Auto box downhill "engine braking"

[NorthDownsMerc]

As I live on top of the North Downs, the only way is down so to speak, and that usually mean s-t-e-e-p hills. My latest W220 is doing something different downhill to the last one, and I just wanted some feedback or explanation of what's going on.

The old one (00 S320, 5 speed auto) used to select the highest gear possible and almost freewheel down the steep hills, meaning that a foot on the brake was very much required.

The new one (04 S500, 7 speed) exhibits a much greater engine-braking effect, almost as if it is detected the steepness and has changed itself down to a lower gear. Indeed, if when in "D" you knock it down to a lower gear (using the tiptronic thingy) it will select 2 or 3, rather than 5 or 6 at around 40, indicating to me that it is holding it lower than a freewheel setting. I think it's only doing this after I brake for a corner, and then it's holding the gear rather than changing up and rolling, but I may be wrong.

Am I making sense...? Does this sound normal...? Have Mercedes introduced a hill-descent control logic chip into the system somewhere that I haven't noticed before in any literature...?

Rich

 

[jon_harley]

My CLK definitely does this, when going down a steep hill on cruise control. Gave me a bit of a shock the first time it did this, suddenly hearing the revs soar, until I realised it was doing it for engine braking.

 

[NorthDownsMerc]

aha I think on cruise control maybe something different - changing gear is the only way the car can maintain it's speed I suspect. I can't hear the revs in the "S" so no shock value either.

 

[jberks]

I've noticed that my 211 behaves differently to my 210 despite them both being 5sp tip boxes. The 211 is far more eager to select a lower gear for better engine braking. Both did this with criuse or the speed limiter but gently braking on an incline can get the 211 to shift down. I don't remember the 210 doing this at all.

 

[Glenn Smith]

I've noticed that my 211 behaves differently to my 210 despite them both being 5sp tip boxes. The 211 is far more eager to select a lower gear for better engine braking. Both did this with criuse or the speed limiter but gently braking on an incline can get the 211 to shift down. I don't remember the 210 doing this at all.

did they both have esp?

 

[NorthDownsMerc]

Tried going downhill on Cruise Control set at 40 this morning and yes the car definitely changed gear to try and maintain the speed - not before it ran away to nearly 50 though. Definitely wasn't the same effect as I experience usually and which was the reason for the post.

 

[television]

Its all to do with the programing on electric controlled gearboxes in the same way that the holds were used to warm up the CAT. Having 7 gear bands the hold probably works on the first 3 or 4.
Though most people say how smooth the 7g is, and was an option in late 02 and not standard until well into 03 on the SL, I could not find one with the right spec and bought a 16k mile 02. its almost impossible to detect any changes, this must be down to oil changes. Sinse the sealed for life idea was scapped and oil changes are now 60k, I will do mine at 30k in a few years time, just to keep it smooth.

malcolm