Why the Mk8 Golf R AWD is better than anything they've given us before
In case you haven't seen THE LATEST EPISODE (CLICK HERE) MOOG has gone mad and started modifying a brand new car he literally took straight from the dealership into Super Garage. But why is he now doing a Mk8 after having such an absolute cracker of a Mk7 Golf R?
The new model Golf R is just a tickle and fiddle of the award-winning late-model hot hatch recipe at first glance... well, if you aren’t a Das Auto nerd like MOOG (see his videos on the Mk8 Golf R HERE and also HERE). However, the turbo all-wheel-drive (AWD) pocket rocket has significant upgrades in key areas under its skin, including a new AWD system based around torque vectoring technology, which really improves handling.
However, to fully grasp the genius of the Mk8 we really need to understand where we’ve come from, so let’s take a look back at the what go-fast VAGs have used over 20 years: Haldex.
Most VAG fans know that the term “Haldex” refers to the AWD system used in everything from Golf Rs to RS3s, Passat R-Lines, Tiguans, Transporters, and even Lamborghini Aventadors and Bugatti Chirons. However, it has also been licenced by Ford, Mercedes-Benz, Land Rover, Volvo, Saab, and General Motors (Opel, Buick and Cadillac).
The Haldex Coupling is a product of Swedish company Haldex Traction, and was introduced in some 1998 year-model Volkswagens and Audis, including the TT and the Golf. Interestingly enough, while most people know of “Haldex” from Volkswagens, it was actually born in the Saab competition department, the brainchild of an engineer by the name of Sigge Johannson who patented the multi-disc clutch technology in the 1980s before selling the patent to Haldex Traction in the ‘90s.
The Haldex Coupling differs from the earlier VW Syncro and Audi Quattro AWD set-ups as those were based around a mechanical connection using Torsen differentials, while the Haldex Coupling is uses an electronically-controlled hydraulically-actuated clutch to sense front-wheel slip and send torque to the rear wheels.
Normally based around a transverse-mounted front-drive (FWD) style engine layout (except in Lamborghini and Bugatti vehicles), Haldex typically sends most torque through the front wheels and allows the car to drive in a FWD manner during day-to-day operation. Side benefits to this include better packaging of interior space from a transverse drivetrain, and improved fuel economy from only driving two wheels instead of four.
Criticisms of the original Haldex system mainly centred around the fact it was reactionary which meant it only send drive to the rear after the front wheels had begun spinning. There were new generations of the coupling system launched in 2001, ’06, ’07, and ’09 as the electronic technology in cars radically improved.
Huge leaps forward in ECU and sensor technology, plus new features like electronic throttle bodies, Electronic Stability Control (ESB), yaw sensors, and modern ABS systems mean electronically-controlled AWD systems are no longer just something you read about in top World Rally Championship cars.
The 2007 GenIV Haldex Coupling used in Golf Rs (and other VAG models) was simplified over older models. The Gen IV and GenV use an electro-hydraulic clutch assembly to get rid of the complex set-up that needed an accumulator, solenoid and the replaceable filter, and it uses wheel-speed sensors and stability control protocols to proactively sense slip
For the Mk8 Golf Volkswagen has moved on from Haldex-style electro-hydraulic tech. Known as Magna torque vectoring this electrically-operated system allows a greater amount of torque to be sent to the rear wheels and, crucially, for it to also be split side-to-side.
Haldex could only send up to 50% of the drive to the rear-end, and each rear wheel got 50% of that drive. But, in a hard-cornering situation the new-gen AWD can send more torque to the outside rear wheel, radically improving the Golf’s cornering abilities, limiting understeer, and allowing mad drifts.
While the Haldex unit sat in front of the rear differential, the Mk8 has clutch packs mounted on either side of the rear differential in front of the driveshafts. Worm gears driven by electric motors engage and disengage these clutches, splitting drive side-to-side but also allowing the rear drive unit to be completely disengaged for the car to drive completely as a FWD. This is unlike the Haldex system, which always ran a minimum of 5% or up to 10% of the drive to the rear-end.
Though both electric motors carry the same part number they operate in a slave-master type relationship, with the right-hand motor calculating the left-right torque split. Traditionally torque-vectoring technology has used computers to compile data from a mix of wheel speed sensors, throttle position sensors, and steering yaw sensors to calculate load on driven wheels, as this is faster-acting and more accurate than a mechanical or hydraulic coupling.
Interestingly because the electric motors can completely uncouple the clutch packs removing all drive to each rear wheel, the diff in the back of the Mk8 Golf R doesn’t actually feature spider gears. Also, the left and right-side clutch packs are designed to be serviced with different fluid from the centre “differential” unit in the middle.
It adds up to a great handling car that is a lot of fun to drive. But is this AWD system better than Toyota's advanced clutch-based system used in the GR Yaris and Corolla? Check out THIS story for the full run-down on that set-up!