BMW continues to dole out info on the new R 18 boxer bits at a time. This closer look at the motor is fascinating. Although it may look like a vintage powerplant, inside it’s pure 21st-century technology. Here’s what you need to know about the motor, which BMW calls the Big Boxer.
- The R 18 displaces 1802cc, and focuses on low-rpm power production. To get to 1802cc, the R 18 motor has a 107mm bore and 100mm stroke, so it is a bit oversquare. Peak horsepower is modest—just 91 horsepower is produced at 4750 rpm. However, the torque numbers are serious. From 2000 to 4000 rpm, it puts out at least 110 ft/lbs of torque. Torque production peaks at over 116 ft/lbs at 3000 rpm. Redline is 5750 rpm, and the R 18 idles at just 950 rpm.
- Those are four-valve heads with dual ignition. Screws and locknuts adjust the steel valves. Intake valves are 41.2mm set at 21 degrees, and the exhaust valves 35mm at 24 degrees. Fork rocker arms are employed. 48mm throttle bodies feed them.
- The Big Boxer has two camshafts with pushrods. The cams are situated above, and to the left and right of, the crankshaft. They are chain driven.
- To smooth things out, and prevent the high-displacement engine from shaking itself into oblivion, the Big Boxer has an additional main bearing for the forged-steel crankshaft.
- Air and oil cool the R 18 powerplant. Those fins on the cylinder are not just for show. Also, it gets a wet sump design, along with a two-stage oil pump.
- Including the transmission and intake system, the R 18 tips the scales at 244 pounds.
- The constant-mesh six-speed transmission has a single-disc, assist-and-slip dry clutch. A reverse gear is optional, and driven by an electric motor.
- No surprise, power is transmitted to the rear wheel via a shaft. It’s a universal-shaft drive, matched to a universal joint—both are nickel-plated and open, which BMW used in boxers up to 1955. The rear axle drive gets a bevel and ring gear.
BMW R 18 Big Boxer Specs
Type: Horizontally opposed twin
Bore x stroke: 107 x 100mm
Maximum power: 91 horsepower @ 4750 rpm
Maximum torque: 116 ft/lbs @ 3000 rpm
Compression ratio: 9.6:1
Valvetrain: Dual cams w/ pushrod-actuated valves; 4 vpc
Fuel: Premium unleaded
Fueling: 48mm throttle bodies
Emissions: Closed-loop three-way catalytic converter; Euro 5 compliant