Another day, another tuned BMW B58 engine. There really is no stopping the venerable 3.0-litre turbo six these days, everyone from Morgan Plus Six to Toyota GR Supra owners having access to a lot more horsepower very easily indeed. If people tell you the good old days of tuning are done, tell them about what can be done with a £15k M140i and a laptop. It’s still possible to go very fast with a sturdy straight six for, relatively speaking, not much money.
The latest B58 baby to get a boost is the BMW M440i, a car recently tested on PH and one that, while nice, would benefit from perhaps a little more attitude. G-Power has certainly delivered that. Its latest package for the G2x 4 Series starts with just software, which frees up 420hp and 442lb ft from the standard 374hp and 369lb ft. Enough to make a significant difference, undoubtedly, from just ECU interrogation. From there, a sport downpipe and something called a ‘GP DEEPTONE’ rear exhaust section is added for 450hp and 470lb ft; a better intercooler on top of all that liberates 480hp and 485lb ft.
For the full monty, however, all 520hp and 516lb ft (10hp down on an M4 Competition, 37lb ft up), a turbocharger upgrade is required on top of those other bits. It gets more air into the blower through a larger turbine and compressor wheel (found in new CNC milled housings), with new blades and increased boost pressures as well. That’s when things start getting a little more serious; remember the M cars are using two turbos to reach similar power. But then if you want power and torque up about 150 points each, it’s going to need some work.
Seemingly aware of just how popular BMW B58 tuning can be, G-Power has decked out a trio of 4 Series with its goodies: a Gran Coupe, a Convertible, and a two-door coupe. It mentions the 3 Series saloon and Touring versions, too, plus the M240i Coupe. A good business to be in, seemingly. All three here are on 20-inch G-Power Hurricane RS forged wheels, but seemingly few other modifications. The spoiler is exclusive to the two-door hardtop, though G-Power does offer extras like a sports air filter and a top speed limiter delete for all models.
Apparently this latest upgrade ‘emphatically demonstrates that the M440i can still be catapulted into new spheres of performance.’ Which seems eminently believable given how big the numbers now are. Even with the wheels, too, these M440is look a more discreet prospect than the fully fledged M equivalents.
To get the full 520hp, G-Power quotes €16,580, or just under £14,000. It’s the hardware that accounts for the bulk of that, of course, with almost €5,000 on the exhaust and and more than €3,000 on the boostier turbo. That initial 420hp/442lb ft pick-me-up is €4,685, or just under £4k, which feels more palatable. Earlier M440is are now less than £35,000; easy to imagine a lovely green-over-tan Gran Coupe would be even more so with in excess of 400hp…
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