power gains with cat bypass pipes

[Johnny Danger]

Originally Posted by The Radium King

i will agree that the throttle response on my '00 S feels 'disconnected'; i've always attributed that to the e-gas. further, any improvement in throttle response does not necessarily mean that you are making more hp/torque. your car sounds like it is a lot for fun to drive, however.

to jd i would ask (a) the hp increase was where in the rpm range, and (b) any hp effect that a cat bypass pipe is +/- say 5 hp on a 200 hp vehicle; can any of us say that we can 'feel' a 2.5% change? there is a larger variation between two stock engines, or two engines at two different altitudes, or a hot vs cold engine, or a driver with a fat girlfriend vs a driver with a skinny girlfriend. and what effect does the audio component have on how you feel the power response (ie, it 'sounds' more powerful; the 'sound' makes you want to rev higher)?

all i know is what i've seen, and all dynos of aftermarket exhaust show a minor torque reduction at lower rpm (if they show lower rpm at all; often the dynos start at 3000 rpm).

not being argumentative; just being conversational and trying to distill the facts given the sometimes difficult nature of electronic conversation.

trk.

My "journey" toward creating a better exhaust system for my vehicle began with the installation of an aftermarket cat back exhaust. My first impression was, that this upgrade produced a much more uniform engine response, and of course better sound. Subsequently, I deleted and by-passed the secondary cats. Again, the vehicle just felt "better", with no sense of loss with regard to low or mid range torque. It wasn't until I began experimenting with the header/pre-cat setup that I experienced varying results. To make a long story short, the design that ultimately lead to the best results for me was a set of custom fabricated headers that incorporated longer, equal length primaries that flowed into a well devised merger collector - followed by a set of 200 cell tri-metal HJS cats. Dyno results later showed consistent gains in hp through out the entire power curve.