are bathed in oil. A heat resistant light-metal-alloy is used for the cast pistons. The combustion chamber is integrated into the piston. For compression, the pistons have two piston rings which slots are cast into the piston. The pistons are also equipped with an oil control ring. The cylinder liners are made of centrifugally cast iron, two rubber rings seal the liners off from the crankcase. The engine has two cast iron cylinder blocks with two cylinders; every block has a head, which makes two cylinder heads. Valvetrain and fuel Injection The engine uses OHV. The camshaft is gear driven by the connecting gear as described earlier. Every cylinder head has four overhead valves, which are activated by tappets, pushrods and rocker arms. The injection nozzles are connected to the cylinder heads with a flange. The valve seats are made of a heat-resistant material and unlikely to be worn out. The injection duct is grooved. Cooling The engine has a water cooling system with a centrifugal pump, which is driven from the crankshaft with a belt; it runs always. A thermostat controls the water amount. Starting at 80 °C the water is pumped into the water cooler, before this temperature level, it circulates in the engine block only to increase the engine temperature fast. The engine fan runs always, except from later versions of the engine which have a fan with an electro-magnetic clutch, which is activated at 92 °C by a temperature sensor. Lubrication The oil pump in the crankshaft bearing housing creates oil pressure and pumps the oil from the oil sump through the engine. In the main oil flow a sieve filter cleans the oil, the secondary oil flow has a centrifugal oil filter. Some engine variants don't have a sieve filter but a paper filter instead. The lubrication of the injection pump and the air compressor may either be attached to the main oil flow or be attached to a separate oil lubrication system. For oil cooling the engine has an involute heat exchanger or a shell and tube heat exchanger. Shell and tube heat exchangers are found mostly in engines for the IFA W50. Fuel system Fuel is pumped from an inline injection pump to the injection nozzles. The injection pump is a pump with a rotational speed controller, fuel filter and a pump clutch. Some engines have an injection timing device instead of the