I think it has more to do with pressure ratios and compressor efficiency than with VE of a motor. Most turbos are more efficient at a higher pressure ratio versus a lower pressure ratio when compared at a given (or constant) mass flow rate.

for example, take 2 motors with the exact same VE, but one is a 2liter and the other is a 4 liter. with everything the same, the 4 liter will be able to consume twice as much air as the 2 liter at the exact same rpm, etc. so, to make both engine produce the same power, we are going to have to double the manifold pressure (absolute pressure, not gauge pressure) of the 2L engine to equal the power of the 4L engine. Of course, this is all "theory" as no 2 engines are truly alike.
Continuing, lets look at the compressors "islands" of a GTX42. at a pressure ratio of 2:1 (29.4 psi absolute/ 14.7 gauge pressure) and an air flow of 90 pounds/min, the engine has exceeded the efficient range of this particular turbocharger. But if you take the 2 Liter engine of the exact same efficiency, etc and we double the "boost pressure" to 58.8 PSI absolute (44.1 psi gauge), the turbo is now operating at a 4:1 pressure ratio. Looking at the exact same air flow of 90 pounds/min, we are now in a very efficient operating zone for this turbo (approx. 75% efficiency.)

In summary, both engines are consuming the same amount of air (90 pounds/min) and being that both engines have identical effiencies, friction losses, etc.....these engines should be makign the same power. the only difference is that the turbo on the 2L engine running at a 4:1 pressure ratio is running more efficiently (and cooler) than the same turbo on the 4L engine (which is not in an efficient zone - <60% ). the lack of efficiency and added heated on the 4L motor will, in turn, result in the 4L motor making less power than the 2L motor.

Obviously, this is a theoretical example that one would never be able to truly recreate, but it gives an exagerrated example of why it is so important to properly size a turbo compressor to an engine and the engines capabilites.

where turbo selection is super critical is organized racing. in many organizations, the sanctioning body limits the size of the compressor in each class. as such, you need to build a motor that can best take advantage of the turbo you have to work with. On enthusiast forums such as these, people aren't limited to certain compressors or stuck with boost restrictions, and because of this... alot of people just assume that bigger is better and more boost makes more power. A turbo is the "great equalizer" and it is an easy way to make power. Quite often, there is knowledge left behind and the "why" is never understood, all int he great quest for more power.

 

Whats the status on this? Did something bad happen?

 

Absolutely not! We have been waiting on a couple of things and I am in constant contact with Vlad. His new street wheels have finally come in and he is picking the car up soon to get a drag alignment and have a little fun with the car in it's current status. He will then bring it back and we'll toss some of the C16 I have stashed for him and turn it up!

We have been doing a few final adjustments as per Vlad's request such as relocating the CAN gauge and installing the iBoost setup. Lots of good things to come with this bad boy.

Reid

 

ya if I could make 900whp on the dynodynamics, this car should break the 1k mark with alot more displacement!

 

any more updates about this car?

 

What about the feasibility of using a 4L80e trans? I see that you guys offer it for the Supra. It would be nice to have a 4th gear for overdrive.

(Got some bad news today about a friend's built 5AT and looking at my options in case my built 5AT trans FAILS to hold the power on my G)

 

What size cooler do you guys recommend? What size cooler is on Vlad's car?

 

If i recall the 4L80E is bigger than the TH400, so you may just need a bigger hammer.

Tom

 

I believe you are right. I looked into the 4L80E but settled on the TH400 instead for my car. I remember reading that the TH400 was smaller and would fit better which is one of the reasons I choose it.

 

What about using the 4L60 trans? It is the TH350 with an overdrive gear. It should be smaller than the 4L80, but I don't know how it compares to the TH400. I am actively seeking a stouter trans for my build, so any feedback on how the TH400 drives and handles on the street/highway would be appreciated.

 

UPDATES!!!!

Vlad picked the car up yesterday. We finished up the CAN gauge relocation, iBoost control install, ProEFI software update, and did some final pump gas tuning. We also took all the measurements needed to see what we can do in the drag wheel department. I have the slicks and skinnies here but the wheels themselves have been difficult to track down. I am looking to Bogart and Billet Specialties with hopes of getting some meats under the fenders.

Vlad is getting his wheels and tires mounted and getting a professional drag alignment done and is bringing the car back ASAP so we can toss in some C16 Race gas and make the big numbers. Our Open House is next weekend on Saturday June 12th and expect to see this monster there!!

On 93oct pump gas, it made 640whp @ 17psi!!!! Larry was a giddy little school boy in the driver's seat on the dyno. I can't wait to see how Vlad likes it on the street. Here's a little video I put together as well as some pics:


http://www.youtube.com/watch?v=j6kuR7kS0J8

 

Thanks

What is that on the differential. A brace?

What street rims does he have to fit the 275 tires?

What is that filter by the battery cover?

Where does the hose from the PCV valve go?

Can the ProEFI with that CAN gauge be made to work on a stock Nav screen?

 

I think what is on the diff is two braces to try and eliminate wheel hope. My buddy has it on his Z but he just has one.

 

There is one of SP's Diff braces (same brace that is on the shop car, so it must do something right).

They made a real trick hidden catch can that is located where the battery was (battery relocated).

Tom

 

275? Thats it on the street, no doubt you will need more! You can get 285s or even 295s if you roll with the correct offset.

 

I've seen 295s so that's correct. Here are 295s.

 

Wow jus gettin to this thread, that sedan is a f'in BEEEAAASST!

 

Sounds like she's ready for the racegas tune....

674rwhp on pump gas at SP's open house saturday!!!!!!

Tom

 

cant wait to see the curves and how they compare to the SP race car and to mine.

hows the owner like 3 speeds on the street, or does he have an overdrive? does he have a transbrake installed?

 

Answered!

The width isn't the most important part, it's how tall the tire is. Regardless, his tires will definitely be holding on for dear life!

TH400's are only 3 gears. It does have a transbrake.



UPDATE: The car made 833whp @ 25psi (uncorrected) and 848whp @ 25psi (corrected). It was spinning the tires at that power level which won't do much for power numbers but it's going to be killer on the drag strip when it gets the power down. Look at that power curve!!