lart951

Correct, the 951 without a muffler and cat sounds like a fart can.

from the inside



from the outside

951_RS

Alright so basically if I'm running 16 psi I should hope to see 32 psi or less on the exhaust side, correct?
And less on the exhaust side would be that much better I'm guessing. With a target of near 16 psi on both sides (intake and exhaust)

Rogue_Ant

Yes.


-Rogue

toddk911

The basic concept is to get as much air in as possible and get it out as fast as possible with out any bottle necks/excessive back pressure.

333pg333

I remember being told that turbo cars needed some exhaust restriction to help with spoolup. The theory being that if you had too big of an exhaust it would increase lag. I wonder how the 3.5"-5" SFR unit will eventually go?

TRP951

They mean restriction before the turbo Patrick. If you have too large a crossover there wont be as much of velocity there hurting your spoolup but too small and you have a restriction. Post turbo you want as little as possible

333pg333

This info was given to me back in the 80's Tim so I'm sure it was pretty early stuff.

lart951

Correct, Special tool before he turned into a thief confirmed the same thing.

Duke

Exactly, less restriction after the turbo will help spool up.

toddk911

What is the best way to tap in to get backpressure readings?

toddk911

Yep as we ahve all seen real world proof of this as the cat delete is such a major before and after difference because it is a major point of backpressure.

I think most see 500rpm or more in better spool up and more over all boost made as well just from the cat delete alone.

My mech has about 20 years of racing exp under his belt mostly with prepping other's cars and he worked with Alex Job, etc. and he always said if you want some major gains with the 951 do some work on the exhaust side of the head.

951_RS

I missed out on a bit, did he actually keep that guys car in the end that he was working on or what?

Rogue_Ant

Easiest is using the test port on the crossover... Best would be to tap right before the turbo.


-Rogue

DanaT

Do you run the pressure gauge into the car? It seems it needs a bit of copper tubing to get the gas cool before it would go into a gauge? Maybe you are you are using a pressure transducer type gauge?

Thanks
-Dana

m73m95

Related question...

Is there a formula for how big to make the crossover compared to the engine size, rpm, and turbo size?