PowerLabs

Have you guys seen this video?



If you've read any of my posts, you know I *LOVE* boosted cars... No matter how big the engine in your car is, it will never compete with an engine that's being force fed, simply because once you start pressurizing the manifold, the only limit to how much power the engine will make is how much boost it can take before coming apart (OK, OK, I'm simplifying here, but you get the idea)...
I'm a little over 22000 completely trouble-free miles on my A&A centrifugal supercharge kit making just shy of 600hp at the wheels, and it is an absolute blast to drive. I did, however, have a chance to experience a twin screw car first hand when Charlie (from RPM motors) took me for a ride in Kenne Bell C5 Z06 car when I was at his shop having my car dyno tuned.
It was about as fast as my car. Maybe a tad slower (I think it made 550ish WHP?), but it had all the torque I have *RIGHT NOW*. It literally broke 500RWTQ by 2000RPM, so it could do 4rth gear pulls without downshifting... It was epic. And I wanted one.
But Kenne Bell have shown themselves completely incapable of producing a kit for the C6 Corvette. Plus, with their kit you have to run a high rise hood, which I really don't like...
When Techo hit the scene I was excited that we might finally have a proper twin screw that fits under the stock hood. But their results were mediocre and then the company went belly up.
Sure, you've got the TVS system, with the new 4 lobe Roots, but lacking internal compression, no roots supercharger will ever be as efficient, or move as much air for the same size package, as a twin screw. Plus, again, you are stuck with the high rise hood.
Also, I paid $5200 for my A&A kit, and got 600WHP from it on an otherwise bone stock car with headers and a tankfull of pump gas... Its hard to argue with that kind of power when you're paying so little for it. I can't justify coughing up 7-8 grand for a blower that makes less power than that just because its got a little more low end torque. If I'm paying more, I want more power. At least 700WHP with torque to boot. And plenty of low end!
Enter Dragon Race:


Their kit packs a twin screw under the stock hood, and, by the looks of it, actually delivers real power!



So I just wanted to give them a cheers. Keep it up guys. I'll be in the market for a new FI kit next year when I purchase an LS3 car, and right now, you are first on my list

1bdasvt

But just like Techno,,,,,I'm not too sure about "new" Companies!!

PowerLabs

Remember every single company in the world was "new" at some point in time

Hell, Microsoft began in a recession...

1bdasvt

,,,but some make it,,,,and others don't!!!''

bgreen83

at least this one got a 900hp car out there first and this company doesn't seem to be burning through cash.
Hope it works out for them though. never want to see anyone crash and burn esp in this economy

old motorhead

I wish the Dragon Race boys well. Another F/I option can't be anything but good for C6 owners. I hope they get their ducks aligned pronto.

Powerlabs, when you speak of a blower's effeciency, what makes one less effecient vs another one? Is it simply the ability to push air? One revolution = X amount of air in all circumstances? If a blower is blowing less than 100%, wouldn't it use less power per cfm produced? If the blower isn't being used near it's capacity, would the effeciency you're speaking of be less important?

When the twinscrew blower is just along for the ride, how much power does it take to turn it?

Appreciate your knowledge and contributions to the board. Some of your expanations get over my head rather quickly. Dumb this one down a little so this farm boy can understand.

Greg A

I would not worry about Dragon not making it in these crappy economic times. They are a local shop and the guys are first class all the way! Have seen some of their work up close and all I can say is they have produced several fast and reliable Colorado cars.

PowerLabs

That's actually a somewhat complicated question, but you asked for a simple answer, so here it is:
There are two types of supercharger efficiency. The one you mentioned is the volumtric efficiency; how much air the blower moves as compared to how much it should be moving. This is only really a consideration for positive displacement blowers (Roots and Twin Screw). A TVS 2300, for example, is supposed to move 2.3litres per revolution; this is related to how much air space is in between the rotor lobes and the casing. In reality, since rotor seals are not perfect and there is a small gap between both lobes that carries back some of the airflow, the blower may only move 2.2 or 2.1 litres of air per revolution. So due to volumetric efficiency losses you have to turn the blower faster to move the amount of air you want. This, of course, takes more power. Centrifugal superchargers have no volumetric efficiency per se because they are not fixed air volume devices. On a PD blower it varies with rotational speed and boost, and is highest at high speeds and low boost numbers. Twin Screw superchargers have higher volumetric efficiencies. Yes, as you pointed out, running the blower at less than 100% of its capacity takes less power, but moving the blower at all, at any speed, takes some power, and the more efficient the supercharger is, the lower that power requirement is.

The other efficiency number, and the one that accounts for most of your supercharging losses, is thermal efficiency:
Compressing air causes it to heat up. Theoretically, that relationship is linear (PV=nRT): doubling the pressure of a gas will cause its (absolute) temperature to double also. In a supercharger, this would only be true if the supercharger were 100% efficient.
The Thermal efficiency of a supercharger is how much heat it puts into the air it compresses as compared to how much heat the air should acquire theoretically. Since air expands as it heats up, any extra heat you put into the air is wasted work.
Another way to look at it then is that for any given boost number at any given airflow (engine RPM), the supercharger requires some horsepower to drive. The efficiency of a supercharger determines how much more power it takes to drive it at any given boost number and RPM as compared to what it should theoretically take.
Since thermal inefficiencies show up as additional heat in your intake air, they represent heat that needs to be dissipated by the intercooler. Since no intercooler is 100% efficient, a supercharger that is more efficient will heat up the intake air less, resulting in a cooler intake charge which is less likely to cause detonation. Cooler intake charges allow you to run more boost and more ignition timing advance, thus making more power. At the same time, the more efficient supercharger takes less horsepower from the engine to drive, again making more power available at the wheels.

That depends on several factors; how fast it is turning (pulley ratio and engine RPM), how restrictive your intake and engine are, and how effective the bypass valve is. Some tuners claim that their FI kits gain fuel economy, so if you were to believe that, you'd have to also believe the blower takes a negative horsepower number to drive it when its not making boost
In reality the parasitic drag figure is probably a small number, maybe 1-3hp or so. I've never seen it quantified anywhere but when I did the math for my Vortech turning at 2000RPM making no boost it came out to about 1.2HP.

I hope my explanation made sense?

0Jeff @ TPE

Although you discussed thermaldynamics, you left out one of te most critical aspects of top mount twin screw blowers. That is the Adiabatic Efficiency. Although you say that increasing pressure automatically increases tempratures, each compressor design has a different adiabatic efficiency table. Since you are an engineer, you know that Adiabatic efficiency is the ability of the compressor to increase or decrease pressure WITHOUT a change in teprature.

So, being that KB has among the highest Adiabatic Efficiency of all automotive twin screws, if you were to line up 2 competing blowers, for each pound of boost, the thermal increase would be less with the KB. This means means lower discharge temps, denser air, and more power, from the same pound of boost.

0Jeff @ TPE

I would like to point out a couple other things.

You are saying that KB is incapable of producing a C6 KB car, yet we've been doing them for over a year now. You yourself was going to deliver your car to TECHO in order to have one of their kits installd. You could have dome this for over a year with the KB also. The TECHO kit was never released to the public as a DIY kit, so in essence it is the EXACT same situation of the KB.

Although you wouldnt have had KB install the system (case they dot do that) you could have ery easily had the designer install the system (us) for less than what TECHO was selling their kit for.

What im getting at, is its frustrating to hear people say that they CANT get a KB on their C6, when in reality anyone in the United States could schedule an appointment on monday, and have their kit beginning to be installed within a week.

You are correct about the hood. But seriousy, the C6 requires a nearly un noticeable hood. PLUS the hod is included at no charge, for the same price as other kits WITHOUT a hood.

So you can either choose to go with a S/C that requires a hood (look of your choice) yet allows you to have a large an efficient intercooler, and the ability to reverse the install at any time and go back to stock.
OR, you can go with a S/C that doesnt need a hood, yet requires you to hack up your car and permamently damage (and de-value) your car by cutting the firewall, Or with another one that wont release what the intercooler looks like stating "Patent Issues"

If ANY top mount blower shows promise, its the DRE. But I am willing to bet my busiess that the intercooler design will not permit that blower to run charge temps anywhere near other current designs. Its not just an opinion, but an engineering and physics FACT.

Personally, I think DRE should get over the whole "Fits under the stock hood hype" and put a nice fat intercooler under there. THEN we could have a front mount twin screw WITH an efficient intercooler. Even "I" would be a buyer. People think I am only loyal and Bias to KB. But that is fase. I am also an educated consumer that is looking for the BEST for my car. Be it KB or otherwise.

But please remember, just because KB doesnt post on this board, doesnt give anyone the right to beat up on them. They are still a supporting vendor, that has distributors on this site. In accurate information is just plain wrong.

For the record, 13psi on a 427 Z06 is NOT a huge feat.

We've done 684rwhp on a 402 with 13psi, a 2.6L and an auto with 3600 stall on a mustang dyno. I would have expected 800+ rwhp


DRE if/when you read this, I would be interested in a tal intercooler design like whipple already has.

PowerLabs

Adiabatic Efficiency is defined as the ratio of work done to raise the pressure of a gas as compared to the theoretical amount of work required without loss of heat. It has nothing to do with increasing or decreasing pressure without a change in temperature, since the only way such a thing would be possible is if volume was simultaneously reduced; hardly a useful situation and one in which zero net work would be performed (PV=nRT ).
As far as Adiabatic Efficiency goes though, I did address that: Since I mentioned both positive displacement and centrifugal superchargers on my post, I used the term "Thermal Efficiency" to refer to both Adiabatic Efficiency and Isentropic Efficiency. Corky Bell does the same in his book, "Supercharged! Design, Testing and Installation of Supercharger Systems" Here it is, from my original post:

That only remains true if we are comparing two superchargers of equal displacement... If you were to compare a 3.3L Twin Screw with a 2.6L Twin Screw, both feeding the same engine, you would see that the smaller supercharger needs to be driven at a higher RPM to flow the same air; as more and more airflow is required, the smaller blower will start to run outside of its peak efficiency "island" very quickly...

PowerLabs

Jeff, you seem to have taken some offence to my original post. Please don't. I admire your work and your shop, and this thread was meant as props to Dragon Race, not as a bash to any other shop.
The truth remains though that Kenne Bell has been promising a C6 kit for about 4 years now, and a quick search for their name on this forum will reveal that I am by no means alone in my frustration.
The fact remains that DRE has a twin screw supercharged car that, when strapped down to a dyno, put down some really impressive numbers. I haven't seen anyone else do that.

0Jeff @ TPE

No, I have not.. I respect your input, and think you have a wealth of knowledge.
I am just tired of hearing that yo can not get a KB on a C6, when in reality to you. that is all..

I completely agree with you that KB has ben writing checks their azz cant cash. That is why we even did the C6 kit in the first place. They are always pre occupid with another vehicles kit. Mainly because the C5 kit did not do so well (because of the hood), and now they are gunshy with the C6. But the car is on the dyno now with a KB DIY kit.

I will answer more, but I promised I would go get my 2 y/o a doll, and she"s hounding me..

CONMAX

I live close to their shop and Peter, the owner, is also a member of our Corvette club. His shop did the first tune on my car. I drove the first whipple charged car they built which was a stock LS-2 with headers are MT DR's. It had so much low end torque that it blew the tires off when I nailed it in 1st from a roll and then again after I let it recover in 2nd.

The car in the video is his personal car and started out as a yellow C6 LS-2.

Luweegy

Was there a Dyno sheet I missed somewhere?

auctiondepot

very good information from PowerLabs,

Why dont the manufacturers consistently provide the blower Maps comparison of
Flow vs Pressure vs HP required?

When I see more flow for less HP at the same pressure, that's for me.

Eaton Automotive is the only company Ive seen publish these number and even then they dont supply them consistently.

Could you provide yours so that we might compare them to say the 1900tvs?