The BMW 8 Series combines luxury and performance into one expensive package. It’s a halo car for the brand at a time when crossovers and SUVs still reign supreme, and the hopped-up M performance version only adds to the driving experience.

Out of the box, the M8 offers 600 bhp (447 kilowatts) – 617 bhp (460kW) if you upgrade to the Competition model. That’s plenty for most people, but those seeking more can look to G-Power, the aftermarket tuning company, which now offers the G-Power G8M Bi-Turbo – an 820 bhp (603 kW) supercar.

G-Power offers three tunes for the BMW M8, with the most potent offering upping both horsepower and torque – up to 738 pound-feet (1,000 Newton-metres). The added oomph from the M8’s twin-turbocharged 4.4-litre V8 comes from both software and hardware upgrades. The turbochargers feature larger compressor wheels while the factory engine control unit receives new programming. Downpipes with or without sports catalytic converters are available, as is a titanium exhaust system with carbon tips.

There are two other tunes available, but they are less powerful. The entry-level upgrade increases the M8’s output to 720 bhp (529 kW) and 627 lb-ft (850 Nm) of torque. That’s achieved with a simple performance software upgrade. The other tune falls right in the middle, combining the software update and downpipes with the sports catalytic converters. This tune produces 770 bhp (566 kW) and 686 lb-ft (930 Nm) of torque. Visually, G-Power adds 21-inch Hurricane RR forged wheels with a black diamond-cut finish.

Gallery: G-Power BMW M8 bi-turbo

The G-Power tunes offer a variety of performance levels, which is excellent for customers who may not want to go all-out with an extra 200 bhp (149 kW). While BMW retailers may be struggling to move 8 Series models off their lots, it’s nice to know some aftermarket companies are catering to M8 owners who want to take BMW’s M brand to the next level.

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G-POWER G8M Bi-TURBO with 820 hp: BMW F91 M8 taking performance to new heights

For more than 35 years the brand G-POWER has stood for optimized BMWs with extraordinary performance values. The fitting platform is traditionally mostly one of the top models, which are built in the hallowed production halls of M GmbH. This was also the case for the latest creation by the G-POWER specialists, headquartered in the Swabian part of Bavaria. The G-POWER G8M Bi-TURBO is based on the equally sporty and luxurious M8 Competition Cabriolet.

In its standard production version, the open Gran Turismo already features the extremely powerful S63B44T4 eight-cylinder engine with an output of 625 hp and 750 Nm. It is even more brutishly powerful following transformation to the G8M Bi-TURBO – with a whopping output of 820 hp (603 kW) and 1,000 Nm torque! To achieve these values, G-POWER relies on a combination of software and hardware upgrades and on the one hand installs the GP-820 performance software, which includes individual, optimized programming of the maps on the factory engine control unit.

On the other hand, upgrade turbochargers with a larger compressor wheel plus improved turbine wheel and CNC-milled housings, downpipes with or without sports catalytic converters that reduce exhaust gas back pressure, and a titanium exhaust system are used. The latter produces a rousing sound backdrop that is even reminiscent of motorsport vehicles. The tailpipes are carbon-tipped. The 820 hp version is the most powerful performance upgrade for the M8, and two further upgrades are available. The entry-level upgrade is the increase to 720 hp (529 kW) and 850 Nm, which is achieved exclusively via the GP-720 performance software. In between is the version with 770 hp (566 kW) and 930 Nm, in which case the BMW gets the GP-770 performance software and the downpipes with sports catalytic converters. The G-POWER G8M Bi-TURBO stands out visually thanks to its HURRICANE RR forged wheels. The lightweight, ultra-strong twin-spoke wheels boast a 21-inch format, a black diamond cut finish and Michelin tires in the sizes 285/30 ZR21 and 295/30 ZR21.