Limo-Green’s powertrain consists of a home-charged 360-volt lithium ion battery bank – weighing 93kg and housed in the spare wheel well – feeding a 200hp brushless DC electric drive motor with two-speed gearbox, located down where the original ZF automatic used to be and driving the rear wheels.
There’s a featherweight 60bhp, 1.2-litre, lean-burn, three-cylinder Lotus engine mounted back to front in the nose, configured by clever electronics to start automatically and drive an on-board generator when the battery bank needs more charge, as it will on any journey greater than about 30 miles.
However, because the consortium’s research indicates that anything up to 80 per cent of an average XJ owner’s journeys fall well within EV range, hence the estimated 50g/km CO2 output (not including power station emissions) in real-world use, although the figure is 120g/km when the engine is running.
The test drive
We came away deeply impressed from our drive in the prototype, not because the performance was different from a normal petrol or diesel-powered XJ, but because it was so very similar.
This prototype, more frugal than a Ford Fiesta and with a touring range of well over 600 miles, could be driven in just the same way as any conventional XJ. It had the same strong acceleration (0-62mph in 7.5sec) and the same easy-rolling cruise for which Jaguars are famous.
It feels powerful, because electric motors develop full torque from standstill. The ‘throttle’ pedal is a little more sluggish than in a standard XJ, but Limo-Green engineers have made it so; a car like this gets driven by dozens of people, including heavy-footed politicians, without much in the way of mechanical sympathy. The drive is exceptionally smooth and if you want to go faster you just press harder.
Sure, it had a few jerks and rattles, and its top speed was restricted to around 90mph by the transmission’s two gears, but it was instantly clear that the next two prototypes, nearing completion at MIRA, will banish most of these glitches. Jaguar’s plan is to have around 100 Limo-Green prototypes running globally by 2012.
Limo-Green project boss Steve Nicholls points out the essential versatility and simplicity of his car’s layout. “This is a pure electric vehicle,” he says. “The electric motor is its only form of propulsion. The petrol engine’s function is to drive the generator. It is carefully specified to be small enough to be efficient, but big enough to keep you going.
“The generator, which works as a starter for the engine, switches polarity as the car stops to provide regenerative braking and recover some battery charge in the process.
“As time goes on, the engine could potentially be replaced by a diesel, an engine running on CNG, a gas turbine, a fuel cell or whatever makes sense for the future.”
The project appears to demonstrate that lighter, quieter and much more frugal XJs are coming to tomorrow’s showrooms. Which means the major happiness is coming to the big Jaguar owners of the future.