Internal combustion engines Automobiles 82 Motors 70 Design and construction 53 Fuel systems 43 Testing 34 Combustion 32 Spark ignition engines 21 Diesel motor 18 Two-stroke cycle engines 18 Cylinders 13 Exhaust gas 13 Mathematical models 13 Maintenance and repair 12 Noise 12 Valves 12 Environmental aspects 10 Ignition 10 Biodiesel fuels 9 Combustion engineering 9 Compressed natural gas 9 Engines 8 Fluid dynamics 8 Hydrogen as fuel 8 Motor fuels 8 Motor vehicles 8 Thermodynamics 8 Computer simulation 7 Jet propulsion 7 Mechanical wear 7