First, a little aside: With my old V6, the fuel economy was shocking. I barely got 27 mpg if I drove like an old fart, but with an onboard computer giving fuel economy readouts, I noticed some very interesting things. I know it’s obvious that acceleration uses more energy and therefore fuel but quite how much I didn’t realise, and then there’s also the efficiency of the engine over the rev range.
At a constant indicated 47 mph on the motorway I could achieve the car’s best economy – an instantaneous reading of nearly 50 mpg, although at lower speeds, even in the same gear, with less air resistance etc. it dropped to 30-35. At 47 mph the engine was pulling 2,000 rpm, and it’s interesting to note how often the phrase “and 80% of that peak torque figure is available from just 2,000 rpm” is used in car magazines. Something going on there I think…
But also, consider this. That car had 200 bhp, and could accelerate to 60 mph in 7.5 seconds, using a lot of fuel on the way. However, just about any car these days can haul itself from 100 mph back down to rest, in under 5 seconds. Granted, some of that can be attributed to aerodynamic and transmission losses, but even at low speeds when these things count for less, cars can dissipate energy through their brakes far, far faster than their engine can produce it.
That means you basically waste tons of fuel every time you slow down, so recovering that energy makes a lot of sense.
And so back to KERS, which as most of you probably know, stands for Kinetic Energy (otherwise know as movement) Recovery System. Instead of dissipating energy through conventionally heating up the brakes, the energy is collected, and made available again later on. And best of all, clever electrical KERS systems can be set up to give you the choice of either using this energy to extend the range of your car, or to supplement the engine’s power, on demand.
To my mind, that’s the best of both worlds. Imagine a Ferrari with bucket loads of horsepower, (not too hard), AND also being able to return a decent mileage figure. What’s even more exciting, is that this will soon filter down to more realistically affordable cars too. Imagine a hot hatch with 25% more brake horsepower, but the fuel economy of it’s diesel variant!
That day may be much closer than you think.