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      11-14-2015, 11:07 AM   #21
grayforge
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Drives: 2008 E90 335xi
Join Date: Sep 2014
Location: Seattle

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I installed AA Catless Downpipes and was disappointed. The right DP did not fit properly: the lower flange was twisted a few degrees, not allowing the bolt holes to line up.

Initially, AA swore that this couldn't happen since they use a jig for fabrication and final testing, but when I showed them photos of the misalignment in the car and compared with the stock DP on a bench, they were quite gracious and paid for me to ship the pipe back to them next day air, then turned it around in a day for Saturday delivery back to me.

It turns out that there is a significant gap between the downpipe flange and their jig's holes, so there's more play for getting bolts installed on the jig than in the actual stock system. Also, I wish they used studs or at least welded the bolts onto the flange to make install easier. It's a royal pain to hold those bolts in place within the tight confines under the car. I finally dropped the stock exhaust and bent a box end wrench to get access to those bolts for tightening.

Alas, the repair shortened the pipe by 3/16" or so and it wouldn't quite fit length-wise. Tiring of having my X5M on jack stands, I managed to get it to fit without leaks after a couple attempts by installing 2 stacked gaskets that I luckily had laying around that fit perfectly. These went between the DP flange and transmission bracket, taking up the gap that the shortened pipe caused.

A final fitment issue was the little heat shield cups that the O2 sensors fit into that help seal in the heat under the heat shielding. The O2 bungs were too far below the heat shield for the cups to reach. I ended up grinding the lip off the 2 cups so they would slip deeper down into the heat shield.

Oh, and their instruction manual (as of when I installed the system) was specific to the N63, not the S63 and had some errors to boot. I mentioned these to them, so hopefully, they'll update the manual.

Results: I'm sure there's better response and power potential since turbos love bigger pressure differentials. It's got a loud, raspy cold start sound that I'm slightly embarrassed at, but sounds nice once past this. I might have considered a resonated version knowing this.

So while I managed to get the DPs installed without leaks, the process was too painful. I'd go with AR if I were to do it again.


DP alignment issue in the car:


Flange alignment compared to stock:
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