ASR- doesn't stop one wheel spinning away the power!

[stevesey]

After 2 days with no snow issues - I got stuck on my drive twice at the weekend - most suprising becuase it's flat - well that's flat apart from the depressions in the gravel where the car sits.

I'd parked 9in to the left of where the car was went it snowed, so the passenger side was on snow/ice and in the drip. Drivers wheel was on tarmac (other 3 on the gravel). Started car, put it in reverse, feet off the pedals, ASR cuts as the passenger rear slowly rotates. Tried W, tried some gentle throttle, ASR off, but id didn't want to come out of the depressions. Got out and chucked a handful of loose gravel under the tyre and it rolled out no problem. After the second time, I got the yard broom out and swept the gravel to level the drips.

Anyway to the point, I questioned myself afterwards, why wasn't the ASR dabing the brake on the passenger rear and allowing the power to go through to the drivers wheel, which being on tarmac would have pulled the car out. The ASR does dab the brakes on a spinning wheel (and cut the throttle) doesn't it? Or does it just cut the throttle? Or was the cycle happening too quickly/aggressively that there was never enough power going to the other wheel?

Apart from this, when moving, the ASR has been excellent in the snow any slight rear end twitches are bought rapidly under control, with only a little input from me to correct the direction the car is pointing in. In just doesn't seem to cope with being stationary with one wheel on ice the other on tarmac - which I guess in understandable, as it's a fine balance between not allowing the car to move off because the brake is applied to hard to the "spining" wheel, and not applying it enough to allow power to go to the other wheel.

 

[wemorgan]

some info from MB:

Mercedes-Benz - Transporter Safety Special - Vehicle - Drive stability - ASR

'Giving your wheels real grip
Acceleration Skid Control (ASR) is, like ABS, EBV and BAS, a component of the Electronic Stability Program ESP®. In an abrupt take off on a wet or loose surface, ASR prevents wheel spin, thereby also ruling out any sideways drift. The brakes are automatically applied to individual wheels and the engine output is reduced, thereby markedly improving both the driving stability and the traction.'

the animation is a bit naff, I'm sure MB could have done better

 

[219]

Perhaps , being related to ABS , it does not work when the car is in reverse , same as ABS ?

 

[renault12ts]

But ESP works in reverse, my yellow triangle was flashing as I reversed on our icy gravel. Is ASR different?

 

[BTB 500]

Standalone ASR (all my SL has) is older and probably less sophisticated than ESP.

 

[wemorgan]

Standalone ASR (all my SL has) is older and probably less sophisticated than ESP.

ESP:

'Braking on uncertain surfaces is just one situation that puts a high demand on both drivers and vehicle technology. ESP®, the Electronic Stability Program, comes as standard in your van to help you keep your grip on the road. If, for example, a wheel starts to spin or is about to skid, then sensors recognise the first signs of a potentially uncontrolled situation. Active motor management and electronic brake force distribution (EBV) then apply specific braking forces to individual wheels in order to stabilise the vehicle. ESP® prevents the vehicle under or over steering in critical situations, thereby noticeably improving both the traction and driving stability. It combines the functions of ABS, ASR and BAS, to which it also adds a stability aid.'

Mercedes-Benz - Transporter Safety Special - Vehicle - Drive stability - ESP

So I think ASR is for accelerating and ESP for braking.

 

[BTB 500]

ESP works under power ... not just when braking. It will try to correct over & under steer by yawing the vehicle via differential braking (something the driver cannot do).

ASR (standalone or as a component of ESP) is basically old-fashioned traction control, and as you say only acts on acceleration.

But as per the OP I'm very surprised it lets one wheel spin.

 

[whitenemesis]

ESP functional description

http://www.MBClub.co.uk/forums/899638-post5.html

 

[KillerHERTZ]

Yeah as I found out 1st hand the other day, ASR only works when your foot is on the accelerator (I knew anyway), nearly lost it on a roundabout.

In answer to one of the above questions, yes ASR does work in reverse.

 

[219]

I remember finding out whilst amusing myself in a large car park , by reversing on hard packed snow and braking fairly hard in my 300TE , that ABS does NOT work in reverse : the warning triangle in the middle of the speedo lit up , the ABS warning light came on indicating the ABS had dropped out , and I had no ABS until I stopped and restarted the engine ! Repeated the test a couple of times .

The car had an ASD , but not ASR .

 

[tim.100]

Anyway to the point, I questioned myself afterwards, why wasn't the ASR dabing the brake on the passenger rear and allowing the power to go through to the drivers wheel, which being on tarmac would have pulled the car out.

My 97 facelift 202 ASR does work to stop the spinning wheel. It is effectively an electronic differential lock.

 

[219]

ASD ( auto-speer-differential or automatic locking differential ) is the electronically controlled , but hydraulically actuated , locking differential .

ASR , electronic wheelspin control , is automatic application of the brakes .

 

[kth286]

I remember finding out whilst amusing myself in a large car park , by reversing on hard packed snow and braking fairly hard in my 300TE , that ABS does NOT work in reverse : the warning triangle in the middle of the speedo lit up , the ABS warning light came on indicating the ABS had dropped out , and I had no ABS until I stopped and restarted the engine ! Repeated the test a couple of times .

The car had an ASD , but not ASR .

Derek

try that going forward on ice next time and see if it is any different.