The Ultima RS is one of the most extreme road-legal kit cars ever developed, combining race-car architecture with staggering power and minimal mass. In this track test, Ben Collins puts a heavily modified example through its paces at Dunsfold, investigating whether its extraordinary power-to-weight ratio can translate into a competitive lap time.
The car tested is powered by a Katech-built Chevrolet LT4 V8 fitted with a Magnuson TVS supercharger and an aggressive camshaft. Following dyno development, the engine reportedly produces 1,150 horsepower. With the Ultima weighing just 930 kilograms, its theoretical power-to-weight ratio reaches approximately 1,180 horsepower per tonne—higher than that of the road-legal Koenigsegg Jesko Absolut and surpassed only by extreme machines such as the track-only Bugatti Bolide.
The chassis was also substantially reworked for circuit use. Originally supplied with 500-lb/in front and 700-lb/in rear springs, the RS was upgraded to 750 lb/in at the front and 1,000 lb/in at the rear. The objective was to provide the additional control required for track driving without introducing excessive chassis loads.
Collins initially runs the car at a reduced 700-hp setting while the new brakes and drivetrain components are bedded in. Early impressions reveal exceptional mechanical grip, strong braking performance and immediate throttle response, but the first sessions expose serious reliability challenges. Elevated intake temperatures trigger misfires, forcing the team to repeatedly cool the engine and make adjustments.
Once full power is introduced, the RS records a 122.6-second lap, matching the Porsche Carrera GT benchmark. However, the car remains compromised by overheating, chassis movement under braking and inconsistent damping control. A particularly significant limitation is the electronically controlled paddle-shift gearbox, which Collins finds too slow and poorly matched to the engine’s enormous torque output.
Further attempts produce a torque-limit intervention, preventing the engine from delivering its full potential. Although the RS demonstrates the pace, grip and outright performance to become a formidable track weapon, its reliability and drivetrain calibration prevent it from realizing that potential.
The test ultimately highlights the fundamental character of the Ultima RS: despite carrying a license plate, it operates much closer to a competition car than a conventional road car. Its extraordinary performance is undeniable, but extracting that performance consistently requires the level of engineering support, cooling management and setup work normally associated with a dedicated race machine.
Source: Ben Collins Drives
