Mercedes CLA Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Tried this tonight. Last time I ever do it. The grinding sound from the rear end is mind numbing. It sounded like the rear end was going to explode.:eek:

I race Corvettes, and build professional intake systems for GM products.

Maybe someone with more knowledge than I have in 55 years of engine design and building can explain what just happened?

Seriously, I did it all by the book, floored it to 4,000 rpm, brake on until it displayed launch, and it took off. Some serious grinding sound coming from the rear of the car was as scary as it gets. Normal?
 

·
Your Mercedes CLA Admin
Joined
·
246 Posts
Tried this tonight. Last time I ever do it. The grinding sound from the rear end is mind numbing. It sounded like the rear end was going to explode.:eek:

I race Corvettes, and build professional intake systems for GM products.

Maybe someone with more knowledge than I have in 55 years of engine design and building can explain what just happened?

Seriously, I did it all by the book, floored it to 4,000 rpm, brake on until it displayed launch, and it took off. Some serious grinding sound coming from the rear of the car was as scary as it gets. Normal?
Ouch - was is wheel hop/spin or did it dead hook?
 

·
Registered
Joined
·
3 Posts
Discussion Starter #4
Dead hook, with no wheel spin. It is really hard to describe the sound but I drag raced for many years, and have never heard this kind of sound. Maybe the clutch? The sound was really not a good sound, and lowers my confidence in this factory technique to zero.

I tried a dead stop and start right after that without the intervention Race Start, and got a pretty decent launch without the grinding sound. no wheel spin.

I was hoping someone else that has tried this factory technique could tell me what I am experiencing. I fully understand spooling up the turbo, which is what I used to do when drag racing our Pro-Street Motorcycle. 9 second CBX with 150 traps.
 

·
Your Mercedes CLA Admin
Joined
·
246 Posts
Dead hook, with no wheel spin. It is really hard to describe the sound but I drag raced for many years, and have never heard this kind of sound. Maybe the clutch? The sound was really not a good sound, and lowers my confidence in this factory technique to zero.

I tried a dead stop and start right after that without the intervention Race Start, and got a pretty decent launch without the grinding sound. no wheel spin.

I was hoping someone else that has tried this factory technique could tell me what I am experiencing. I fully understand spooling up the turbo, which is what I used to do when drag racing our Pro-Street Motorcycle. 9 second CBX with 150 traps.
Weird, I had an SRT8 Jeep and it kinda made a weird clutch/grind sound when I would brake torque from 2500rpm. Think that was a Benz trans in those also. I think I know the sound as a car guy it was always hard to pin down.

Hopefully some owners can chime in or my buddy @Blownaway
 

·
Registered
Joined
·
16 Posts
The launch control should not be causing any issues as it is designed for this. If you were staged too long at the light you can overheat or overboost, I have done this in my GTR in Texas. Did the car issue a clutch temp warning?
 

·
Registered
Joined
·
16 Posts
I launch my dual-clutch all the time and there's always weird noises, especially with the type of diff that's in this particular car.

I haven't launched the AMG yet but it's most likely the LSD opening and closing throwing power around. Nonetheless, if it's a reoccuring thing, I'd go launch it with a Merc Tech in the car

Here's a couple videos where you can hear all the sounds during launch pretty well, was it different than these?


 

·
Registered
Joined
·
57 Posts
the AMG trainer forewarned us about the noise. its normal. and think, the launch in that is more violent in the CLA45 than the E63. its VIOLENT. which i think is awesome. there is no playing around. its a pure race car in race mode.
 
1 - 9 of 9 Posts
Top