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Brabus B25S - Stepping Up

Brabus takes the A250 to the next level.

Date Published: 11 Dec 2019
Brabus B25S - Stepping Up

Bottrop, Germany - When the latest A-Class made its entrance last year it was more than just a refresh. The fourth generation compact Mercedes hatchback was sleeker, blessed with a revised chassis and engines, and the state-of-the-art MBUX infotainment system.

As usual Brabus was one of the first out of the starting blocks with their tuning programmte for the new A-Class with their B25S conversion for the (M260) 1,991cc turbocharged i4 motor in the popular A250 and A250 4-Matic.

Brabus B25S - Stepping Up

The heart of the engine upgrade is the Brabus PowerXtra CGI module that intercepts signals from the input sensors, modifies the data, and then outputs the revised fuel, spark and boost settings to facilitate the power and torque increases. A plug and play device, the module sits between the engine and factory ECU and is supplied with a bespoke wiring harness.

Brabus B25S - Stepping Up

The only hardware changes are the bespoke air intake pipe that directs a greater volume of ram air from the front grille to the factory air filter box, and the Brabus valve-control sports exhaust at the business end. This joins the factory exhaust aft of the now mandatory particulate filter.

Brabus B25S - Stepping Up

The ECU mapping takes the greater intake air volume and lower exhaust backpressure into account in its maximisation of the revised power and torque curves. Peak power goes up by 46hp, taking the installed 224hp at 5,500rpm to 270hp at a lower 5,200rpm. This is underpinned by an 80Nm increase in the twisting force from 350Nm at 1,800rpm to 430Nm at 3,500rpm.

Although the improved peak torque figure arrives 1,700rpm higher up the rev band it is important to note that the tuned motor matches the standard peak number at 1,800rpm anyway. Unlike in the good old days when a naturally aspirated motor with high-lift camshafts often traded off top-end horsepower against low-end torque, the turbocharged B25S CGI engine has more muscle all the way.

One thing the B25S conversion has in common with all Brabus tuned engines is sharper throttle response. Thanks to the drive-by-wire electronic throttle used on modern cars it is possible to shorten the engine’s response time to inputs from your right foot.

OE manufacturers deliberately keep this reaction time to an average value that accommodates a wide spectrum of drivers, but someone who goes to Brabus to have the claws of their car sharpened is clearly going to be an enthusiast after better pickup.

Brabus B25S - Stepping Up

The stopwatch shows a significant improvement in performance, with 0.3 second shaved from the benchmark 0-100km/h (0-62mph) sprint, which now falls in 5.9 seconds. Breaking the 6.0 seconds mark is a big deal for a non-AMG A-Class when you consider that this puts it on par with the mighty 326hp 5.0 litre V8 powered 500E super saloon of 1991. In fact the standard A250 is just 0.1 second behind the 500E’s 0-100km/h time, all three sharing the same electronically limited 250km/h (155mph) top speed.

Long-term reliability is a big deal, especially as Brabus offer a 100,000km warranty on their conversions. The factory engine protection systems are untouched so if the engine temperature reaches the factory limits when the car is fully loaded and being driven hard in the mountains in hot weather, the B25S module will revert to the factory engine mapping, which then engages its power limiting safety protocols.

Brabus B25S - Stepping Up

The simpler, more elegant lines of the new A-Class have won over many customers from other brands as well as existing owners replacing their older versions. With less modelling lines on its flanks the new car might seem plainer to some eyes, but we think the new shape will age better because of this.

The A250 that Brabus used as the base car for their demonstrator had the AMG Line package, which includes sports suspension. Importantly, the A250 gets the independent multi-link rear suspension that gives it superior turn-in, handling, grip and comfort compared to the torsion beam axle on lesser models.

Brabus B25S - Stepping Up

The 10mm lower ride height of the AMG Line sport suspension is a perfect match for the 8.5J x 20-inch Brabus Monoblock R alloy wheels shod with 235/30ZR20 Pirelli tyres that sit exactly in the middle of the wheel arches and give the car its more purposeful stance.

Brabus offers these five double-spoke wheels in 18, 19, and 20-inch diameters in different finishes. The wheels on our test car had the Liquid Titanium finish on the right and Gloss Black on the left to show off possible choices. Alternative wheel styles are the nine double-spoke Monoblock F in 18, 19 and 20-inch sizes, and the 19-inch only five-spoke Monoblock T.

Brabus B25S - Stepping Up

Brabus B25S - Stepping Up

The AMG Line package also features the more sporting front and rear bumper mouldings and side skirts to which the Brabus aerodynamic parts are attached. The Brabus factory front splitter and intake inserts attach directly to the factory bumper/spoiler, while the big three-pointed star on the grille is replaced with the distinctive Brabus double B.

Brabus B25S - Stepping Up

At the rear the new lower valance insert consists of a small diffuser flanked by cut-outs for the Brabus sports exhaust’s four outlet pipes. The aero kit is literally topped off by a roof spoiler for the rear hatch.

You cannot see any of this when you are stuck in traffic, which is where the interior trim upgrades come into play. These include the alloy pedal set, and Brabus branded floor and boot mats in black with Nubuck edge and silver piping. The only interior offering that requires wiring in is the illuminated door entrance panels whose LED lights are linked to the cars 64-colour interior lighting.

Brabus B25S - Stepping Up

Brabus B25S - Stepping Up

All current Mercedes models have a sporty thick-rimmed steering wheel, and paddle shifters if the car has two pedals on the floor. The long Brabus alloy paddle shifters with their skeletal design look great and help you select ratios more easily if you have to manually shift in a tight bend.

Brabus B25S - Stepping Up

Brabus B25S - Stepping Up

Brabus B25S - Stepping Up

Brabus B25S - Stepping Up

On the road the difference the B25S conversion makes to the car is immediately apparent. As lively as a well run in A250 is it simply would not see which way the B25S went, especially down a twisty road where the greater mechanical grip perfectly decants the extra 80Nm of torque, helping you to rocket out of bends and down the straights.

As with the previous model the A250 is the sweet spot of the new A-Class range, its well-judged balance between ride, handling, and straight-line zing making it a great daily driver, albeit one that falls a bit short on sheer visceral thrill factor.

Perhaps some of this is down to the dual-clutch paddle shift transmission being the standard partner for this most powerful front-drive A-Class. While it is a rapid and responsive gearbox the previous generation A250 came with a manual gearbox as standard. It was a good one too with short and precise shifts and pedals perfectly set up for heel and toe action.

In the absence of a manual gearbox for the new A250 the extra power, torque, crispness and grip conferred by the Brabus B25S conversion certainly adds plenty of extra sparkle.

Brabus B25S - Stepping Up

On the downside the ultra low profile 20-inch rubber brings the ride just to the edge of firmness. That said, if you feel they are an inch too far for markets where the roads are not as smooth as in Germany, you can always opt for 19s, or even 18s if you wish to retain optimum ride comfort.

The Brabus B25S conversion turns the A250 from a warm hatch into a properly hot one without upsetting the cars overall balance. In our books it and adds an extra half star to the A250’s four star rating.

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