Just got my stillen y-pipe in about 2 days ago, and yesterday I noticed a strange noise under hard first gear acceleration. It seems to happen while hard accelerating from a stop in 1st. It kinda sounds like a scraping or rubbing noise. At first, I thought the screw that was holding the y-pipe to the frame was loose, but I just tried tightening it this morning and it's still tight. Also, I'm thinking it could just be the flex joint flexing. Anyone else have sounds like this?

 

Any ideas guys? I'd really like to figure this out, thanks.

 

In first gear only?

Y-pipe might be hitting the subframe. Make sure the y-pipe has at least 1/2" clearance from any part of the frame. If not, shim the pipe (loosen all the bolts, move the pipe and have someone retighten the bolts while you hold the pipe in place) or take a hammer to it.

 

I think I finally figured it out. There is an unused mounting bracket on the Stillen y-pipe that points straight up, and I believe that it was hitting the underside of the car everytime the engine flexed. Time to bust out the hacksaw.....
Thanks for the reply brianw

 

I had the same problem. What's happens is that during the expansion of the flex pipe under WOT the pipe resonates and hits the heat sheild which causes the scarping or pinging sounds. You can either bend the shield to give the pipe more clearence or remove it all together. I removed mine and it sounds perfect. Plus you don't need the extra weight

 

I just installed my y-pipe last night and I get the same WOT clank/groan. The upwards pointing flange does have a use, it connects to the rubber hangar but it is only about a quarter inch away from the metal to which the rubber attaches.