Need more power!!!!

The flanges between the headers and Y-pipe aren't points of restriction. Those are straight through, without a reduction in size. Unlike the y-pipe to catback flange. There is a large and clear reduction in tubing size there. On the OEM Y, they reduced the tubing diameter prior to the flange, so that both merging tubes are the same diameter. The outlet is still only 2.25". When both legs of the URD Y-pipe are 2.25" each, and then go into an outlet of 2.25" it is easy to see the restriction point. If you add the cross-sectional areas of each leg of the URD mandrel bent Y-pipe, you will see that combined, they are actually larger than a single 3" tube's diameter. Thus again, the 2.25" flange outlet really impedes flow into the catback.

There have been a few to V-band flange the outlets of the headers. It is usually those that have to remove the y-pipe a lot though. The cost of doing so is fairly expensive.

A few others have cut the collectors of the headers back to a point where the diameter is 2.5", and run the Y-pipe from that point. I.E. the APR Y-pipe. However, on an N/A engine, you will loose exhaust velocity to soon, and in turn low end torque. So that is a better Y-pipe for boosted applications.

I can post up pics of that as well if need be.

 

Interesting, thanks for the info! I was more curious than anything, like I said, I don't think I'd have the balls to cut up a new $500 Y-pipe... yet

 

Took me a while myself. Until I actually spent the time to think about what was really going on. Now, I share.