Why does the intake valve open during the intake cycle?
During the intake stroke, the fuel and air mixture is drawn into the cylinder with the exhaust valve closed. Then the air and fuel mixture is compressed in a compression stroke. The gases expand completely, the exhaust valve opens, and the gases are expelled out during the exhaust stroke.
How to calculate the duration of intake valve timing event?
To calculate the duration of any intake valve timing event, add 180° to the intake opening and closing time. For example, if an intake valve opens at 12° before top dead center (BTDC) and closes at 40° after bottom dead center (ABDC), the duration of the valve timing event is 232°. Exhaust timing follows a similar calculation.
What to do if your intake valve is stuck?
An intake valve stuck in the open position allows too much fuel to pass through the exhaust system without proper burning. Remove the valve covers of the engine, using an appropriate socket and wrench. Remove the single valve cover in the case of a four-cylinder or straight-six engine.
How are intake and exhaust valves open and closed?
Every engine has intake and exhaust valves. Valves open to intake fuel or expel exhaust. They close when their cycle completes. Valve stems sit in long tubular guides that provide a track for them to move up and down in. The camshaft lifts and drops the valves singularly, or they have rocker arms, springs, lifters and push rods to assist them.
When does the intake valve reach its maximum lift?
This is called the intake stroke (figure 3), where the engine “breathes” and fills itself with another charge of fresh air/fuel mixture. The intake valve reaches its maximum lift at some defined point (usually about 106 degrees) after top dead center.
To calculate the duration of any intake valve timing event, add 180° to the intake opening and closing time. For example, if an intake valve opens at 12° before top dead center (BTDC) and closes at 40° after bottom dead center (ABDC), the duration of the valve timing event is 232°. Exhaust timing follows a similar calculation.
When to close exhaust valve and intake valve?
Once the piston passes through Top Dead Center and starts back down, the intake charge is being pulled in quickly so the exhaust valve must close at precisely the right point after the top to keep any burnt gas from reentering. This area around Top Dead Center with both valves open is referred to as “overlap”.
Why do you need to open intake valve before TDC?
Opening the intake valve slightly before the piston reaches TDC can increase high-speed volumetric efficiency. Rapid piston movement creates both a faster moving air charge and pressure differential in the cylinder. The piston’s rapid movement nonetheless surpasses air charge velocity.
This is called the intake stroke (figure 3), where the engine “breathes” and fills itself with another charge of fresh air/fuel mixture. The intake valve reaches its maximum lift at some defined point (usually about 106 degrees) after top dead center.