What is it?
Think of the VW Group’s TwinDrive powertrain – found in this Seat Leon TwinDrive Ecomotive test car - as three low-emission propulsion systems in one: a pure EV, a series hybrid and a parallel hybrid. And with a plug-in capability besides.
Sound complicated? It is, and costly to make too, but it’s a system that allows this experimental Leon to turn in a spectacular 166 official mpg while emitting a mere 39g/km of CO2. It can also travel 32 miles on electric power alone, and has a potential range of over 550 miles.
So, how does it work? Under the bonnet is a standard 113bhp 1.4 TSI petrol engine. Bolted to this are a 40bhp generator, a clutch, a reduction gearbox and an electric motor, also of 113bhp.
What’s it like?
When the Leon starts, it sets off electrically. But if hard acceleration is required at low speeds, the petrol engine fires up to generate additional energy for the electric motor to consume. In these circumstances, usually brief, the powertrain turns series hybrid, the clutch open to separate the petrol engine from the electric-drive motor, allowing it to act as a generator.
At higher speeds the clutch closes to yoke the 1.4 engine and the electric motor together, their combined outputs limited to 161bhp. The 40bhp generator provides an extra accelerative boost at low speeds, besides being driven by the petrol engine to recharge the battery.
But while this propulsion strategy sounds – and is – complex, driving the TwinDrive Leon is easy. There’s the momentarily disconcerting EV experience of twisting the ignition key to hear silence, the Leon advancing on amperes, but the automatic transmission lever is entirely conventional, selection of ‘D’ allowing an immediate departure. Pull it back a notch further and you get Sport, or you can sink a green button for electric drive only, perhaps for zero emission city travel.
For many commuters the Leon will rarely use its petrol engine what with that 32-mile range, the battery best charged overnight from the mains.
Driven gently, the Seat is much like any other electric car, advancing in eerily brisk and restful silence. Accelerate hard and you can hear the petrol motor kicking in, though in the same slightly disconcerting style as an engine harnessed to a CVT transmission, the revolutions of its crankshaft bearing little relation to those of the driven wheels. But a prototype is what this car is and Seat is about to trial five examples with Spanish fleets to get an idea of how the car will be used, and what drivers think of it.