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Two exhaust questions...
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12-25-2014, 10:54 AM | #1 |
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Two exhaust questions...
Hey guys,
What are your thoughts/experiences on cold air working it's way backward into the engine with a muffler delete. My dad used to do this type of stuff all the time back in the day, and the one issue he ran into was cold air working back. What are your thoughts? Also, any recommendations for tips for a 328? I need to get some. Merry Christmas to the community! |
12-26-2014, 01:27 PM | #3 |
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How is cold air going to make its way back to the engine? When in motion the the exhaust fumes are pushed out under a good deal of pressure, so there is no way for air to get sucked back in. Tnd the exhaust system only pushes air out, while the intake pulls air in; so I don't understand how this could be a problem.
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12-26-2014, 01:30 PM | #4 | |
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12-26-2014, 01:39 PM | #5 |
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12-26-2014, 02:09 PM | #8 |
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Exactly what I'm planning to have done with the upcoming race exhaust install although with a Coast Fabrication muffled 4" tip and a slight turn down. Was assured the shop could modify the Aero bumper's diffusor to make the other side's cutout disappear, cool to see it done, thanks!
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12-26-2014, 02:23 PM | #9 | |
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Once I install my AA Headers I gotta see what my dB reading is with secondary cats and a resonator and go from there. Ideally I'd like to cut the pipe after the resonator and dump there, but since I'm driving to and from events I'll probably have a exit with a turn-down as well (perhaps adjustable depending on how close I am to sound so I can turn-down away from the mic...lol (SCCA Nationals we must maintain 95 dB at 100' IIRC) Also, this is relevant to our interests |
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12-26-2014, 02:34 PM | #10 | |
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328i here but changing to BMW Performance Aero bumper (not M Performance) with 335i diffusor for single pipe exhaust at the same time. Not very costly to close up the unused cutout. And I'm looking to keep the noise down to this level or lower as well. Using a 17" Coast Fab glass packed muffler without the secondaries. Built out of thinwall 304 from the headers back. Not sure if they'll fab the collector or just use one from Burns Stainless though. The muffled tip might not be necessary but it can't hurt I figure. An adjustable turn-down to turn-out to turn-away - there's a patent in there somewhere...
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2011 E90 328i 6MT, BMW Aero, CF hood/boot, PI+CAI+RM+3IM+BPC, SS+CI528+ThermoTec+SS#1+2XBurns, AKG 75D eng/trans, Al/Delrin diff/RS, CM 850, UCP, CAE, AKG DSSR, DiffsOnline 3.91 30/90 LSD+BW cooler, C&R, Setrab, Accusump, AST 3-way+Swift, Aurora PR+BW spherical, Vorshlag CPs, M3 brace+UR bar, ARC-8 18x8.5, 255 R1R, RB/CSL rotors+cooling, 135i calipers, RS29, RT700, Safecraft, OMP HTE-R+804F+QD Superquadro, 6pt cage+FIA, Braille, RT DL1Mk3
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12-26-2014, 06:12 PM | #11 | |
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Why do you need tips? Damage, changing the look, etc.?
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2011 E90 328i 6MT, BMW Aero, CF hood/boot, PI+CAI+RM+3IM+BPC, SS+CI528+ThermoTec+SS#1+2XBurns, AKG 75D eng/trans, Al/Delrin diff/RS, CM 850, UCP, CAE, AKG DSSR, DiffsOnline 3.91 30/90 LSD+BW cooler, C&R, Setrab, Accusump, AST 3-way+Swift, Aurora PR+BW spherical, Vorshlag CPs, M3 brace+UR bar, ARC-8 18x8.5, 255 R1R, RB/CSL rotors+cooling, 135i calipers, RS29, RT700, Safecraft, OMP HTE-R+804F+QD Superquadro, 6pt cage+FIA, Braille, RT DL1Mk3
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12-26-2014, 10:20 PM | #12 | |
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I'm considering a muffler delete. Thanks for the responses! |
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12-26-2014, 10:23 PM | #13 | |
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Sure you want to do a muffler delete? Backpressure will be lower but not all that much. It is the lowest cost solution though compared to straight pipe mufflers and single run build.
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2011 E90 328i 6MT, BMW Aero, CF hood/boot, PI+CAI+RM+3IM+BPC, SS+CI528+ThermoTec+SS#1+2XBurns, AKG 75D eng/trans, Al/Delrin diff/RS, CM 850, UCP, CAE, AKG DSSR, DiffsOnline 3.91 30/90 LSD+BW cooler, C&R, Setrab, Accusump, AST 3-way+Swift, Aurora PR+BW spherical, Vorshlag CPs, M3 brace+UR bar, ARC-8 18x8.5, 255 R1R, RB/CSL rotors+cooling, 135i calipers, RS29, RT700, Safecraft, OMP HTE-R+804F+QD Superquadro, 6pt cage+FIA, Braille, RT DL1Mk3
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12-27-2014, 08:25 AM | #15 |
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Here is the deal with the OP's question. Way back in the day (and I am talking way back) there were two prevailing thoughts; one was that cold air could warp exhaust valves and two, straight pipes could burn exhaust valves. Primarily this had to do with racers running open exhausts; and with respect to this post, once an engine is shut off, cold air (by means of a very short exhaust tract) could potentially find its way back into the engine and play havoc with a hot exhaust valve. But both of these thoughts, or should I say myths, have proven to be old wives' tales.
And even if these myths were to be true, in a modern BMW that cold air would have to find its way past not one, but two very hot catalytic converters, and a very warm exhaust manifold before reaching its final destination.
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12-27-2014, 11:50 AM | #16 | |
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2011 E90 328i 6MT, BMW Aero, CF hood/boot, PI+CAI+RM+3IM+BPC, SS+CI528+ThermoTec+SS#1+2XBurns, AKG 75D eng/trans, Al/Delrin diff/RS, CM 850, UCP, CAE, AKG DSSR, DiffsOnline 3.91 30/90 LSD+BW cooler, C&R, Setrab, Accusump, AST 3-way+Swift, Aurora PR+BW spherical, Vorshlag CPs, M3 brace+UR bar, ARC-8 18x8.5, 255 R1R, RB/CSL rotors+cooling, 135i calipers, RS29, RT700, Safecraft, OMP HTE-R+804F+QD Superquadro, 6pt cage+FIA, Braille, RT DL1Mk3
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12-27-2014, 12:09 PM | #17 | |
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Last edited by Tom Droze; 12-27-2014 at 02:29 PM.. |
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12-27-2014, 12:16 PM | #18 | |
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2011 E90 328i 6MT, BMW Aero, CF hood/boot, PI+CAI+RM+3IM+BPC, SS+CI528+ThermoTec+SS#1+2XBurns, AKG 75D eng/trans, Al/Delrin diff/RS, CM 850, UCP, CAE, AKG DSSR, DiffsOnline 3.91 30/90 LSD+BW cooler, C&R, Setrab, Accusump, AST 3-way+Swift, Aurora PR+BW spherical, Vorshlag CPs, M3 brace+UR bar, ARC-8 18x8.5, 255 R1R, RB/CSL rotors+cooling, 135i calipers, RS29, RT700, Safecraft, OMP HTE-R+804F+QD Superquadro, 6pt cage+FIA, Braille, RT DL1Mk3
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12-28-2014, 04:53 PM | #19 | |
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12-28-2014, 09:46 PM | #20 | ||
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12-28-2014, 10:37 PM | #21 |
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