Incredibly, new MH4 900 does what it says on tin

Manhart has charmed 922hp and 878lb ft of torque from a G82 M4. Best brace yourself...

By PH Staff / Thursday, 22 May 2025 / Loading comments

Going increasingly mad with output possibilities is obviously a tuner’s job. The last time we encountered a BMW M4 that had been breathed on by Manhart, it was a CSL with 150hp added to the total. To us, 700hp sounded like plenty enough - and it was sufficiently ‘out there’ for the firm to christen it the GTR; not the sort of letters you apply to anything without it being on the edge of the conceptual envelope. Plus it was a one-off, and that always means the gloves have come off.

The new MH4 900 (which follows the similarly bonkers MH3 Touring) it seems, is not a one-off. And yet Manhart has seen fit - presumably with sufficient customer demand to justify it - to coax an astonishing 922hp and 878lb ft of torque from the S58 lump. For context, should you really need it, that’s very nearly 100hp more than Ferrari equips the 12Cilindri with using a 6.5-litre V12. Manhart doesn’t treat us to any performance data, yet it seems fair to assume that the MH4 is absurdly brisk in almost any given scenario - and possibly a bit of a handful, too.

Even taking the endlessly tuneable nature of BMW’s 3.0-litre straight-six into account, you won’t be surprised to hear that it requires some significant upgrades to get the standard unit beyond 900hp. Manhart says the centrepiece of the entire effort is the (presumably much larger) TTH turbocharger and uprated intercooler, though it is accompanied by forged pistons and connecting rods, a carbon intake and (inevitably) a remapped ECU. The transmission has been enhanced to what Manhart calls ‘stage 2’ - a name that denotes its newfound ability to handle up to 1,300nm of twist.

Naturally, you get a new exhaust, too - specifically a valve-controlled, stainless steel one with quad 110-millimetre tailpipes. There’s also the choice of either sport downpipes or an OPF-deleting alternative. Elsewhere, the MH4 900 adds height-adjustable H&R coilovers and some additional unspecified chassis modifications, not least to get those 20-/21-inch black Raffa rims perfectly positioned in the wheel arches. In the case of Manhart’s demo car, these are intended to offset the paint job (not to mention the champagne-coloured decals or the GTR-inspired carbon fibre bodykit), but other colours are available.

Inside, the tuner keeps it admirably simple, adding its Clubsport roll bar and floor mats to the familiar M4 cabin, presumably to keep our attention focused on what’s beneath the carbon fibre cover under the bonnet. ‘For a long time, performance figures of around 1,000hp were unimaginable in road-legal cars. Today, they're reality, but still reserved for high-end supercars worth millions, or at least priced in the upper six-figure range,’ says Manhart. The MH4 900 is said to be all about entering ‘this highly exclusive circle’.

Whether or not you’d actually want to do that is, of course, all to do with personal preference. Personal experience in our case suggests the current M4 (in any spec) is plenty quick enough to satisfy most people’s aspirations on a public road - and even away from them. But perhaps we’re guilty of being too narrow in our outlook; we thought the GTR was probably a bit too much. Now look.