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      12-28-2008, 06:39 PM   #1
JuniorM3
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Cool exhaust sound when just started

Can anyone tell me why the exhaust sound of our cars is cooler when we've just started it? (Cold start)

After 20 or some sec. it's gone.

There are no valves right?...

It's quite a big differance.
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      12-28-2008, 07:11 PM   #2
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Exhaust sound

Because it's cold.
Once the engine and exhaust warms up, the sound changes.
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      12-28-2008, 07:16 PM   #3
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Quote:
Originally Posted by pino9 View Post
Because it's cold.
Once the engine and exhaust warms up, the sound changes.
Mmmm strange. Because the sound change is sudden.
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      12-28-2008, 08:34 PM   #4
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I've noticed that too, but to me when it's cold it just sounds like a cammed up V-8 with a nice lope. When it's warm that lope is gone.
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      12-29-2008, 05:58 AM   #5
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I've been told that it runs very rich for a short time when cold to get the cats up to temperature in order to decrease emissions quickly.
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      12-29-2008, 06:01 AM   #6
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Initial warm-up of the engine.. after about 10-20 seconds it drops to normal idle.
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      01-01-2009, 04:54 PM   #7
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I foud out this noise is due to a "cold air pump" that runs for 10-20 seconds along with a load of fuel to warm the cats up.

Shame it doesn't sound like it all the time
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      01-01-2009, 07:55 PM   #8
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      01-01-2009, 08:20 PM   #9
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In the manual it says that on cold start up the engine may sound "metalic" Not sure if I'd call it metalic but does sound different at start up. The cold-pump and burning rich for cat heating does make good sence on why it'll sound like that. I actually like the sound after it has warmed up a bit as it prrrs a bit better IMO.
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