i heard a rumor that if i put a bigger size exhaust on my car that it would improve the boost. i have a vortech supercharger and i have 2 1/2 right now, would i gain any boost/improvements from putting on 3 inch exhaust?

 

2 1/2" exhaust is good for about 600 hp. Ask MD, I think he told me before that he wouldnt gain anything off of running a bigger exhaust.

 

You wont gain boost. If anything you'll loose a small amount because of all the free flowing that will be going on. Unless your exhaust right now is too small for your application.

 

yea the bigger exhaust you run, the less back pressure, = less resistance and less boost

doesn't necessarily mean less hp though, only that 2 1/2 is usually more than ample enough for our little 4.6 & 5.0 motors. 3" won't be overkill on a boosted motor though but its not worth upgrading if you already forked out the $$ for 2.5" IMO

 

^Couldn't have put it better myself.

 

does this apply to the 03-04 cobra's??? i'm asking because slp's kit is 3.5 inches.

 

no i think that's the diameter of the exhaust tips

 

i think i read somwhere that 3" is for 400+ hp cars.

correct me if im wrong, but exhaust diameter should have no effect on boost. boost happens when the exhaust valves are CLOSED and the intake valves are open, so if the exhuast is blocked off the rest of the system should not affect boost (unless ur tubo, where a smaller pipe will increase exhaust velocity, which will spin it faster, which will increase boost). just my $.02

 

would putting 3" on a bolt on car be overkill? would it affect it any...

 

yes it would, and you would only loose bottom end torque (because you decrease velocity to gain airflow)... and you won't gain any real power because 2.5" would already be more than enough to flow all but a high hp car.

Anyways, bigger exhaust will decrease boost a small amount because your decreasing backpressure - boost is created partly during a close exhaust valve but also because of restrictions in the intake and exhaust system. Gotta think ... boost is caused by backpressure - if theirs less back pressure then theirs less boost... but thats a good thing because hp will increase and the air won't be compressed as much so their will be less heat.