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      09-06-2012, 04:17 PM   #1
E30 Racer
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Aftermarket midpipe to OE catback question

Presumably, the post-merge aftermarket pipe diameter is larger than that used by BMW. How does this affect the ability to join them without replacing the coupler on the catback side?
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      09-06-2012, 06:14 PM   #2
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I'm not sure if I fully understand your question but every aftermarket mid pipe I've seen is same diameter and bolts straight on to oe exhaust. The changes are usually the removal of the cats and/or the resonator. Not a change in diameter.
Hope this helps.
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      09-06-2012, 07:55 PM   #3
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This is not the case for Akrapovic. The base OD if their gasket (i.e., at the small end of the taper) is nearly as large as the maximum diameter if the OE flange. No way I'd get a reliable seal.
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      09-16-2012, 12:23 PM   #4
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It's odd that you have this issue. I found that usually when it's bigger diameter, they end up being tappered down when it gets closer to the flange. Does this happen to your Akrapovic?
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      09-17-2012, 08:39 PM   #5
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Quote:
Originally Posted by dlai
It's odd that you have this issue. I found that usually when it's bigger diameter, they end up being tappered down when it gets closer to the flange. Does this happen to your Akrapovic?
Unfortunately that is not the case here. In their defense, I doubt Akrapovic ever intended their midpipe to be used with anything but their axle back exhaust, whose inlet is quite a bit larger than that used by BMW or many aftermarket offerings. Oh well, I'm having Burns Stainless fabricate an adapter.
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      10-19-2012, 10:52 PM   #6
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Update: the adapter from Burn Stainless arrived today. I designed the part, sent them the Akra midpipe with a new new graphite sealing gasket, and they fabricated it. As always, their quality was outstanding, with welds that could pass for robotic. Assembly was uneventful, although I'd like to find some springs that will allow me to use the OE flange bolts.









I'll post a sound clip soon, but my initial impression is that cold start, idle, and revving aren't that much louder than stock. Since I haven't actually driven the car, I cannot comment on interior volume at speed or drone yet.
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      10-28-2012, 04:35 PM   #7
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On ramps, but the sound is pretty accurate.


Last edited by E30 Racer; 10-28-2012 at 04:55 PM.
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      10-28-2012, 07:54 PM   #8
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Quote:
Originally Posted by E30 Racer View Post
On ramps, but the sound is pretty accurate.

Like you've mentioned before what I hear from this clip is not too different than the stock soundwise, just a notch louder. Definitely closer to a N55 mid sound than a Maddad. More burbles.
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