When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'll tell you this. On the track, we have done side by side comparisons of the bypass pipes vs. the stock Porsche exhaust. The bypass pipes are faster down the straights than the stock mufflers. No doubt. Now, this is wide open, high revving comparisons and so may not apply to street performance unless this is how you drive. And we used the same car for both applications and compared acceleration to a baseline car.
I don't have the data in front of me but it worked out about the way I expected. With restriction we gained a significant amount of torque from the start of the run up to 4700. From that point on the open pipes steadily gained both hp and torque peaking at 17 more hp and a similar amount of torque with the open pipes. The restriction was added by adding 16 Supertrapp plates which may not have been the most efficient but I still think the results are directionally correct. I may make a run with cats on someday when I have some time to see how they compare to the Supertrapps although I can't see adding all that weight back on the car.
We plan to run with open exhaust and focus on keeping the revs up for now.
Jim