Originally Posted by milelin

Just an update on the y-pipes, few days ago, we had the piece removed for more testing as we are planning to come out with another design and immediately i can feel the increase of tq with the O.E pipes back on. This is especially felt when crusing. I do have the HFC so we are suspecting that further reducing back pressure wasnt a good idea. My center pipe is stock.

I know our dyno shows small gains but that was on 4th gear with the padle to the floor. plus this car is electronically throttled which made things very complicated when it comes to real life driving. Well, the truth is, the car does have much more usable tq under normal driving conditions with the O.E y-pipe back on. Looks like this will be hard one to match..

Also, just for reference, the O.E y-pipe has a 2.5 opening connecting to the center pipe, the 1.75 is only for the sections following the cat. We will try to make some changes and hopefully we can get something to work well in all conditions or else we will have to scape this project. Also, unlike the O.E cat, the O.E y-pipe is very light already, a stainless steel part wont make much difference in weight

Originally Posted by amoney805

How can a catback not make any power? Assuming the piping is bigger diameter.