Horsepower Limits: 600 is the Magic Number

When it comes to driving dynamics, it's pretty hard to beat the good-old front-engine, rear-wheel drive setup. At one point, Volvo swore by it for its stability. BMW and Mercedes-Benz are also great believers in it, although both have also started to produce front-wheel drive and all-wheel drive models to suit a more diverse market. Front-engine, rear-wheel drive setups (or FR setups) are regarded as great for sports cars because of their good 50-50 weight distribution and fairly predictable handling characteristics. 

But there is a practical limit to everything. Where FR setups become impractical is when you start putting a lot of power through them; the amount of power you have is really only as effective as how much of it you can put to the ground. Even with great leaps in tyre technology and compound, it seems that we have reached the point where "mass-market" performance cars are packed with enough performance to overcome those rear tyres. 

The magic number seems to be around 600 horsepower. Some of the crazier Europeans believe that you can get used to any figure up to 700 horsepower-per-tonne, but these are also the same people that invented Gatebil and pour cement into their engines' water jackets for strengthening. Of course there's a little variation around this depending on the tyres you run and the weight of the vehicle, but Mercedes-AMG has abandoned the FR layout for their newest E63 S and opted for all-wheel drive. Even if you look at Lamborghini, the rear-wheel drive version of the Huracan is detuned to roughly 580 hp- although arguably with a mid-mounted engine or rear-mounted engine there should be more traction on acceleration.  

Why all-wheel drive? Put simply, it allows you to put more power to the ground without spinning up the wheels. One engineer from Jaguar has said the maximum physical limit on current tyre technology is a little under 1G of acceleration in a straight line for FR setups, while their all-wheel drive system allows them to exceed 1G without wheelspin. This is the key to the ferocious launches of cars like the Nissan GT-R and the Bugatti Veyron. 

But what’s the trade-off in adopting all-wheel drive? There are a few penalties, although over time they have become less and less of an issue. The first is weight: with the extra driveline components like a front differential and transfer case, the weight naturally goes up (and of course, weight is bad). The second is that the driving dynamics change, although modern all-wheel drive systems can electronically vary the front-rear torque distribution to make it handle more like a rear wheel drive.

Purists will argue that this flies in the face of everything that is good and true and blah-blah-blah.

No.

Stop.

Be sensible for a moment.

There comes a point where a car has so much power that it simply becomes difficult to drive without electronic stability systems. While these systems are refined to the point that you hardly feel the intervention unless you look at the flashing warning lights, the fact remains that there is intervention. There is a delay in power delivery. There is a moment of hesitation when you need to accelerate, and cannot. This is why there are people who feel that cars like the Mercedes-AMG C63 S have turbo lag, when the reality is that the systems are kicking in and cutting power to prevent the car from spinning.

And this is the reason we need all-wheel drive. It’s because the vast majority of drivers, purists included, cannot handle this much power in a rear wheel drive car- and this is something they need to come to terms with. There’s a certain irony when a BMW X5 M in its over-two-tonnes of SUV glory can out-accelerate a BMW M5 through a corner, simply because it has all-wheel drive instead of only sending power to the rear.

The real question to ask yourself is this: would you have a 600 horsepower rear wheel drive car but only be able to use 80% of it, or would you prefer a 600 horsepower all-wheel drive car and be able to use 100% of that power? Are your predispositions towards all-wheel drive worth that sacrifice in performance? And if you argue that “it’s about fun, not performance”, then perhaps you should consider that constantly lighting up the rear wheels when you don’t want them to is a lot more frustrating than it is fun.

And if you truly, madly, deeply want something that fits your traditionalist views, then look to an older, lighter car instead. A Nissan S15, a BMW 1M, or a Honda S2000- these are cars that will suit you far better than a behemoth packing over 6 times the power of your standard family car. While you may not be getting the same number of looks as you roll past your nearest upscale shopping mall, you will probably care a hell of a lot less as well.