► Is this the hot hatch of the future?
► We test new Golf GTI by Mahle
► E-supercharged 1.2l 3-cyl puts out 256bhp
Downsizing is affecting every model of car, from supercar to supermini – but could it really result in a hot hatch benchmark, such as the VW Golf GTI, being fitted with a three-cylinder engine?
British engineering firm Aeristech believes so, and has produced a prototype to demonstrate what’s possible. It features a 1.2-litre engine that punches out a mind-boggling 256bhp and 232lb ft, thanks in part to the use of an electrically driven compressor.
Driving the downsized VW Golf GTI
Aeristech, a burgeoning technology firm based in the Midlands, has teamed up with automotive parts and engineering company Mahle to produce this working prototype. Both companies reckon that powerful, flexible engines are still viable even with the increasingly stringent emissions legislation being placed on modern manufacturers – but the proof, as they say, is in the pudding.
The concept of the prototype is relatively simple: take a VW Golf GTI, whip out the regular four-cylinder 2.0-litre turbo, and drop in Mahle’s 1.2-litre triple. Pretty standard downsizing job so far, but here comes the clever bit: Mahle’s engine has a very big turbo and a patented liquid-cooled eSupercharger – the latter powered by a 48-volt subsystem. The gargantuan turbo aids the engine in delivering that headline 256bhp power figure (a 39bhp increase over the standard GTI), yet it’s the eSupercharger which allows the engine to work smoothly and controllably in the real world.
Using this electrically driven supercharger allows Aeristech and Mahle to sidestep one of the common problems of using larger turbochargers on smaller engines – lag. Floor the throttle at lower rpms and the turbocharger won’t come on song for a long time, meaning no power and no go. Something which, as many drivers will know, is a massive pain if you don’t fancy driving like a rev-happy hoodlum everywhere.
The eSupercharger by Mahle and Aeristech
Th eSupercharger fills in the gap between the turbo’s sweet spot and low revs, spinning up to its 120,000rpm operating speed in a blink-and-you’ll-miss-it 0.4 seconds. From there it’ll keep on producing boost continuously for as long as required, unlike other systems which only offer short bursts. The electric compressor in Audi’s SQ7, for example, is only operational speed for a split second at lower engine speeds.
Aeristech engineers claim they've had the eSupercharger – which reputedly uses a cooler-running electric motor – boosting for 20 hours straight during testing. The upshot of this is that there should, in theory, be a nice wave of meaty torque from the lower revs to somewhere after the turbo kicks in. That means plenty of go in any gear and no need to drive like you’re trying to lose the cops.
Very clever. But does it work?
The system serves up oodles of torque – 232lb ft to be precise – from 1500rpm, all the way to 4500rpm. We only tested the car on a circuit, but the benefits were evident. For example, flooring the throttle from near idle speed in second gear (designed to imitate rolling up to a roundabout) – a point at which all other 1.2-litre engines would struggle – resulted in the eSupercharged Golf GTI pulling away smoothly and with urgency.
There’s little perceptible rise in torque output, like in a regular turbocharged car; instead, maximum pulling power is summoned the moment you press the pedal. No jump, no judder, just instant go – almost like, ironically, an electric car. It pulls similarly well in higher gears and at higher speeds, with the now-awakened turbocharger providing the extra mettle required to keep the GTI accelerating.
Punch it in second gear and you’ll get all 256bhp and 232lb ft almost instantly, leading to rapid acceleration. The engine’s output doesn’t feel like it tails off until just shy of the redline, either, further aiding this hot hatch in feeling like a seriously quick car. Run it through the gears from a standing start and 0-62mph comes up in 6.4 seconds, and it’ll top out at 155mph. There’s even a raspy exhaust note, more akin to a Golf R than the typical three-cylinder rumble.
Sounds pretty stout. Are there other benefits?
On paper the Mahle-engined Golf GTI doesn’t perform that much differently from the donor car. The regular Golf GTI – although less powerful, at 217bhp – completes the 0-62mph dash in a near-identical 6.5 seconds and outputs a higher 254lb ft
However, there’s a reason the concept is dubbed 'extreme downsizing' by its makers. The Mahle unit smaller than the regular 2.0-litre Golf GTI engine yet its performance is nearly identical. It certainly doesn’t feel or sound anything like a victim of downsizing, with its fruity engine note being a marked improvement over most humdrum four-pot offerings.
It’s worth also bearing in mind that all the usual downsizing benefits still apply, too. That means CO2 and fuel consumption decreases of around 25%, while production costs are claimed to be very similar. However, no hard emissions or economy figures are available yet...
Plenty of promise, then. What’s next for the eSupercharger?
As with all burgeoning technology, bringing it to the general market is the next step according to Aeristech CEO, Richard Wall. 'We are now beginning discussions with manufacturers about pre-development programmes and additional vehicle demonstrators, while looking to get the product into their powertrains,' he told CAR. 'We’re expecting in the next few years that you’ll start to see this product going out to the market.'
There are a few more things in the pipeline too. Wall suggested that the company has a smaller, 12v eSupercharger on the way, plus patents for use in diesel engines and as the sole source of boost in smaller A- and B-segment cars.
The biggest questions are whether the eSupercharger can deliver those improved efficiency figures in the real world, and if it can do so at a cost comparable to today’s powertrain solutions. One thing’s for sure, though – in this case, downsizing certainly doesn’t mean downgrading.
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