AC Schnitzer ACS2 40i review

As ever with Aachen-based AC Schnitzer, you can choose which upgrades and accoutrements you want, ranging from aluminium pedals that cost £198 right up to the full conversion package, which totals roughly £20,000 and morphs the M240i into a 414bhp, 443lb ft Porsche 911-baiter. This example, belonging to UK importer Rossiters near King’s Lynn, forgoes the upgraded 3.0-litre straight six, not least because the standard car’s 368bhp and 369lb ft is understandably considered ample. However, this car has almost everything else and, well, we can use our imagination for the missing 46bhp.   

It means the most valuable and effective modification is fitted, and that is the bespoke coil spring and passive damper set-up known simply as Sports Suspension. It consists of Schnitzer-unique Eibach springs controlled by custom-valved Bilstein dampers. The behaviour of the two elements working together has been formulated with fast road driving plus the odd track day in mind. And as we know from previous conversions, getting a Goldilocks balance in this regard is something of a speciality for AC Schnitzer. Note also that it’s no problem if the donor car is wired for BMW’s factory-spec adaptive dampers, because AC Schnitzer can neatly deactivate that functionality.

Elsewhere, this example features AC Schnitzer’s exhaust silencer (which is homologated, so keeps the GPF but still adds a subtle degree of gruffness to an already very smooth, very rich engine note), M2-style exhaust tips, some cabin trim and bodywork including a chin spoiler made of durable thermoplastic. A dedicated boot spoiler is also in the works back at HQ but for now the understated original part remains in situ. 

It’s those enormous 20in wheels you simply can’t miss, though. They give the ACS2 40i a considerably larger front contact patch (interestingly, unchanged at the rear) than the M240i, but it’s what you can’t see that matters just as much. Being flow-formed – a process that yields wheels lighter than casting but is less expensive than forging – means they save around 10kg of mass, all of the unsprung variety, where every gram counts. Fitted with tyres, these wheels cost £4750. While we’re at it, the Sports Suspension is £2150. Total outlay to fundamentally alter your M240i for the better? Just under £7000.

The manner of the ACS2’s dynamic improvement over the standard car really isn't hard to appreciate. Minutes after collecting this car, I’m already looking forward to spending the day in it. Straight away it feels more alive yet is just as approachable as the regular car. Even pulling slowly off the mark you can sense that this thing is more in control and command of that substantial body than the standard BMW M240i. There’s less inertia, more positivity, and more feedback – not from any particular part of the car but just in terms of its whole. That said, the ultra-firm, perforated AC Schnitzer steering rim is a worthwhile upgrade over BMW’s squidgy M Sport rim, and genuinely heightens road feel, adding to the sense of connection. Levels of intent have been dialled up but not in any pointlessly reactive way.

At speed the ACS2 pulls off that trick where you can seemingly detect every vagary of the road surface but are never buffeted by sharp jolts or head toss. Call it cast-iron plushness. And while the base M240i is already nicely balanced with a well-tuned xDrive set-up, the ACS2’s lower rates of roll and, duly, more responsive steering allow you tap into that poise and enjoy it more easily. Where the standard car often needs babying into bends (this is all relative, note), the tuned car scythes in noticeably more neatly, loads up its rear axle more promptly and puts down its power more cleanly on exit. Perhaps those springs can unload a bit abruptly after a severe compression but this is only a marginal complaint and you’d need more expensive two-way-adjustable coilovers to get better composure than this. 

Otherwise the car feels impeccably well sorted, batting off the worst of British B-roads while somehow keying you into that same surface. While you might only be 20mm closer to the road in real terms, at times it feels more like 120mm. Satisfaction really is guaranteed. You might even wonder whether the Schnitzer bods have been over here in the UK, plotting how to bring our B-roads to heel, so sweetly does the ACS2 conduct itself. 

Yet perhaps the best thing about the package is that, as alluded to, the regular car’s usability is barely diminished. Yes, casual owners are best leaving their cars untouched, as ultimately the ACS2 is less rounded than an M240i. But not by much, and for those keen to see how compelling the M240i can be when its compass points more towards ‘sports car’ than ‘GT’, this is an enlightening way to find out.