Red Bull Global Rallycross
Regulations limit them to 2 liter engines and 45 millimeter turbocharger restrictor plates, which ultimately are the two factors limiting power. The engines produce about 600 horsepower, and over 650 lb-ft of torque, rocketing these machines from 0-60 in as fast as 1.9 seconds.
1.9 seconds! If we do the math, 60 mph is equivalent to 88 ft per second. 88/1.9 = 46.3 ft/sec squared, or if we divided by 32.2, it means the cars accelerate at over 1.4 longitudinal g’s!! That’s faster than any production vehicle, regardless of how much it costs.
So how do they achieve such mind blowing acceleration? First and foremost, you’ll need all wheel drive and an absurd power to weight ratio. With a minimum weight of 2921 pounds including the driver and all fluids, the vehicles are carrying less than 5 pounds of weight for every horsepower the engine produces.
All wheel drive is obviously critical for maximizing acceleration, but it’s also important that the engine torque finds its way to the wheels with the most traction. To do this, plate and ramp style mechanical limited slip differentials are used front and back. A shallow ramp angle in an LSD will lock up more easily under throttle. With the differential locked up, torque goes wherever it finds grip. A steep ramp angle will provide little lock-up, or if it’s as steep as 90 degrees, no lockup.
If you use too shallow of an angle, you’ll have too much lock-up under cornering or braking, resulting in the car running wide. If you use too steep of an angle, you won’t be able to fully put the power down to optimize your start, or acceleration through-out the race. Often though, coming down to the precise angle is not only a matter of what’s best from an engineering standpoint, but what the driver prefers as well, depending on how they like to attack the course.
Now all of this sound great so far, but ultimately the power gets put down where the rubber meets the road. BFGoodrich supplies their g-Force RC02 Rallycross tires, which are developed specifically and exclusively for Red Bull Global Rallycross. Built for 17 inch wheels with a profile of 235/45, the radial tires are molded slicks specially designed for mixed surface events. For both the front and the rear, BFGoodrich recommends negative 2.0 to negative 3.0 degrees of static camber, with a cold pressure of 20-22 psi. The tremendous grip these tires provide is the last mechanical step of getting to 60 in less than two seconds.
Huge thank you to Red Bull for sponsoring this video!
Also published on Medium.