SMG pump: can you hear it running when driving?

[sapote]

I can hear the pump running and stopping when park the car, but can't tell during driving. I just want to have a sense of how long the cut off time during driving between the running periods. Long cut off time means very low internal leaking and still good Accumulator.

Wanted to convert to manual but have no time yet.

[PowerSax]

Mine is the same way. Quickest way to measure pump /accumulator health while driving is INPA. Best to have a second person. One set of eyes on the road, and one on the laptop.

[sapote]

Funny I can hear clearly when driving my 1973 Citroen SM when the pump cut off at 180bar (2600 psi) for about 2 to 3 minutes before it running again. The hydraulic in the Citroen runs steering rack, 4 suspension corners, brake system (it also shift gears for the DS cars with sort of "SMG tranny" with no computer back then).

I guess the higher pressure causes higher noise in the pump.

[domibln]

There is a test procedure in Inpa / ISTA-D for evaluating the pressure accumulator. This is much more accurate and reliable than the test with measuring the intervals.

As for internal leaks, you measure the intervals between the pump cycles when the car is parked, SMG in neutral and engine running. The system should hold pressure for at least 60 seconds, 2-3 minutes would be better. It makes no sense to measure the intervals while driving, because depending on the driving style, traffic conditions, route, etc., the SMG is constantly working and consuming pressure. Such a measurement would be rather subjective and meaningless.

[jayjaya29]

I have an AA catback exhaust and I cannot hear the pump while driving.

[Pnick]

When I had my M3...the only time I heard it running for a short period was when unlocking the door (waking from hibernation). Any other time I couldn't hear it cycle. Sadly, I lost my love in March 2020 the beginning of Covid.

[Shonky]

Can't hear it driving and as noted it will vary depending on usage.

Note that there are a couple of codes it can throw for taking too long to gain pressure and/or frequency ie being needed too often.

[sapote]

When I had my M3...the only time I heard it running for a short period was when unlocking the door (waking from hibernation).

I don't understand why the engineers had the pump priming when the trunk lid opened. This drains the batt and wear on the pump for no reason.
As about pump priming when doors opened, this feature should be a convenient option and can be coded out instead of a hard code. Anyone had it coded out?

[Pnick]

I don't understand why the engineers had the pump priming when the trunk lid opened. This drains the batt and wear on the pump for no reason.
As about pump priming when doors opened, this feature should be a convenient option and can be coded out instead of a hard code. Anyone had it coded out?

That was my concern when I first acquired mine considering every cycle wears the bloody brushes/commutators. I used to do electrical motor rewind so I knew then...SMG pump was my biggest worry at first and was hesitant to drive it out of state and had to grow some cajones to do so. Thankfully it was a pleasant experience 'til I lost it (05 IB, Cinnamon, Competition-slick top).
Am not aware of coding it out but, I would consider it a very good idea or have a temporary deactivating switch much like I have on the start/stop function of my 19 Audi A5 (I don't know if all other manufacturers' start/stop have it). This way if you're doing maintenance it won't cycle over and over to re-pressurize the system.

[Shonky]

Think how many times it cycles because you open a door or something. With ignition off it will only do it when a door/boot/bonnet opens/closes/unlocks. If ignition is on then it will keep running every few minutes or whatever (as it would if driving without changing gear presumably)

Now consider how many times you change gear and how long you actually are driving. A few extra cycles on the pump is not worth worrying about to me.

That said I do agree for something like a boot or bonnet I don't see much point in triggering it. They just want enough pressure so it can get in to neutral immediately when you start and not have to wait the 10 or so seconds to pump up. It won't start in gear anyway. So you just have to wait for it.

[eacmen]

For me I don't like the pump priming constantly as the car sits in the garage and it will kill the battery.

[sapote]

Am not aware of coding it out but, I would consider it a very good idea or have a temporary deactivating switch much like I have on the start/stop function of my 19 Audi A5 (I don't know if all other manufacturers' start/stop have it). This way if you're doing maintenance it won't cycle over and over to re-pressurize the system.

Good idea here. I also can use this hidden switch to fool the thieves. Recently someone posted on Fanatics of his E46 M3 was stolen, they bypassed the EWS to crank the engine and it seems either swapped out the DME or updated it with EWS delete software and drove away.

[sapote]

Now consider how many times you change gear and how long you actually are driving. A few extra cycles on the pump is not worth worrying about to me.

But the batt is discharged every time this high power pump running.

[jayjaya29]

But the batt is discharged every time this high power pump running.

The pump doesnt run continuously when the trunk is opened. It only runs for 8 to 10 seconds to prime the system. The battery has more then enough capacity for the pump to prime numerous times and still be able to start the car.