turbo exhaust

[Skinny_Pedal]

im wondering how i should do the exhaus on the turbo truck. i was thinking from the down pipe, then run 2 1/4" w/o cat and a flowmaster. to turbos run better with or without the cat?

[CTENG in KS]

Well, like any turbine, the one that spools your turbo will function better the more laminar the air entering the turbine, and the freer (sp?) the air leaves the engine.  This is a case where, even on a smaller engine, back pressure is not your friend.  On the other hand, weigh the gains against the consequenses...a good cat nowadays isn't terribly restrictive, and if you want to smog your truck, then you will want to keep the cat.  It is also not a terribly large turbo, therefore the exhaust pressure necessary to spin the turbine is not that great, so the gains you reap from running without the cat are only very small percentages.

You would see better gains by minimizing the turns in the exhaust and adding veins to the turbine intake pipe.
mass flow rate in equals mass flow rate out when you have a turbine intake and nozzle of equal area, and temp in = temp out...(turbine exhaust will be slower due to energy transfer to the impeller.)
If you try to push air into the turbine faster than it can get out of the turbine you end up with thermal choking which equals NO POWER!   

edit: I can't spell for crap!
another edit for bad engineering...

[Weldo]

You may need bigger than 2 1/4" pipes for a turbo application.  I'd go 3" on the exhaust.  A lot of guys run 2 1/4" on a naturally aspirated motor, and a turbo will move a lot more air, even if it is small, so bigger exhaust is a must.

[CTENG in KS]

That is good advice...don't forget, that turbo is going to help quiet down your exhaust as well.

[BigMike]

I think for a 22R, 2.5" is about as large as you'll ever need to go.

But I'm my opinion, the C20 turbo is a little POS. It is an extremely restrictive Turbo, so regardless of a free flowing exhaust or not, you will always have backpressure at a low rpm when you are using the stock Toyota turbocharger.

With that said, I dont think you will notice much of a bottom end difference if you have a restrictive system vs. a non-restrictive system. So just go all out and run a 2.5" system. Cat or no cat is purely your own preference.

My friend who has a TEC Garret turbo kit on his 22R-TE is using a 2.5" system with a 2.5" cat. His truck runs great and is nearly as fast as my '81.

BigMike

[oddball]

I dont know if youve seen this but its cool, good info too well.com/~mosk/

[Willy Mammoth]

I agree with Mike here, 2 1/2" is plenty. I used 2 1/2" on my 2.8 6cyl's and hade no problems at 25 lbs of boost, I have seen mixture problems from using too big of pipe.

You can buy mandrel bends from JC Whiteny and make a real nice exhaust. A turboflow muffler sounds best too.

[CTENG in KS]

My friend who has a TEC Garret turbo kit on his 22R-TE is using a 2.5" system with a 2.5" cat. His truck runs great and is nearly as fast as my '81.

BigMike

[BigMike]

Better believe it   Check the story: http://board.marlincrawler.com/index.php?topic=11286.msg116810#msg116810

My 2.7 will take on stock Turbo 22R-TEs all day long, and my friends TEC Hybrid engine can only catch me around 70 mph with 33s vs. my 35s. He is a *hair* faster then me but only on long pulls. He does have more power than me, which I am not disputing, and much more potential as he is only running 5 psi boost right now. But for some reason his ecu doesn't like anything more then about 6psi. He hits fuel cut.

I've out launched turbo yotas every time I've raced them. Better have 180+ torque to catch me and the stock Turbo can't push that unless modified.

3RZ