The BMW M6 Gran Coupe represents the pinnacle of the Bimmer’s 6 Series family. In a lot of ways, it’s also the model that represents everything BMW stands for as a pioneer in the auto industry, bridging the sporting performance of the M family with the luxury credentials of the 6 Series->ke320 lineup and the technological pioneering of the German automaker as a whole. So the M6 Gran Coupe is an important model for BMW,->ke178 which is why it is surprising that we don’t see a lot of tuning kits for the model compared to other BMWs.

So thank goodness for G-Power, right? The German tuner made its bread by building programs for BMW models and this latest kit is another step towards strengthening that legacy. It doesn’t have any aerodynamic kits to speak of. It doesn’t even have any interior modifications. But neither of those things are G-Power’->ke1323s forte. The tuner’s meal ticket are its engine modules and it’s given plenty of other BMWs the extra power they’ve needed to really become instruments of power, luxury, and performance.

Now it’s the M6 Gran Coupe’->ke208s turn and for better or worse, the variety of engine programs that are available should give owners plenty to choose from. Good, better, best; it doesn’t matter. G-Power has you covered whichever direction you take.

Continue after the jump to read the full review.

Exterior

The exterior upgrades on the BMW M6 Gran Coupe were limited to just a new set of G-Power’s own 21-inch Hurricane RR-forged alloy wheels shod in 255/30ZR21 tires at the front and 295/25ZR21 tires at the back. Outside of these wheels, the M6 Gran Coupe retains its standard configuration, right down to the headlights and the mirror caps. So if you’re expecting anything more from G-Power in this regard, you’re setting yourself up to be disappointed.

Interior

It’s pretty much the same story with the interior. G-Power didn’t touch it so whatever BMW put into designing the cabin of the M6 Gran Coupe, that’s what you’re going to get. All’s not lost though considering that Bimmer actually gave the M6 a cabin that really doesn’t need a lot of upgrades to stand out. On its own, that interior already speaks highly of the German automaker’s design ability. If anything, it might be a good thing that G-Power didn’t do anything to mess up the luxurious ambience of the M6 Gran Coupe’s cabin.

Drivetrain

Now that we’ve gotten the design upgrades – or lack thereof – out of the way, let’s focus on the real meat and potatoes of G-Power’s program for the M6 Gran Coupe. I don’t know if BMW’s trying to make up for the absence of exterior and interior refinements, but it definitely feels like the tuner has something to prove with what can only be described as comprehensive upgrades on the M6 Gran Coupe’s 4.4-liter twin-turbo V-8 engine. Yes, you read that right. We’re talking about upgrades here because G-Power has not one, not two, but three different stages of engine upgrades for all you power-starved owners out there.

The first and most modest of these kits mainly involves remapping the M6’s ECU unit. G-Power is actually offering two variants for this stage, including the Bi-Tronik 5 power module that’s really just a plug-and-play kit that’s best suited for those living outside Germany, including us here in the U.S. The other option is the Bi-Tronik 2 factory ECU remap. This one’s a little more permanent because G-Power will do the ECU remap itself depending on the kind of power and response a customer wants. Either way, these two modules can increase the output of the M6’s eight-banger to as much as 650 horsepower and 612 pound-feet of torque.

The Stage 2 kit makes use of a Bi-Tronik 5 V2 conversion kit and is assisted by gas-flow optimized stainless steel downpipes and catalytic converters. This particular kit bumps up the output to 700 ponies and 667 pound-feet of torque. Rounding out the engine upgrades is the Stage 3 kit. This kit is made up of the Bi-Tronik 2 V3 module, which, in addition to the downpipes included in the stage 2 kit, adds a full-length titanium exhaust system with a four-pipe sport rear silencer and titanium link-pipes with integrated resonators. Total output here? 740 horsepower and 719 pound-feet of torque. Pull out the calculator, do a little addition, and you get an increase of 180 horses and 217 pound-feet of torque from the “normal” output of the M6 Gran Coupe.

G-Power didn’t release the performance numbers of the first two stages, but the third-stage kit does help the M6 sprint from 0 to 124 mph in just 10.5 seconds to go with a new, supercar-like top speed of 202 mph.

Pricing

G-Power’s Stage 3 kit is priced at €14,772 euros, which converts to $16,813 based on current exchange rates. That amount is broken down to the following items: €3,750 ($4,270) for the Bi-Tronik 2 V3 module; €668 ($760) for the Vmax increase; €6,493.08 ($7,390) for the new titanium exhaust system with the four 100mm carbon tailpipes; and €3,860 ($4,392) for the downpipes with the 200-cell sport catalysts.

Competition

Mercedes-AMG C63 S By Brabus

You know it was coming. A tuning kit for the BMW M6 Gran Coupe will always draw comparisons to its counterpart at Mercedes, namely the Mercedes-AMG C63 S. Fortunately, a recent program for the high-performance Merc-AMG was unveiled by no less than Mercedes tuner extraordinaire Brabus. The German tuner presented a comprehensive tuning kit made up of a carbon fiber aero kit to go with a fancy set of wheels and a well-dressed interior. The kit, in particular, came with a front spoiler, front fender vents, side mirrors, air intake surrounds, rear spoiler, and a carbon fiber diffuser.

The AMG C 63 S also benefited from the German tuner’s very own PowerXtra B40S – 650 module. The kit came with a pair of turbochargers with larger compressors, new core assemblies, and reinforced axial bearings. An engine-specific remap was also included, resulting in an increase of 140 horsepower and 80 pound-feet of torque for the AMG C63 S’s 4.0-liter bi-turbo V-8 engine. That equates to a new output of 650 horsepower and 604 pound-feet of torque, enough to propel the performance coupe to 62 mph in just 3.9 seconds to go with a top speed of 200 mph.

Read our full review here.

Mercedes-AMG S65 Rocket by Brabus

If that Brabus kit isn’t to your liking, the German tuner also has one for the big brother of the AMG S family. This one is for the AMG S65 and it’s been been bestowed with the Rocket name. In other words, it’s Brabus at the peak of its powers. That’s evident with a carbon fiber aero kit made up of a front spoiler, rear spoiler, and rear diffuser. Brabus also took time working on the car’s interior, giving it a fancy leather and trim combination made up of light brown and magnolia leather. The leather itself is complemented by a beige topstitching and “Fire” piping while the pedals, paddle shifters, and door pins were all replaced with aluminum versions.

It’s fitting that Brabus gave the AMG S65 the Rocket treatment. Not only did the tuner increase the displacement of the V-12 engine from 6.0 liters to 6.3 liters, it also replaced the standard turbochargers and dropped in a larger pair to increase the amount of power that can be squeezed out of the engine. A special billet crankshaft with a longer stroke, a high performance exhaust, and a reprogrammed ECU unit were also included in the kit, giving the AMG S65 a mouth-watering 887 horsepower and 1,106 pound-feet of torque. That translates to a 0-to-62-mph sprint time of just 3.7 seconds to go with a top speed of 217 mph. Pretty impressive.

Read our full review here.

Conclusion

There aren’t that many programs for the BMW M6 Gran Coupe so in some ways, this G-Power kit is a god-send for owners of the high-performance 6er. The lack of any exterior and interior upgrades may turn some people off, but the German tuner made up for it by giving those who are interested in the kit plenty of options to choose from with regards to the amount of extra power they’d want in their M6s. It’s a common trade-off that’s routinely part of the aftermarket industry so if you’re the type who prefers to keep the upgrades on the engine, this kit is as good and as versatile as it’s going to get.