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      08-03-2011, 07:08 AM   #1
bmw13
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Question EXHAUST VALVE LIKE 135i? Golf Tee Mod?

I noticed that the stock 1M exhaust gets extra loud all of a sudden around 2200-2300 RPM. I recall this happening on all N54's and there being a exhaust flap/ valve in which opens around that RPM range. As I did the golf tee mod on my last car I quickly found myself under the car looking... and I found nothing similar to that system. Are all four open? If all four really are open, there has to be a valve somewhere in which his suppressing the sound, if anyone knows the source of this low rpm restriction, please do tell. I strongly feel this will give me that close to stock purr a lot of us are looking for.
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Last edited by bmw13; 08-03-2011 at 07:19 AM.
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      08-03-2011, 09:04 AM   #2
KIYO
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I have noticed the same thing.

For the first one or two minutes when I start the engine, it is also loud.
After that, it becomes rather quiet.

I have no idea what is controlling that loudness.
I also want to know how to keep it loud all the time.

Last edited by KIYO; 08-03-2011 at 10:15 AM.
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      08-03-2011, 09:07 AM   #3
IZAGLO
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There is a flap and ATM the JB4 has a function that can leave it open..

Sorry...i was thinking 135i...
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      08-03-2011, 09:09 AM   #4
marcel b
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The exhaust on the 1M does not have a valve (mentioned in an interview)
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      08-03-2011, 09:13 AM   #5
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Yes, exhaust is louder upon start-up. I suspect it's due to a cold-start feature (likely to quickly heat-up the cats), but haven't yet looked into it.

I like the throatier exhaust note and would like to retain it even once warmed up.

Neil

Last edited by MDORPHN; 08-03-2011 at 09:39 AM.
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      08-03-2011, 09:55 AM   #6
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Quote:
Originally Posted by marcel b View Post
The exhaust on the 1M does not have a valve (mentioned in an interview)
1) Can we confirm this? I hope not...

2) I wasn't referring to start up. Cold start is always louder When normally driving, if you slowly accelerate from 2000-2500 you will notice a big jump in drone noise especially around 2200. I want more of that deep drone noise to exist under 2200 not just above. There definitively is something keeping it quiet in those low rpms, there has to be, for such a change in sound so quickly.
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      08-03-2011, 10:19 AM   #7
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I think it is controlled by some formula.
I am monitoring the engine load and the RPM.
I found out that if the engine load is low, it doesn't get louder at around 2500RPM.
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      08-03-2011, 10:28 AM   #8
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What happens if you go catless? Secondary or both?

Quote:
Originally Posted by KIYO View Post
I think it is controlled by some formula.
I am monitoring the engine load and the RPM.
I found out that if the engine load is low, it doesn't get louder at around 2500RPM.
This is a good point. So it does not just depend on RPM, but also which gear you are in and the speed in which you are traveling at...

I wonder what the loss/ gains would be to going catless or secondary catless. I am very tempted, I just do not know enough to make the educated decision. Will I lose power? Would I gain power? Is it more complicated than that? Does BMW have a special formula to make the cats work in junction with everything else? What is truth in this matter?
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      08-03-2011, 10:39 AM   #9
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Most performance exhausts are loud at cold start up. The 1M does NOT have an exhaust flap. Check realoem.com if you don't believe it. The flaps that are found on some BMW models are all vacuum controlled. The additional sound is exhaust drone which is usually louder under load.
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      08-03-2011, 10:55 AM   #10
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A source has been provided, no vaccum hose on 1M!

Quote:
Originally Posted by bdaddylo View Post
Most performance exhausts are loud at cold start up. The 1M does NOT have an exhaust flap. Check realoem.com if you don't believe it. The flaps that are found on some BMW models are all vacuum controlled. The additional sound is exhaust drone which is usually louder under load.
It is not that I do not believe, I just wanted to confirm before I keep looking for a vaccum the doesn't exist lol thank you very much for providing a source it is much appreciated .

I guess the next issue would be catless vs stock...
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      08-03-2011, 12:29 PM   #11
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+1. The 1M does not have a flapper.
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