CarBahn Amplifies the BMW M4 Experience. Here’s How.

Nobody would call the current BMW M4 Competition xDrive’s performance lacking. With over 500 hp on tap from a 3.0-liter, twin-turbo inline-six (dubbed as the S58 among enthusiasts), and all-wheel drive, the model variant is impressive straight from the factory. Despite its 3,900-pound curb weight, it’s a precision tool for not only achieving notable speed, but maintaining it to a point surpassing where the lateral grip of other performance cars begins to falter. BMW has the formula pretty well figured out.

Yet, could it possibly get any better? As it turns out, it can. Just ask Steve Dinan, a man whose name carries its share of gravitas in this field when it comes to picking up where the engineers at BMW’s M Division leave off. His company, CarBahn, specializes in performance tuning for modern European automobiles, but goes a step further by offering a factory-matching warranty, full-emissions compliance, and a shop in San Jose, Calif., that offers installation.

Recently, we had the opportunity to drive a BMW M4 Competition xDrive sporting CarBahn’s CB3 Signature Package—a carbon-fiber-clad monster dressed in black and bronze. It’s hard to imagine finding any more power than what BMW’s twin-turbo S58 produces. It already has well over 100 hp per liter, and even with modern turbocharging technology, how long before the ceiling of everyday reliability is reached? By CarBahn’s engineering, the answer is well over 100 hp per cylinder.

The engine now delivers 668 ft lbs of torque, which is an increase of nearly 200 ft lbs from that provided by BMW. This output is achieved by fitting an upgraded heat exchanger to send cooler water to the power plant’s air-to-water intercooler, as well as revised ECU tuning, a better-flowing titanium exhaust system, and a cold-air intake.

Chassis-wise, the CB3-modified BMW M4 sports a set of specially tuned coilover springs, along with bigger anti-sway bars, a beefier carbon-fiber strut brace under the hood, stiffer adjustable toe links at the rear, and front monoball bushings. Interestingly, CarBahn found the M4’s braking system to be fine as is, so the next area of improvement was its body and wheels.

Carbon-fiber brake ducts, a front splitter, the grille, canards, a lower skirt, the spoiler, and fender vents were fitted to not only ensure the car’s show matches its go, but to improve aerodynamics and cooling as well. Additionally, forged CarBahn wheels wrapped in sticky Michelin Pilot Sport Cup 2R tires were bolted up. The end result is a tasteful mix of stock and aftermarket aesthetics; enough to signify that it’s not an ordinary M4, but in no way a display of excess. The rear spoiler and front splitter, for example, help balance out the big coupe’s lines and make the vehicle look far more stylistically pleasing.

If there’s one word to summarize CarBahn’s CB3 BMW M4, it’s “amplified”—literally, especially upon a cold start, when its awakened inline-six bark reaches a few more decibels over stock due to the titanium exhaust system. Once rolling, we quickly find out that the CB3-tuned S58 is much more powerful than that found in a base M4. The throttle is more sensitive in all of its power-train settings, and acceleration is wildly rapid—we really have to recalibrate our perception of proper throttle position, as even mundanely pulling away from a stop sign onto a 35 mph street takes some getting used to. It’s one of the most ready-to-pounce sports cars that we’ve recently piloted.

A well-launched stock M4 Competition will hit the 60 mph mark in just 2.8 seconds on lesser Michelin Pilot Sport 4S tires; we can’t help but think the CB3 on its Cup 2Rs would come closer to 2.0 seconds.

As for this M4’s ride quality, sportier adaptive damper settings make it noticeably stiffer, though the worst features of Los Angeles roadways were still nicely filtered out. Chassis communication is already quite good in any stock M4; now, though, its precision tuning relays every miniscule change in weight balance and grip. Like the factory setup, steering is a tad too light, but its chassis, wheel, and tire improvements relay far more about the tarmac’s surface. Finally, its steering action delivers outstanding yaw response to up engagement to the next level.

More speed, more grip, and more communication translate to bolstered confidence for the driver on any twisty road. What CarBahn has created is an ultra-high-performance modification package for this front-engine BMW; one that we find hard to beat.

Click here for more photos of this CarBahn-tuned BMW M4 Competition xDrive.