Brettus

iTrader: (2)

already been done (less the ball bearings) - It's called a "Greddy" .

Seriously - the greddy kit sounds almost perfect for what you want to achieve .


I actually can't see how going smaller will achieve anything . To drive the turbine you need to run all the exhaust gasses through the turbo which will create huge backpressure at high rpm - can't be good .

thewird

The RX-8 has an extra gear but that 6th gear is much shorter then the FD's 5th gear. Also, an RX-8 is heavier then an FD. Your not going to improve your fuel mileage by adding a turbo, your going to worsen it. Boost = more fuel. With a tiny turbo, you'll be hitting boost often even regular driving.

And do you really want to choke the Renessis with a tiny turbo?

thewird

Loki

iTrader: (1)

The Supra is twin turbo: 1 turbo per 3 cylinders running through a common intercooler into 1 throttle body. On V6 setups (Supra is inline) we sometimes see completely symmetric setups with each bank having its own piping.

You're right, it is the amount of air and fuel you're pushing into the cylinder. However, that is not measured in PSI, that is CFM. A big turbo at 2 psi can push as much into the engine as a small turbo at 8psi... the difference is, the bigger turbo takes more work to get to a point where the energy consumed by it is less than the energy produced by burning the additional air (in boost), which gives you turbo lag.

But back to your project, I really don't recommend a tiny turbo, that creates a restriction and while that may help your fuel economy, it will raise exhaust temps even higher than they currently are. In general, a turbo will not improve the base fuel economy of any engine since it's not possible to cram less air and fuel into the rotor/cylinder than what the engine takes without the turbo. The turbo makes it more efficient to make more power, which is where ideas like Ford's Ecoboost and Saabs entire engineering direction come from. It lets you have a small engine with good economy that, when called upon, will spin up to much higher horsepower than you would get from the engine alone.

I've been thinking about improving the 8's fuel economy though, and there are some tricks that hypermilers use that get results: electrical ancillaries (water pump, power steering pump, a/c, etc), so that you have less parasitic loss, adding a cut-out for the alternator and a solar charger to help charge the battery, so that we don't have to burn fuel to charge it. Then there is aerodynamic improvements, removing any unnecessary vents and vortecies from the air stream, and of course, driver mods. These are the guys that get 100-150% improvements over EPA rating.

For a rotary, the problem is you have an ignition event 3 times a revolution per rotor... so as rpm goes up, the rate of fuel consumption goes up 3 times faster, whereas in a 4-stroke, you have 2 ignition events per revolution. So I wonder if it's possible, for example, to deactivate one rotor face per rotor when below a certain throttle position. Might unbalance the engine though.

Actually, on the note of putting less air and fuel in the engine than stock... you could fashion some sort of intake restriction before the MAF that would accomplish this, perhaps on an electronic switch so you can toggle it on and off... but on the other hand, you could just go lighter on the throttle.

Brettus

iTrader: (2)

I like the idea of an electric supercharger that supplies about 1psi in the midrange but is seperated from the main air intake so that it only supplies air at low low rpm . Once the engine started flowing more air than the SC could make it switches over to the normal intake .

Could add about 10whp to the midrange .....

Loki

iTrader: (1)

Actually, here is something interesting I came across just now. Definitely worth a read.. it borrows examples from aircraft turbo-rotaries and applies that to the Renesis.. difference is, an aircraft engine rpm usually varies very little (since there are no gears) and its usually always in boost.

http://www.rotaryeng.net/RX8-TC-eng3.html

White_Shadows

Gearing can be changed. Currently the car will run in 6th gear at roughly 22mph without chugging, but being in this gear is unrealistic as you can put the accelerator on and in about 4 miles you may achieve acceleration lol. Increase torque, you can sit in this gear more often.

Weight issue will be one of the first things looked at. Carbon fiber for the front doors, fenders and trunk lid. No one ever sits on the back seat maybe take those out.

Look to previous post. 1 Turbo per port with the joined middle port open. Shouldn't be any issues with choking at all.




^^ Greddy kit is not good for me as it is single turbo. Read rest of thread.

Heat issues are a bigger thing to look at as heat is the main reason the car is nowhere near stoichiometric.

Turbo charging increases torque (main benefit) also helps atomize air as well as decrease if not eliminate negative pressure in the intake manifold. (Vacuum pumping losses.)

One thing to think of also while it was spat out, the eliminate everything power driven. (a/c, power steering, alternator, ect)
Has been done by bmw long long time ago, but was far too complicated (can be simplified now and days), but use the velocity of the turbo (exhaust is wasted energy) to create electricity.

Loki that is what I said. I know it's a twin turbo setup, but it's sequential which is a setup that would never work if the intake was seperated. Works on V6 because it's parallel (Stealth TT, Fair Lady)
I do understand the amount of air per time, but i'm talking combustion. It is measured in PSI.
Also if you are measuring output from a turbo into an identical sized intake. Pressure would be proportional to the amount of air being moved....If you blow up a bike tire, no matter how fast you blow it up the same amount of air is there at 100psi. Yes it takes less time to blow it up if you are moving more air, but im after 100psi no matter how quick it gets there. Yes a larger turbo moves more air per minute, but you are wrong sir if you think that 8psi on a small turbo creates the same power as 2psi on a large turbo with the same intake diameter. I want 1-5 psi in the intake at all times. Not said amount of air per hour.

Keep comments coming keeps me thinking.

thewird

Have you considered the extra weight you are adding with the little turbo's is not worth any possible theoretical benefits they may provide? Atomizing the air before the throttle body provides no benefit imo.

thewird

shaunv74

Your analogy is incorrect. Your trying to compare a static volume example to a mass flow rate. it's about flow rate and efficiency when sizing a turbo not pressure.

nvrfalter

iTrader: (1)

cool thread. anxious to see what comes out of this. subscribed.

pdxhak

iTrader: (2)

Replacing any of the doors is not smart. Part of the built in safety with the RX8 is the door designs and the structure they provide. Also the back seats are just seat cushions so you will not save any weight. There is a thread dedicated to how much things weigh on our car so you should review it and then choose what you want to remove and or replace.

bsteimel

iTrader: (5)

This seems like a really cool idea, not the usual 3 rotor, ha.

But the only question is, if your going to spend all that time adding essentially another engine, why not just add a tiny electric motor. You will have no MPG and the technology already exists. If your adding another tiny rotor would all of its additional parts have to be added as well, could you reuse the intake, exhaust, throttle body, etc of the larger engine?

White_Shadows

I have read through the thread. Many things and weights are missing.
Also I daily drive a motorcycle, if I was worried about my door squishing me I sure as **** wouldn't ride lol. If the DOT would approve the Peel p50 I would drive it every day.
I chose those pannels as the rest of the pannels are aluminum and would yeild low results, but the front doors, trunk lid, fenders are all steel. Also back seats would probably include pass through and anything else I can remove without A. Dealing with the gas tank B. structure. Prolly pull out the air bags too!! lol (yes in a production atmosphere this would be considered, but i'm just experimenting) Thanks for looking out though.


Thewird:
Weight really..So i'll remove a/c......
Hmm the engine susceptible to flooding. Nope atomization of fuel doesn't matter. Really? Got anything better then in your oppinion? The more the fuel is broken down from a liquid into a vapor the closer to stoichiometric it can become as vapor burns liquid fuel does not.
Oh wait I wrote air my bad, no, fuel dude the fuel. My bad, no swirling air around before the throttle body won't exactly do anything haha. Sorry I must have been thinking air/fuel ratios donno why I wrote air, but yes atomize the fuel. Yes fuel injectors play a massive role in doing this, but it isn't perfect.

shaunv74:
I wasn't arguing sizing up the turbo based on the amount of air is moved per time. A larger turbo will in theory move more air at a much lower pressure (Bernoulli's Principle http://home.earthlink.net/~mmc1919/venturi.html ), but I will not agree that if at the port when closed you are reading 8psi with one turbo and 2psi with another, it is the same power. It isn't. Also power is not based on how much air over time is moving around. It is how much air/fuel is compressed inside the combustion chamber. Measured in PSI.
I am just after that pressure does come into play and that I am after 1-5 psi of pressure infront of a closed port and to maintain that exact constant flow as it enters the combustion chamber.
I donno imma look at this more. You guys are giving me alot of the "utuh your wrong", but I need more information then that. Yes I get Mass air flow sensors so yes I see where that is, but still looking at the pressure in the piping leading to the throttle plates and eventually the port. Give me some more diagrams and explaination of where you're coming from.

Reason it is difficult is I'm not looking at it in terms of flow the maximum amount of air possible into port while it's open in the quickest time. (as most of us are thinking because the word turbo always means lets make massive power)
I'm looking at motor comes around port starts to open, hope the air falls in add some fuel and hope for the best. I want to eliminate that and have constant amount of air being flowed into the motor without using vacuum from the previous "stroke". I will claim ignorance right now though. What is pulling the air in? I understand vacuum when a piston travels down a cylinder with the valve open, but what pulls the air in on a rotary?

Keep it coming. If anything I type sounds mean it never is, (unless what you said was straight stupid) I encourage productive arguments. I'm just as ignorant as the next person. I will be harsh towards the "nut uh" comments. I always want more information then that. "Just cuz" is not the answer either.

Brettus

iTrader: (2)

I think if you drove a conventionally turboed 8 for any length of time and paid attention to what happens at part throttle /vacuum you would realise you are barking up the wrong tree .

So some Prius owner got better fuel consumption after fitting a turbo - big deal . I garantee i could produce some figures that proved I get better fuel consumption under certain conditions also . However this is mostly due to tuning and has little to do with the turbo itself.

Brettus

iTrader: (2)

I'll tell you what will come out of it - a lot of hot air

Mawnee

bur.....er....Turbo buuuurrrrn!

pdxhak

iTrader: (2)

It is more than just side impact you have to be concerned out with replacing the doors. When closed they for a B pillar and the CF doors will not have that support built into them. Good luck with you project

thewird

This is a question about not knowing enough about the RX-8. Does the RX-8 have any air atomization lines? The FD has 2 big air lines that go directly to the primary injectors and are hooked up right after the turbo before the intercooler. This improves fuel economy and smooths out low load situations. Does the RX-8 have anything of the sort? Given the RX-8 uses a MAF to calculate load, something identical wouldn't exactly work but maybe Mazda came up with something else?

Another idea that would be simpler to implement and have minimal downsides if any would be a small electric fan possibly triggered by RPM. You can get 250+ cfm fans for $40 in 120mm form factor.

thewird

Brettus

iTrader: (2)

There are 'jet air' nozzles that help prevent pooling of fuel in the intake - these come from the throttle body side of the intake .
I like an electric supercharger as a concept (done right and not impeading airflow at high rpm) and i think the op should be looking into this instead of his tiny turbo idea ....

shaunv74

Um. So you just contradicted your own statement. You're correct power is based on how much air and fuel is compressed and is ignited. The amount of air is measured in mass not pressure because we have a MASS AIR FLOW SENSOR. Even in a Manifold Absolute Pressure setup it's still used to ultimately calculate the mass of air going in to the engine. Mass of air to mass of fuel is your air to fuel ratio not pressure of air to pressure of fuel. It comes down to how many molecules of air and molecules of fuel. That is measured in mass. Ultimately you need to know the mass of air your are putting in to your engine in order to calculate the mass of fuel to inject. If you don't know this you need to do a bunch of research on how the internal combustion engine works and, as I said before, sizing a turbo for your goals.

thewird

A fan like this can pump out 252 CFM @ 12 volts for $47 shipped. Even more at higher voltage. I don't believe this fan would choke the rx8 but just in case it would, you can setup it up like this... When the fan reaches a choke point, the engine could suck around the fan and therefore be no restriction.


My guess is the rx-8 is in the ballpark of 200-300 CFM at peak. Don't ask me how I came up with that number though



I have considered doing a setup for my FD to try and promote response but haven't gotten a chance to test it.

http://cgi.ebay.com/ws/eBayISAPI.dll...m=230390109627

thewird

Loki

iTrader: (1)

With all due respect sir, thermodynamics doens't require that you agree, only that you follow, plus I've actually built a boosted car or two with my own two If we follow your logic, the same Supra (which is not sequential by the way) that makes 200hp in the naturally aspirated version, and 300hp at 8psi stock (iirc), and can reach 1000hp on the same 3L engine, which is fairly easily accomplished, they would need ... 71psi? Yet somehow they manage at a mere 32-36 :P

If anything, PSI goes in proportion to the amount of work you have to put into the system to produce whatever power you're currently producing. The energy required to compress air goes as the square of the compression magnitude, so if you're pushing 30psi, you're robbing yourself of a significant amount of power, in other words your turbo is working too hard. If you had a larger turbo that is more efficient at the flowrate that you're getting with the old turbo at 30psi, you could get the same flowrate, so the same amount of air going into the engine and being combusted, at a lower psi. The difference is, less of the produced energy will be wasted compressing the air in the first place.

When you're sizing a turbo, the first thing you look at are your cfm requirements, and how much lag you can tolerate... which you usually find by comparing effiency graphs, like this:





So, anyway, if you're after recapturing your exhaust energy and want to try out a turbo approach, go for it. The main issue here is that you're wanting to go for a tiny turbo, which isn't necessary, pick one that is right for your engine. BTW, given the wide range of airflow in a rotary from idle to redline, I don't think there is any turbo dynamic enough to give you 1-5psi at all times, and anything that is big enough to not be a deadly restriction at redline, probably won't give you any boost at all under 4k where we spend most of our time if we're going for economy.... now if you had a variable-geometry turbo...

bsteimel

iTrader: (5)

Wow the VTG turbos are awesome. Checkout the 07 Porche 911 turbo. They basically open and close vanes depending on exhaust gas flow. This would be perfect for our wide range. The only problem would be $$ as I'm sure these turbos are expensive. Here is a good site explaining the technology.

http://paultan.org/2006/08/16/how-do...geometry-work/

anybody have a wrecked 07 911 lying around to slap this into an 8.

ilovemy8

interesting read.. srry no input available..


but loving the knowledge gain!

thewird

You can't run VGT turbo's on a rotary due to exhaust heat.

thewird

bsteimel

iTrader: (5)

They have been using them in diesels for years because the exhaust heat, but is seems the turbo i the porchse has solves this problem. The turbo uses completely different materials to be used with a petrol engine. What are the heat limits of these materials, i'm not sure but i bet its pretty high with a high performance straight six gas engine? I don't think you can say that it can't be put in a rotary considering that this product didn't come out but less then 2 years ago. While VGT turbos are used in a few different cars the Porsche turbo is the only one that uses a VGT that is willing to withstand high heat conditions.