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Originally posted by SE-Man:
once more, were getting into "what you think I should have" and not the question posted. What do you think would be the effect of a 2" turbo piping on my set up.

Sorry If i sounded sarcastic, I didn't mean it that way. I have the same question on three other boards and Marshmellow is the only one how has given somewhat of an answer.

well how about you give alittle more info on your set up that would help I dont think many have checked your web page so they dont know you running daul exhuast. Plus how you going to do it run both bank into one turbo then split down a dual exhaust system or is your system a phoney daul sytem where it run down to the muffler then the muffler has two tips. If you want a more desired answere you have to give a lot more info and you have yet to do that.

like i said before for best results with your engine, i would go to 3" exaust on Turbo application only. 2" isnt big enough. for N/A cars the genral rule of thumb is 1" for every 1L of displacement. yours is a 2.2L so 2.5" would be ok if your running 5psi. if you plan on upping the boost at all like 10-14psi i would definatly go with 3".

im running 21/4" on my 1.6, and corksport told me that the boost on my turbo is rated at 7psi but in reality im probably hitting closer to 13psi because of the bigger exaust.

and there are alot more people running 3" than some of you think. most people with an aftermarket turbo system go to 3".

You can apply the rule "bigger is better" on the piping after the turbo.You don´t need any backpressure to use it as a cylinder scavenging helper as on n/a. before the turbo, you must keep contended sizes for reducing turbo lag. I am building all my post-turbo piping with 3" tubing. I am working on a Kl engine. As soon as I have it all toghether I´ll post a dyno graph (I swear I will do it this time!)

Thanks Mx-K thaths exactly what I needed to know. The rest of my exhaust system is unimportaint after the turbo, It was designed for a future turbo add-on, so its good to go. The only thing that I feared was that if i went 2" piping that I'd blow a valve or have to much back pressure a brake some of the custom parts. It will only take once and I will not be able to get it replaced (for a decent price at least). The diagram was perfect, I'm planning to run two 2" pipes (the equivilant of a single 3") to get the desired results. Maybe with a nice fuel pump upgrade I might be able to get 250 wheel HP on a twin 2" set up.

BTW I'm going to get my Max.Boost book today, it finaly came in.

SE-Man: To answer your question directly, a 2" exhaust will restrict exhaust flow and reduce velocity.

Now, Don't go with 3", Don't go with 2", Go with 2.5" or 2.25"

""The larger the better" is not the case". He talks about trying to achieve an exhaust gas velocity of 250ft/sec, and having too large of piping will lower your exhaust velocity.

That is your answer SE, it's all about acheiving the best constant velocity flow/restriction. Not too tight and not too loose. 2.25-2.5 would be the answer...you'd have to do research to find where the difference for best results.

my old car needed 3in instead of the 2.5 i had on there.

hes got the engine built up for turbo app. so 3" would be the best idea. espically if hes planning on running higher boost. that 2" exaust wont do at all. major loss in power. i would put 2.25 on it, if it were going to be NA. 2.5 would be the smallest id go with turbo app. but still when you try to put upwards to 10 PSI its not going to perform the way it could. and since you want twin turbos i would definatly go with 3". i dont care what all of you say. with the setup he has and for what he wants to do with it 3" is by far going to be better.

then after i put my foot in my mouth again i realized hes going to run two 2" pipes, which should and will sound very sweet. i would probably put in an H pipe too. but im not sure if an H pipe would help on a duel turbo app. or if you would even want the backpressure. anyone know?

Close josh, I'm using a 6cylinder engine, on most 4cylinders turbo aplications they use a 3" for 4 cyilinders, I'm planning to run seperet pipes to a single turbo, so I'll be able to get away with a 2" pipe for 3 cylinders.
After the turbo back pressure is useless so dual pipes from the turbo to the rear of the car, so no x-over pipe will be needed. Its only going to be a single turbo set-up, so it will do me no good to go over 2" on each pipe cuz Mr. Bell's info states that twin 2" piping is the same as a single 3" piping, and due to most turbo's exhaust Inlet is no bigger than 3", but before the turbo, were the pipes will join will have to be 3". Now any one with Max.Boost, am I understanding this wrong?

i can understand running a dual exhaust setup if you are planning on running dual turbos (one for each exhaust manifold), and i can also understand going back to a single exhaust pipe after the turbos much like a lot of high displacement inline 6 twin turbo motors, but i cannot understand why in the hell you would use a dual exhaust setup after a single turbo...that's probably the most inefficient, heaviest, and most expensive way to get less exhaust velocity and more awkward bends and Y's that the exhaust has to deal with before exiting the car. the exhaust exits the turbo from a single hole (excluding the wastegate outlet of course...it would be most efficient to run a separate outlet for that) so why not keep it that way?