Cool exhaust sound when just started

JuniorM3 · 12-28-2008, 04:39 PM

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.

pino9 · 12-28-2008, 05:11 PM

Because it's cold.
Once the engine and exhaust warms up, the sound changes.

JuniorM3 · 12-28-2008, 05:16 PM

Quote:

Originally Posted by pino9

Because it's cold.
Once the engine and exhaust warms up, the sound changes.

Mmmm strange. Because the sound change is sudden.

VictorH · 12-28-2008, 06:34 PM

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.

swamp2 · 12-29-2008, 03:58 AM

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.

William Blake · 12-29-2008, 04:01 AM

Initial warm-up of the engine.. after about 10-20 seconds it drops to normal idle.

biscuits · 01-01-2009, 02:54 PM

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

Oakleyguy · 01-01-2009, 05:55 PM

+1

BimmerRob08 · 01-01-2009, 06:20 PM

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.

12-28-2008, 04:39 PM	#1
JuniorM3 Captain 134 Rep 204 Posts Drives: BMW F13 M6 CP GT3 Join Date: Dec 2008 Location: Ethiopia iTrader: (0)	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, 05:11 PM	#2
pino9 Registered 2 Rep 3 Posts Drives: 2009 BMW E93 M3 Convertible Join Date: Dec 2008 Location: Brisbane QLD Australia iTrader: (0)	Exhaust sound Because it's cold. Once the engine and exhaust warms up, the sound changes.
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12-28-2008, 06:34 PM	#4
VictorH Major 433 Rep 1,286 Posts Drives: '09 M3 Join Date: Dec 2007 Location: SC iTrader: (4)	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, 03:58 AM	#5
swamp2 Lieutenant General 611 Rep 10,407 Posts Drives: E92 M3 Join Date: Sep 2006 Location: San Diego, CA USA iTrader: (3)	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, 04:01 AM	#6
William Blake Private First Class 4 Rep 105 Posts Drives: 08 MINI Cooper S Clubman Join Date: Nov 2008 Location: Europe iTrader: (0)	Initial warm-up of the engine.. after about 10-20 seconds it drops to normal idle.
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01-01-2009, 02:54 PM	#7
biscuits Dimmer than a dim thing 80 Rep 1,291 Posts Drives: M4 GTS, EQC, X5 40d, simrig Join Date: Oct 2008 Location: UK iTrader: (0) Garage List 2016 BMW X5 (F15) 4 ... [0.00] 2016 BMW M4 GTS [10.00]	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, 05:55 PM	#8
Oakleyguy Resident Engineer 135 Rep 748 Posts Drives: Land Cruiser Join Date: Oct 2008 Location: Denver, CO / Tulsa, OK iTrader: (0) Garage List 2014 Toyota URJ200 [0.00] 2017 BMW M2 [0.00] 2015 BMW M4 [10.00] 2005 Toyota UZJ100 [0.00]	+1
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01-01-2009, 06:20 PM	#9
BimmerRob08 Major 110 Rep 1,311 Posts Drives: 2008 M3, Space Gray Join Date: Mar 2008 Location: KIKR (ABQ), NM iTrader: (0)	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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