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Internal Combustion Engine Basics

Internal combustion engines provide outstanding drivability and durability, with more than 250 million highway transportation vehicles in the United States relying on them. Along with gasoline or diesel, they can also utilize renewable or alternative fuels (e.g., natural gas, propane, biodiesel, or ethanol).  They can also be combined with hybrid electric powertrains to increase fuel economy or plug-in hybrid electric systems to extend the range of hybrid electric vehicles.


Combustion, also known as burning, is the basic chemical process of releasing energy from a fuel and air mixture.  In an internal combustion engine (ICE), the ignition and combustion of the fuel occurs within the engine itself. The engine then partially converts the energy from the combustion to work. The engine consists of a fixed cylinder and a moving piston. The expanding combustion gases push the piston, which in turn rotates the crankshaft. Ultimately, through a system of gears in the powertrain, this motion drives the vehicle’s wheels.

There are two kinds of internal combustion engines currently in production: the spark ignition gasoline engine and the compression ignition diesel engine. Most of these are four-stroke cycle engines, meaning four piston strokes are needed to complete a cycle. The cycle includes four distinct processes: intake, compression, combustion and power stroke, and exhaust.

Spark ignition gasoline and compression ignition diesel engines differ in how they supply and ignite the fuel.  In a spark ignition engine, the fuel is mixed with air and then inducted into the cylinder during the intake process. After the piston compresses the fuel-air mixture, the spark ignites it, causing combustion. The expansion of the combustion gases pushes the piston during the power stroke. In a diesel engine, only air is inducted into the engine and then compressed. Diesel and gasoline engines then spray the fuel into the hot compressed air at a suitable, measured rate, causing it to ignite.


Over the last 30 years, research and development has helped manufacturers reduce ICE emissions of criteria pollutants, such as nitrogen oxides (NOx) and particulate matter (PM) by more than 99% to comply with EPA emissions standards. Research has also led to improvements in ICE performance (horsepower and 0-60 mph acceleration time) and efficiency, helping manufacturers maintain or increase fuel economy.

Learn more about our advanced combustion engine research and development efforts focused on making internal combustion engines more energy efficient with minimal emissions with inverter generator. 

How Gasoline Engines Can Survive in an Electric Car Future

Combustion engines won't completely disappear any time soon, if ever. Certain transportation tasks or operating environments simply don't lend themselves to battery- or hydrogen-powered electric propulsion. A century and a half of research and development has greatly increased the efficiency of combustion engines, and engineers have loads of additional tricks up their sleeves that promise to extract even more work from a molecule of fuel while producing even fewer harmful emissions. Here are but a few we're keeping our eyes on, listed in order of complexity and cost to implement. 

A 98-Octane Fuel Standard

Simply being able to design an engine to run 15:1 or higher compression greatly improves its thermodynamic efficiency and power density, permitting further engine downsizing. That requires higher-octane fuel, and a research-octane number (RON) of 98 represents a sweet spot, above which producing/refining the fuel consumes more energy, decreasing the well-to-wheels energy/CO2 benefit. 

Smart Cylinder Deactivation

Engines are sized for worst-case scenarios like quarter-mile acceleration or towing heavy trailers up Davis Dam. Cylinder deactivation improves efficiency during less extreme driving situations by making a few cylinders work Davis Dam hard while the others do nothing. Dynamic Fuel Management can shut off any or all cylinders in GM's 5.3- and 6.2-liter V-8s to boost EPA fuel economy by up nearly 12 percent. Tula Technologies and Eaton now propose similar systems for long-haul diesel engines, where a smaller fuel efficiency payoff (1.5-4.0 percent) pays huge NOx dividends by maintaining exhaust temperatures needed to keep catalysts lit.

An engine's power is limited by the amount of air it can ingest, which is why crankshaft-powered superchargers and exhaust-powered turbochargers were developed more than a century ago. Electric superchargers using recovered energy power the the Volvo Drive E and Mercedes M256 engines, among others; adding a motor/generator to a turbocharger eliminates lag under power and permits energy harvesting while cruising. Two interesting riffs on crank-powered superchargers are the Torotrak V-Charge centrifugal blower, which employs a CVT to quickly match speed to demand, and Hansen Engine Corp's Lysholm-type blower, which features a window that opens or closes to match demand for air pressure while minimizing losses to deliver turbo efficiency with supercharged responsiveness.
  • Created: 19-01-22
  • Last Login: 19-01-22

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