2023 BMW AC Schnitzer ACS1 F40

Can a series of subtle AC Schnitzer upgrades bring out thebest in BMW’s hottest hatch? We drive the ACS1 to find out...

If there’s one name in the BMW tuning world that stands head and shoulders above the rest it has to be AC Schnitzer. Founded way back in 1987 it’s been fettling BMWs and MINIs of all types for 35-years now and over the years it’s constantly had to reinvent itself and respond to both the market and changing technologies within the cars themselves. Long gone are the days of increased capacities, hotter cams and traditional engine tuning and since then we’ve sampled supercharged Schnitzer cars and many that have featured reworked electronics to liberate more power. The one thing that’s linked just about every AC Schnitzer car I’ve ever driven though is the company’s ability to make it better than the car on which it was based. I’ve been fortunate enough to sample a raft of Schnitzer machinery from its first tuned E46, the S3 A.R.T., right up to one of its latest hits, the i3, perhaps an unlikely candidate for the tuner’s art. And while some extra power has been a feature of the majority of cars I’ve tested that’s not always been the case. Schnitzer wisely leaves the i3’s electric motor well alone and even its take on the i8 didn’t feature any tweaks to its turbocharged three-cylinder engine.

Of course, there’s always been more to a Schnitzer car than a simple engine upgrade with styling additions, interior embellishments, wheels and suspension enhancements, and it’s perhaps that latter item that’s really been Schnitzer’s forte over the years. I’ve lost count of the number of its cars I’ve driven that have really hit the sweet spot when it comes to a wonderful balance between ride and handling and I think it’s safe to say that with its latest creation, the ACS1, Schnitzer has really hit the jackpot.

There’s one item that’s conspicuously absent from the spec sheet – a power upgrade

This particular example is based on the hottest hatch in the BMW range, the F40 M135i xDrive, and it’s an entirely different kettle of fish from the 1 Series models that have come before it. Unlike all the previous incarnations of the 1 Series this one is now based on BMW’s front-wheel drive layout which brings an entirely different platform and a transversely mounted engine instead ofthe traditional longitudinal BMW layout. It also means that for packaging reasons the superb six-cylinder unit that’s graced previous 135is and 140is has been replaced by a four-cylinder turbocharged unit.

Now this engine certainly isn’t short of a bit of get up and go – 306hp and 332lb ft of torque is enough to slingshot the M135i from standstill to 62mph in a scant 4.8-seconds and with its xDrive all-wheel drive set up it can transmit it all to the tarmac pretty effectively, too. As a point-to-point all-weather back road blaster it’s one of the best in the BMW range if covering ground quickly and securely is your primary concern.

However, there are a couple of blots in its copybook. Firstly, that four-pot might be pretty powerful but it’s not quite class-leading, both in terms of output and excitement – it’s not the most stimulating unit to sit behind despite coming with an M Performance exhaust as standard. Then there’s its transmission – just the one choice – and it’s an eight-speed auto. It’s a sad fact that the majority of buyers will opt for an auto/DCT/DSG gearbox these days as opposed to the more involving manual set up but where the ‘box in the vast majority of BMWs is the excellent ZF eight-speed unit the M135i xDrive makes do with an Aisin eight-speed unit that is suitable for transverse engine layouts and whichever way you look at it it’s just not as good as the ZF. And then there’s the M135i’s suspension set up which seems to border slightly too much on the comfort orientated side of things and it’s not a system that encourages you to get into the car and drive it hard. There’s not enough feel and feedback as to what’s going on underneath you and it doesn’t inspire confidence or seek to excite the driver.

Which leaves AC Schnitzer with plenty to do. While the exterior upgrades you can see here certainly enhance the M135i the standard car already has plenty of twinkly bits from the BMW accessories catalogue as standard. Thus Schnitzer’s additions are actually pretty subtle – a more pronounced front splitter to sit under the front spoiler and a painted section thatsits on top of the rear spoiler at the top of the tailgate. Both work well and help the ACS1 to stand out a little from the myriad M Sportkitted 1 Series that are becoming a common sight on our roads.

You’re more likely to notice the set of rather attractive AC4 20-inch alloy wheels fitted to the ACS1 though as they really fill out the arches rather nicely and look like a significant step up from the standard 18-inch or optional 19-inch wheels that the M135i is equipped with from the factory. The flow-formed Schnitzer rims are a new design and can either be specced in black or black with silver faces. I’m a traditionalist – wheels should be predominately silver – so it’s the latter option I prefer. These wheels are wrapped in a set of high performance Michelin Pilot Sport 4S tyres measuring 235/30 all round.

It’s not just the wheels that are making this 1 Series sit quite so well though as the ACS1 is equipped with Schnitzer’s RS suspension set up, a fully adjustable coilover set up. This has been set up by Schnitzer to hopefully offer the best of both worlds – a compliant ride and an involving steer. Inside there are a couple of tweaks which include an AC Schnitzer pedal and footrest set along with a set of Schnitzer’s upgraded paddles for swapping cogs mounted behind the steering wheel.

So far there’s one item that’s conspicuously absent from the ACS1’s spec sheet, and that’s a power upgrade. Schnitzer has decided not to offer one on this car as the Aisin transmission simply can’t cope with any meaningful gains before its internals wilt and it was felt that customers wouldn’t be keen on an expensive power upgrade if it was only going to offer an additional 20hp or so. Schnitzer doesn’t do things by halves – all its engine upgrades carry TüV approval – and are thoroughly engineered and tested so there was no way to offer a few extra horses on the cheap. It’s just not the way the company does business which we feel is to be applauded. There is an exhaust system though which has been designed primarily to elicit a better note from the B48 engine and the sports set up certainly looks the part with its carbon-tipped tailpipes.

Before I’ve slipped behind the wheel I have to say that I’m quite taken with the way the ACS1 looks but the proof of the pudding will be in the eating so to speak. Its number plate hints at its testing site at the Nürburgring while the Individual San Remo Green paint echoes the ‘Green Hell’ theme. Easing away from AC Schnitzer’s UK HQ it’s immediately obvious that there’s a hint of additional menace from the exhausts and that while the suspension is stiffer than standard at low speed it is already having an effect on the steering, seemingly more weighty and insightful than the standard set up.

As is quite often the way the most important aspect of the morning is to get the pictures in the bag and while Smithy’s hopping about with his lenses and asking me to clean various parts of the car I have a quick peruse of the price list for the AC upgrades. The bottom linefigure comes to a total of just under £11,600 and that includes parts, labour, paint and VAT. The front splitter comes to £992.85 while the painted rear spoiler insert is £574.41 but it’s the wheels and tyres that account for the greatest cost at £4539.01 including the tyre pressure monitoring set up and locking wheel bolts. The exhaust is £1816.73 while the RS suspension comes in at £2888.79, including wheel alignment. Lastly, the interior bits and bobs come to a total of £474.70 for the pedals and footrest while the paddles are £349.05, and all those costs include parts and labour when fitted at AC Schnitzer’s UK base. Once the static pictures are in the bag it’s time for some action and while the roads are still quite greasy and damp it soon becomes apparent that the ACS1 still has huge reserves of grip and that even wearing high performance tyres that give their best when the temperatures are a little higher it’s incredibly sure footed. When running back and forth for the cornering shots I take it relatively easy to start with so as to properly judge the conditions but such is the confidence that the ACS1 gives that I’m soon barrelling along at a far greater pace than I originally thought judicious.

But it’s not just the car’s pace that impresses, it’s the level of feedback and connection you feel with the car. Sure, the standard machine is equally fast but you don’t have the feeling of immediacy and adjustability that the Schnitzerfettled car has and the new-found precision to the steering really allows you to place the car accurately. At lower speeds the ride isn’t perhaps quite as composed as in the standard car but it’s by no means overly harsh and the flip side is excellent damping and body control when pressing on and it’s certainly a price I’d be prepared to pay for the additional pizzazz the RS suspension endows the 1 Series with. Elsewhere the exhaust does offer a more strident tone than the standard set up that suits the car’s character but even Schnitzer can’t hide the engine’s somewhat humble origins and I reckon that just about every M135i owner would probably be prepared to sacrifice a little bit of interior space for a sonorous straight-six up front instead. The gearbox isn’t the greatest either, sometimes feeling a little slower than the changes you’d experience with the ZF box, but to a certain extent the inadequacies of the Aisin unit can be driven round and don’t really detract fromwhat is ultimately a very entertaining and interesting package indeed.

Once the pictures are finished with I can finally give the M135i a proper blast and as I head out in search of some good local roads I can’t help but be impressed with the Schnitzer changes. There’s a still a little bit of writhing from the steering wheel in your hands as the tyres try to sniff out the best grip but on drier roads this becomes less of an issue. It’s still something that someone brought up exclusively on rear-wheel drive BMWs can find difficult to get their head round and even though the ACSs1 is very much a four-wheel drive machine it’s one that’s based on a front-drive platform. As the pace rises the tugging from the steering virtually disappears though and you can concentrate on the steering precision and the better feedback you’re receiving from the RS underpinnings. In terms of sheer pace when blasting along the backroads it’s right up there with some of the best BMWs I’ve driven and thanks to the Schnitzer upgrades it’s now a fun machine to do it in.

Yes, the upgrades do add to the cost, but it’s important to remember that you don’t have to do them all at the same time, and if it’s just the suspension you’re interested in then by all means that would be a great option. However, if you want your 1 Series to stand out from the crowd both visually and in terms of its driver appeal then we can heartily recommend the full works ACS1 conversion. It’s definitely the best F40 1 Series we’ve driven and continues a long and illustrious tradition of excellent AC Schnitzer machinery.

Can a series of subtle AC Schnitzer upgrades bring out the best in BMW’s hottest hatch? We drive the ACS1 to find out...

AC Schnitzer Upgrades

• Dual Sports Exhaust with Carbon tailpipes: £1753.73
• Front splitter: £830.85
• Roof spoiler: £313.41
• RS coilover Suspension: £2456.79
• AC4 20-inch alloy wheel set with tyres: £4406.08
• Pedal set: £188.47
• Footrest: £225.48
• Paddle set: £295.05

All prices are for parts only, paint and fitting at additional cost.

It’s right up there with some ofthe best BMWs I’ve driven...

2023 BMW AC SchnitzerACS1 F40

• ENGINE: B48 four-cylinder, turbocharged
• CAPACITY: 1998cc
• MAX POWER: 306bhp @ 5000-6250rpm
• MAX TORQUE: 332lb ft @ 1750-4500rpm
• 0-62MPH: 4.8-seconds
• TOP SPEED: 155mph
• ECONOMY: 35.8mp
• EMISSIONS: 157g/km

20” wheels are each 1kg lighter than BMW’s 19” option (with tyres), the reduction in unsprung weight asssits the suspension in doing its job.

It’s not just the car’s pace that impresses, it’s the level of feedback and connection you feel with the car.