Volkswagen Golf 1.5 TSI MHEV prototype review

The regular MHEV feels fully integrated to drive and pretty much production-ready. Its power delivery is smooth and linear and stop-start events are as smooth as promised. The main difference between this and a conventional Golf is that the gearbox can decouple from the engine, allowing it to shut down so the car can coast to save fuel. That’s where the smooth restarts are of most benefit. When the car is slowing with the engine running, the BISG acts as a generator to charge the 48V battery.

The MHEV Plus is more noticeably a prototype, mainly because adding an additional motor creates a far more complex system. Bringing the second motor into and out of play and smoothly blending the torque between the two motors and the engine is extremely complex, so at this stage, slight steps are noticeable. Production versions will have fully refined software, making transitions seamless.

The advantage of the second motor is that when the Golf is coasting and the engine shut down, the second motor can perform regenerative braking to recover energy. The standard MHEV can only recover energy when the engine is running, so engineers think that the MHEV Plus will give greater economy.

We weren’t able to drive the all-wheel-drive version but did observe an engineer extracting a Tiguan from deep, wet sand using it. In front-wheel-drive form, the SUV was stranded, but with the rear drive switched on, it managed to drive out of trouble with reasonable ease on winter tyres. In a similar demonstration, the Tiguan was driven up a steep slippery slope that it couldn’t manage in front-wheel-drive mode. 

The likelihood is that in a few years time, you may not have much choice. Electrification of cars to recover and reuse kinetic energy through regenerative braking is the only way manufacturers will meet future CO2 and emissions regulations.

However, the good news is that MHEVs are even better to drive than standard cars. The electric boost neutralises turbo lag, sharpening response to the accelerator; the systems don’t add as much cost as a high-voltage PHEV or full hybrid system; and the fuel consumption benefits should be significant, as long as cars don’t become further bloated with even more heavy features.