BMW M5 Forum and M6 Forums banner

1 - 3 of 3 Posts

·
Registered
Joined
·
63 Posts
Discussion Starter #1
I planted my foot in M mode and applied the brake few miliseconds after to warm up the rear tyres before a race (a burnout - simply said) and my car just bogged down, puzzled by what happened I repeated the step and same thing happened exept this time around I received the yellow "clutch overheated" message, burning clutch smell was overwhelming... I turned the car off and let it cool down and drove it normal for another 300miles.

Both clutch, flywheel and centre bearing have been replaced 5 months ago prior to this incident, SMG pump and clutch slave accumulator were replaced 2months prior to the incident, all 4 brake rotors and pads were also repled a week prior to the incident... I am thinking the new brakes gripped the rear tyres too much which caused it to bog down during the burnout stage?

Ever since this happed I now get a shudder during slow/normal driving type gear shifts. Only happens in 2nd gear at around 1,300 RPM, minimal clutch smell is still noticed (could be the clutch remains still flaoting around in the flywheel?) not sure what to do now to resolve the shudder???

Car has done 400 miles since the clutch overheat message and the slight gear shudder is still there :( and minimal clutch smell is also noticed after short and normal drives :(
 

·
Registered
Joined
·
5,673 Posts
I planted my foot in M mode and applied the brake few miliseconds after to warm up the rear tyres before a race (a burnout - simply said) and my car just bogged down, puzzled by what happened I repeated the step and same thing happened exept this time around I received the yellow "clutch overheated" message, burning clutch smell was overwhelming... I turned the car off and let it cool down and drove it normal for another 300miles.

Both clutch, flywheel and centre bearing have been replaced 5 months ago prior to this incident, SMG pump and clutch slave accumulator were replaced 2months prior to the incident, all 4 brake rotors and pads were also repled a week prior to the incident... I am thinking the new brakes gripped the rear tyres too much which caused it to bog down during the burnout stage?

Ever since this happed I now get a shudder during slow/normal driving type gear shifts. Only happens in 2nd gear at around 1,300 RPM, minimal clutch smell is still noticed (could be the clutch remains still flaoting around in the flywheel?) not sure what to do now to resolve the shudder???

Car has done 400 miles since the clutch overheat message and the slight gear shudder is still there :( and minimal clutch smell is also noticed after short and normal drives :(
Have the SMG readapted. The overheat warning is a result of a mathematical calculation of heat load vice actual temperature measurement. The inputs to the calculation are:
- motor torque (fed by CAN bus from DME to SMG module)
- transmission input speed (read from crank position sensor)
- transmission output speed (read from layshaft sensor)

The algorithm basically calculates thermal generation by looking at the difference in input and output speeds and crunching that against applied torque to determine if the heat load is excessive.

Any slippage of the clutch accentuates this and can trigger it.

Performing the adaptation again may not fix anything since the SMG basically release all slave cylinder pressure when the clutch is engaged, so slippage is more a function of surface friction and spring tension on the pressure plate. However, adaptation may help (specifically the clutch slip point) as the burnout you mentioned may have moved the clutch to the "kiss point" which is also used by launch control.
 

·
Registered
Joined
·
63 Posts
Discussion Starter #3
Thanks for the reply, I asked BMW to perform the adoptation yesterday and that didnt seem to help. the slight shudder is still there but as mentioned it only appears in 2nd gear when taking off slowly between 1,000 to 1,300 RPM
 
1 - 3 of 3 Posts
Top