KEY ASPECTS OF PERFORMANCE
- Power/Weight. This is a commonly used ratio and is often quoted by people who realize that just raw horsepower number is a poor predictor of car performance. However, one must keep in mind that if a car can't put the power down due to poor traction, or has too much drag at speed for its power, even a car with an excellent power/weight ratio may not be all that fast overall. That said, power is a good thing. The production dp1 will have power/weight of around 2 lb/hp. To achieve the same ratio, a Bugatti Veyron would need around 2,000 hp (instead of its mere 1,001). A Ferrari Enzo would need upwards of 1,400 hp instead of the 660 it comes with.
- Power/Drag. Aerodynamic drag becomes a significant factor at speeds over 80 mph. Lightweight cars of moderate power, such as Lotus 7 and Ariel Atom, can have a good power/weight ratio enabling them to perform well at lower speeds, but they often run into a 'brick wall' at higher speeds and can be frustrating to drive at trackdays where one can only pass on the straights. For example, my 4,000 lb M5 surprised me by being faster than a 1,300 lb Ariel Atom at Pacific Raceways - because it could hit 145 mph on the front straight vs Atom's 125. With 400+ hp and diminutive size the dp1 has a very favorable power/drag ratio. It is difficult to draw direct comparisons but suffice it to say that the dp1 has about 1/2 the frontal area of a typical sportscar with similar drag coefficient, while its power is in the same ballpark.
- Power/Traction. This ratio is not often talked about but is very simple to understand. If a car lacks the traction to deliver its power to the ground, any attempt to accelerate will just send the tires up in smoke unless electronic traction control is used (which works by reducing power, so really you're only driving a car as powerful as the traction will allow and not using all of the engine's capacity). This is the biggest reason that supercars don't really do any better than much 'lesser' machinery at the track - they can't use the power that they have at typical trackday speeds, so a 660 hp Enzo is no faster than a 400 hp Corvette which itself is only marginally faster than a 190 hp Elise. The dp1, with its AWD and wide performance tires, is optimized to put its power down. To achieve the same power/traction ratio, the Veyron would need to roll on 500 mm wide tires and Enzo, due to being RWD, would need tires nearly 800 mm (over 2.5 feet) wide! When race organizers want to artificially limit performance of the cars they limit effective tire width, either directly or by requiring grooves in the tread like F1. When writing your own rules, more tire is good.
- Tire/Weight. Because a tire's traction in cornering, acceleration and braking is a function of contact patch size (all other things being equal), a heavier car needs bigger tires to generate same traction forces as a lighter one. There are many variables there but the fundamental fact remains true. Again, the dp1 is optimized with very low weight and wide rubber to generate optimum cornering, braking and acceleration forces. For example, a peak of 1.7g cornering force has been demonstrated by the prototype whereas a Lotus Elise on same compound tires only generates 1.35g. This is because the Elise tires are actually a little narrower but the car weighs twice as much. Going back to the supercar comparison, to achieve the same tire/weight ratio as dp1 a Bugatti Veyron would need 1,100 mm (over 3 feet) wide rubber!