yeah, the 2.5 should be good, though it might be a little big for a mostly stock motor, it leaves a little room for growing. but pay the extra for mandrel bent piping, itll about double the power gains over that POS crush-bent stuff most muffler shops will try to use.

 

What is "mandrel bent piping" exactly?

 

manderal bent is piping actually bent in a pipe bender...a manderal bender to be exact...i think crush bent means the piping that is ribbed in some places and you can bend it real easy with somthing stiff to lay it over...i think..someone correct me if im wrong on the crush bent thing

 

close. crush bent piping is sometimes ribbed, and sometimes its smooth, but it gets smaller on corners. mandrel bent piping has a flexible tube put through it that wont crush down, then its bent on a machine. that way, the interior diameter stays constant even around bends. some places test the diameter by dropping a billiard ball through. it fits exactly, so if its not perfect, it gets stuck.

 

I figured that was it. But I see how it can effect flow. BTW what is the stock HP of a 00' civic?

 

an EX right? 125 i believe. and so you dont have to ask, expect from 0-10 hp from the new exhaust, depending on the quality of the job.

 

You know it's a common misconception that going bigger on the exhaust pipe diameter will cause you to loose tq and make your car slower. The tq that is supposedly lost is just moved higher up in the Rpms. The extra hp you make from having less backpressure makes up, well somewhat, for the tq curve moving up. The extra power is sign higher up and does make a significant gain. I know a few buddies at the track that run cutouts (which in theory would be the same as running big pipe. Less Back pressure) and usually see gains of 2. to .3 if they use them. Yes the car does feel slower in the lower rpms, but the slips don't lie.

Matt

 

no, cutouts are WAY different than big pipes. ive explained this a couple of times before, but its been awhile, so heres the cliffnotes. the power loss from bigger pipe is NOT from loss of backpressure, its from loss of exhaust gas velocity. if the exhaust pulses are moving faster, then they cause a small bit of suction behind them, which helps scavenge the burnt fuel and air from the cylinder and helps pull more fresh into the cylinder during the overlap period in the cam timing. so if you use cutouts, it allows the exhaust to maintain the velocity to the end of the pipe, where the small amount of vacuum is dispersed, so it never causes any stagnitation of the exhaust flow. if you use a bigger diameter of pipe, it causes the exhaust to slow down and that causes the flow to slow down, resulting in less scavenging of the cylinder. so still use smaller pipes, but cutouts arent a bad idea for track use.