The four stroke engine was first demonstrated by Nikolaus Otto in 1876
The vast majority of modern automobiles are powered by internal combustion engines. These engines use a fuel, such as gasoline, which is ignited to produce the power stroke that drives the vehicle. The internal combustion engine essentially creates a series of small explosions and transfers their power to the driveshaft via the transmission. Most internal combustion engines are four-stroke engines, with four distinct procedures:
1. Intake
During the intake stroke, the piston moves downward, drawing a fresh charge of vaporized fuel/air mixture. The illustrated engine features a poppet intake valve which is drawn open by the vacuum produced by the intake stroke. Some early engines worked this way; however, most modern engines incorporate an extra cam/lifter arrangement as seen on the exhaust valve. The exhaust valve is held shut by a spring
2. Compression
As the piston rises, the poppet valve is forced shut by the increased cylinder pressure. Flywheel momentum drives the piston upward, compressing the fuel/air mixture..
3. Ignition
At the top of the compression stroke, the spark plug fires, igniting the compressed fuel. As the fuel burns it expands, driving the piston downward.
4. Exhaust
At the bottom of the power stroke, the exhaust valve is opened by the cam/lifter mechanism. The upward stroke of the piston drives the exhausted fuel out of the cylinder.
2. Diesel Engines
The diesel engine was first patented in 1892 by Rudolph Diesel
Diesel engines are internal combustion engines that use diesel fuel rather than gasoline. Diesel fuel may be distilled from petroleum or a number of other sources. Some modern biodiesel fuel comes from vegetable or animal fats. Diesel engines ignite the diesel fuel by mixing it with hot air, rather than a spark plug as used in gasoline engines. Diesel engines are more efficient than comparable gasoline engines and also produce less carbon emissions. The diesel is similar to the four stroke, but uses a different method to ignite the fuel:
1. Intake
The intake valve opens, and fresh air (containing no fuel), is drawn into the cylinder.
2. Compression
As the piston rises, the air is compressed, causing its temperature to rise. At the end of the compression stroke, the air is hot enough to ignite fuel.
3. Injection
Near the top of the compression stroke, the fuel injector drives fuel into the cylinder. The fuel immediately ignites upon contact with the hot compressed air.
4. Power
As the fuel burns, the gas in the cylinder heats and expands, driving the piston.
5. Exhaust
The exhaust valve opens, and the exhaust is driven out of the cylinder.
3. Rotary engines
The Wankel rotary engine is a fascinating beast that features a very clever rearrangement of the four elements of the Otto cycle. It was developed by Felix Wankel in the 1950s
The rotary engine is an internal combustion engine developed in the early-20th century as an alternative to the standard reciprocating piston engine. Instead of the up-and-down motion of a piston, the rotary engine uses a rotating plate inside the engine to seal off sections of the engine, which serve as the compression or combustion chambers. The rotary engine weighs less than a piston engine with a similar volume. Rotary engines are uncommon today, but are still notably used on Mazda's RX series of sports cars.
In the Wankel, a triangular rotor incorporating a central ring gear is driven around a fixed pinion within an oblong chamber.
4. Hybrid engines
Some modern hybrid electric vehicles use an electric motor to produce forward motion. The electric motor is powered by either an on-board gasoline engine or by storing energy during braking or when driving downhill. These electric engines must be supplied by battery packs, which add to the cost and complexity of hybrid electric vehicles. However, cars using primarily electric power produce few emissions and can achieve fuel economy far above even the most modest gasoline or diesel engine.
