hey guys im thinking about putting a 4in exhaust from the turbo back on on my truck since the one on there now is a 3in non mandral bent. what i was wondering was, does a 4in down pipe really make a difference in performance over the stock one?

my pyro question is this. since im re- doing the exhaust i want to get rid of my post turbo pyro and make it pre turbo but im not quite sure where to put the sensor on my ats manifold. i have been trying to find some pics. but no success.

thanks

 

Dunno bout the 4" pipe cause I haven't put mine on yet, but as for the pyro, look at my gallery and I have a pic in there of it. Piers has some instructions on their site, http://www.piersdiesel.com/TechPyroInstall.htm Hope that helps,

Brian

 

thanks brian. those pics on piers site were exactly what i was looking for.

 

i have a pic of my probe installed in my gallery if you need a sec pic. most ppl claim a 100 degree drop but not sure how much it really helps if the turbo housing has a 3 inch outlet, the gas is still restricted some what.

 

I installed a 4 inch system (with a muffler), but the downpipe stayed at 3 inch. Even with that I saw some pretty big performance gains...3 to 4 psi boost, much quicker spoolup and quicker cooldown.
Can only be better with a 4 inch downpipe.
Jay

 

I'd like to know the answer to the 4" headpipe also. I scored two monster 4" madrels, just need to find a cheap flange to hook one of them up.
But I want to know if it's worth the trouble.......
Aw, who cares, I'm going to do it anyway!

 

I am convinced that the best results would come from a stock 3" bend behind the turbo tapering up to a 4"bend at the bell housing. Sudden changes in diameter cause turbulence and back pressure at high rates of flow . . . BUT I have not tried it yet, and you would really have to have the same truck, a dyno, and all the different pipes to really test the theory out.

 

Alec can you get a pipe that would slowly taper out like that, in the given distance you want it to? i see what your saying. it would be interesting to make some dyno runs and see what happens. do you have that setup on your truck now?