Is a 3 inch exhaust necessary for turbo?

96 LS

New Member
Is a 3 inch turbo exhaust necessary??

is it absolutely necessary to have 3 inch exhaust for boosted applications? i want to boost the nonvtec but i really dont want a loud 3 inch exhaust. i was looking around at different turbo kits and found that most kits include 2.5 in downpipes. cant i just run 2.5 all the way back?
 

TegSox

Super Duper Moderator
It's not absolutley necessary. You could use a stock exhaust with a turbo, it's not like it gonna keep the turbo from working or anything. It's just that, the bigger you have your exhaust system, the more gases that can be expelled as quickly as possible and the turbo can work more efficiently. Exhaust flow quality doesn't matter on a boosted car like it does on an NA car. On an NA car, the exhaust piping activley helps draw exhaust gases out of the engine. That's why a properly sized exhaust is so important for an NA car: To maintain flow quality, flow speed, and to hit peak volumetric efficiency in the right area of the powerband.
Here's a turbo exhaust vs. an NA exhaust analogy: Turbo exhausts, it's like a kid spitting out his peas, just get rid of it all as fast as possible, as much as possible. It doesn't matter if pea after pea is coming out of his mouth timed perfectly and spaced apart perfectly from all the other peas.
NA exhaust is a controlled release and expulsion of gases from the head, it's one exhaust pulse creating a vacuum behind it, and that vacuum pulls on the next exhaust pulse, and so on. Turbo exhaust gas is complete chaos, there aern't perfect little exhaust pulses pulling on one another like NA exhaust. It's just a whirlwind of a whole lot of hot air that needs to get spit out.
 
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