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      01-19-2013, 09:33 AM   #1
whiteM5
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Exhaust bypass on f10 M5

Anybody played with the idea of the exhaust bypass valve. I've seen systems on AMG's and various other cars, for off-road use only of course. But it would be a toggle switch that would be a side exhaust exit just aft of the downpipes. Real loud, no emissions.

Just curious what this would do to the car? For $8k on an akrapovic system I think my fabricator could mock this up nicely, with a nice button in the cabin to toggle between the two setups.

I assume this would throw a check engine light but would the car still run ok?

Thanks in advance.
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      01-19-2013, 11:54 AM   #2
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My son had this exact thing done on his M3, except the cutout is just before the mufflers. It cost him $500 total including the valves and switch, including labor to install and weld the valves in place. He did the wiring himself. Sound is awesome open. Better than my $7000 aftermarket system on my M3.

That being said, it does not create any horsepower like my system does. My full race exhaust system gives me about 35 HP. We dyno'd our cars with valves open and closed, and there was 2 HP difference on his car.
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      01-19-2013, 12:57 PM   #3
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I like this idea. I've seen it done on several V8 muscle cars but never a BMW much less an F10 M5. Very intrigued though. So who's going to try this first!
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      01-19-2013, 01:26 PM   #4
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Quote:
Originally Posted by cpiguy
My son had this exact thing done on his M3, except the cutout is just before the mufflers. It cost him $500 total including the valves and switch, including labor to install and weld the valves in place. He did the wiring himself. Sound is awesome open. Better than my $7000 aftermarket system on my M3.

That being said, it does not create any horsepower like my system does. My full race exhaust system gives me about 35 HP. We dyno'd our cars with valves open and closed, and there was 2 HP difference on his car.
So your car had 35hp over his car on the same day and same dyno?
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      01-19-2013, 01:36 PM   #5
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Valve after the downpipes? If that's the case on the F10 M5 you'll still have the cats (emissions) as they are in the downpipes, unless you gut them

Still, wondering about the sound and any HP increase.
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      01-22-2013, 01:13 AM   #6
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Not exactly sure how it would work on a f10, but the idea is to install cut out after the primary o2 sensors and before secondary ones. If you install them pre-o2 (primary) you ecu might go into limp mode. Electric cut-outs in the right spots will actually help a ton when it comes to a car with forced induction.
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      01-22-2013, 09:12 AM   #7
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im having a local tuner fabricate, we'll do pre and post dyno runs, give me a week or so and should have an update.
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      01-23-2013, 03:05 PM   #8
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Quote:
Originally Posted by whiteM5 View Post
im having a local tuner fabricate, we'll do pre and post dyno runs, give me a week or so and should have an update.
Do you know exactly where he is installing it?
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      01-23-2013, 03:25 PM   #9
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Cool. Hamann also makes a bypass kit.
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