4 Strokes and 2 Strokes Engine

A 2-stroke engine needs backpressure in its exhaust system to prevent unburned air/fuel mixture from passing directly to the exhaust. Without backpressure, the unburned mixture can escape before it has a chance to combust fully, resulting in decreased engine efficiency and increased pollution. Backpressure helps to maintain the proper flow of exhaust gases, allowing for better combustion and reducing the amount of unburned fuel that reaches the exhaust.

The term BTDC stands for "Before Top Dead Center." This refers to the position of the piston in an internal combustion engine, specifically the position of the piston before it reaches the top of its stroke. It is a crucial timing measurement used in the ignition system to determine when the spark plug should fire, ensuring optimal combustion and engine performance.

The term 'CDI' stands for Capacitor Discharge Ignition. This is a type of ignition system used in internal combustion engines. It works by storing energy in a capacitor and then releasing it in a high-voltage discharge to create a spark for igniting the fuel-air mixture in the engine's cylinders. This system is commonly used in motorcycles and other small engines due to its simplicity and reliability.

A 2-stroke engine does not have a camshaft system. Unlike a 4-stroke engine which uses a camshaft to control the opening and closing of valves, a 2-stroke engine relies on ports in the cylinder walls to control the flow of air and fuel. These ports are uncovered and covered by the movement of the piston, eliminating the need for a camshaft. Therefore, the correct answer is No.

Big bore + short stroke is a configuration commonly used in engines designed for high rpm. This combination allows for larger valves and better airflow, which is crucial at high engine speeds. The short stroke reduces the distance the piston travels, allowing for quicker and more frequent combustion cycles. This results in a higher power output and better performance at high rpm. Additionally, the shorter stroke helps to reduce piston speed, minimizing stress on the engine components, making it suitable for sustained high-speed operation.

During the compression cycle in a 4-stroke engine, neither the intake valve nor the exhaust valve is opened by the camshaft. The compression stroke occurs after the intake valve closes and the piston moves upwards, compressing the air-fuel mixture in the combustion chamber. During this process, both the intake and exhaust valves remain closed. Therefore, the correct answer is "None".

Pre-ignition/detonation, also known as knocking or pinging, occurs when the fuel-air mixture in the engine's cylinder ignites prematurely before the spark plug fires. This uncontrolled combustion creates pressure waves that can damage the engine. Several factors can contribute to this phenomenon:

High compression ratio: Increases the temperature and pressure in the cylinder, making the fuel more prone to spontaneous ignition.

Incorrect timing chain marking: Leads to improper valve timing and spark timing, potentially causing the fuel to ignite too early.

Engine overheating: Raises the temperature inside the cylinder, increasing the likelihood of pre-ignition.

Low-octane fuel: Has a lower resistance to knocking and is more likely to ignite prematurely under high pressure and temperature.

Carbon deposits: Can act as hot spots in the combustion chamber, triggering pre-ignition.

The letter 'W' in the grade 10W-50 represents "winter". In the context of this grade, it indicates the oil's ability to flow smoothly in cold temperatures. The lower the W number, the better the oil performs in colder conditions. Therefore, the presence of the letter 'W' suggests that the oil is suitable for winter use.