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      05-22-2021, 05:15 PM   #1
Zack G.
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Can my N63 TU 650i always sound like it does during cold start?

I've got a Meisterschaft on my 650i and during cold start it sounds loud and mean (which I LOVE!).

Is there a way that the same exhaust note/sound can be made to stay even after cold start is over?!

Thanks!
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      05-22-2021, 09:21 PM   #2
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Quote:
Originally Posted by Zack G. View Post
I've got a Meisterschaft on my 650i and during cold start it sounds loud and mean (which I LOVE!).

Is there a way that the same exhaust note/sound can be made to stay even after cold start is over?!

Thanks!
Go with catless downpipes and intakes. It will always sound like it should then.
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      05-25-2021, 12:01 PM   #3
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Originally Posted by AccordTR View Post
Go with catless downpipes and intakes. It will always sound like it should then.
But will doing that make the exhaust note sound like “cold start” constantly?
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      05-25-2021, 12:41 PM   #4
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Quote:
Originally Posted by Zack G. View Post
But will doing that make the exhaust note sound like “cold start” constantly?
Yes.

Easier to just "zip tie" the exhaust flaps in the tailpipe in the open position.
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      05-29-2021, 12:38 AM   #5
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Quote:
Originally Posted by Walt White Coupe View Post
Yes.

Easier to just "zip tie" the exhaust flaps in the tailpipe in the open position.
The zip tie method keeps the flaps open, but it does not make the car sound like a cold start every time. My valves are zip tied but it still only "cold starts" when its cold.
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      05-29-2021, 04:10 PM   #6
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I could be wrong but I think only two things happen in a cold start. The engine idle speed is kicked up for 30 to 40 seconds and the exhaust flaps are opened.
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      05-29-2021, 08:14 PM   #7
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This may not be valid on N63 cars but I suspect it is the same. On S63Tu cars the turbo wastegate flaps are completely open to get as much heat as possibly into the Catalytic Converters. Once they are up to temp the wastegate flaps shut which coincides with the rpm reduction back to normal idle level.
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      05-29-2021, 08:33 PM   #8
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Quote:
Originally Posted by Walt White Coupe View Post
I could be wrong but I think only two things happen in a cold start. The engine idle speed is kicked up for 30 to 40 seconds and the exhaust flaps are opened.
I think that in addition, the mixture is run slightly richer to heat up the catalyst quicker.

quote:
The purpose of the secondary air system is to perform exhaust re-treatment during the engine warm-up phase. During this process, fresh air is blown directly into the exhaust manifold thus increasing the rate at which the catalytic converter is heated (thermal post-combustion of exhaust gas)
end quote

This might contribute to the loader sound during that initial cold start
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      05-29-2021, 09:36 PM   #9
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Bootmod3 lets you choose when the exhaust flaps are open. To be fair, it wont always sound like a cold start, but i have mine set up so that in sport or sport plus the exhaust valves are 100% open, but in comfort they follow the factory settings. That way the exhaust is loud when i want, and quiet when i dont. I did fit the M6 mufflers though, so it is always a bit louder than stock.

If you are running aftermarket exhaust with out the valves, as others have said, catless down pipes are what you are looking for.
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      05-30-2021, 02:32 PM   #10
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No option to keep the sound of the car like during cold-start while idling.
I have even asked custom tuners if this would be a valid options but no one is able to do that.
I think the cold-start table is hard-coded, you cannot change the duration or the behaviour (like cold-starting again with the engine at temperature). You can only enable or disable this feature and set the rpm (with bm3).
As mentioned, the car runs slightly rich in cold-start.
Also no one is able to increase the rpm idle (the lovely sound you are hearing is the sweet-spot between 1500 and 1800 rpm when there's a little bit of drone.
Would be great to have this rpm range as the normal idle (just from an acoustic stand point, not sure if it does stress the engine)
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      06-02-2021, 05:04 AM   #11
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I thought the cold start sound was down to the EGR valve (exhaust gas recirculation valve) recirculating exhaust into the inlet manifold until the engine temperature reaches the required level....
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