This sound is normal right? - The Unofficial BMW M5 Messageboard (m5board.com)

nixter · 4th April 2006, 08:47

Hey guys,

In first, and the lower rpm portion of second gear the engine sounds somewhat "growly" if that makes sense. I'm pretty sure this is what it's supposed to sound like... right guys??

n

farrell · 4th April 2006, 09:55

Hi
I assume this noise is from coldstart.
If so, its the air injection pump forcing extra oxygen into the exhaust manifold to dilute the gases, improving coldstart emissions & pulling the cats up to operating temp.

This cold start calibration can be bypassed by blipping the throttle above 2,500 rpm & the growl of the pump usually goes.

My 2 cents

Farrell

nixter · 4th April 2006, 10:10

I'm familiar with that particular sound but no, that's not it. I'm refering to the slightly rough sound (compared to regular cars) that the m5 has coming off the line. It doesn't sound particularly bad or wrong, I think perhaps I'm just new to the car and not used to it.

n

Alan Archer · 4th April 2006, 10:12

acoustically the engine should sound no different in 1st and 2nd gear
compaired to the higher gears,
However perhaps you have some transmission noise in the lower gears.

The 280 getrag gearbox is quite sturdy, but with age displays a characteristic
whine...which tends to start through 1st and 2nd gear then progress with age
to 3rd.

Perhaps this is the background noise you're picking up ?

Or as Farrell states, it could be the emissions air pump from cold start.

Other low speed noises include the under engine shields and catalyst heat
shields vibrating...

regards,

Alan.

Sebring NL · 4th April 2006, 10:12

Quote:

Originally Posted by farrell

This cold start calibration can be bypassed by blipping the throttle above 2,500 rpm & the growl of the pump usually goes.

only on a 3.8 I believe by blipping throttle, haven 't really revved mine anywhere over 2900 when air pump is in use ( in order to prevent her from pulling under 2000rpm in 3rd one must make 2900 in 2nd) and the pump shuts off EXACLTY at the same place every day in same weather conditions, give or take a yard distance. It's not distance related, but I feel it is temperature related, as in summer it shuts off earlier .

Correct me if wrong, maybe mine is faulty?

nixter · 4th April 2006, 10:17

I know the air pump noise, not it. Could be the getrag, but I think it's probably just me. About the air pump, It's definately temp related. I had the car parked outside for the first time until 11pm when it was quite chilly. Pump stayed on for a good 3 minutes.

n

DookSD · 4th April 2006, 10:39

my guess is that it's normal. These beasties do sound a bit angry compared with your normal automobile.

vadas1 · 4th April 2006, 14:53

Quote:

Originally Posted by Sebring NL

It's not distance related, but I feel it is temperature related, as in summer it shuts off earlier .

Correct me if wrong, maybe mine is faulty?

I've read some where ( probably on M5 board ) that the pump comes in ( with a musical bong ) whenever the ambient temperature is below 30 C. Certainly in Rome in 2003 ( a hot summers day just after the Memorial Run )there was no bong when I started the car.

With mine I only have to blip the throttle ( 1100 to 1200 rpm for a brief second ) to get the pump to switch off.

ralph (vadas1)

Sebring NL · 4th April 2006, 15:20

Quote:

Originally Posted by vadas1

I've read some where ( probably on M5 board ) that the pump comes in ( with a musical bong ) whenever the ambient temperature is below 30 C. Certainly in Rome in 2003 ( a hot summers day just after the Memorial Run )there was no bong when I started the car.

With mine I only have to blip the throttle ( 1100 to 1200 rpm for a brief second ) to get the pump to switch off.

ralph (vadas1)

This is exciting. Like farrell said the objective of the pump is watering down the total amount of emission in order to bring down the poluting particles on a certain quantity. Your statement would mean that BMW thinks the engine emission gets more poluting when outside temp rises above 30 degrees.

I have never heard a bong connected to the pump.

I think mine will not come on at all when I leave the car standing for 12 hours in 30 dgr temp and start.

Blipping the throttle has never ended my pump's operation

I could make sense that the pump kicks in whenever the ENGINE temp drops below a certain point, still, driven even in cold conditions I doubt engine temp will be colder than startup and the following 2 minutes in Dutch climate. Might be different over where Jahangeer , Sakke , Donati etc live, but in UK and Holland, I 'd like to see that pump go on whilst driving in very cold conditions.

unesential · 4th April 2006, 15:24

IMHO it is normal engine sound you are hearing while accelerating thru the gears and when attaining speed you start to lift on the throttle reducing the growl.

I gave an explanation of pump operation sequence by the book in this post Air pump?