Testing the BMW M440i from AC Schnitzer

Oh yes, the 4-seater convertible has done it to us. It squirts in corners and likes to let the rear hang out more often. And now AC Schnitzer has given it even more power and torque.

The sun is slowly disappearing. The temperatures drop from 15.5 to 13 degrees Celsius on this still quite mild autumn day. In contrast, the mood behind the wheel improves by the minute. It's still warm enough to open the soft top in 18 seconds. The blower blows your neck while the BMW M440i alternately whirls up the green, brown and gold-colored leaves on the side of the road - either with the 20-inch wheels or a throat clearing through the modified sports exhaust, the four panels of which are encased in carbon fiber. Cost point: 3,918 euros.

M440i xDrive Cabrio meets tuning by AC Schnitzer. It affects the aerodynamics, the outer skin, the interior, the engine performance, the background noise. Let's continue with the sports suspension (almost 2,500 euros), which lowers the open-hearted 4 Series by about 15 millimeters on both axles and thus slightly lowers the center of gravity. That should help a bit in the corners given the considerable total weight of 1,932 kilograms - and it does so in combination with the tires, which are ten millimeters wider per axle compared to the production model.

You give in, the front axle grabs. You're already stuck in the middle of the curve. Meanwhile, the super-agile all-wheel drive bends the BMW underground. The convertible pushes with the rear, thereby strengthening the dynamics in order to pepper the next straight with spin. In tennis one would speak of a vigorously hit backhand. The play instinct that characterizes the series M440i has remained to a large extent.

The tuned version also integrates the rear part into the lateral dynamics. However, a shot has drawn in more seriousness. With the new springs and dampers as well as the larger wheels (4,641 euros), AC Schnitzer has improved the road holding. Towards a somewhat more neutral driving behavior without robbing the BMW of driving pleasure. You can still throw it into corners, spin around, enjoy the transverse drive that unfolds. However, the tuner from Aachen has raised the limit a bit.

Or in other words: The agility was left to the 4er. Only the somewhat wild (but always very easy to control) rear has been talked out of the sporty convertible. Example slalom: In sport auto 10/2021, the M440i had to be driven with a steady hand and careful right foot. Otherwise, the rear gave out a bit too much. In the Schnitzer you even intersperse a targeted load change to get through the streets faster. What succeeds because the 4 Series never wedges on the rear axle. It stays safe and prances around at an average speed of 68.6 km/h, 0.7 km/h faster than its production counterpart. A minimal difference.

R6T with 420 hp and 600 Nm

The lowering makes the chassis crisp in everyday use, but within the right framework. The ACS4 4.0i, as the vehicle is called, finds a compromise between tension and relaxation, so that any bumps or depressions in the asphalt are no obstacle.

Curves: Check. Everyday comfort: Check. Now let's take a look at this wonderful Bavarian buddy under the hood - staged by the engine optics for 535 euros. Six combustion chambers, three liters displacement, turbocharged. In the standard trim, the R6T delivers 374 hp and pours a maximum torque of 500 Newton meters over the axles. Logo, AC Schnitzer rams even more power and, above all, more torque on top - across the entire speed range.

An additional control unit increases the boost pressure, but does not touch the protection parameters programmed by BMW for the engine. The upgrade gives the M440i 420 hp. The torque peaks at 600 Nm. During the test period, the bundled package worked absolutely smoothly.

With more steam on the crankshaft, AC Schnitzer should undercut the presented sprint values โ€‹โ€‹of the series convertible. In sport auto 10/2021 (at an outside temperature of 24 degrees), the BMW brought it to country road speed in 4.9 seconds, confirming the factory specification. After 18.3 seconds it passed the 200 km/h mark. And what is the tuned 4er doing with its new possibilities? He delivers. Sprints to 100 in 4.5 seconds. Increases speed to 200 in 16.2 seconds. The relatively cool temperatures help with this.

The increase in performance also unfolds its effect in intermediate sprints. Therefore, you can save yourself tugging at the left rocker switch, even if the look tempts you to do so. The shift paddles cost 400 euros extra.

Boost becomes downforce

In the upper gears, the 4 Series quickly pulls out of the low rev range thanks to the high torque. At 2,200 tours, the in-line six now inflates the cheeks more. We know it in a similar form from the production model. As soon as the digital needle approaches 3,000 on the right of the display, a small additional boost follows.

The Schnitzer-M440i dashes forward, ups the ante with the sound and then revs happily up to 7,000 rpm. Then the next gear has to go in, or you get stuck in the limiter in manual mode. A pluck - ugh, the automatic converter switches one step higher.

The sound spectrum is quite atmospheric. However, the ACS4 4.0i has not become a poser or a riot skull. He lets you enjoy driving a convertible without blushing. The optics are served not only by the lowering, the 20-inch wheels and the exhaust, but also refinements around the body. Front splitter (1,266 euros), front spoiler elements (1,251 euros), side skirts (1st033 euros), rear skirt foil (154 euros) and the black lettering (40 euros) on the sides characterize the 4 Series as a carver. There's also something for fans of aerodynamics: the front splitter reduces lift on the front axle by 35 kilograms at a speed of 200 km/h. In this way, buoyancy (series) even turned into a contact pressure of around 20 kilos.

This is how tuning works

The following alternating curves on the country road do not give this speed. It wouldn't even be allowed. When changing direction, a simple pawn trick helps. Step on the gas slightly and the open four-seater allows the rear to contribute with a slight impulse. Good-natured reactions to changes in load: the set-up is tailored to drivers who want to drive in a sporty manner without having to worry about breaking a sweat behind the wheel.

One menu item is still on the list: the interior changes. In addition to the steering wheel rockers, they also include the aluminum pedals (269 euros), the aluminum footrest (260 euros), the key holder (122 euros) and the cover for the rotary pushbutton (185 euros). Kassensturz: There is a tuning surcharge totaling 20,904 euros โ€“ including VAT and installation.

So, now take another quick lap before AC Schnitzer picks up the fast 4er again. Eat curves, devour straights, indulge in tuning. Good work!


The package from AC Schnitzer for the M440i costs almost 21,000 euros if you increase the performance, change the look, update the aerodynamics, lower the chassis, buckle on new wheels, revise the exhaust and order accessories for the interior. The handles are right: The 4-series retains its character, increases cornering dynamics and whets straight ahead faster. The balancing act between sport and everyday life succeeds. You can only get good grades for that.


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