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also stops instantly if you roll down the windows,
That is very strange. The cabin is vented in the trunk or at least should be. Anyway sounds like one of those issues reported when pipe length is wrong. Clearly the trapped air seems to be the amplifier or I guess boom box? Interesting to say the least.
 

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Discussion Starter #22
I’d guess lowering the windows effectively changes the volume of the cabin “box”, which would change the frequency at which it resonates.

Anyhow with the new mufflers seems I don’t need to worry, but I am hoping the Magnums are loud enough, the race ones sounded really good on this setup, but I already ordered the magnums before I had any clue I could test the race ones!
 

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100% the exhaust. Mounted supersprint race cans my shop pulled off another m5 and let me borrow until my magnums come, and it’s fixed. It is the low end frequency the dianan exhaust makes, it is the correct frequency to resonate the cabin with windows up. Again if you sat in the car you’d know- it actually resonates you inside the cabin, also stops instantly if you roll down the windows, you can do it while holding 800 rpm (clutch in or out doesn’t matter).

I guess that’s the difference between buying and exhaust from an exhaust manufacturer who makes complete systems for the car vs a tuner who had mufflers made by someone else 20 years ago for a package car. Also a company that the owner sold and is no longer a part of. Really what’s Dinan without Steve Dinan?

To be fair, maybe the Dinan exhaust works great with the Dinan headers and factory cats, I can’t expect the same type of sound with different headers and cats from the original application.

Agian all motor, tranny, diff mounts, guibo, driveshaft have about 4K on them. CSB perfect. Exhaust hangers have less than 6k on them. Car has 72k. It’s perfect now, hope the magnums I ordered are loud enough because the race are pretty seeet.
Thanks for circling back with results. I have the Dinan parts sitting in a box waiting for me to get off my butt.

Dinan actually made their own exhaust in house before they were sold. The company is definitely not the same though without Steve.
 
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I’d guess lowering the windows effectively changes the volume of the cabin “box”, which would change the frequency at which it resonates.
The vents should allow for that, but there is resistance in the vents and the vents only work one way, out. Maybe you should check your vents just to be safe. In many a car they have been removed then re-installed backwards. Seems to be that common sense tells people to try and let air in rather than out. Some even find them and switch them around just because of that logic. If you find dirt in the space near the vents they are likely backwards. Of coarse the resonance might be released on the vacuum side of it. Again very interesting situation.
 

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Discussion Starter #25
Dinan actually made their own exhaust in house before they were sold. The company is definitely not the same though without Steve.
Ah I always assumed they contracted that, cool. I’m not knocking the product in any way, just noting that I might have a different outcome in sound quality in matching the Dinan exhaust to SS headers and cats than they had when making the exhaust for their S line of M5s (with the Dinan headers).
 

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Discussion Starter #26
Magnums are on- and might be too quiet. Dammit. Before I go swapping these though I’ll wait for the SS x-pipe to arrive. I guess if that setup is too quiet I’ll swap to the race mufflers. Never ends...

Monday I’ll finally be flashing the ECU for the headers and sport cats.
 

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Hmm, I love the deep boomy bass of the low rpms with my Dinan exhaust... I do have a rogue X pipe now, but the low RPM bass boom was there before I installed the X pipe. If things are rattling that piss you off because of the boom, fix them tighter so they stop rattling! I am SURE the people behind my car love it even more than me, OH I WISH I COULD LIVE BEHIND MY CAR WHEN I DRIVE IT!
 

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Here's a little bit of my low rpm boom you can hear when I start to take off, son sitting in passenger seat. This was right after I installed my new Eventuri Intakes, had already previously installed the Rogue X pipe and Dinan rear section. Yes I get a lil excited in the end HA!

 
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