what size exhaust pipe for a sts turbo

Hey guys I had a question regarding rear mount turbo's and boosting quicker.
And i know some people HATE and some LOVE the sts turbo and for the most part im loving the kit. i was running 5#'s and since than i forged the engine and put my intercooler so im gonna move on up to the 13#s.

i was boosting my 5#s easy at about 2800ish rpm with NO lag and NO intercooler. I just installed my intercooler and keep the 5#s and its taking a bit longer to boost, 3500ish the 5#s.(probably the added pipes and intercooler to fill up)

Now STS makes claims to keep the factory manifolds and exhaust pipe (which i believe its 2 1/4) for best results. But than they told me that if I'm boosting over 11 lbs, which i am doing 13, that i should move up to a 3 inch exhaust pipe to get the air moving and not starve the turbo as a 2 1/4 in pipe would at the top end.

I have on my car a set of LT headers (wrapped) and 3 inch pipe all the way to the turbo. (exhaust pipe wrapped as well) I have a list of things done to the engine such as 9.0:1 compression, forged engine, mild cam (not made for the turbo but will be changing soon after someone can grind one for me) Is there anything, such as changing my exhaust pipe to a smaller diameter, to boost a bit quicker or am I just falling into one of the "I HATE STS TURBOS" kinda guys?? I never had the turbo running at the factory manifolds or exhaust size pipe so i dont know if i should be boosting quicker. Any ideas if any of this matters???

Its the lower compression that is causing the extra lag.

I agree with joe. What size is the exhaust housing on the turbo? How do you have the inlet for the turbo run(what size air filter and kind, what size pipe)?

Let me see if I can explain it a little better for you.
Think of a garden hose and one of those whirrly things that blow in the wind. If you take a garden hose and just let the water flow out it won’t turn the propeller fast at all. Now, if you put a nozzle on it and create velocity in the water it moves the propeller pretty quick doesn't it. Well, same concept for exhaust gases. The first thing you need to remember is LT headers will hurt you on a turbo setup. They are designed to dissipate heat and with turbos you want heat. It’s not so much the compression ratio that is causing the lag. Think about it, you’re forcing air into the cylinder so when all is said and done your compression ratio is up there already. Compression ratio is just making sure you don’t get detonation in the motor. Now I’m not a big fan at all on the STS kits. I’ll never install another one. Just too many design flaws to even go into. Put it up front where it belongs and you’ll be a lot happier. Stick with the stock manifolds they will serve you well.

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Originally Posted by CAMSS2002

Hey guys I had a question regarding rear mount turbo's and boosting quicker.
And i know some people HATE and some LOVE the sts turbo and for the most part im loving the kit. i was running 5#'s and since than i forged the engine and put my intercooler so im gonna move on up to the 13#s.

i was boosting my 5#s easy at about 2800ish rpm with NO lag and NO intercooler. I just installed my intercooler and keep the 5#s and its taking a bit longer to boost, 3500ish the 5#s.(probably the added pipes and intercooler to fill up)

Now STS makes claims to keep the factory manifolds and exhaust pipe (which i believe its 2 1/4) for best results. But than they told me that if I'm boosting over 11 lbs, which i am doing 13, that i should move up to a 3 inch exhaust pipe to get the air moving and not starve the turbo as a 2 1/4 in pipe would at the top end.

I have on my car a set of LT headers (wrapped) and 3 inch pipe all the way to the turbo. (exhaust pipe wrapped as well) I have a list of things done to the engine such as 9.0:1 compression, forged engine, mild cam (not made for the turbo but will be changing soon after someone can grind one for me) Is there anything, such as changing my exhaust pipe to a smaller diameter, to boost a bit quicker or am I just falling into one of the "I HATE STS TURBOS" kinda guys?? I never had the turbo running at the factory manifolds or exhaust size pipe so i dont know if i should be boosting quicker. Any ideas if any of this matters???

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Well the exhaust housing for the turbo is A/R .81... the charging pipes are 2 1/4 to the intercooler and 3 inch after that. The problem now is that I'm boosting 10#s at bout 3500 rpm gets to bout 5300 rpm and starts to drop down to bout 8ish... any ideas with that problem????

frow what ive gathered, if you change your charge piping from 2.25 to 2.5 and weld as much as you can together so as to get rid of any chance of boost leak this should help on the intake side. Also make sure all the exhaust piping is clamped and welded tight.

had a strange question for you guys, does filter size or location affect boost?