Related by context. Frequent words. (Click for all words.) 66 combustion engine 66 internal combustion engines 62 internal combustion engine 61 internal combustion 56 diesel engines 55 diesels 53 electric motors 52 turbocharging 52 diesel engine 52 electric powertrain 51 combustion 50 powertrains 50 electric propulsion 50 powerplants 50 diesel 50 nonpolluting 49 diesel particulate filter 49 particulate filter 49 electrically driven 49 hybrid propulsion 49 exhaust emissions 48 diesel powered 48 rotary engine 48 hydrogen fuel 47 acid batteries 47 hydrogen powered 47 drivetrains 47 hybrid powertrain 47 piston engines 47 hybrid electric 46 alternative fuels 46 electric motor 46 Lithium ion 46 hybrids 46 electrically powered 46 powertrain 46 automobiles 45 fuel injector 45 engines 45 fossil fuels 45 BlueMotion 45 V6 engines 45 lithium ion batteries 44 nitrogen oxide NOx 44 PEM fuel 44 electrochemical 44 cleaner fuels 44 electric hybrid 44 BMW #d 44 electric hybrids 44 PHEVs 44 fuel injectors 44 fossil fuel 44 bio ethanol 44 NiMH batteries 44 Hybrid Synergy Drive 44 mechatronic 44 propulsion systems 43 motors 43 Cyclone Engine 43 Audi R# 43 cylinder diesel 43 proton exchange 43 SOFC 43 nickel metal hydride 43 powertrain components 43 propulsion 43 drivability 43 Hybrids 43 hydrogen 42 flywheels 42 cylinder engines 42 turbo diesel 42 lithium ion battery 42 lithium ion 42 gearboxes 42 catalytic converter 42 speed automatic transmissions 42 desulfurization 42 Li ion batteries 42 zero emission 42 turbodiesel 42 drivetrain 42 turbocharged engine 42 microturbine 42 conventionally powered 42 Li Ion 42 supercapacitors 42 EVs 42 Fossil fuels 42 turbocharger 41 piston engine 41 ultracapacitors 41 gasohol 41 TFSI 41 hydraulic pump 41 turbos 41 manual transmissions 41 manual gearbox 41 variable valve timing 41 #g/km [001]