sorre im new to all this...but pplz say dat a larger diameter (3") in an exhaust takes away from the low end but have gains at the high end? n vice versa with a smaller diameter (2.5")..wha does all this mean? n how does this affect a car's hp n race times...

any inputs u guyz?

 

Yeah, its true. 3" is good for higher rpms. Main reason for this is that the 3" has a larger area for the exhaust to flow through. With the larger area, the exhaust in turn has less velocity, so at low end rpms there is even less flow velocity and is less efficient. But at high rpms it has less restriction on the velocity (where a smaller diameter might choke up the high exhaust flow) allowing for more power output.

Tighter exhaust will give more torque on the low end, but will taper off a little as the flow gets too quick for the diameter. And larger exhaust will show more power gains at higher rpms which will thus probably show more of a larger peak hp. If you're racing and keeping in the powerbands you might want something more open for that increased flow.

I don't think people need to dwell on the difference of exhuast diamters from 2.5"-3". i'd say 2.5" would do for most people, especially if you get rid of all of the restriction like getting straight flow mufflers and resonators and taking out the cat. A free flowing straight through exhaust will post more gains than the diameter changes (although some diameter changes are needed on the stock exhaust to free up the flow). Thats probably why GMPP 2.25" exhaust posts gains over stock exhaust and is comparable to most 2.5".

i hope this helped, a little at least, i tend to ramble

 

Nice little write up^^^

 

agree wit ctorangesc..GREAT WRITE UP..xplains alot 2 me..and didnt mind the rambling if thats wha u call it, helped alot..thnx

oh and since it seems like you know what you're talkin about...do u recommend me go with a 2.5 or 3" exhaust if im planning to have about 290-300 hp?

 

GMPP Exhaust is only 2.25" I thought it was 2.5" isn't that what are stock size is 2.5"??

 

If you are running up to 290hp I would recommend 3" remember less restriction on your exhaust = less stress on your supercharger. I have 3" on my car and when I first had it put on my car dyno was 12 more hp and 2 ft pounds less torque I would say it was worth it. You know in these cars if you just had a little less torque in the lower rpm band you might not spin as much off the line.