YOU can’t have too much power, right? But what about specific output – power-per-litre? In recent years, big manufacturers have got into an arms race over boosting smaller capacity engines to deliver unfeasible outputs, and Volvo has pretty much jumped past the sand with this, a 2.0-litre four-cylinder engine that produces 330kW thanks to two turbochargers and an electric supercharger.
The Tri Boost engine is only a prototype at present, proof that Volvo’s modular Drive-E architecture can stretch this far, but also confirmation that the company’s switch to smaller engines – five- and six-cylinder units are set to be phased out by 2017 – doesn’t mean an end to its performance ambitions. R&D boss Peter Mertens hints this engine, or something close to it, could well power a future Polestar model.
The prototype engine is fitted to a hard-worked S60 development hack, which we’re driving at Volvo’s Experience Centre in Gothenburg. This is a short, twisty course that’s pretty much all corners – with a posted 80km/h speed limit that we completely ignore – but is enough to discover that the new engine feels as brawny as its numbers suggest.
The Tri Boost uses two Borg- Warner turbos that are plumbed in parallel, with the electrically driven supercharger sitting upstream of these (and powered by a 48-volt supercapacitor pack in the boot). The supercharger doesn’t feed the engine directly – it switches out at higher revs – with its role being to pre-charge the intake air to help reduce turbo lag.
The two turbos deliver up to 3.5bar of boost, and to keep up with them the fuelling side needs high-flow injectors and twin fuel pumps.
It’s not lag-free; there’s a noticeable surge if you put in a big throttle input below about 2000rpm. But once the turbos are spinning, the responses are impressively linear, and the engine pulls hard all the way to its 6700rpm limiter, without any of the top-end tightness you often get from modern turbos.
Unfortunately, the prototype wears an over-loud exhaust that fills the S60’s cabin with droning harmonics, but the engine itself seems impressively refined considering the forces within it.
The big question is whether Volvo can make a car that can keep up. The prototype’s auto ’box showed signs of distress when asked to deal with throttlerequested kickdowns, and the chassis (based on an AWD T6) couldn’t deliver anything but understeer at the limit.
But the engine is mighty: one for V8 Supercars’ post-V8 future? out
VOLVO has confirmed it will be downsizing with the launch of a new threecylinder petrol version of its Drive-E engine. This 1.5-litre unit is claimed to deliver just 95g/km on the European consumption test and will be available with up to 133kW. We drove it in a V40 prototype, where it delivered decent performance, without the sort of thrumming soundtrack we’ve come to associate with three-pots.