By-pass pipe.... how much real hp?

[chrisbruck]

Anyone know how much real HP a bypass pipe adds to my stock 3.2 Carrera with a stock muffler modified with a second passenger side exhaust outlet?

Reason I ask is I recently installed a Steve Wong chip (most awesome) but it makes the car smoke like crazy due to some bum valve guides so I put the cat back on. I'd like to run the cat to clean up the smoke till I rebuild the top end next spring. Butt-o-meter says I have more low end torque with the cat ON and just a slight reduction in overall power compared to the bypass pipe. Hard to really tell because of the sound difference (loud isn't always faster). I actually kinda prefer the mellower sound with the cat and the modified muffler.

Curious how much power I might be giving up. Anyone have dyno results to confirm?

[Bob Kontak]

Here is a dyno from an SC that had a cat bypass and a few other flow improvements.

Dyno results for an SC?

You can search for others but you are not giving up too much - my guess is less than ten and closer to five.

Run oil through your cat for too long and those numbers will change.