Sudden braking!!?

[sparkynw]

I took the cla for a short spirited drive at lunch today and it did something new??
I thought I let it warm for around 6 miles and water was well up to normal, I had a safe bit of road so nailed it in 2nd in manual and as it got up to 6kish a large red simbol appeared briefly in the centre of the dash and it totally threw the anchors on!? It was quite alarming! I clicked up a gear and off it went no issues. I tried again a few miles later and it did it again? I'm suspecting that maybe the gearbox wasn't up to temp? It has been almost freezing last couple of nights but it was midday and sunny plus I thought it was warmed through? Should I be worried??

 

[davidjpowell]

Sounds like collision detection kicking in.

 

[sparkynw]

There was nothing in front of the car in its line of site and there was no audible alarm it was like the car was protecting itself just shutting the power off?

 

[whitenemesis]

I had similar in the (much older) CLS, turned out to be the ESP detecting loss of traction. Quite a brutal reduction in acceleration but all totally controlled.

 

[markjay]

.... a large red simbol appeared briefly in the centre of the dash and it totally threw the anchors on!...

..
it was like the car was protecting itself just shutting the power off?

So were the brakes fully applied - as in emergency braking?

Or did it just cut spark/fuel to the engines causing sudden deacceleration?

Or both?

 

[AndyRan]

My a220 has done this once or twice and once in the cl, the triangle and braking is just as in an emergency situation
The radar / sensor possibly picked up on a road.sign or similar thinking it was an object in the way

 

[leef44]

It could be just a simple case of engine oil temp not warmed through. 6 miles is not that far for warming up. I find it normally takes about 20 minutes for the engine to warm through.

 

[Riverside Red]

You usually have an AMG display which allows you to view engine oil temperature (and gearbox in the C63). You'll find that the water temp will get up to normal quickly but oil temp could take 10 miles or more to get to normal. (gearbox even longer)

Hitting any limiter at full acceleration feels like the brakes have been applied.

RR

 

[Peter DLM]

You might have your speed limiter set? Did it do this as you let off the throttle? If not it's the rev limiter.

 

[Riverside Red]

You might have your speed limiter set?

Good point......

 

[sparkynw]

Ok I've been trying a few things, I've found the true fluid temps in the menu and yes it takes a good while for the gearbox oil to get up there like 20mins normal driving when it's been frosty the night before. Also on Saturday I tried a hard sport + start from some lights in manual and as the revs hit 7k they bounced back to zero in a flash making it feel like the throttle was suddenly cut. No brakes were applied but it was quite alarming how quick it shuts off, I clicked up and off it went. From the very helpful advise here I'd say I have a limiter set, is this factory default to protect the engine? I think I'll leave manual for a bit and stick with auto and a bit of paddle. Is the limiter removable or Ecu controlled? These cars have so much clever engineering built in, you just keep discovering more and more about your car and I haven't even tried Appleplay yet..

 

[zipdip]

Not sure I will ever see that symbol,as I would never rev a car to 6k in second gear,thanks for letting me know its there,but like the top of mount Everest a place I will venture too.

 

[st13phil]

If it behaves in a similar way to the E63, then the sequence of events in Manual gearbox mode are:

1. Accelerate on full throttle
2. As engine speed nears the redline, an upshift instruction appears in the speedo in red
3. Rev limiter engages which feels like hitting a brick wall

#3 very quickly follows #2 if you don't upshift!

In 1st and 2nd you have to anticipate the upshift point while accelerating as the combination of your own and the gearbox's reaction times are enough that if you wait to see the upshift instruction before pulling the shift paddle, the engine will hit the rev limiter before the next gear is selected.

And in answer to your question, the rev limiter is fixed where it is to protect the engine and is not user adjustable.

 

[sparkynw]

If it behaves in a similar way to the E63, then the sequence of events in Manual gearbox mode are:

1. Accelerate on full throttle
2. As engine speed nears the redline, an upshift instruction appears in the speedo in red
3. Rev limiter engages which feels like hitting a brick wall

#3 very quickly follows #2 if you don't upshift!

In 1st and 2nd you have to anticipate the upshift point while accelerating as the combination of your own and the gearbox's reaction times are enough that if you wait to see the upshift instruction before pulling the shift paddle, the engine will hit the rev limiter before the next gear is selected.

And in answer to your question, the rev limiter is fixed where it is to protect the engine and is not user adjustable.

That sounds spot on! So now I know! Thanks. I didn't really expect to rev it quite so hard but being a biker I like revs and it does get up there very fast in 2nd. I have driven it very sedately for its first 1500 miles and it does get generally an easy life as a weekend car I normally have the family with me. However that said I've spent a fair bit of money on that AMG badge on the engine which I'm sure can take a few red lines..

 

[Peter DLM]

Not sure I will ever see that symbol,as I would never rev a car to 6k in second gear,thanks for letting me know its there,but like the top of mount Everest a place I will venture too.

You're joking here, right :bannana: