For those with deep pockets who feel that BMW's 4.4-litre turbo-V8-powered M6 is just a little, well, tame, German tuning house G-Power has developed a package it calls the Bi-Tronik III, that pushes the standard car's 410kW and 680Nm up to 472kW and 777Nm - and a top speed of 315km/h.
Also available are 21” 'Silverstone RS' forged-alloy rims wrapped in Michelin Pilot Supersports - 265/30 in front and 305/25 at the rear - multi-adjustable coil-over suspension, a titanium exhaust system and carbon ceramic brakes.
But to start with the engine: the G-Power boffins reckon the turbocharging technology on BMW's 4.4-litre V8 M engine isn't intrinsically different than the superchargers the company usually uses to make big numbers - after all, each uses a centrifugal compressor to force-feed the intakes.
Boost is moderately increased, say G-Power, but most of the extra kilowatts come from the ECU mapping. Unlike BMW, who use a standard, compromise mapping for all 4.4-litre engines, G-Powers tunes each ECU to the specific requirements of that particular engine - or, in fact, of individual cylinders.
Not only that but, based on the experience gained in building 590kW BMW M5 Hurricane conversions, the ECU also backs off the power momentarily during gearshifts - like a quickshifter on a racing motorcycle - to reduce the stress on the transmission.
All that power needs a voice, say G-power, so the entire exhaust system from the downpipe catalysts onwards is replaced by titanium link pipes with resonators, ending in four 100mm titanium or carbon-fibre drainpipes (sorry, tailpipes), giving the M6 a deep, throaty sound and saving about 12kg in overall weight.
But power, of course, is useless without control (ask anybody who's driven a Shelby Cobra on a wet road!) so suspension is entrusted to G-Power GM6-RS continuously height-adjustable coil-over dampers with nine selectable settings each for compression and rebound.
Road testers have found that even with the standard engine set-up it's possible to induce a bit of fade in the stock braking set-up under extreme conditions. To take care of this G-Power supply 420mm carbon-ceramic front brake discs (half the weight of the standard steel platters - and that's unsprung weight we're talking about, remember) and special, much more powerful, six-piston callipers with stainless-steel brake hoses, increased pad area, a higher friction rate and greater heat-dissipation capability.
NOW FOR THE BAD NEWS:
The engine tweaks cost €5200, (R62 000) including the individual tuning of the customer's car, the titanium exhaust system is €5985.71 (R71 750), carbon-ceramic brakes for the front axle will set you back €14 460.50 (R173 000), the GM6-RS coil-over kit costs €2179.83 (R26 150) and 21” rims with Michelin Pilot Sport tyres will add a further €8 325 (R99 800).
That's over and above the cost of the BMW M6 itself, which retails in South Africa for R1 401 076.