Just in time for the start of the warm weather, BMW rolled the convertible version of
the current 4-series generation into dealership showrooms last March. The
spearhead of the open-air 4 Series – apart from the brand-new M4 Competition M
xDrive Convertible – is the M440i, which is powered by a factory-fitted 275 kW (374
hp) and 500 nm 3.0-liter inline six-cylinder engine with twin-scroll turbocharging.
But: As we all know, you don’t get used to anything as quickly as engine power. Of
course, the performance tuners at dAHLer Competition Line, based in Belp near
Bern in beautiful Switzerland, know this too, which is why they help the B58B30TÜ1
gain even more steam with their sophisticated performance upgrade “powered by
dAHLer”. The stage 1 upgrade already provides a whopping 316 kW (430 hp) and a
torque mountain of a powerful 610 nm – and, as usual with dAHLer Competition
Line, of course with WLTP Euro6d testing, EU/CH homologation, and a reliable
supplementary warranty to the factory warranty.
Also rubber-stamped with the extensive approvals and warranties are – optionally in
combination with each other or solo – the stainless steel exhaust system “built by
dAHLer,” specifically developed for use on vehicles equipped with gasoline particulate
filters, which sounds sporty and powerful from its ceramic-coated 90-millimeter twin
tailpipes, and an Eventuri intake system.
In addition, dAHLer Competition Line offers a CAN-bus-guided exhaust flap control
system: It allows maximum sound at the push of a button – regardless of driving
mode, rpm, and speed range.
For contemporaries for whom the stage 1 performance increase is still not enough,
Christoph Dähler and his team also have more up their sleeve: Stage 2 generates
up to 334 kW (455 hp) and 640 nm and is already in preparation.
dAHLer Competition Line also leaves its customers spoiled for choice when it
comes to deciding on chassis upgrades and wheel/tire combinations: While the
sport spring set “built by dAHLer,” which is explicitly tuned to the electronic damper
system (ECD) of the BMW M440i, mainly creates a crouched look and slightly
optimizes its cornering behavior by lowering the vehicle’s center of gravity, the
alternative Competition coilover suspension “built by dAHLer,” with its options for
height as well as damping adjustment in compression and rebound damping, allows
an individual setup according to the purpose of the car and the driver’s preferences
– from Sunday open-air cruising to dynamic exits over winding country roads or
The differences in the rims, on the other hand, are more technical than visual: The
sporty and elegant “dAHLer CDC1” is available either as a conventional cast wheel
or as a FORGED variant. The latter significantly reduces unsprung and rotating
masses thanks to its state-of-the-art forging process, giving the M440i a noticeable
lightness of foot – in the truest sense of the word. It fits the BMW in the dimensions
9×20 and 10×20 inches perfectly in combination with Michelin Pilot Sport 4 S tires in
the sizes 245/35ZR20 and 285/30ZR20.
For a styling of the M440i that puts the gained driving dynamics in the right light,
dAHLer Competition Line offers additional exterior mirror caps in M-Style, which are
optionally made of real carbon. These can be seen on the three convertibles shown
here, one of which is painted in the equally sporty and elegant color dravit gray
Furthermore, a front splitter that continues the lines of the bow downwards is
currently in preparation in two variants.
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