What I am saying is PSI does not tell the whole story. If I took a t67 turbo and bolted it to a 6.0 it would make lets say 600hp at 8psi. Now I could take a t76 and it will make alot more hp at the same psi. You have to look at efficicency of the blower as well. Same thing with the 112 vs 122. The 122 is going to make more power than the 112 at the same psi on the same motor. Because its getting more air at the same psi or is it because it's just compressing more effectivly. One is going to be able to compress more air at the same psi. IAT's are also an issue that is not being said here. Like throttle bodies, the bigger one flows more cfm normally, right?

 

Not this one.

 

Thats a Z06, not a vette. You left before all this happened anyway. You missed me and Lance have a go on street tires.

Side note. I found where I was leaking boost last night and my next trip to the track will be stronger.

If I mail you a copy of a dvd, will you post it Kyle???

 

Ok i got ya now man... i wasnt that far off on my thinking.....

appreciate it!!!

 

You can send me your copies and i can email them or post them..

 

Something about this doesn't seem right to me. I agree that PSI at the manifold is not the whole story(forget about PSI at the turbo or I/C), but I think that has more to do with downstream components. Flow is based on the difference in pressure between the intake and chamber, and the restriction in flow. If you had 2 identical engine/turbo setups, except one has ported heads, the ported one would flow more at the same PSI. A bigger turbo has the ability to flow more at the same PSI, but with no changes to the engine, it will not flow more at the same PSI.

I hope this makes to sense to anyone else.

Paging Dr. Parish....



I don't mean to hijack, but this is a good discussion. Perhaps to a new thread?

 

A bigger turbo has the ability to flow more at the same PSI, but with no changes to the engine, it will not flow more at the same PSI.


The dyno will argue you on that one. Ask the people that have upgraded turboes and made no other changes "same psi" and made more power!

 

Usually power gains in a scenario like that are because the smaller turbo is work out of it's efficiency range and was robbing power to begin with. Then installing a larger turbo allowed said turbo to be in it's efficiency range and the made for a more efficient combo with less parasitic loss. Boost for Boost, it's all about an efficient setup with the least amount of parasitic loss, turbo or blower.

 

That is what I was trying to say, and is only 'in theory'. But we also have to add 'at the same RPM'

This contradicts what I said and your comment above. But the bigger turbo will make more boost at lower RPM, unless your boost controller can be programmed to give you exactly identical boost profiles vs. RPM(I know some can), we may be comparing apples and camels. I'm sure there are many other dynamic factors that I cannot comprehend without experiencing cranial decompression.

'I'm just the electrician'

'When you do things right, people won't be sure you exist at all'

 

Your probably right. Now that I think about it, the examples I am thinking about are in the higher boost ranges. It is probably just because of efficency of the bigger turbo. Like parish, he was making something like 700hp with the t76 turbo and swaped to the pt88 and almost gained 300hp. (if I remember correctly) Or like when I swaped the turbo on my Typhoon it was a big difference. Stock boost was like 14 psi. So the bigger turbo was just more efficent.

But I still think that all the bends and turns in the intake piping of the sts setup is going to slow the amount of air going to the manifold (more restrictive). You may have 5 psi of preasure but not same amount of air. Kind of like the example you gave ported and non ported heads. I remember a change of manifold boost preasure just from changing intakes from the truck intake to ls1. I think I lost boost if I remember correctly. Its like blowing through a straw vs blowing through a garden hose. THe garden hose will need more air to make 5 psi.