The epitome of racing feeling in everyday traffic starts a new round. 35 years after the debut of the first BMW M3, BMW M GmbH presents the latest generation of its high-performance automobiles in the premium mid-size segment. Time to introduce the two new vehicles. In the #M3M4explained series, the developers have the floor.
When Torsten designs something, he devotes himself above all to the question of how the engine's torque reaches the wheels as perfectly as possible. The BMW M developer is responsible for the drive shaft of the new BMW M3 and M4 automobiles. In the video, Torsten introduces it and explains its advantages.
BMW M ENTHUSIASTS ASK, BMW M EXPERTS ANSWER.
What is the maximum load of the driveshaft?
The maximum peak load at the shaft is about 3500 Nm.
What is the weight of the drive shaft?
The weight is about 11kg for the RWD, however the drive shaft is longer than the predecessor.
What is the weight difference between F8x CFRP and G8x steel driveshaft?
The delta is about 3.5 kg.
What is the length of the drive shaft?
The shaft for the RWD is about 1.5 m.
Out of which material is the driveshaft of the new BMW M3 and M4 exactly made?
It's made from a special high-alloy cardan shaft steel.
Is there any difference between the drive shaft of the manual vs the automatic transmission?
Yes, they have a different length due to different gearbox length.
Is there more power train loss on the M4 with M xDrive compared to the RWD model?
Spoiler alert! Watch out for another episode to come.
Was a different design for the driveshaft considered for markets without particulate filters?
We always planned an identical shaft for worldwide use.
How do you ensure the adhesive capsule (see video) has sealed properly during fitting?
There is enough adhesive in the capsule to fill 3/4 of the remaining volume. The glue displaces the air due to its liquid properties.
What kind of fluid is in the capsule?
It is an anaerobic adhesive.
How has the adhesive been tested? Might it wear down over time and cause vibrations?
It was validated by a huge variety of endurance tests. The adhesive remains stable over time and temperature.
Would the old 90mm shaft be stronger compared to the new 50mm shaft?
Both variants can transfer the maximum forces just as well.
Are all drive shafts individually balanced still using counterweights?
Yes.
What was the problem with CRFP design? Too much deflection or resonance?
Both. A smaller diameter leads to a low natural frequency and this ultimately leads to an impermissible deflection. In terms of design, we at BMW currently always keep a certain safety margin to the natural frequency in order to avoid negative effects for the customer.
How do you balance the need to limit vibrations with transmitting mechanical feel to the driver?
There is a rubber coupling between transmission and drive shaft that is tuned for this vehicle.
How much force does the crash element take to decouple? Is it then destroyed?
The force to trigger is adapted to the respective vehicle. Once the crash element has been triggered, it is destroyed.
How to replace a defective driveshaft when it is glued to the differential input shaft?
The connection can be loosened by the repair process as specified in the repair manual. Additional cleaning is required.
Did the smaller driveshaft compromise the maximum torque output of the engine?
No, the cardan shaft does not limit the engine torque.
Which CAD and CAM software are you using at BMW?
CATIA V5.
What is your favorite classic BMW?
The one and only: M1.
What car do you drive?
M340i Touring, because the M3 Touring does not yet exist :-).
