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Explained: Lexus’ Multi Stage Hybrid system
LC500h’s new hybrid powertrain uses a CVT and a 4spd auto. Here's how it works
“Both are my babies, but maybe I would buy the hybrid.” So says Koji Sato, the new Lexus LC’s chief engineer, when asked whether he’d rather have the V8-powered LC500, or the petrol-electric LC500h, both on sale in Spring 2017. It’s a bold call, given Lexus’ current range of hybrids aren’t exactly what you’d call dynamic, but then this 500h is something entirely new.
Let’s start slowly, with the basics, because by Lexus’ own admission it’s the most fiendishly complicated powertrain it has ever produced. Much like the RX450h it combines a 295bhp 3.5-litre V6 with a CVT gearbox, a generator motor (that also controls the ratio of the CVT) and an electric motor for a total of 354bhp and a 0-62mph time of under five seconds. So far, so familiar. But there’s more…
To answer criticism (a fair proportion of it from us) that with a CVT gearbox the engine revs rarely match the throttle position (something often referred to as ‘the rubber-band effect’, or ‘that infuriating whine when I use anything more than half throttle effect’) Lexus has tacked on a four-speed auto gearbox at the end of the transmission, with four real fixed ratios.
If four seems like a low number, fear not – in manual mode the driver will have 10 steps to select from with paddles behind the wheel. The first three gears in the new auto ‘box are combined with three artificially chosen ratios in the CVT (that’s nine gears right there), while the fourth gear is an overdrive – taking the total to 10. It’s no coincidence that’s the same number as the V8 model’s real 10-spd auto, an engineer told us “studies have shown that a 10-speed gearbox gives the best dynamic reaction.” Sounds like a few too many to us.
On the face of it, it’s a lot of effort to go to ‘simulate’ a 10-cog gearbox. Why not just bolt on a real 10-speeder and be done with it? The answer, of course, is efficiency: with the CVT and the four-speed auto working together the LC500h can pull a handful of neat tricks.
A much higher first gear ratio means the LC500h can spin its not-insubstantial rear tyres on dry tarmac. We look forward to putting that claim to the test. The greater spread of ratios means it can now run all the way to 88mph without switching the engine on (the RX450h runs out at 62mph), and at high cruising speeds the engine can tick over at very low rpm to replenish the battery.
“Basically it locks up and feels great when you’re going for it, but then packs up and goes into maximum efficiency mode when you’re not,” says Stefan Ramaekers, Lexus’ senior technical trainer and the man tasked with explaining the tech to a group of puzzled journalists.
There were promising noises from Alain Uyttenhoven, Lexus’ European boss, too, who mused that he “could imagine two lines of high-performance LC, but the heart of the market is in improving the V8, not the hybrid”. Interesting stuff. Makes sense too, because adding more power to the hybrid would mean a bigger electric motor and a bigger battery pack to deliver the extra current, adding more pesky weight and blunting agility.
“Priced somewhere between the 6-Series and the Porsche 911” is Uyttenhoven’s only guide on positioning of the LC at this stage, with the hybrid and V8 model priced “extremely closely” in the UK. So it’s not a £350,000 LFA replacement - under the £100,000 mark seems likely - but this is the beginning of a brave and more emotional Lexus brand, he claims. We approve.