I need to get a bigger exhaust soon for when I start to turbo my car. Its a d16y8 and I am just goin to be running 7 lbs. Would 3inch piping be the best or 2.5, 3inch kinda seems overkill to me for only 7 lbs.

 

with D16 and 7 pounds I'd use 2.5 - 2.75 depending on the block /head mods. too small bottle necks the engine and too big reduces exhaust velocity which creates torque. If block is stock use about 2.5. If internals modified use 2.75. My personal opinion is that 3 inch is too big because it will create a few extra horse up top but also drop torque across entire rpm band. hope this helps.

 

ummm maybe all motor. remember there is a turbine in the way first.

OP, use 3" and be done. Larger exhaust will have lower post turbine pressure which will increase turbine efficiency and spool time.

 

alright im thinking ill go 3inch, unless I get a super good deal on a cheap 2.5, thankyou

 

3" will make more power and spool quicker. Ignore anything S2Integra said (sorry i mean no offense)

 

ya what he said applies more to N/A cars

 

The 3" will allow more power because of the release of back pressure, but the turbo will not necessarily "spool faster" from direct result of the larger exhaust system.