This Megan downpipe and Random Technology 3" catalytic converter, plus the midpipe from the SRS catback system went for a little trip to the the welder with me last weekend. The results turned out pretty great! Look inside for a build video.
Let's start with the Megan downpipe I purchased off of Amazon. I had to buy a new downpipe because the stock original piece was rusted and cracked through. I should have guessed this would be the case when I pulled out the stock catback, which was rusted through at one of the hangers which had broken off and taken a 1" X 2" piece of the pipe wall with it. So of course the front part of the exhaust would be rusted through too! Because I found a pair of 3" cats on my local craigslist for a pretty good price, I was going to have to do some fabrication work. This would include splicing one of the big cats into the 3" midpipe from the catback system which would place the new cat pretty close to the stock position. Then I had to shorten the new Megan 2.5" downpipe to make room for the longer catback midpipe.
The 3" SRS midpipe (the section all the way to the right in the photo above) has a neckdown to 2.5" at it's inlet. This pretty closely mates up to the stock catalytic converter, but I believe is meant to mate up to these Off Road downpipes that eliminate the catalytic converter like the Megan Racing piece that I bought. I, though, wanted to retain a cat and since I wasn't able to find a downpipe that retained the stock cat at a reasonable price, new that I was going to have to do some fabrication anyway...so putting in a high flow cat seemed like a good idea anyway!
So yeah, I took all three pieces to a local welder familiar with stainless steel and explained how I wanted them cut and welded back together. I feel like he did a fine job, but some of the welding professionals had a lower opinion of the job stating that the insides of the pipes should have been purged of oxygen (what the gas flow does at the tip of the welder), too. Lots of other welders have said that purging the inside would have been overkill and after learning about the process I fall on this side of the fence. Yes, I believe that if the inside had been purged, the welds would have probably been absolutely perfect inside AND out...but I feel like they are still going to outlive the rest of the car!
Here's the finished product. My fabricator, Sully, did a great job of measuring the correct amount to remove from the downpipe to make up for the addition of the Random cat to the midpipe. While doing this he had to also make sure that he kept all the flanges clocked to their original positions. I didn't drive the car over to his place so keeping everything lined up was paramount. We didn't have the luxury of test fitting any of this...and yet, it all bolted up perfectly! Those of you who have mounted an ill fitting catback know that you only have a tiny amount of tolerance between the piping where it crosses over the rear crossmember. If that fit is off by even a tiny amount, the pipe will contact the body or the crossmember causing awful sounds. No such problems here, happy to say! Anyway, check out the video if you like to watch stuff getting built.