The borla catback should be meant to couple with the stock midpipe which has a rounded flange at the end of the pipe. I guess the easiest way to explain it is the picture in your second post imagine a round lip that is on top of the surface.

You are probably going to need to take the parts to an exhaust shop to have a flange made that will bolt up to the downpipe.

IMO I would replace the flange on the borla unit because it will be cheaper but ask the guy because I might be wrong.

 

i also would get the flange replaced on the borla. have a competent muffler shop weld on a flat flange to hook up to the helix down pipe.
as for what kind of flanges after market down pipes use, i think most or all use a flat style flange.

 

The Borla hush system is designed to mate up as a catback to the stock system thus using a doughnut gasket to connect it.

There are a couple of ways to connect the Borla hush to a aftermarket downpipe.

1) Reverse the stock doughnut gasket (not something we have done or would recommend)

2) Cut the piece protruding through the flange on the Hush system flush and weld the flange so it does not move.

3) Replace the last 2" of the Borla hush flange section with striaght 3" piping and weld a 3" flange on.

I hope this helps and sorry that information has not been made clearer sooner.

Mike

(510) 487-4447
www.mpjperformance.com
www.gb-motorsports.com

 

how about if you get a mid-pipe that connects both flanges of a Bosal downpipe and Borla Hush

 

the donut style flange is for flex. I've noticed that alot of aftermarket DP and/or TBE don't account for flex.

If I had the hust cat back adn my DP didn't have a flex section. I would try to get the DP "fixed" to match the hush catback. you want the flex.

 

I am looking at getting a hush and then an aftermarket dp in the future also. I've heard that the PDE dp matches with the hush. Oh and if you weld a new flange onto the hush wouldnt it void the million mile warranty because you changed the product?? - Justin

 

Kind of off-topic but do some DPs replace the stock midpipe and some don't? Just looking at pics some look longer than others or am I totally off? Basically if you go cat-back + dp are you removing the 3rd cat altogether or is it brand dependent?

 

^^^ you're correct about the DP. some aftermarket replace the stock DP+cat pipe.

for example the bosal DP only replaces the stock DP. so if that is your only mod, then you keep the stock 3rd cat pipe and cat back.

the helix for example replaces both upto the catback.

 

Cool thanks, makes sense now. I had a shop do mine *hides in shame* but I will do my own UP to make up for that.