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4 inch down pipe.

2.2K views 8 replies 8 participants last post by  06crtd  
#1 ·
I've got a 06 5.9 that has a 5 inch down pipe but want to try a 4 inch to make the turbos spool up faster. Does anyone know where to get a good one or even a stock one? Thanks.
 
#3 ·
I have stock exhaust that I straight piped, looking to get a 5 inch system. How does the 4 inch down pipe help with spool up? There are cheaper kits with a 4 inch down pipe that go into 5. I thought fuel/ heat/ and housing sizes are what determined spool up?? :confused013:
 
#6 · (Edited)
I'm a bit confused. You says turboS? Why do you not want all the flow you can get if you you've got two snails? Small exhaust won't make up for improperly sized housings/trims.
 
#7 ·
Won't make any difference at all.......The turbo works best with the lesat amount of resistance.......which means better intake and better exhaust!!!!!
 
#8 ·
I agree with extremesledder, it won't make a difference. I built and raced turbocharged vehicles for a long time and the less back pressure after the turbo the better.

Think of those big, old water wheels. There's always a small pipe with fast flowing water to make it turn, but there's a large river after it to not impede it's rotation. The turbine wheel works on the same principle...high velocity in, low restriction out.
 
#9 ·
I understand what you're all saying about backpressure. This is for a buddies truck, he's got the Diesel Power Source stock/ht3b twins on the truck. When he went to the 5 inch he said it seemed like it spooled slower and get up and go as fast. Not sure about all this since I don't drive it but I think his trans is starting to go as well. Just was wondering if I could find one since he doesn't have the stocker anymore to try it out.