Distronic Plus help

[Andman99]

I found the speed limiter more useful than cruise control in temporary speed limit areas.
Does your car have this?

I thought I was limiting the speed - at 50mph - and the car would brake and accelerate (to 50mph - the limit I had set) according to traffic conditions. That's what I am asking for help with here as the dealer hasn't been helpful thus far.

 

[John N]

Speed Limiter: RH Toggle Switch with the "Clock" above it, once Set Limits the Speed the Car goes at, as far as I am aware is overidable using the Accelerator!

Cruise Control: Far RH Toggle Switch Sets or Cancels, Centre Toggle Switch can be used to increment the Speed (or decrease) by 1 to 5 MPH depending how it is used, as far as I am aware the Cruise Control will allow your Car to travel at the Speed Set UNTIL you approach Slow and or Static Traffic! (Distronic) When the Traffic moves on or Speeds up the Car will revert to the Speed Setting!

Which one are you Using?

 

[Diesel Benz]

Hi All. I have a C300DE which has been a wonderful experience, mostly. The big problem I have is with Distronic Plus. Specifically when the car suddenly rapidly accelerates above the limit I have set. As an example, I set the limit to 50mph on a stretch of motorway with this reduced speed limit. At some random point, where there are no visible 70mph or national limit speed signs (played dashcam footage back), the car resets the limit and accelerates from 50 to 70mph. I am told by the dealer it is meant to do this. Surely not?! Any suggestions gratefully received.

Not sure if this was already covered as the thread is long and I just browsed it through. Anyway, I would say the car is not faulty but the implementation of the active speed limit assist is poor.

My car (223 MY 22 but should be the same in this respect) does what you explain under certain traffic conditions. Even the manual states that the car increases speed if it detects a higher speed limit. This "speed limit detection" occurs via the traffic sign camera and via the navigation database. It is a complicated issue but in my opinion the car makes use of the speed limit database in a very stupid way. The road may have a temporary reduced limit (or the driver has set a lower speed) but the car only keeps the current speed until the database reports a new section of the road after which the car "forgets" the latest observed speed limit sign and accelerates to the database speed. The fact that the sections of the road are not defined from junction to junction but sometimes appear in the middle of nowhere creates most of the confusion.

Don't know if it would be sufficient to keep the reduced speed at least until another speed limit sign has been detected (on the current road)? It still makes it difficult to intentionally drive a bit slower than the true speed limit (further than the next sign or database section change).

The active speed limit assist has other flaws, better to leave these for other threads.

 

[markjay]

Not sure if this was already covered as the thread is long and I just browsed it through. Anyway, I would say the car is not faulty but the implementation of the active speed limit assist is poor.

My car (223 MY 22 but should be the same in this respect) does what you explain under certain traffic conditions. Even the manual states that the car increases speed if it detects a higher speed limit. This "speed limit detection" occurs via the traffic sign camera and via the navigation database. It is a complicated issue but in my opinion the car makes use of the speed limit database in a very stupid way. The road may have a temporary reduced limit (or the driver has set a lower speed) but the car only keeps the current speed until the database reports a new section of the road after which the car "forgets" the latest observed speed limit sign and accelerates to the database speed. The fact that the sections of the road are not defined from junction to junction but sometimes appear in the middle of nowhere creates most of the confusion.

Don't know if it would be sufficient to keep the reduced speed at least until another speed limit sign has been detected (on the current road)? It still makes it difficult to intentionally drive a bit slower than the true speed limit (further than the next sign or database section change).

The active speed limit assist has other flaws, better to leave these for other threads.

This makes sense.

On my other car (not MB), I have road sign recognition via a camera, navigation-based speed limit via the maps, and real-time speed limit via GSM (motorways only) - and with all three, it still gets the correct speed limit only around 80% of the time. These systems are still in their infancy... maybe a Tesla owner can say if their system is more accurate.

At current, I just drive using adaptive CC and regularly change the desired set speed as needed via the steering wheel controls. As far as I am concerned, whatever the car displays as the current speed limit is there 'for information purposes only'.

 

[BoristheBounce]

Speed Limiter: RH Toggle Switch with the "Clock" above it, once Set Limits the Speed the Car goes at, as far as I am aware is overidable using the Accelerator!

Cruise Control: Far RH Toggle Switch Sets or Cancels, Centre Toggle Switch can be used to increment the Speed (or decrease) by 1 to 5 MPH depending how it is used, as far as I am aware the Cruise Control will allow your Car to travel at the Speed Set UNTIL you approach Slow and or Static Traffic! (Distronic) When the Traffic moves on or Speeds up the Car will revert to the Speed Setting!

Which one are you Using?

One other point is that if you push the far right switch up twice it will then follow the speed limits automatically.

 

[Andman99]

Thanks for all your posts so far.

To quote the general manager of the dealership: "The car will indeed speed up when Distronic Plus is active if it "sees" a speed sign that is higher than the current fixed speed. Similarly, it will brake if it "sees" a speed sign that is lower than the current speed."

I then decided to test this theory. Off I travelled with Distronic Plus set to 30mph. Soon after I entered a 50mph zone and passed about 8 x 50mph speed signs...at 30mph. Ironically, this is what I want it do when traveling in the restricted speed zone on the M6, i.e. stick to the limit I have set. I didn't try it the otherway round - be just my luck to have police around the corner.

The general manager came and sat in the car and we had a discussion; he played with the settings and then decided there may be a problem with it after all!



A "tech specialist" from Mercedes will be contacted next week to see if they can't get to the bottom of the problem.