Jaguar XFR: 225mph

The longstanding Jaguar speed record has just been broken by the new XFR. The record was previously set by Martin Brundle in an XJ220 in 1992 at Nardo where he reached a speed of 217.1mph.

The new Jaguar speed record is now a staggering 225.675mph after a mildly modified XFR achieved this speed at Bonneville Salt Flats on November 7 2008.

The car was prepared by Rocketsports, a race preparation company based in East Lansing in Michigan. The engine was mildly modified by speeding up the supercharger slightly to give higher boost pressure, while the ECU modified accordingly. The result was 600bhp at the same peak power rpm as before. Other mods include a rear spoiler to reduce drag and a flat floor underneath the car. Amazingly, the gearbox and rear diff remained as standard.

When they began the initial runs at Bonneville, the main problem Rocketsports faced was keeping traction at high speed and in the end 250lb of ballast was needed in the boot of the car to help press the rear tyres into the salt surface. The tyres were in fact standard Michelin Pilot Sport 2s running at 50psi to help minimize the drag on the relatively soft salt surface.

The driver who did the run was Paul Gentilozzi, who is the founder of Rocketsports and he told evo the main aim was just to beat the XJ220’s time so the 225mph peak was a nice surprise to everyone. With the Salt Flats being at an altitude of 4200ft and the salt surface having a higher drag factor than regular tarmac a car capable at 200mph at sea level would only achieve 180mph on the salt flats so 225mh was a fantastic achievement.

The engine was at 6650rpm when 225.675mph was reached and when they analyzed the data after the record run it showed they were still getting 6% wheel slip when the record speed was reached. Paul admitted he couldn’t use full throttle until he was beyond 150mph and then at 200mph the Jaguar would get a little ‘lose’ but once through this wobble stability returned and the top speed was achieved after only 9 runs.

Read about the new XFR and XKR which have just been unveiled at the Detroit motor show.