Mechanical + electric differentials = hybrid fun?
GKN, best known for the all-wheel drive system from the Ford Focus RS, is working on a new 'All Twinster' torque-vectoring system for plug-in hybrid SUVs.
GKN Driveline is currently testing a Mercedes-AMG GLA45 with a combination mechanical and electronic torque vectoring system, a plug-in hybrid powertrain and all new control systems. Sounds complicated, right?
Up front, the car has a mechanical Twinster unit mounted directly to the gearbox, replacing the existing final drive and differential. According to GKN, that allows it complete control of the torque distribution across the front axle – grunt can be sent from side-to-side through its unique twin-clutch system depending on where it's most needed.
Along with the new front end, the GKN team has ripped out the GLA45's existing power transfer unit, prop shaft and rear axle. In their place is a two-speed eTwinsterX and battery pack, delivering 120kW and 210Nm to the rear wheels.
The company says its "integrated e-motor's coaxial format" makes the unit significantly smaller than conventional hybrid systems capable of handling that amount of power and, by extension, easier to integrate into existing vehicle platforms.
Both axles are controlled with new ECUs and software developed and calibrated in-house by GKN to ensure they all work harmoniously. Along with its torque-vectoring, tyre-shredding potential, the system allows cars to be driven on pure EV power, and opens the door for decoupled 'sailing' for lower emissions.
When we said this is complicated, we really meant it. Guess how many extra parts GKN fitted to the GLA45 to make its new drivetrain work. Nope! You're wrong, it's 1340 – a total of 99 assemblies needed "significant" tweaks, either electrical or mechanical.
For now, the GLA45 is just a prototype. It's being put through its paces at the moment, with no word on when it might show up in production vehicles – but we're hoping for sooner rather than later.