520kW and 1000Nm take this Grand Cherokee from 0-250km/h in 12.85 seconds, at Reef altitude.

Johannesburg - Colin Chapman achieved outrageous performance by making his Lotus lighter, Enzo Ferrari with dramatically streamlined bodywork and Soichiro Honda with lots and lots of tiny pistons flying up and down at insane speeds.

Rob Green does it the old-fashioned way, starting with the biggest engine he can get and pumping in copious quantities of fresh air - and the results are truly outrageous.

This, fellow petrolheads, is the RGMotorsport Jeep Grand Cherokee SRT-8, with all the lightness of a granite headstone, the aerodynamic finesse of a brick outhouse and pistons the size of coffee cans.

But it also has an RGM-Whipple twin-screw supercharger, with its own self-contained lubrication system, feeding its 6.4-litre Chrysler V8 through a dedicated high-volume air-to-liquid intercooler and breathing out through a 76mm Techniflow exhaust system, orchestrated in muscular harmony by customised RGMotorsport software.

SKY-HIGH POWER

The result, according to Green, is 520kW and 1000Nm, enough to launch this imposing SUV from standstill to 100km/h in a V Box-verified 4.74 seconds, rip off a quarter-mile in 12.85 seconds at 177.2km/h and blitz the standing kilometre in a little more than 23 seconds, topping out at 230km/h.

But perhaps most important of all, in the hands of not-quite-tame race driver Jacques 'The Stiglet' Joubert, it accelerated from 0-250km/h in just under 30 seconds - and it needed only 1408 metres to get there.

Bear in mind that all these big numbers were laid down at Gauteng altitude, where a standard SRT8 Grand Cherokee needs almost twice the time and distance to hit the same speed.

If you think you have a quicker, street-legal SUV, Green challenges you to put your timing slips where your mouth is. Alternatively, RGMotorsport will do the same for your Jeep Grand Cherokee SRT8, or the similarly-engined Chrysler 300C SRT8), starting from R190 000, including RGMotorsport's standard six-month or 20 000km warranty on parts and workmanship.