NefMoto > Technical > Tuning > Why is coldstart on V8/V10 (MED9) so loud but warmstart not?
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Author Topic: Why is coldstart on V8/V10 (MED9) so loud but warmstart not?  (Read 4481 times)
black
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On coldstart the cars are pretty lound and after a minute, they go to "silent mode"

I allways thought, the reason for that is that the exhaust gas flaps are open on coldstart and beeing closed after a minute or so.

But, after using an endoscope its clear, the exhaust gas flaps are staying open, while the exhaust sound is getting silent.

On warmstart, sound is silent almost from the beginning.

So I suspect the cold start ignition angle + maybe camshaft angle for that sound behaviour!??

Any opinions?
« Last Edit: May 15, 2017, 11:24:40 PM by black » Logged
KasperH
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« Reply #1 on: May 15, 2017, 11:45:59 PM »
It's a combination of ignition retard for idle stability(and cat heating?) Raised idle speed and valve timing overlap for cat heating Smiley

I have remove all the cat heating/emissions stuff since I don't have a cat, and it sounds pretty much the same on cold and warm start. Maybe a little louder on cold Smiley
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black
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« Reply #2 on: May 16, 2017, 01:40:19 AM »
Quote from: KasperH on May 15, 2017, 11:45:59 PM
It's a combination of ignition retard for idle stability(and cat heating?) Raised idle speed and valve timing overlap for cat heating Smiley

I have remove all the cat heating/emissions stuff since I don't have a cat, and it sounds pretty much the same on cold and warm start. Maybe a little louder on cold Smiley

Thanks for reply - after reading FR now I came to the same result.

idle:
KFNWLLA -24.0
KFNWLLE +16.0

coldstart:
KFNWKHA +5.0
KFNWKHE -0.0
TKHMX 60s
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prj
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« Reply #3 on: May 16, 2017, 09:43:22 AM »
Disable cat heating and SAI and it will go away.
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black
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« Reply #4 on: May 16, 2017, 10:32:15 AM »
Quote from: prj on May 16, 2017, 09:43:22 AM
Disable cat heating and SAI and it will go away.

thanks for confirmation  Smiley
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