newtlicious

My bad dude. Jeez, I'm starting to act like I got a hole in my crotch or something. Must be my time of the month.

Rotarian_SC

Yes that is originally what I intended, the 150 Lightning engine, which I do believe uses a screw s/c like the GT.

Rotary God, from my understanding, this Lightning engine and the GT engine are pretty close to being similar. That is what I found ironic in your post about how "The twin screw supercharger was a factory option on the Mazda Millenia S and is standard on the new Ford GT. Used mainly for trucks huh? I can't think of a single truck that uses one". I am sorry, I wasn't quite trying to say wrong, but instead sometimes we can be able to be correct or inform you, which is meant to be taken as a compliment. I don't dispute your position on the screw vs. roots type s/c. I have no doubt that your automotive knowledge is much more vast than mine.

Father LeadFoot

Just to set a few things straight the Lightning uses a roots style blower like the new cobra does, its practially the only SC car manufactures use, with a few exceptions from Toyota and Mazda. Whipples, Twin Screws etc are by far one of the best blowers, they are capable of up to "turbo" like HP but with all the advantages of the low end and always boosting characteristics we love (not capable of 24+ psi in most applications, but at similar boost levels they make turbo like HP numbers). The Navigator uses the DOHC 5.4L at 300HP, but after that the motors are about 80% different, Ford really went through that puppy to handle more power than its putting out, (read a HOTROD back issue, they went through a build up on one)
TRD also uses the roots style blowers for their Celica, Tacoma etc kits.

rotarygod

Rotarian_SC: I wasn't being defensive or hostile. I apologize for coming off that way. We're all friends here.

Zokk's 8

Haven't seen any posts about it but they had a proto type Supercharged RX-8 at the Rotary Revolution in Indy. Forgot to bring my camara I would have posted pix. They would not run it at the events said it was still not completely developed and didn't want any posted numbers out there yet. It was all stock brand new still had window sticker from Sunflower Mazda. Tech onhand to answer questions said expected to retail under $5,000.00 About 6 PSI Intercooler right behind front spoiler opening, Supercharger itself replaced airbox. Very slick professional install, needed aftermarket exhaust big time sounded like a golf cart driving around the parking lot. No sound but the quiet supercharger wine. Said the air fuel was controlled by a modified Canzoomer Stage One and expected the rear wheel hp to be up between 30 to 40 % Said they are hoping to get a deal finalized with Sunflower Mazda to do the install and even offer it as a warrentied option in the next year or so once they prove reliability.

Genom

Sunflower has been extensively discussed here. Just search for it. There's pics as well as a ton of info on the car/warranty/kits.

RoTaryStYleZ

Just Talked to SSR, Turbo Kit will Be Realsed In a week or 2, they have posted some pictures on there website, check it out. Guy said there finishing the Dynos and then it will be ready. price still TBA but this guy said it will be around 5 G's

shawnio

Just to mention it ... the Koenigsegg CC8S uses a 4.7l supercharged v8 ... it uses a centrifugal supercharger

it tops out at 650 hp or something but doesnt accellerate as quickly as the screw type supercharged supercars, SLR, Ford GT, or even the NA supercars with similar peak power ... 617hp Carrera GT is .7 or so seconds faster 0-60; I think the Carrera GT even weighs slightly more.

Just goes to show what kind of performance you get out of a centrifugal supercharger.

rotarygod

That car does 0-62 mph in 3.5 secs, the standing quarter mile in 10 seconds flat and tops out at 240 mph. That's pretty damn impressive. While I am a fan of positive displacement superchargers, neither the Ford GT nor the SLR are going to catch this car.

http://www.classicdriver.de/uk/magaz...0.asp?id=11867

Hymee

iTrader: (1)

The cost is why you find the Eaton as OEM on so many mass produced cars. It is cheaper.

Although Eaton have the rights to manfacture TwinScrew blowers, I am not aware of any that they make. IFAIK, all of the Eaton OEM models are Roots blowers with the 30 or 60 degress twist. That does not changes the basic operating principle of the Roots.

IMHO, the TwinScrew design (Lysholm, Kenne-Bell/Autorotor, Opcon, Whipple, Sprintex) is superior in a number of aspects compared to a Eaton "modified" Roots in a comparison of Positive Displacement superchargers. And they make pretty much constant boost over a wide RPM range.

The upside of constant boost is you pretty much have heaps of punch on tap when you need it. The -ve is it could be harder on the internals with the sudden surge in torque.

Centrigual superchargers, such as Vortex et. al. These make more progressive boost, as has been mentioned earlier. The benefit of that as the torque increases progressivly as RPM's rise, the additional forces on the internals come on "gentler". (A slight benefit over turbos is that they can be tuned to be already spinning over pretty high at low engine RPM's, to give some low-down boost.) The -ve is that you don't get that tire-frying low down grunt.

It would be interested is seeing what sorts of developments pan out.

Cheers,
Hymee.

PS - I wonder if the Millenia's twin-screw's characteristics suit the Renesis? What I need to find out is the displacement / revolution, and the max RPM it can operate at (RPM of the blower, not the motor).

babylou

Hymee,


You took my quote completely out of context. My entire post was redarding rotor clearances and efficiency.

Drewstein

God gave us 14.7 psi of boost at sea level. This is simply the weight of earth's 100 mile high atmosphere. At 5000' in Denver, Colorado,
this "God's boost" would be only 12.2 psi, as the atmospheres height at 5000' is only 99 miles high vs 100 miles at sea level. So, of
course, your non supercharged engine will perform better at sea level where it has more boost (14.7 vs 12.2). Without this atmospheric
weight or "boost," the engine would not run. Why? Because an engine creates a vacuum as it rotates thereby allowing the higher
pressure atmosphere to rush in and fill the vacuum with 14.7 psi of boost. Note: This boost does not show up on a typical 0-20 psi / 0-30"
Hg gauge as 14.7 but instead as "0" on the 0-30" Hg scale. Now imagine on an ascending scale that the 30" Hg is 0 psi and the 0" Hg is
14.7 psi and you have an "absolute" pressure gauge.Add the 20 psi to the 14.7 psi and the gauge markings would be 0-34.7. Floor the
throttle at sea level and the gauge will read 14.7 psi and 12.2 psi in Denver (with "0" inlet restriction). With a supercharger and 6 psi
boost, your new absolute pressure gauge will read 20.7 (14.7+6=20.7) at seal level and 18.2 (20.7-2.5=18.2) in Denver. Here's how
you determine if your engine is utilizing all of "God's boost." If the gauge reads 4" of vacuum at wide open throttle, your engine is losing
13.6% of it's power or 2 psi of "God's boost." This is a simple equation that few really understand. 2 psi lost÷14.7=13.6% HP loss. To
eliminate the pressure losses, install larger non restrictive inlet components (filter, MAF meter, throttle body and/or inlet manifold). The
2 psi loss with a 6 psi kit (18.7 psi absolute) is 2÷18.7=10.7% HP loss. This is a big number as 10.7% of the supercharged HP is 32
whopping HP on a 300HP engine. Whether fuel injected or carbureted, ALWAYS try for a "0" reading. That's the way we've done it at
Kenne Bell since the 60's.O.K., now let's talk a little about choosing a supercharger.
There are many factors to consider when purchasing a supercharger. For one, "bigger" isn't necessarily "better." You don't buy the
biggest carburetor or injectors - or tires just because they are "bigger." So you should never buy a supercharger based solely on size or
rating. Before making a decision, one should first understand the basic terminology (size, ratings, volumetric efficiency, thermal
efficiency and adiabatic efficiency).We will attempt to make this a no B.S. straight forward overview of supercharging.
Asupercharger is merely an air pump that pumps more air into the engine than the engine, which is also an air pump, can discharge or
exhaust. The excess air from the supercharger creates a back pressure which we commonly refer to as boost. 1 psi of boost is
approximately 13RWHP. For example:Agood 300HPengine is pumping out or sucking in approx. 450 cfm at 6000 rpm (see Kenne Bell
FAQ's "I'm confused about cfm and HP"). So if the supercharger pumps 850 cfm into the 450 cfm engine, the result will be a back
pressure build up (boost). The more air the supercharger pumps in, the higher the boost and theoretically, the higher theHP.
If boost drops off with an unrestricted inlet as engine rpm increases, that is a tell tale sign the supercharger volumetric efficiency (air cfm
in vs. air cfm out) is dropping off. That's exactly what happens with the Eaton supercharged '03 Cobra. It loses 3 psi boost from boost
drop off (13-10 psi) and the HP from the lower boost decreases power by 39HP (1 psi=13HP) Then there's the higher power
consumption of the Eaton. More on that later. Volumetric efficiency indicates how efficiently the supercharger breathes and leaks. For
example: If a supercharger has a displacement of 10 liters but only 7.2 liters exits the supercharger, then it has a 72% efficiency.
7.2÷10=72%. It's as simple as that. When the VE drops off, so will the cfm, boost and engine HP. If the VE is low, the boost is low.
Remember, lower cfm supercharger output equates to less boost. Boost will not drop off with a supercharger that has a high volumetric
efficiency throughout the engine's rpm band. The Kenne Bell Twin Screw supercharger maintains the same rated boost throughout the
engine's rpm, so the Twin Screw enjoys a high VE at any engine rpm.At higher boost levels in the Lightning and Cobra, the Eaton boost
- and VE - drops sharply. Centrifugals have a relatively poor VE at the low and mid range rpm band, but are equal to the Twin Screw at
peak boost.
Basically, this indicates how efficiently the supercharger utilizes the energy (HP) that "drives" the supercharger. A high adiabatic
efficiency means the supercharger consumes less energy (HP) from the engine to drive it, thereby leaving more engine power for
acceleration - and higher dyno numbers. A low adiabatic efficiency means the engine must "waste" more of it's HP output to drive the
supercharger. This is a very important consideration because the higher the parasitic loss/power consumption of the supercharger, the
more HPyour engine must "waste" to drive it. This clearly shows up on a Dynojet when 2 superchargers are tested on the same engine
with equal boost. Two superchargers may have comparable volumetric efficiency (VE) but one may have lower power consumption
(higher adiabatic efficiency). That is the case with the Lysholm 2.3L vs the Kenne Bell/Autorotor 2.2L which uses approx. 10% less
power (HP) than the Lysholm 2.3L. The Kenne Bell/Autorotor 2.4L has a comparable VE, but the power consumption and discharge
temp are both better than the Lysholm 2.3L(See "PerformanceTests").
Temperature efficiency is the difference between the temperature entering the supercharger as compared to the boosted discharge air
temperature. Superchargers with lower air temperatures are more "temperature efficient" than those with hotter discharge
temperatures (See "Twin Screw vs Roots"). Be aware that a temperature reductionAFTER the supercharger will not make more HP -
as many experts would falsely lead you to believe. It's impossible. At Kenne Bell, we understand intercooling. We've done it for 16
years. Look at it this way. Your supercharger discharges 90 cfm of air in one revolution. Now let's trap all that air in a balloon. The
oxygen in the balloon will always weigh the same regardless of how much it is cooled. Then how can this trapped airmagically acquire
more molecules? It cannot. So always remember - cooling air after the supercharger cannot make more power and therfore,
UNDERSTANDINGBOOSTPRESSURE
SUPERCHARGERS
VOLUMETRIC EFFICIENCY
ADIABATIC EFFICIENCY(OVERALLEFFICIENCY)
TEMPERATUREEFFICIENCY
intercoolers do not increase HP. When will everyone out there get this right? The cooler air will, however, allow the engine to run
more ignition advance and/or more boost on a given octane. Obviously, cooler air the supercharger increases power at the
rate of1%for ever 10º. So lose that power robbing underhood exposed filter.
Superchargers are rated by liters (L) or cubic inches (cfm). For example;An Eaton 90 (90 cu.") is actually 1.5L. One should exercise
extreme caution in using supercharger "ratings" as the only criteria in selecting a supercharger. These ratings can be deceiving.
Just look at the differences in HPand efficiencies between the Eaton 90 (1.5L) and Kenne Bell 1500 (1.5L). See comparison tests in
our catalog and website (dyno test comparison "Positive Reinforcement," "Eaton vs. Autorotor in a Supercharger Slugfest" and
"Snake Bite Hit" (Eaton 112 vs. Kenne Bell 2.2).
Now that you understand the 3 basics of supercharging, let's assume that two superchargers have identical 1. volumetric efficiency
2. power consumption/parasitic HP loss and 3. discharge temp at 6000 engine rpm. Further assume these superchargers take
turns blowing air into an engine at 6000 rpm. Since an engine has no eyes or fingers, it cannot possibly distinguish between the 2
superchargers. The engine only sees air flow/cfm and boost. Subsequently, the superchargers will both produce the same HP.
Why?Again, the 1. power consumption 2. cfm/boost and 3. temp are identical. There is no "4th dimension" or unknown source of
power that will make one supercharger produce more power than another. Let's summarize: If 2 unrestricted inlet superchargers,
regardless of type or manufacturer, have the same VE, power consumption and discharge temp, then both will produce exactly the
same peak HP. If more power is required, then raise the boost level. Boost is what makes the power. That's what superchargers do.
They make boost. However, it is very important to understand that they don't allmake the same boost at 2000, 3000, 4000 and 5000
- so they cannot possibly produce the same HP at 2000, 3000, 4000 and 5000. For example: Centrifugal superchargers are also
very efficient, but where they produce the most cfm and boost. At lower engine speeds, the centrifugal
produces proportionately less air and, therefore, less boost (engine back pressure) and power.
The Twin Screw produces approx. the same boost at any engine rpm. Every revolution of the Twin Screw delivers the same cfm or
liters per revolution i.e. 2L per revolution at 2000-6000. That's why these superchargers are referred to as "positive displacement."
Unlike a positive displacement supercharger, the centrifugal might produce 1/2 L@1000 engine rpm, 2/3L@2000, 1L@3000, 1-
1/3L@4000, 1-2/3L@5000 and finally 2L@6000. That's because the centrifugal relies on engine speed to generate exponentially
higher cfm/L - and boost. Boost is approx. 1 psi per 1000 rpm on a 6 psi centrifugal kit whereas the boost may be 6 psi at 2000-6000
on a positive displacement type.
The centrifugal boost curve is not exactly linear as indicated above, but it's close enough for discussion. For example: Here's an
actual test. 11 psi at 6000, 7 psi@5000, 4.5@4000, 2.5@3000. What's important to remember is that the Twin Screws pump out
approx. the same displacement or cfm per revolution at any engine speed. Twin Screw efficiency (actual displacement or cfm
discharged) will depend on the overall design of the supercharger itself. Besides VE, temperature efficiency and power
consumption, you should obviously also consider a superchargers construction and it's reputation for performance, reliability and
longevity. Equally important is the manufacturers reputation for tech support and service.
For those interested in additional information and technical discussions, there are numerous SAE (Society of Automotive
Engineers) papers written on supercharging.
entering
only at higher engine speeds
SUPERCHARGERRATINGS&OUTPUT

Kenne Bell

canaryrx8

iTrader: (3)

holy snikes that is one long **** post, so what are you trying to say anyway? heh

Hymee

iTrader: (1)

Sorry if you thought I was arguing with you. I quoted you because I wanted to add some more to what you were saying. I wasn't flaming you or arguing with you. I didn't dispute the facts about rotor clearances and efficiency.

My personal view is the twin-screw is much more efficient (from my research). I just made the point that the reason that the Eaton is so popular in OEM circles is purely cost based, and not because it is superior.

I'm sorry if you misunderstood my point.

Cheers,
Hymee.

rotarygod

I own that book already. For those that don't, thanks.

To just read something in a book is meaningless. To understand it is knowledge. Interpret it for us.

Drewstein

Heh, I own a supercharged vehicle and have dynoed on both the eaton an kenne bell and the KB always made 40+rwhp more at less boost(14psi VS 13psi). I'm hoping to help out fellow gurus with my blower and nitrus experience.

bureau13

I'm a bit confused about the "intercooling after the supercharger doesn't add power" bit. I know for a fact people have upgraded the IC on their FD and dynoed with more power with NO other changes. Perhaps it is reduced pressure drop then?

jds

rotarygod

There are ways that intercooling can hurt or help make power. If the intercooler isn't getting enough air, it will heat up and store air. It is now an interheater. The other way that it can hurt power is if the piping is so long and restrictive and the intercooler core is so poorly flowing that it actually takes more boost to get the same amount of power that it had without. This can happen. Usually a good intercooler with proper ventilation will easily help make more power. If you are under boost for long periods of time you are suseptible to heat soak. This will hurt performance after a while. Generally though an intercooler helps make more power. As with anything there are always exceptions but proper intercooling will always make more power than without it. It's not difficult to do it properly so there is no excuse not to.

Drewstein

"Your supercharger discharges 90 cfm of air in one revolution. Now let's trap all that air in a balloon. The
oxygen in the balloon will always weigh the same regardless of how much it is cooled. Then how can this trapped airmagically acquire
more molecules? It cannot. So always remember - cooling air after the supercharger cannot make more power"

"The cooler air will, however, allow the engine to run
more ignition advance and/or more boost on a given octane"

This is after the air is compressed and no air can add to it even if it gets cooler. So since after the air is in your motor it's density cannot increase or decrease, the only reason for cooling it would be to prevent knock. This is VERY important when talking about the not so knock friendly rotory.

So I would rather be pushing a higher volume of air at lower pressure and cooler temp through my motor. That is why we all toss the "Heaton" as it's known for twin screw blowers. One of these on an RX8 would be the safest and most efficient way of making power.

babylou

Huh? I think you didn't say what you were thinking because your statement is obviously incorrect.

IKnowNot'ing

I don't see how Roots is better than Twin-screw (same costs and integration, better adiabatic efficiency for twin screw because of internal compression) !? Centrifugal superchargers only work at high rotating speeds and thus usually at high engine operating speeds.

Turbine_pwr

Drewstein,

While I understand your arguement... unfortunately one of your basic assumptions is incorrect. You are assuming that the supercharger/turbocharger flows the same amount of air at a fixed speed. This is not the case. The engine is a volumetric flow device. It moves a specific volume of air at a given speed. If I can make the air more dense... then I can increase the number of air molecules that fit inside that volume. When I burn that air with fuel I can make more power. As a result, engines make more power on cold days then they do on hot days and engines with (well designed - low pressure loss and high effectiveness) intercoolers make more power than engines without. I'm sorry you've had this wrong for 16+ years but you have. The facts are that the super/turbo charger will be operating on a different part of it's corrected speed line with and without an intercooler. Efficiency, flow and surge margin will be changed due to the intercooler. In order to verify this all you have to do is put together a simulation to see what happens. I will submit a simple EXCEL spreadsheet to characterize this behavior with and without intercooling to back up my claims. Please note: I'm not trying to flame you. I'm just pointing out a different perspective on this topic.

Regards,
Turbine_pwr

Hymee

iTrader: (1)

Turbine,

Nice graphs / analysis.

Can I ask one thing? I suppose you are really showing the effect of intercooling, but you lump turbo's and superchargers together. Turbo's and centrigugal blowers don't make constant boost (increases with shaft RPM), while PD blowers make constant boost over a wide operating range.

Not flaming you - like I said, nice stuff. I'd like to take it further, and compare many other factors on a screw.

Well done!

Cheers,
Hymee.

rotarygod

If you install an intercooler in a hot engine bay with no ventilation running through it what so ever so it can't easily get rid of heat, not only will it pick up ambient engine bay heat but it will also not be able to dissipate heat that the turbo/supercharger is introducing it. Since it is now storing heat it becomes an interheater. An air/air intercooler only works good if it gets enough flow across it to dissipate the heat introduced into it. Most do. Think about it a little harder. The statement was fine. The interpretation was incorrect.

rotarygod

The colder balloon while weighing the same and possessing the same number of molecules as the hotter one, will be physically smaller in size. The molecules are not increased or decreased. The smaller balloon molecules are not moving as much so they are closer together. We learned all of this in junior high physical science class btw. Since the colder air is more dense, it takes up less space. The less space it takes up the more room there is for more air molecules. You are correct in the sense that cooling the air does not make more air molecules. That would be impossible. By cooling them and keeping them closer together we do have room to fit more molecules in the same space.

So always remember - cooling air after the supercharger makes more power because it leaves us more room to fill up with more air molecules. More room for air is also more room for fuel. More air and more fuel equals more boom which equals more power.

Also by cooling the temperature down we are also affecting the actual temperature of combustion. It may not seem like much but the higher the combustion temperatures and pressures, the easier the onset of detonation and the lower the total power potential. How is proper intercooling bad again?