Engine Cycle

Two-Stroke Engines

Car Lift Repair Near Me  Engines operating on the two-stroke cycle utilize two strokes, one upward and one downward, for each power stroke. These engines lack dedicated intake or exhaust strokes, necessitating alternative methods for cylinder scavenging. In spark-ignition two-strokes, the downward piston motion pressurizes fresh charge in the crankcase, which is then forced into the cylinder through ports in the cylinder walls. While compact and mechanically straightforward, two-stroke engines are typically noisier, less efficient, and more polluting compared to four-stroke counterparts. They find common use in applications such as snowmobiles, lawnmowers, and outboard motors. However, their scalability to larger sizes is limited. Notably, the largest compression-ignition engines operate on the two-stroke principle, employing forced induction for cylinder scavenging. The inherent design of Car Lift Repair Near Me  two-stroke engines often leads to lower fuel efficiency due to the potential escape of unspent fuel from the combustion chamber. Without specialized exhaust processing, this can result in elevated pollution levels, prompting the adoption of four-stroke engines in many small engine applications, while smaller two-strokes may require catalytic converters in certain jurisdictions.

Four-Stroke Engines

Car Lift Repair Near Me  Engines adhering to the four-stroke cycle, also known as the Otto cycle, feature one power stroke for every four strokes (up-down-up-down). These engines, commonly found in cars, larger boats, and light aircraft, offer advantages such as reduced noise, increased efficiency, and larger size compared to their two-stroke counterparts. Variations such as the Atkinson and Miller cycles further enhance performance. While most automotive Diesel engines operate on a four-stroke cycle with compression heating ignition, known as the diesel cycle, gasoline engines dominate the four-stroke landscape in various road vehicles.

Five-Stroke Engines

A derivative of the four-stroke cycle, five-stroke Car Lift Repair Near Me  engines introduce a fifth cycle, refrigeration, alongside the traditional intake, compression, combustion, and exhaust cycles. Innovated by Delautour, these engines boast up to 30 percent greater efficiency than equivalent four-stroke engines.

Bourke Engine

The Bourke engine features two diametrically opposed cylinders linked to the crank by a scottish yoke. Unlike conventional two-stroke engines, the Bourke design segregates burnt gases and incoming fresh air within the cylinders, leading to cleaner and more efficient operation. Its scotch yoke mechanism minimizes side thrust, reducing friction between pistons and cylinder walls. Notably, the combustion phase of the Bourke engine closely approximates constant volume combustion, contributing to its efficiency and simplicity compared to both four-stroke and conventional two-stroke cycles.

Controlled Combustion Engine

These cylinder-based engines, whether single or two-stroke, employ counter-rotating concentric cams instead of a traditional crankshaft and piston rods. The profiles of the cam lobes determine piston travel versus torque delivered, with each pair of counter-rotating cams corresponding to two cylinders. 

Wankel Engine

Operating with a similar phase separation as four-stroke engines, the Wankel engine, though lacking piston strokes, delivers three power “strokes” per revolution per rotor. This design yields a superior power-to-weight ratio compared to piston engines, making it suitable for applications like the Mazda RX8 and RX7.

Gas Turbine

Gas turbine cycles, notably jet engines, eschew the conventional piston mechanism in favor of separate compressors and gas turbines. This setup ensures continuous power generation by compressing and combusting intake gas (typically air), with the resultant hot gas driving the turbine.

Disused Methods

Some antiquated Car Lift Repair Near Me  internal combustion engines attempted to mimic piston steam engines by employing non-compressing mechanisms, with fuel/air mixture intake, combustion, and exhaust phases synchronized with piston motion.

Engine Emissions

Internal combustion engines, particularly reciprocating ones, generally produce elevated levels of pollution. This is primarily due to incomplete combustion of carbonaceous fuels, resulting in emissions of carbon monoxide, soot, oxides of nitrogen and sulfur, and unburnt hydrocarbons. Factors influencing pollution levels include operating conditions and fuel/air ratio. Petrol engines, for instance, operate near the stoichiometric ratio to achieve combustion efficiency, although excess air would facilitate more complete combustion. Additionally, the cooling effect of cylinder walls can hinder flame propagation, leading to incomplete combustion.

Diesel Car Lift Repair Near Me  engines emit a range of pollutants, including aerosols of fine particles (PM10) that can deeply penetrate human lungs. Conversely, engines fueled by liquefied petroleum gas (LPG) exhibit lower emissions due to the clean-burning nature of LPG devoid of sulfur or lead.

Sulfur present in many fuels contributes to sulfur oxides (SOx) in exhaust emissions, exacerbating acid rain formation. High combustion temperatures also yield higher proportions of nitrogen oxides (NOx), known to pose health risks to both flora and fauna. While net carbon dioxide production is inherent in most fossil fuel-powered engines, engines fueled by biomass can achieve carbon neutrality, as growing plants absorb equivalent or more carbon dioxide during growth.

Hydrogen engines theoretically produce only water as a byproduct, but when air serves as the oxidizer, nitrogen oxides are also generated.

Internal Combustion Engine Efficiency

Efficiency varies among different types of internal combustion engines. Typically, gasoline-fueled engines, despite advancements like turbocharging, exhibit mechanical efficiencies around 20%. A significant portion of energy from gasoline is lost: approximately 36% as heat to the cooling system, 38% through exhaust emissions, and 6% due to friction. Efforts to harness wasted energy for useful purposes have met limited success, although various add-on devices and systems can enhance combustion efficiency.

Hydrogen Fuel Injection (HFI) systems improve fuel economy by introducing hydrogen into the intake manifold as a combustion enhancer. This increases octane rating, enhances flame velocity, and allows for advanced ignition timing, higher compression ratios, and leaner air-to-fuel mixtures, resulting in reduced pollution, increased power, and improved efficiency. Some HFI systems generate hydrogen on board using electrolysis, while others rely on pressurized hydrogen tanks requiring periodic refilling.

Emerging internal combustion Car Lift Repair Near Me  engine designs, such as the Scuderi Split Cycle Engine, employ high compression pressures exceeding 2000 psi and combust after top-dead-center, promising efficiencies as high as 50-55%.

Battery: Responsible for supplying electricity to initiate engine startup and power vehicle electronics and accessories.

Electronic Control Module (ECM): Oversees fuel mixture, ignition timing, and emissions systems, monitors vehicle operation, protects the engine from misuse, and identifies and resolves issues.

Exhaust System: Guides exhaust gases from the engine to exit through the tailpipe, featuring a three-way catalyst to reduce emissions within the system.

Fuel Filler: Connects a fuel dispenser nozzle to the vehicle’s receptacle for tank refilling.

Fuel Injection System: Delivers fuel into the engine’s combustion chambers to initiate ignition.