BMW developed with Rotax a 798 cc (48.7 cu in) parallel-twin engine with a 360 degree firing order. This produced an exhaust note reminiscent of BMW's signature air-cooled boxer twins. However, this firing order required both pistons to move up and down at the same time. To counter the significant inertia produced by the pistons reciprocating, BMW devised a third vestigial connecting rod to a balance weight. The result was a parallel twin with significantly reduced vibration compared with other parallel twin engine designs. The engine is oiled by a dry sump system, and a soft ignition-cut rev limiter engaged at 9,000 rpm. BMW tuned the F800 series engine to run lean, typically with air-fuel ratios in the range of 15:1 to 16:1.