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Discussion Starter · #1 ·
How much of a restriction is the stock exhaust? I have a 91 Spirit 2.5 turbo, ported head, intake and exhaust manifold, T2 Daytona IC, MP controller, grainger valve, 88 T2 garret and stock exhaust with no muffler, it has a stock resonator behind the cat. Is the stock exhaust enough of a restriction to limit boost to 12-13 psi? I've tried unhooking the wastegate vacuum with little to no effect.
 

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Mr. Moderator
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I unhooked my wastegate on my baron and it has a 2.5" exhaust and hit overboost going 35 mph if that tells ya anything
 

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Not to sound offensive...but a full exhaust is one of the first things i do, or atleast a cat back. I've seen gains of 15 to 20 hp just going from stock to 2 1/2 mandrel bent, w/ h/f OBD2 cat, and a straight through muffler....

I don't know what your local laws are but the less restriction on a turbo motor is the best...no cat, no muffler, and a full 3inch exhaust you should be getting gains of something like 30-40hp maybe even more with all the other mods you have.......t
 

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Discussion Starter · #4 ·
I my 87 Shadow I had before it put down 215 whp and 280 lbs with the stock exhaust and the same mods but at 16 psi. It seems like others here are saying the factory "built in" restriction into the mitsu turbo cars to reduce boost creep so thats why I was asking.
 

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Mr. Moderator
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Ya with a bigger exhaust the mitsu loves to boost creep. But since you have a t2 garret on there you shouldn't have problem. You will see a lot more gain with a bigger exhaust on your car.
 

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Mostly area under the curve is where you'll gain. You might make 5 peak hp but could see a gain of 30hp earilier in the rev range. With a ported setup like yours the T2 turbo is a restriction. The reason you're not seeing over 12-13psi probably is you have the small can wastegate which is a weak little thing. It would fall off to 11psi on my 2.5. Once I got a big can from an 89 T2 turbo I didn't have any issue's anymore.
 

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Discussion Starter · #8 ·
Yeah I need to find a big can, I shimmed the small can out and it helped a little. Has anyone ported there swingvalve housing or would it help.
 

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The T2 turbo is stock on a T2 car. It's a stock factory turbo. Just depends on what car/motor you got to make it stock for you.
 
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