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.
Karsten always knows what goes round: the engineer, responsible at BMW M for transmission development of the M3 and M4 automobiles, explains the M Steptronic Sport transmission used in the Competition models. In the video he explains all the technical details and how exactly M GmbH has optimised the transmission.
BMW M ENTHUSIASTS ASK, BMW M EXPERTS ANSWER.
Which has quicker kickdown, DCT or the new transmission?
Due to the possibility of multi-gear change at once the 8-speed M Steptronic is faster most of the time.
Do shift pressures change based on the selected drive mode or are they fixed?
The hydraulic system pressure does not depend on the drive mode.
What are the differences between the transmission programming of the F90 M5 and the G8x M3/M4?
It is a completely different programming which perfectly suits the different engine characteristics of the V8 and I6 engines. Please, have a look at Episode 7 "Drivetrain Competition models".
What is the additional weight compared to the manual transmission?
In the car (including the additional oil cooler for the 8-speed M Steptronic) the difference is 23.8kg.
Will excessive use of launch control void the factory warranty on the transmission?
No.
How long is the lifetime of the "small" friction clutches between the planetary gears?
The clutches within the 8-speed M Steptronic are designed for the entire vehicle's life.
What is the maximum torque the ZF8 can handle vs DCT?
The same transmission is also used in the BMW M5 CS with 750Nm which it handles quite well. The old DCT handled a maximum of 700Nm in last generation's M5.
Top speed at max RPM for each gear?
1st: 57km/h, 2nd: 89km/h, 3rd: 133km/h, 4th: 166km/h, 5th: 217km/h, 6th: 285km/h, 7th/8th: 290km/h (limited Vmax with optional M Drivers Package) Reverse: 40km/h. However, different tire dimensions have an influence on these speeds.
Under light loads will the transmission skip ratios for improved fuel economy?
Yes, it will under certain circumstances.
How much torque multiplication is present through the torque converter when unlocked?
The torque multiplication factor is 1.8
Is the external oil cooler only part of the M transmission or is it also part of the AG transmission?
The AG transmission uses an indirect water-oil-cooler whereas BMW M uses a direct air-oil-cooler.
Which transmission is suited better for acceleration at over 200kph? Manual or 8HP?
Given the additional power of the Competition models in combination with avoidance of the power loss during shifting, the 8-speed M Steptronic ones are faster.
Do you design by solidworks software?
We use CATIA V5.
What's your university major?
I graduated in mechanical engineering.
What car do you drive?
Something with lots of room for my family with 3 children ;)
What is your all-time favourite BMW you would own?
For me, that is going to be the BMW M5 (F90).
