There’s something raw about a fast car with no roof. G-Power’s latest build takes the BMW M4 Convertible and turns it into something far more serious: the G4M Bi-Turbo Convertible, a machine with supercar numbers and the ability to enjoy them under open skies. The visual upgrades are sharp but not overdone. A GP-VENTURI carbon hood, GP-SHURIKEN carbon grille and bumper corners, and a set of GP-HURRICANE RR forged wheels set it apart without shouting. Other add-ons—like splitters, wings, or a retrimmed interior—are available, but the real transformation is under the hood.
The GP-720 Package
This M4 runs G-Power’s GP-720 performance software, lifting the 3.0-liter twin-turbo inline-six to 720 hp (529 kW) and 850 Nm (627 lb-ft). That’s nearly 200 horsepower more than BMW’s own M4 Competition Convertible. Top speed climbs to 330 km/h (205 mph), moving the car firmly into territory usually reserved for exotics. Backing it up is the G-POWER DEEPTONE stainless-steel exhaust, tuned for a deep burble and fitted with a distinctive quad-tailpipe setup—two 100 mm tips paired with two even larger 110 mm tips, all finished in carbon fiber. It’s the kind of sound you won’t confuse with anything stock.
With these numbers, the G4M Bi-Turbo Convertible sits eye-to-eye with some of the fastest cars of the last two decades. The difference here is that you can drop the roof and hear the turbos and exhaust working in the open air, an experience not many closed-roof supercars can match.
The interior reveals that this G-Power G4M is built on the pre-facelift M4 Convertible; easy to spot thanks to the smaller LCD screens with iDrive 7. You will also see that the use of carbon fiber spreads across the entire dashboard and center console, while the steering wheel gets its own carbon fiber inserts.
How Much Power Costs
The GP-720 upgrade isn’t cheap—€35,700 ($41,630) in Germany. Lower stages are available too: 600 hp, 620 hp, 650 hp, or 670 hp, starting at €3,685 ($4,295). The 700 hp package tested here sits in the middle at €14,900 ($17,375). It’s a wide range, but even the entry level comes at the price of a decent used car.
The standard BMW M4 Convertible is already one of the most complete open-top performance cars on the market. G-Power’s version doesn’t just turn up the volume—it rewrites the car’s limits. With 720 horsepower, 330 km/h top speed, and a roof that disappears, the G4M Bi-Turbo Convertible is less about subtle improvements and more about giving the M4 the kind of performance it was always capable of.
[Photos: G-Power]
