Colin Chapman, the famed Lotus engineer of old, would design his cars using his now well-oiled mantra: Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere. Wise words indeed and a formula that continues to work well for those little Lotus and Caterham nippers still on sale today. But…
…that’s not the way many supercar makers are going lately, with the extra weight of hybrid systems – batteries and motors – used to back up already powerful petrol engines; all in search for lower CO2 outputs. The quoted fuel economy figures are never matched in the real world, but it is the benchmark by which all manufacturers must be measured, and so the hybrid research continues.
The new Porsche 918 Spyder – all £800,000-worth of it – claims a combined economy figure of 85mpg, with CO2 at 79g/km. That’s better than many hatchbacks, yet the 918 still turns in some searing performance figures; 62mph in 2.8 seconds and a 211mph top speed. How can this be in a car that in its most expensive, lightest form (‘Weissach’ package) weighs a hefty 1,640kg?
Well, we all know that the benchmark European test for fuel economy doesn’t translate to the real world, but us motorists understand this now and take the manufacturer figures with a pinch of salt – your own dealer test drive before you buy will give you a better idea of actual miles-per-gallon. But with this new Porsche it’s surely just a cynical headline-grabbing stunt. Thrash this thing for an hour or two and see what economy you get from its 599bhp, 4.6-litre V8 petrol engine!
Publicity stunt aside, the Porsche engineers have spent a great deal of time and knowhow integrating the hybrid system into their supercar; maximising the potential benefits of having a torquey electric motor driving each axle. And it’s these motors, plus a light-as-possible-chassis, torque vectoring cornering assistance, and active suspension that all help to mask the 918’s substantial weight to out perform the petrol-only Porsche mega-models before it, like the comparably-priced V10 Porsche Carrera GT supercar.
The Carrera GT has a 605bhp, 5.7-litre V10 petrol engine, and that engine has to carry 1,380kg around with it. On the Nurburgring, the GT laps at 7:34s. The 918 has so far set times some 20 seconds quicker, carrying a weight of at least 1,640kg, with a combined power of 875bhp. So, as the 918’s weight has fattened, so has its power output, and while those hybrid batteries and motors are indeed a juicy weight penalty, the extra instant torque from the motors seriously sharpens immediate acceleration, and allows for cunning digital cornering advantages, like torque vectoring.
The GT is rear-wheel drive only, but the 918 makes motion-use of all four corners, with the electric motor up front – with its own gearbox – doing some clever things during hard cornering. Torque vectoring uses the independent control of each wheel to best corner the car, like a differential; if the inside wheel is moving slower than the outside wheel, the car will pull through the corner with a tighter line.
Electric motors are perfect for this role as they can make noticeable torque instantly; reacting to driver inputs and road conditions to corner the car as hard as possible. Throw in Porsche’s experience in active suspension, and light and stiff chassis tech – with a carbon fibre reinforced polymer (CFRP) monocoque for the 918 – and you’ve got a very high tech, very expensive, and somewhat overweight supercar, but one that can corner like no Porsche before it.
Nifty stuff indeed, but is it a ‘real’ Porsche? And will we feel the ‘real’ thrills associated with driving a mechanical machine at ten-tenths speed? Or will the whole driver / car / road interaction in the 918 be too digital and lifeless? Well that’s still up for debate, but I’m afraid it’s a pretty pointless debate, because the new 918 now sets the template for all Porsche sportscars to come.
By Dan Anslow