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A power-to-weight ratio

that beats Ferrari

Straight out of the box, the TwinPower Turbo S55 engine in the M3/M4 makes a healthy 431 hp and 406 lb-ft of torque in Euro-spec. The AC Schnitzer tuning program takes this to a robust 570 hp and 476 lb-ft. That’s an additional 60 hp and 70 lb-ft over AC Schnitzer’s Stage 1 ECU-only upgrade, and it comes via a larger volume carbon fiber intake and a custom exhaust system built in-house, with ECU remapping to suit.

“While it would have been nice to push the headline horsepower number all the way out to 600 hp, this would have entailed changing or significantly modifying the turbochargers, which are right on the limit at 570 hp,” explained AC Schnitzer development chief Roman Fenners.

Tipping the scales at 3,190 lbs., the ACL2 is lighter and more compact than the 3,546-lb. M4. Against the stopwatch, it can scoot from zero to 62 mph in 3.9 seconds, and to 134 mph in just 10.9 seconds. Top speed is 205 mph.

To bring chassis performance into line with that of the engine, a mechanical Drexler limited-slip differential with 25 to 95% locking capability sits in the M4 rear axle casing. While the excellent M Differential was available, the M235i’s wiring loom and ECU are different from those in the M3/M4, and the software additions and revisions to make this widened 2 Series with its unique kinematics work properly with the electronically-controlled, hydraulically-actuated M Differential would have presented a calibration nightmare.

The car rides on AC Schnitzer Clubsport suspension with adjustable ride height, compression and rebound damping. Uprated front suspension top mounts reduce strut wiggle under dynamic loads, while the M4 carbon fiber strut brace stiffens the engine compartment structure to keep the front suspension geometry truer under acceleration, braking and cornering loads.

Also from Issue 143

  • Willi Martini's 1979 CSL racer
  • 2017 Alpina B7 track test
  • 1981 Alpina B7 S Turbo, restored
  • 2016 F30 340i road test
  • Buyer’s Guide: E60 5 Series
  • 1957 507 #70089 ex-Helm Glöckler
  • People: Steve Dinan
  • Casey Pruit's 1996 E36 328i
  • Bimmerfest East and West
  • Paddock Pass
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