körting engines (initially paraffin engines and later diesel engines) were used extensively in early german submarines. the 6 cylinder 2-stroke submarine engine was reviewed in "the engineer" magazine in august 1906. this utilised crankcase compression, with the piston controlling all the ports. it was referred to as using petroleum, though this was almost certainly the less volatile paraffin/kerosene type, as it had exhaust heaters for the carburetors, and electric pre-heating of both cylinders and vaporisers, with the engine being turned over for some time by electrical power before being put to work. this allowing the engine to be started after 5 minutes. the engine was rated at 200bhp at 500rpm, and two were installed per submarine.