VW's 48V mild hybrid technology is still a few years away from production, but we’ve sampled a prototype Golf fitted with it and are suitably impressed

Our Verdict

Volkswagen Golf

New 1.5-litre petrol engine promises to help keep the refreshed Volkswagen Golf ahead of rivals

23 November 2017

What is it?

Volkswagen’s Golf 1.5 TSI MHEVs (mild hybrid electric vehicles) are engineering prototypes equipped with the firm's new 48V electrical systems, which are likely to become commonplace in the next couple of years.

The 48V systems are simple, mainly because, unlike a full hybrid or plug-in hybrid, they operate at low voltage, making them relatively cheap and easy for manufacturers to install.

They consist of a belt-integrated starter generator (BISG) and 48V lithium ion battery that's about the size of a conventional 12V battery. The 12V battery is retained to drive the conventional electrics and is charged from the 48V system. The BISG can boost acceleration, recover energy and store it in the lithium ion battery when the car slows or the brakes are applied. It makes stop-start much faster and smoother because of the extra power compared to a 12V starter system.

We briefly tried two versions, the Golf MHEV and Golf MHEV Plus, at Volkswagen's Ehra-Lessien proving grounds. The first is a straightforward front-wheel-drive Golf MHEV powered by a 148bhp 1.5-litre TSI turbocharged petrol engine, equipped with an 8bhp BISG and a prototype of the all-new DQ381 seven-speed DSG automatic transmission. The MHEV Plus has an additional 34bhp electric motor driving its front axle.

The MHEV Plus we tried is one of two configurations – the second motor can also be used to drive the rear axle, effectively giving the car part-time all-wheel drive. In that guise, torque to the rear wheels is less than that of an engine-powered all-wheel drive system but still provides useful traction off-road, and engineers say it can be used to improve cornering balance on the road by neutralising understeer.

Despite the extra input of the electric motor-generators, the total engine's power is likely to stay roughly the same, with the torque of the electric motor-generators being used to reduce emissions and improve economy (by around 7mpg) and driveability rather than increase performance significantly. 

What's it like?

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. 

Should I buy one?

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.

Given the option, at the right price, an MHEV will be an all-round better choice than a standard combustion-engine car.

Volkswagen Golf 1.5 TSI MHEV prototype

Where Lower Saxony, Germany On sale 2019 (est) Price TBA Engine 4cyls, 1498cc, turbocharged petrol plus electric motor Power 148bhp Torque na Gearbox 7-spd automatic Kerbweight na Top speed na 0-62mph TBA Fuel economy 48.5mpg (estimated) CO2 rating na

Join the debate


23 November 2017

No judgement can be made, especially for the non-plug in version.

You need to know what the payback time is for having the mild Hybrid tech option on your average Golf?

If it costs £1,400 more and gives 15% savings, say £200 a year then payback time will be 7 years.

A big no thank you, our 2 car family will be a BEV and a petrol ICE  (hopefully)

typos1 - Just can’t respect opinion

24 November 2017
xxxx wrote:

No judgement can be made, especially for the non-plug in version.

You need to know what the payback time is for having the mild Hybrid tech option on your average Golf?

Depends also on what value you place on an automatic (although, to be fair, Autocar never factor this in when evaluating hybrids - their one-track minds always compare them to manual diesels

23 November 2017

It's a bit misleading to call it a 'MHEV', surely it should be a 'MHV'?  Or, better still, 'MHICEV'?Having 'EV' in this acronym is VW greenwash at its best.  In no way is this an EV.  It's an internal combustion engine car with a better battery and fuel consumption, to be launched somewhere down the line.  VW makes me sick with the way it attempts to deceive and mislead.  Nothing has been learnt since dieselgate.

23 November 2017

This looks similar in concept to the Honda IMA system which the Japanese manufacturer has just abandoned! But Honda used a  more powerful (15kW) electric motor generator that was integral with the flywheel rather than being belt drive. Even with such power, the fuel consumption wasn't terrific and nowhere near that of a good diesel, which was possibly why it was dropped. Or maybe Honda has something better in the pipeline?

It would be interesting to know how  much of VW's effort is driven by the manufacturer, or is it companies like Bosch doing all the hard work and VW just ordering an off-the-shelf system in common with other European makers? 


23 November 2017

Indeed, its a 15 year old idea. But it is a good one . . . for diesels not petrols -  their already excellent fuel econmony and low CO2 figs will be improved further, plus as Continental showed recently, the battery camn also rapidly heat the cat from a start so theres no dirty period when the cats not up to temp and it can do this without wasting energy from the diesel.

XXXX just went POP.

23 November 2017

It's like their BEV effort, get a Golf replace the ICE with an electric motor and battery and you've an BEV.

The principal applies to their armoured personnel carrier too, get a Golf glue on some kitchen work tops and you've a Panzer.

Who needs design from the ground up


typos1 - Just can’t respect opinion

23 November 2017

I think this is pretty cool, and might have severe performance gains on the Golf R.

I just hope down the line 5-8 years time they have a proper Hybrid capable of doing atleast 30 miles only on electric power. Do that and I would very much consider a Golf R, the ICE and electric motor together would be awesome on the track.

23 November 2017
Only problem is why is it still a few years away from production? Magazines including Autocar have been telling us about their Prius rival for two years at least. By that reckoning it should be on sale now as in today; to be more precise this drive train should have been made available with the face-lift version of Golf. That was the impression given by the car media. An explanation is a courtesy a reader can expect from a magazine the calibre of Autocar. And potentially from the group that has ear marked a bank worth of euros for the development of alternative technologies. Or so we have been told and are regularly reminded by a media that appears to have an insatiable appetite for the "stories" of Volkswagen. Yet their first real clean car we are told is years away. What is causing Volkswagen to hold back such a gem? Diesel lobby?

24 November 2017

Suzuki offer a 48V belt integrated starter generator on the Ignis, Swift and Baleno already.

Apparently it works pretty well, though the current price premium means the economics probably only make sense for high mileage drivers. The cost of these systems will come down though.

24 November 2017

These 48v mild hybrid systems were being touted by various component manufacturers 3-5 years back so this is obviously the gestation period for integrating these systems into everyday cars. Given the steps to reduce emissions over the past few years it's the next cheapest step they can take on the way to full hybrid and electrification.

Oh, and MHEV is an industry term and not some VW brainwashing attempt, so calm yourself Mr Daily Mail comments page.


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