in the oil pan!


Tuning : By its nature A SC is always going to be easier to tune because boost is linked to engine rpm. With a turbo there are more variables so its harder to tune. So I contend this is another factor that can contribute to poor reliability.

It's tuned exactly the same way. That's why the int-x can run on both greddy and pettit kits without changes. With the EMU, it's tuned with X psi at N rpm, so that would be the same as well.


Boost from a SC is more gradual . A turbo can be quite severe (especially a big one) which has to be harder on the drivetrain.

I can tell you've got no background with a turbocharged car. If you did, you would know you can adjust the boost controller to increase or decrease the wastegate speed. You can get gradual boost, or you can get neck snapping power. Another bonus for the turbo - adjustability and control.


Anecdotal evidence from all the blown turbos/engines I hear about on this forum that suggest there may be some truth in all the above.

That's bullshit. Improper tuning will cause engine failure. GReddy has had issues with the tune, and even shipped some of the emanage blue units with no map on them. For sure that would cause issues, but that's not a reflection on turbo systems. A SC would face exactly the same fate.


In conclusion, you want to think SC > TC, but in reality you have nothing to back it up other than you wanting it to be that way.

Brettus, Also, we've gone over this before, so I know you know better :P

Apparently you don't listen, or think I'm making this stuff up.

I'm no expert either, but are you seriously saying that it's bad for someone to know what they're talking about? lol..

No - but sometimes you become an expert in one specific area and that clouds your judgement about other related things :)

If you're really worried about heat, get everything coated. The area that the turbo sits is already hot because of the engine exhaust manifold. Most people will install heat wrap on the pipes, so the heat continues out, without raising temps in the area..

Yep - that will help but not eliminate altogether .


That is not the argument I'd make. While it's true the engine oil is shared with the turbo, but it's not as bad as you make it out to be. Use a good synthetic oil and it's fine. I monitor oil temps (racing beat pod), and I rarely go over 180F. This is not an issue. Remember, only a tiny drip of oil goes into the turbo. It's not like it's located in the oil pan!.

It's more the fact that lubrication of the turbo itself is so critical that I was refering to

It's tuned exactly the same way. That's why the int-x can run on both greddy and pettit kits without changes. With the EMU, it's tuned with X psi at N rpm, so that would be the same as well..

See your point here . The tuning would take care of most the variability that a turbo would produce as you say

I can tell you've got no background with a turbocharged car. If you did, you would know you can adjust the boost controller to increase or decrease the wastegate speed. You can get gradual boost, or you can get neck snapping power. Another bonus for the turbo - adjustability and control..

OK but most will go for the neck snapping - not really the fault of the turbo . More the tuner .

That's bullshit. Improper tuning will cause engine failure. GReddy has had issues with the tune, and even shipped some of the emanage blue units with no map on them. For sure that would cause issues, but that's not a reflection on turbo systems. A SC would face exactly the same fate..

How many more blown turbos/engines would it take to convince you that turbos are more likely to cause problems?

In conclusion, you want to think SC > TC, but in reality you have nothing to back it up other than you wanting it to be that way.

I have no vested interest in this argument - you on the other hand have a turbo and it runs very well for you by all accounts so of course you will be in that camp.

It's more the fact that lubrication of the turbo itself is so critical that I was refering to

Still a non issue. Remember the turbo is fed the same oil that lubricates the engine. If you don't have oil, then your going to be worried about more than losing a $1000 turbocharger.



OK but most will go for the neck snapping - not really the fault of the turbo . More the tuner .

Yeah, people like to be thrown back in their seat and go into warp speed. Not always good on wet roads - which is why there's usually a button on the boost controller to toggle between presets.



How many more blown turbos/engines would it take to convince you that turbos are more likely to cause problems?

Just one. Show me where a turbo caused a RX-8 to die, in a situation that doesn't apply to other forms of FI. That is my point - you're adding air and fuel, the same as as SC.



I have no vested interest in this argument - you on the other hand have a turbo and it runs very well for you by all accounts so of course you will be in that camp.

I make no money off convincing you otherwise, I have no vested interest in this. If I saw a SC kit available for the RX-8 that had more advantages over a TC, I'd be in line to get one.

mysql - i'm not saying that the issues I listed can't be overcome . Just that for a car that started out life as N/A - turbos are more of a mission to make reliable than a SC.

mysql - i'm not saying that the issues I listed can't be overcome . Just that for a car that started out life as N/A - turbos are more of a mission to make reliable than a SC.

TC is going to be more involved to install. Aside from that, you haven't said anything that remotely begins to back up your statement.

A SC just adds air, same as a TC. With larger fuel and air, comes added wear and tear on the engine. There's no additional reliability one way or the other for the car.

You have managed to skip answering my question. Show me proof that a single RX-8 has been harmed by a TC that couldn't have happened with a SC. You can't because your argument is completely flawed.

I agreed with you in an earlier post that there is not enough evidence to suggest a SC is more reliable so I'm not going to try and justify the statement .

Those are my beliefs based loosely around the points I put forward .
You have your view as well - can you supply proof that TCs are as reliable as SC's in this application?

What I do know is that i'm continually reading about blown turbos and blown turbo motors - who really knows whether a SC on the same motor would have had the same problem ?

can you supply proof that TCs are as reliable as SC's in this application?

That argument is flawed no matter which way you turn it.

You must be proud of your GED.
:)

Oh -I looked this up .
Come on mysql - you put together good arguments , this kind of thing is surely below you !

lol.

No, I meant it. Numbers aren't your thing if you think that more people with blown engines from being turbocharged means it's less reliable. You're making huge assumptions here, ignoring the fact that there's a risk from going FI, no matter how you do it. Add in people doing installs half assed, issues with the car in NA form, and the fact that there's likely a 100:1 ratio between them, and you'll see why I mentioned GED.

If you install it properly, and tune it properly, you should have no issues with a turbo damaging your car more than anything else. If you don't have it installed and tuned properly, you risk damage, regardless of if it's a turbo or supercharger. That is why I'm telling you one is not safer than the other. Both carry a risk, and both can and will destroy your engine in exactly the same way if not done right.

+1 with Mysql101's last comment. I think the this versus that argument will never be solved (since even the real experts are still arguing about it). But the thing to keep in mind is that they both can blow your motor the same way. It will all come back to the tuning.

I don't see any real experts arguing, at all.

I don't see any real experts arguing, at all.

LOL - at least we admitted as much to start with Charles .

I don't see any real experts arguing, at all.

I am not reffering to "us" at all. I was speaking more about various racing teams, OEM's (Porsche = Turbo, Shelby = SC, etc.) So I think the overall answer I can glean is "it depends"...

So am I interpreting correctly, that in your opinion:
The "real" experts all agree?
Or they all agree to disagree?
Or they all agree "it depends"?

I would concur that they are experts. I would also say that the point was not to argue (at least MY point was not to argue). The point was to educate and allow people to weigh the Pro's and Con's and come to thier own decision. In order to make that happen, I need additional Pros and Cons as I have limited knowledge.

But it is starting to get under my skin that we can't seem to have a normal, rational discussion without becoming jackasses to each other.

And I am not referring to CRH, we argue civilly all the time....

Here's my observation; the reason guys like our agreed-upon experts don't argue is because they either 1) Have their preferences and their customers already know what they might be or, 2) They would all agree that the type of power-adder used is a matter of preference and application and not a matter of technological superiority.

My insistence on lumping nitrous in alongside turbos and superchargers drives some people crazy but that, to me, is just their own prejudices and preferences speaking and not an educated, technical, opinion. I have an on-going conversation with a guy who told me that he looked into having "Shop A" install a nitrous kit for him. "Shop A" is a fairly well-respected shop and they cautioned him that they believe nitrous will not work on the RX-8. Am I correct in assuming that those who have followed my guidance or allowed me to do the install are having success with their systems? If I have a pretty firm grasp of the situation, and an accurate view, I would say that "Shop A" is wrong simply because history proves otherwise. The truth is probably that they tried it, failed, and now caution others away from nitrous use. Not because of any technical inferiority, just because of one or two bad experiences with it. I was also talking to chickenwafer last night about the same concept involving a well-respected author of a book who told a similar story of trying nitrous on an engine and, having failed with it, cautions his readers to stay away from nitrous. These are the same cautionary tales I heard when I examined the possibility of using nitrous on the RX-8. You all know what has happened for the past three years......

I guess it is much easier and self-satisfying to caution others away from the mistakes we have made as if we are now "experts" on certain things simply for having failed at them.

My point is that most of the technological end of these arguments has been settled by those who have the experience and that which is understood need not be discussed between them.

My personal opinion is that all of these power-adders accomplish the same goal; helping a given engine burn more fuel than it would normally be capable of under natural aspiration and they are all capable technologies. There are dozens of example of turbo kits that are working as intended. There are dozens of examples of the same with nitrous. There will soon be dozens of examples of the same with superchargers, too. The cases where they don't work will undoubtedly be installer/tuner/user error.

I dedicate this long post to my friend, TeamRX8. I know he loves reading my long-winded posts. Love ya, Bro.

Well said.

My insistence on lumping nitrous in alongside turbos and superchargers drives some people crazy but that, to me, is just their own prejudices and preferences speaking and not an educated, technical, opinion. I have an on-going conversation with a guy who told me that he looked into having "Shop A" install a nitrous kit for him. "Shop A" is a fairly well-respected shop and they cautioned him that they believe nitrous will not work on the RX-8. Am I correct in assuming that those who have followed my guidance or allowed me to do the install are having success with their systems? If I have a pretty firm grasp of the situation, and an accurate view, I would say that "Shop A" is wrong simply because history proves otherwise. The truth is probably that they tried it, failed, and now caution others away from nitrous use. Not because of any technical inferiority, just because of one or two bad experiences with it......


The lesson I see here:
If your shop says to stay away from any particular application, then listen to them if you intend to engage their services... It probably means they aren't very good at installing it. Go with their recommendation, or look for another shop that is willing to endorse your choice of poison (preferably validated with good customer feedback).

Agreed - but also Know Thyself.

If you tend to be more aggressive than most when it comes to modding; find a shop who is more conservative and vice versa. It never hurts to have a devils advocate. The downside being the point made by Rumboo; lack of exp. But hopefully a happy medium can be found.

The point I am making is this; It is human beings who run/own the shops we patronize and, as such, they often develop prejudices for/against certain things not based on objective observations and experiences but often based on subjective, one-time, experiences that may have included the fact that they didn't exercise due diligence in their preparation. Should my personal experiences and mistakes I made during my rebuild/porting of my engine be used as "proof" that others should shy away from it? No, because those mistakes were my own. Now that I have the engine running properly(thanks to the help of several from this forum) I can more objectively assess the value of such modifications. In other words, when being told to stay away from a certain mod don't give up on the idea just because ONE SHOP says so.

I was also trying to point out that any mod that has the intent of introducing more fuel and oxidizer into the engine is what I consider a "power-adder".

Updated with a tid-bit about Air Fuel Ratios.

Where? I am a dummy and I can't FIND it!

Post #3

I was kidding!

My bad - was that a subtle way to tell me I should have put in a link?

No, I was cracking about the thread title and acting as one.

Rotary Fragility with Detonation
Understanding the "fragility" of a rotary motor as compared to a piston motor is not a simple exercise. Though the inertial loading on the rods of a piston motor are extreme, the dynamics are known and very simple. Piston design is at a state where there are very few variables left to consider.

A rotary motor is under considerably more stress and that stress is highly dynamic, principally because of the engine's simplicity. Think about what an apex seal is being asked to do: it must support two phases of combustion simultaneously on opposite sides while constantly accelerating (and decelerating) along two axes of motion!

Though there are no rods to stress, detonation affects the dynamics of the rotary motor with forces that are exponentially more damaging than they are in a piston motor. (BTW - detonation is not pre-ignition and understanding the difference is pretty important.) The Renesis is FAR more fragile than any other motor in existence. It cannot take ANY overheating. It cannot survive any pre-ignition. It will not survive any oiling malfunctions. Though it might keep running, any failings in the fuel/water/oil will yield a damaged motor. A piston motor's typical failure mode will lower its operational efficiency by some fraction of its total output. A rotary motor - even with a minor failure - typically becomes completely unusable. Similarly, a Renesis is not really rebuildable after a failure. Under optimal conditions however, the Renesis may be the most robust motor in existence because of its simplicity.

I don't know about this. I know the guys with REW's are putting huge boost on them at times (guys talk about being up around 40lbs) The difference is those engines were pulled apart and rebuilt for boost. It could be done with the Renesis just as easily, it just hasn't yet. Lowering the compression of the rotors, maybe even some shaped scalloping on them, beefier apex seals, and maybe some mild porting (extreme porting is usually only done by N/A guys). Big ignition upgrades, methane and water injections, etc, etc. Lots of things that can be done.

The engine is also certainly rebuildable. Guys have been doing it at home with kits for years on the 12A and various 13B's. The 13B MSP is just the latest variant.

Piston engines that aren't reinforced tend to have problems with boost as well. They also have to have parts replaced when they blow, same as rotaries.

Don't sell these engines so short.

All one needs to do to find out how the Renesis differs in terms of durability from previous rotaries is take a look at my nitrous threads.

The engine is also certainly rebuildable. Guys have been doing it at home with kits for years on the 12A and various 13B's. The 13B MSP is just the latest variant.

Piston engines that aren't reinforced tend to have problems with boost as well. They also have to have parts replaced when they blow, same as rotaries.

Don't sell these engines so short.

I agree with most of what you say - the biggest issue for me is scoring housings when apex seals go - last I heard both of Jeff's blown engines were not rebuild-able without new housings.

Kane, I'll straighten ya out when I see ya. The Renny isn't as "fragile" as previous rotaries. I thought I demonstrated that with my nitrous exploits. MM's engine troubles we created under conditions that would have been worse had then been older rotaries. In the first case he wes seeing temps in the 240s(?) while under boost and kept his foot in while knowing bettter(admittedly so) and in the second, his wastegate hose came off causing the boost to spike to 21 psi with no maps to accomodate the pressure.

didnt really know where to post this question so here looked like a good spot. ok well in regards to a turbo how is it that by different tuning, the turbo is able to change how much boost it is providing? like how do you get the turbo to change how much air it is pushing into the engine by tuning. are you somehow increasing exhaust output so that the turbine is spinning more? i know i'm wording it wrong and it probably sounds like a retarded question but i'm just trying to learn so please be gentle :)

didnt really know where to post this question so here looked like a good spot. ok well in regards to a turbo how is it that by different tuning, the turbo is able to change how much boost it is providing? like how do you get the turbo to change how much air it is pushing into the engine by tuning. are you somehow increasing exhaust output so that the turbine is spinning more? i know i'm wording it wrong and it probably sounds like a retarded question but i'm just trying to learn so please be gentle :)

The turbo has a wastegate. It's basically a turbo bypass. When open, exhaust can flow around the turbo blades, causing the turbo to no longer spool up any higher. This is important or your engine will blow up.

The wastegate has a spring that is connected to a pressurized vacuum hose. the pressure opens up the wastegate. So if the spring is rated for 7 psi, it'll start to open up at 4 psi a bit, and by 7 psi it'll be all the way open.

A boost controller can be used too, which sits between the wastegate and the boost signal. All it does is tell the wastegate that there is less psi than there actually is, which keeps the wastegate shut longer, causing boost to build more rapidly. If you wanted more psi, you just tell the boost controller, and it will hold off on telling the wastegate about the pressure till the desired pressure is reached.

The turbo has a wastegate. It's basically a turbo bypass. When open, exhaust can flow around the turbo blades, causing the turbo to no longer spool up any higher. This is important or your engine will blow up.

The wastegate has a spring that is connected to a pressurized vacuum hose. the pressure opens up the wastegate. So if the spring is rated for 7 psi, it'll start to open up at 4 psi a bit, and by 7 psi it'll be all the way open.

A boost controller can be used too, which sits between the wastegate and the boost signal. All it does is tell the wastegate that there is less psi than there actually is, which keeps the wastegate shut longer, causing boost to build more rapidly. If you wanted more psi, you just tell the boost controller, and it will hold off on telling the wastegate about the pressure till the desired pressure is reached.
thats exactly what i was looking for thanks! so then basically the larger the wastegate the more boost will be allowed(taking the turbo limitations into account)

thats exactly what i was looking for thanks! so then basically the larger the wastegate the more boost will be allowed(taking the turbo limitations into account)

The larger the wastegate, and the more control you have over the boost. To make boost the gate is shut, making the exhaust gas push the turbo.

To not make boost the gate opens slightly to let the gas exit out the exhaust. This causes the turbo to slow down because nothing is pushing it.

check my thread, the first post has pictures of the turbo, the big purple thing is the wastegate. http://www.rx8club.com/showthread.php?t=138414

thats exactly what i was looking for thanks! so then basically the larger the wastegate the more boost will be allowed(taking the turbo limitations into account)

Not really. The wastegate just bypasses the turbo, it's function is to prevent boost, not increase it. Also, many turbos have built in wastegates, so you can't replace them.

Like I said, it's the wastegate actuator (spring) that determines how much boost the turbo will reach. A boost controller gives you even more control.

Not all turbos are alike, there are many variations, and configurations.

Also boost is not just boost. You have to consider flow rates too. For example, 9 psi on the greddy turbo is a lot less powerful than 9 psi on the mazdamaniac turbo.

ah, I remember when 300 was a magical unachievable number :)

Now its 400 :)

if you stick with the greddy turbo, 300 will always be just out of reach :P

:banghead: i miss read your post mysql. thanks to both of you for helping me out!:)

now this may be out of left field, but remember a while back some nascar drivers got fined for having a foreign substance in their airboxes...any idea what that substance was and if it is some sort of evaporating oxidizer where can i get some lol.

My guess would be this:
Oxygen Candle (http://www.austdac.com.au/products%20pages%20safety/safbr081.html)

Wikipedia entry (http://en.wikipedia.org/wiki/Chemical_oxygen_generator)

The candle is Iron and Sodium Chlorate, burns very hot though, 600 degrees C.
There is a Russian version that burns at a lower temp.

I thought we were not going to go into that part... :lol:

BTW - There are other oxidizers that can be used both on the intake side and as a fuel additive; but again... velly velly dangerous.

I have a question, I've been reading from different sources for fuel efficiency.

I have seen reports that adding a charger, turbo or super would increase fuel effiency. But i've also heard that adding such devices to increase engine power decreases fuel effiency. I'm guessing there's two type of Fuel Effiency being talked about, but I haven't read 1 source that has both types (if both exist) listed.

I'm interested in getting the highest MPG out of an RX8 as possible and if there's any aftermarket items that would increase the MPG to a more tollerable number - like a low 30s. I don't care about engine power, Im not racing and I don't have any interest in showing off. I'd rather leave a couple minutes eariler and ride without a care, then stress and zoom for that hot flash that'll come over me when I see a parked police car. Thankfully the car must've not noticed me >.>

A gear change would be the only hope, and that would only help on the highway, and would hurt city milage. :icon_no2:
Mazmart has a 3.9 and a 4.1 ratio gear set for sale to replace the stock 4.44.

How does a taller gear only help highway mileage? A higher gear will help all types of mileage.

You would push the throttle more on acceleration (since taller gears would be slower) with taller gearing - therefore MPG could go down.

Thought I would share this. Hadn't seen anything like this since the RX-8 hydrogen protoype.

http://www.autocar.co.uk/News/NewsArticle/Lotus-Elise/232017/

Would be interesting to see this applied to an 8 when it hits production.

Thought I would share this. Hadn't seen anything like this since the RX-8 hydrogen protoype.

http://www.autocar.co.uk/News/NewsArticle/Lotus-Elise/232017/

Would be interesting to see this applied to an 8 when it hits production.

I'll believe it when I see it....; but yeah - it would be cool.

mazdamaniac has already cornered the electric supercharger market so this thing will never fly !

Thought I would share this. Hadn't seen anything like this since the RX-8 hydrogen protoype.

http://www.autocar.co.uk/News/NewsArticle/Lotus-Elise/232017/

Would be interesting to see this applied to an 8 when it hits production.
Hey someone with fewer posts than me! You might want to do a second take on the publication date of that article. Also a forum search will kick up a few old threads.

Yeah... I don't get to login and post as often as I'd like.

The article was from April 1, 2008... no? Either way not real yet.

I hate to be a correcter correcterson and I may get flamed but as an engineer there is a large mistake that has been commented on here several times.

Oxygen is not flammable. The properties of oxygen is that it is an oxidizer that promotes rapid combustion. But if there is no other fuel source the oxygen itself would not detonate or combust. It needs to be treated very carefully (I.E. Read about the apollo 1 crew disaster) because it supports combustion but again, it is not flammable.

Nitrous Oxide is an oxidizing agent, when it's in the presence of combustion it releases oxygen, but it is much safer than pure oxygen.

Sorry, but I had to clear that up.

New more advanced information available on my blog under General Performance - www.ppo2performance.com

Updating as I get some free time.

I hate to be a correcter correcterson and I may get flamed but as an engineer there is a large mistake that has been commented on here several times.

Oxygen is not flammable. The properties of oxygen is that it is an oxidizer that promotes rapid combustion. But if there is no other fuel source the oxygen itself would not detonate or combust. It needs to be treated very carefully (I.E. Read about the apollo 1 crew disaster) because it supports combustion but again, it is not flammable.

Nitrous Oxide is an oxidizing agent, when it's in the presence of combustion it releases oxygen, but it is much safer than pure oxygen.

Sorry, but I had to clear that up.

Oxygen yap your right.....but I believe they are talking about LOX Liquid Oxygen and in that case it will literally burst in flame with contact with fuel or grease...I do follow a long list of precautions when I fill-up the plane with it.... and everybody knows that aircrew like shortcut......but I like to stay unburn :lol:

And before you say only ground crew does that....I'm a Flight Engineer and I can do and sign for any jobs on the plane. :eyetwitch

Great read Kane, thanks for all the work, and to all who contributed.

I get frustrated with the superchargers parasitic loss which will result in a torqe hit witch the Renisis is already lacking

Pittit racing dyno shows 300hp and 195tq,
turbo 300hp and 245tq

on nearly the same boost pressure

that's 50lbft. often hear the expression hp sells cars and touqe wins races?

as far as superchargers being more reliable, hence you hear less engine failures. this comes from the driver/tuner. you can't just raise boost with a supercharger, you got to get another pully and install it.

with a turbo, you have some guy with turbo kit designed for 5-7 psi, but he has a boost controller and sets if for 10, cuz, he can? result = boom

so turbo failures are due to boost controllers and ignorant people

That is true - and I had that in my original post...


However I will say; ultimately it is the POWER that makes a car fast, torque does no work.

power as a form of measurement? as what values?

power as a form of measurement? as what values?

Power is measured in force over time.... torque is just measuring force.

tq is force. work is force x the distance and hp is work done over time. they are all apart of a physics equation. Its a matter of where the power is when usable. I see so many cars with dynos showing 600hp or more but it peaks at 7k rpms and from 2k to 5k there is little power comparatively speaking. Great for tall gearing but not for us. The whole sc vs turbo is a matter of where you want the power and how much. We have more rpms to play with so a turbo would be better but, as someone mentioned, you cannot just boost it and think everything is going to be ok. With either system, it comes down to the same thing, usable power. Both are good but, the real question is, how are going to cool the thing with all that power. So many focus on power and not the cooling and lose the engine.

Second, taller gearing will help in mpg whether in town or highway. Anytime you can decrease the rpms, you decrease fuel used at a given speed. The trick is to use your dynos and figure out when you have enough tq to maintain a speed at a given rpm. If you cannot maintain the speed and are having to downshift, you need a shorter gear for that speed. The 8, even at 45mph at 2250 rpms is maintaining that speed on a 6% grade so there is room for improvement. Its really comes down to what you want and how you want to go about it.

Anytime you can decrease the rpms, you decrease fuel used at a given speed. The trick is to use your dynos and figure out when you have enough tq to maintain a speed at a given rpm. If you cannot maintain the speed and are having to downshift, you need a shorter gear for that speed.

Even if you don't down shift - if you have to increase load (more throttle) to maintain the speed, you may end up using more fuel in the higher gear than you would have in a lower one (higher rpm, lower load).

Even if you don't down shift - if you have to increase load (more throttle) to maintain the speed, you may end up using more fuel in the higher gear than you would have in a lower one (higher rpm, lower load).

To an extent. There is only so much air/fuel available even at low rpms hense the power available at that rpm. If you are at lower rpms, you dont use as much fuel cause you dont have the power available as you are not burning as much fuel. Hope you got that. I can try to explain it a different way if you didnt get that. You have a higher load, yes. At a given rpm, you only have a certain amout of fuel that can be burned. This is simple physics. Have any questions, feel free to ask. :)

Point is, you are better off at lower rpms provided you can maintain the speed, too low and you will lose speed. The 8 is geared too low for highway speed but, for a reason. Some mags stress passing ability in top gear and mazda fell for the 30-50 test and the 50-70 test and made the gearing too short to achieve better fuel economy at highway speeds although the tq is there to keep the same speed at lower rpms. My 8 can maintain a 6% graded hill at 45mph. I am sure where it is flatter, the 8 can be geared so that it would have more like my neon and get 27mph/1000 rpms instead of about 20. I am not sure what the 'happy median' would be as I have not had time to test that. For those that dont like to change gears as much to accel, I am sure you are happy with the current gearing as 6th pulls well at 80mph. :)

That is true - and I had that in my original post...


However I will say; ultimately it is the POWER that makes a car fast, torque does no work.

You are very correct on this and with many that I talk to on other sites, they do not seem to get this and claim to be engineers and such. Due to design, the rotary doesnt do much with tq at first but, it does a lot more work. Part of the reason for this is that it has a handicap at low rpms due to leverage of the eccentric shaft.

The gearing I stated later on this discussion is similar. You stated, and other, that if you used taller gearing, you would use more gas as you would want to press the accelerator more. This is true to a certain extent. With taller gearing, you can get better mpg. The best gearing mazda could have put in the 8 is leaving the first 5 pretty much the same and using a much taller 6th. I believe that mpg could be close to 30 if we had closer to 26 or so mph/1000 rpms for 6th.

I have done this with my neon. I used to have a sport trans with a 3.94 and 5th was a .81. Now it is a 3.55 with a 5th of .72 which changed the leverage in each gear. I get 9 mpg more with the taller transmission and results will vary based on how people drive. The main difference was 21 to 27 mph/1000 rpms. It doesnt pull like it used to but, its the power available at the rpm is what makes a difference in mpg as well. This is why I said to use your dyno if you want to take the gearing thing further.

To an extent. There is only so much air/fuel available even at low rpms hense the power available at that rpm. If you are at lower rpms, you dont use as much fuel cause you dont have the power available as you are not burning as much fuel. Hope you got that. I can try to explain it a different way if you didnt get that. You have a higher load, yes. At a given rpm, you only have a certain amout of fuel that can be burned. This is simple physics. Have any questions, feel free to ask. :)
:)

Normally (with a piston engine) you would be correct - however with a rotary engine your volumetric efficiency at low rpm is way less than at higher rpm . So yes , it is possible to get better fuel economy at a higher rpm .

Normally (with a piston engine) you would be correct - however with a rotary engine your volumetric efficiency at low rpm is way less than at higher rpm . So yes , it is possible to get better fuel economy at a higher rpm .

That would hold true as long as you just have one set of fuel injectors working as you do in a piston engine. We have 6. I hear the new 09 has just 4 now though. My point is, if you are under identical situations and one car has lower gearing, the other has taller gearing, you will get better mpg in the taller gear as you will be going faster with the same fuel used. The rotary is no exception to this. Fuel burned at a given rpm tells power available. I have tested this time and time again and if I drive at lower rpms but stay less than 3000 rpms, I get better mpg. The part that I will agree with all of you to certain extent is load depending on speed and %grade of the hill. It is a fine line.

My point is that if you keep the rpms low, you will use less gas just as a piston would. Engine load is a variable that is hard to pin down cause you will never be constantly going up hill for a full tank of gas and if you go down a long hill and use engine braking, you mpg will not be true cause there will be no load and no fuel will be injected until you either get slow enough that you hit idle speed or you hit the 'gas' yourself. Engine load has little impact in most circumstances. I have gone up and down the appalachain mts and tested this going 35-40mph with cruise on and got better than average mpg both up and down the mountain.

Verify for me if you will, I have heard that at idle, the rotary runs somewhat rich. Assuming this is true, you are better off engine braking than pushing the clutch due to this. There are many variables that can take into account. It may seem like you get better milage on the interstate at speed but with a taller gear (to an extent) it can be much better. I try to draft behind trucks many times but, careful to do so as wind resistance means less air to the radiators as well.

At idle I am at 15 AFR range. But obviously engine braking uses zero fuel, so it would be more fuel efficient.

Anyway, back to the point - I watch the live fuel usage on the scangauge II as my comparison basis. If I am in 6th and need to apply throttle to maintain speed up a hill, I have found shifting into 5th and driving with a higher rpm uses less fuel. This seems counter intuitive, but there is less load on the engine with the lower gear.

when I said it was possible I din't mean it was necessarily true - just possible . Did you know that rotaries can actually be more fuel efficient than piston motors with similar power in competitive circuit racing ?

As far as engine braking goes - yes in most situations better to engine brake than push the clutch . Not only for fuel conservation but for control of the car as well .

one of the reasons why they won le mans.

At idle I am at 15 AFR range. But obviously engine braking uses zero fuel, so it would be more fuel efficient.

Anyway, back to the point - I watch the live fuel usage on the scangauge II as my comparison basis. If I am in 6th and need to apply throttle to maintain speed up a hill, I have found shifting into 5th and driving with a higher rpm uses less fuel. This seems counter intuitive, but there is less load on the engine with the lower gear.

I agree with you to an extent. Sometimes it is more efficient to go to a lower gear. This is why I said there are certain circumstances. I do agree with you. We all know that there are many factors that can influence this. :)

i have a ZEX nitrous system in my car (it came on it when i bought it and im a noob when it comes to nitrous) i was woundering what i would have to do to put a bottle in and run it. any engine mods gauges or any of that sort?

i have a ZEX nitrous system in my car (it came on it when i bought it and im a noob when it comes to nitrous) i was woundering what i would have to do to put a bottle in and run it. any engine mods gauges or any of that sort?

Might want to explain what you mean by "having" the ZEX nitrous system. Pics could help, along with quickly learning how nitrous works.

That would hold true as long as you just have one set of fuel injectors working as you do in a piston engine. We have 6. I hear the new 09 has just 4 now though. My point is, if you are under identical situations and one car has lower gearing, the other has taller gearing, you will get better mpg in the taller gear as you will be going faster with the same fuel used. The rotary is no exception to this. Fuel burned at a given rpm tells power available. I have tested this time and time again and if I drive at lower rpms but stay less than 3000 rpms, I get better mpg. The part that I will agree with all of you to certain extent is load depending on speed and %grade of the hill. It is a fine line.

My point is that if you keep the rpms low, you will use less gas just as a piston would. Engine load is a variable that is hard to pin down cause you will never be constantly going up hill for a full tank of gas and if you go down a long hill and use engine braking, you mpg will not be true cause there will be no load and no fuel will be injected until you either get slow enough that you hit idle speed or you hit the 'gas' yourself. Engine load has little impact in most circumstances. I have gone up and down the appalachain mts and tested this going 35-40mph with cruise on and got better than average mpg both up and down the mountain.

Verify for me if you will, I have heard that at idle, the rotary runs somewhat rich. Assuming this is true, you are better off engine braking than pushing the clutch due to this. There are many variables that can take into account. It may seem like you get better milage on the interstate at speed but with a taller gear (to an extent) it can be much better. I try to draft behind trucks many times but, careful to do so as wind resistance means less air to the radiators as well.

I'll admit that it's not a 13B-MSP, and that the side exhaust ports could make a big difference, but my 12A gets significantly better fuel economy in 4th gear at highway speed than in 5th - 20% or more difference. Overlap could be a factor, but there isn't that much overlap in a stock 12A. Best fuel economy observed was keeping the tach between 4000 and 5500, and that's the highest I've tested. On a 28 year old engine with 200K on it, I don't want to push the revs any higher.

Another...Not sure if this should go in this thread but I hope I can get some direction.

So...I've been reading...thinking...planning...deciding...My head hurst. My current situation is this...Buy a new car for $40k + (I hate payments) or keep the Rx8 and restore her to an even better state then it's original condition. Keeping the Rx8 would mean I could save a significant amount of money by modifying the car over buying a new one ($25K).

My point: I am keeping the Rx8 and my engine is on the verge of death at 94k miles (low compression). I am going to Mazda to see if I can get it replaced under warrantee. Either way I need MORE POWER! I think I decided on what I should do...Greddy Turbo with MM upgrade but I need more guidance to make sure I am making an informed decission. I reviewed several threads discussing all the other Turbo options and compared them with my wants. I even considered a v8 swap :suspect: due to easy reliable power but I don't want to risk loosing that "OMG this thing handles like a dream" feeling I get when driving her!

This is what I want:

- Track level reliability (emphasis on cooling...road course and autocross for more then 20 minutes of racing)
- relative ease of maintenance (can be fixed with hand tools and a little know how)
- Daily driver
- Torque...I heard Chicken and Brettus were making awesome numbers
- No OMG moments due to inconsistant boost (@Brettus...Dyno thread with Greddy Boost controller)
- CONSISTANT
- About 300 to 340 wHP (start low and build up as I become more comfortable with the car at that power level).
- Cobb friendly (I might buy it early in NA form to keep me busy till I take the plunge and go MM Greddy)

Based on this I figured...The greddy setup is the most widely used kit and therefore should have the most reliable setup per HP ratio? My brain is not always utilized correctly so please feel free to correct me.

Things I should get on top of the Greddy kit:

- BHR rad
- Mazsport water pump and thermastat
- BHR coils (got um already)
- BHR fuel pump
- BHR midpipe (already installed and made of the AWESOME! :wiggle:)
- Bigger 2nd injectors (just in case)
- Greddy oil pan?
- Sohn? (I remember reading about this but I forget about the benefits)
- External wastegate (I keep reading about issues with an internal wastegate re: greddy kit...Can someone explain and how hard would it be to convert to external?)
- What else?

Finally...Can it be done for $10k to $15k...and no I can not do the work...I can help but I only know enough to be dangerous. :mdrmed: I am guessing, based on some research, I can get all the parts for about $8k +...Then add installation, tuning, and any other "OMG I need this" moments and I am guessing I will be in the $12k neighborhood?

I think I might get the Greddy MM kit plus the BHR rad and clutch/flywheel first...then work on everything else as I go along.

I will delete this post if it is not appropriate for this thread...Thanks!

Chris

The biggest problem you have is availability. I am not sure the MM can be had anymore, you could go BNR or the SFR kit. Look up wanted two's FI thread, he has a really good dream sheet shopping list. With a motor that old, a d you HP goals, I'd be looking at new motor and turbo at the same time, what you sound on parts you will save on labor of paying to do each project seperatly.

As for low vs top mount etc, I've installed and tuned both, and I don't really see a HUGE differenceesp at our low boost street driven power levels.

Thanks for the advice...I'll check that thread out.

Also...about the engine...my sig says it all...pending warrantee. If Mazda covers it I am going FI.

Is the BNR turbo on the Dyno thread? Whats the difference in laymans terms between the BNR and MM's 3071?

Edit:

Well after reading some more it seems the BNR flows about 10lbs more = moe powa? I also heard we might need to upgrade the greddy's intercooler if we want more then 16 psi? Also, I read issues with a 3" vs 3.5" MAF? Can anyone enlighten me?

:dunno:

Yes, those are all issues! Lol time to hit some threads and get some intel! I can't type it all out on iPad.

1) This is what I want:

- Track level reliability (emphasis on cooling...road course and autocross for more then 20 minutes of racing)
- relative ease of maintenance (can be fixed with hand tools and a little know how)
- Daily driver
- Torque...I heard Chicken and Brettus were making awesome numbers
- No OMG moments due to inconsistant boost (@Brettus...Dyno thread with Greddy Boost controller)
- CONSISTANT
- About 300 to 340 wHP (start low and build up as I become more comfortable with the car at that power level).
- Cobb friendly (I might buy it early in NA form to keep me busy till I take the plunge and go MM Greddy)

2) I will delete this post if it is not appropriate for this thread...Thanks!

1) Early next year.
2) Threats....... :lol2:

Is the BNR turbo on the Dyno thread? Whats the difference in laymans terms between the BNR and MM's 3071?

Edit:

Well after reading some more it seems the BNR flows about 10lbs more = moe powa?

The current turbo in the MM upgrade can flow well over 50 pounds of air. I have yet to actually see a compressor flow graph for the BNR, though I can tell you that the 3 I have run into "in the wild" have made no more power than the regular GReddy turbo.

I also heard we might need to upgrade the greddy's intercooler if we want more then 16 psi?

The GReddy intercooler is good to well over 40 PSI or 500 HP, whichever comes first (for two totally different reasons).

Also, I read issues with a 3" vs 3.5" MAF? Can anyone enlighten me?

You can use ONLY a 3.375" i.d. MAF tube and expect the MAF to work properly because that is the ONLY diameter that puts the sample pickup of the MAF in the center of the tube.
At that diameter, the MAF is accurate out to about 460 g/sec of air (±40).

1) Early next year.


Is that a threat? :lol:

I have yet to actually see a compressor flow graph for the BNR, though I can tell you that the 3 I have run into "in the wild" have made no more power than the regular GReddy turbo.


They need to modify that restritive bend /"volute" coming off the compressor...... heh

and a couple of other things .....

They need to modify that restritive bend /"volute" coming off the compressor...... heh

and a couple of other things .....

You know my system has the same volute, right?

Charles...let's do this!

The current turbo in the MM upgrade can flow well over 50 pounds of air. I have yet to actually see a compressor flow graph for the BNR, though I can tell you that the 3 I have run into "in the wild" have made no more power than the regular GReddy turbo.


Yet? Is it really a limitation of the turbo or the Greddy system design? (Waits for Brettus to chime in on the "...restritive bend /"volute" coming off the compressor..." argument that causes MM "volute" issues) :cwm27:


The GReddy intercooler is good to well over 40 PSI or 500 HP, whichever comes first (for two totally different reasons).


I am guessing in this case size does not matter? I am being serious and cracking a joke. :cwm27:


You can use ONLY a 3.375" i.d. MAF tube and expect the MAF to work properly because that is the ONLY diameter that puts the sample pickup of the MAF in the center of the tube.
At that diameter, the MAF is accurate out to about 460 g/sec of air (±40).


Ok so what do I need to do to resolve this issue? Buy an AEM and modify it or something? (This is under the impression I do not go BHR which there is a 99.9% chance I will cause I trust you mongrels to take care of business!)


They need to modify that restritive bend /"volute" coming off the compressor...... heh

and a couple of other things .....


I have this theory that you enjoy watching MM's blow off valve release pressure. :lol2: To a certain extent I do to, and pretend I understand 50% of what anyone is saying.


Is that a threat?


I am guessing your car is the testing platform for the BHR/MM turbo system. :suspect: