only difference with OEM "sports muffler" is cosmetic

1387 Views 11 Replies 4 Participants Last post by 31st330i, Mar 31, 2002

31st330i

Discussion Starter · Mar 25, 2002

I finally got an answer to this thanks to my local parts manager who called BMW (and I suppose spoke with the district parts manager or a deligate).

apparently the sports muffler has black tips and costs $5 more - that's it.

Fred Meloan did tell me (after checking with his parts guy) that all US cars already have the sports muffler but this didn't jive with me since the ETK showed that there were two additional parts required, a vacuum plug and a tie strap.

so now we know.

oh well, at least the OEM muffler is already a straight through design.

okay, so now I'm thinking about removing the resonator or replacing it with the supersprint straight through resonator.

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Jspeed

· #2 · Mar 25, 2002

So I suppose we can just disable the flap ourselves and essentially get a "sports muffler"? BTW does the flap exist for noise reduction or torque production?

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31st330i

Discussion Starter · #3 · Mar 25, 2002

well, you can disable the flap by unplugging the vacuum line, plugging it then tying it off. I'm pretty sure you won't make any power, though.

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Jspeed

· #4 · Mar 25, 2002

I'm pretty sure you won't make any power, though.

Who said I expected any power gain?

I just don't want any power *loss*. I'm only thinking of disabling the flap for the sake of more aggressive sound.

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31st330i

Discussion Starter · #5 · Mar 25, 2002

I think it may only close durring decel so I doubt there will really be that much of an effect on sound *outside* fo the vehicle. on the other hand, interior resonance will likely increase.

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JK

· #6 · Mar 26, 2002

If the Bentley Manual is correct, the valve is closed only at idle for noise reduction. If you have a friend slowly bring the revs up from idle, you should see the flap open.

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31st330i

Discussion Starter · #7 · Mar 26, 2002

mine stays open at idle and every other 330 that I've been behind at a stop light had the valve open as well (lots of 330's in this area).

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JK

· #8 · Mar 26, 2002

I just read in this month's Automotive Engineering that the new 7 has the same flap arrangement in one pipe that is closed up to appro 2200 RPM. How can you tell the guy in front's flap is open - by the vapor coming out of both pipes? Maybe the flap doesn't close completly.

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31st330i

Discussion Starter · #9 · Mar 26, 2002

it's near the end of the tail pipe so it would be visible if it were closed.

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ChetG

· #10 · Mar 31, 2002

31st330i,

Ive always been curious about the exhaust valve thing. I think the sound of the exhaust with holes open is too boomy and tiresome, not sporting in any way, just horribly boomy, and also creates significant resonance in the cabin which detracts from the engines smoothness. I was wondering if there was any way to remedy this (keep valve closed??), and not loose any power/torque. Does the mechanism work in any way to improve power, or is it purely for acoustic purposes.

thanks in advance.

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ChetG

· #11 · Mar 31, 2002

and also, is the OEM muffler just a dummy box with straight pipes going strait through, i.e. there is no sliencing effect at all from the back box??

thanks again.

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31st330i

Discussion Starter · #12 · Mar 31, 2002

nope, you have to leave it as is.

ChetG said:
31st330i,

Ive always been curious about the exhaust valve thing. I think the sound of the exhaust with holes open is too boomy and tiresome, not sporting in any way, just horribly boomy, and also creates significant resonance in the cabin which detracts from the engines smoothness. I was wondering if there was any way to remedy this (keep valve closed??), and not loose any power/torque. Does the mechanism work in any way to improve power, or is it purely for acoustic purposes.

thanks in advance.

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