Take This Gas Engine Trivia Quiz!

The three important intake valve functions are:
1. Opening at the correct instant to allow the intake of air-fuel mixture.
2. Closing at the correct time and sealing during compression.
3. Having a streamlined shape to ensure smooth flow of gases into the combustion chamber without obstruction.

Compression increases engine power by squeezing the atoms that make up molecules of air and fuel close together, creating heat energy. As a result, the tightly packed molecules try to move apart, generating energy. This energy, combined with the expanding energy of combustion, ultimately provides power to the engine.

Valve overlap refers to the period during the four-stroke cycle of an engine when both the intake and exhaust valves are open simultaneously. This allows for the smooth transition of the exhaust gases out of the cylinder and the intake of the fresh air-fuel mixture. It helps in improving engine efficiency and performance by maximizing the scavenging effect and ensuring proper combustion.

Two-cycle engines can be run in any position because they get adequate lubrication as fuel mixed with oil is passed through the engine. Unlike four-cycle engines, two-cycle engines do not have a separate oil reservoir. Instead, the oil is mixed with the fuel, and as the fuel passes through the engine, it provides lubrication to the moving parts. This design allows the engine to operate in different positions without compromising its lubrication system.

The exhaust valve is cooled mainly by conduction. Conduction is the transfer of heat through direct contact between two objects. In the case of the exhaust valve, it comes into contact with the cooler engine components, such as the cylinder head or coolant passages, which helps to dissipate heat. This direct transfer of heat through conduction allows the exhaust valve to cool down efficiently and prevent overheating.

The correct answer is the splash system and the pump system. In four-cycle engines, lubrication is essential to reduce friction and wear between moving parts. The splash system involves the use of oil that is splashed or sprayed onto the various engine components, such as the crankshaft and cylinder walls, by the rotating parts. This ensures that the moving parts are adequately lubricated. On the other hand, the pump system uses an oil pump to circulate oil throughout the engine, ensuring a constant supply of lubrication to all necessary areas. Both methods work together to provide effective lubrication in four-cycle engines.

During operation, the incoming air-fuel mixture tends to cool the intake valve. This is because the air-fuel mixture is at a lower temperature compared to the hot exhaust gases that are expelled from the engine through the exhaust valve. As the cooler air-fuel mixture flows into the intake valve, it absorbs some of the heat from the valve, causing a temperature difference between the intake and exhaust valves.

The two types of scavenging systems used in two-cycle engines are the cross-scavenged and the loop-scavenged. These systems refer to the way in which air and fuel are circulated within the engine. In a cross-scavenged system, the incoming air-fuel mixture flows across the cylinder and exits through ports on the opposite side. In a loop-scavenged system, the mixture enters the cylinder from one side and exits through ports on the same side. These different scavenging systems have implications for the engine's performance, efficiency, and emissions.

The baffle on the contoured piston is designed to direct the flow of the air-fuel mixture upward in the cylinder. This helps to improve the combustion process by ensuring that the mixture is evenly distributed and properly mixed before ignition. By directing the flow upward, the baffle helps to create a more efficient and effective combustion, resulting in better engine performance and fuel efficiency.

Having the intake port lead directly into the crankshaft allows for the charge of fuel and oil to lubricate the ball and needle bearings until the piston opens the transfer ports on the down-stroke. This ensures that the bearings are properly lubricated, reducing friction and wear, and improving the overall efficiency and performance of the engine.

The four strokes of a four-cycle engine are intake, compression, power, and exhaust. During the intake stroke, the fuel-air mixture is drawn into the cylinder. In the compression stroke, the mixture is compressed by the upward movement of the piston. The power stroke is when the spark plug ignites the compressed mixture, causing an explosion and pushing the piston downward. Finally, in the exhaust stroke, the burned gases are expelled from the cylinder.

In a properly tuned exhaust system, sound waves are used to prevent the air-fuel mixture from leaving with the exhaust. This is achieved through the design and positioning of the exhaust pipes and mufflers. The sound waves created by the engine's combustion process are reflected and redirected within the exhaust system, creating pressure waves that help to push the exhaust gases out while preventing the air-fuel mixture from escaping.

A 4-cycle engine runs cooler than a 2-cycle engine because it has half as many power strokes. In a 4-cycle engine, the valves dissipate heat through seats and guides, which helps in cooling the engine. Additionally, in a 4-cycle engine, the burned gases are removed before a fresh charge is introduced, further aiding in cooling the engine.

The correct answer is the rotary valve system, reed valve system, and the loop-scavenged system. These are three valving systems commonly used in two-cycle engines. The rotary valve system uses a rotating valve to control the intake and exhaust of gases. The reed valve system uses thin, flexible reeds to regulate the flow of air and fuel mixture. The loop-scavenged system uses the motion of the piston to create a loop of fresh air and fuel mixture for efficient combustion. These systems play a crucial role in the operation and performance of two-cycle engines.

The compression ratio must be limited in gasoline spark ignition engines because the heat generated during compression can cause the air-fuel mixture to ignite prematurely. This can lead to knocking or pinging, which can damage the engine and decrease its efficiency. By limiting the compression ratio, the heat of compression is kept at a level where the air-fuel mixture ignites at the optimal time, resulting in smoother combustion and improved engine performance.

Cross-scavenged is the correct answer because in a cross-scavenged type of 2-cycle engine, the air-fuel mixture flows across the cylinder horizontally, rather than vertically. This requires a contoured piston to effectively control the flow of the mixture and optimize combustion.

The correct answer is "All of the above." A four-cycle engine accelerates slower than a two-cycle engine because there is only one power stroke in four, the flywheel is heavier to carry the engine through three nonpower strokes, and there are more moving parts to be driven by the engine.