Open Exhaust

[czy18e]

In short - do you need a retune if you went from a 3" open exhaust to a 4" open exhaust?

I used to beleive that with a 3" outlet on the turbo like a T04z or GT35 that there was no point going 4".

But im meeting more and more people at the track that say the 4" open exhaust lead to another 10 to 20 hp in the top end over the 3".

If the car is tuned to a set boost level with eboost would it need retuning?

Thoughts?

[Leeroy94]

What type of ECU do you run?

[czy18e]

Ems

[Hadouken]

ITll run lean. End of story

[Reese69]

what about a haltech i was running a 3 inch exhaust with muffler and cannon - only thing i done is now running from dump pipe back straight 3inch pipe how would that effect tune? should only effect noise?

[ido09s]

i dont care what ECU your running, i would get it checked. $50 a few dyno runs or several thousand for a rebuild if it isnt checked and did need retuning, no brainer