What is the Intake Stroke?
The intake stroke is the first stroke of the four-stroke combustion cycle. During the intake stroke, the piston moves down the cylinder, creating a vacuum. This vacuum draws air and fuel into the cylinder through the intake valve. The intake valve then closes and the compression stroke begins.
The intake stroke is an important part of the combustion cycle because it allows the engine to draw in the fresh air and fuel that is needed for combustion. The amount of air and fuel that is drawn into the cylinder is controlled by the throttle plate, which is located in the intake manifold. The throttle plate is controlled by the driver’s right foot on the accelerator pedal.
Forced Induction vs. Naturally Aspirated Engines
Forced induction engines use a compressor or turbocharger to increase the amount of air that can be drawn into the cylinder. This results in more fuel being injected into the cylinder, which leads to more power. Naturally aspirated engines do not use forced induction and rely on the vacuum created by the piston to draw air into the cylinder.
Forced induction engines are often used in high-performance vehicles because they can produce more power than naturally aspirated engines. However, forced induction engines are also more complex and expensive to build and maintain than naturally aspirated engines.
Sensors Involved in the Intake Stroke
There are a number of sensors that are involved in the intake stroke, including:
- Mass Air Flow (MAF) Sensor: The MAF sensor measures the amount of air that is flowing into the engine. This information is used by the engine computer to calculate the amount of fuel that needs to be injected.
- Manifold Absolute Pressure (MAP) Sensor: The MAP sensor measures the air pressure in the intake manifold. This information is used by the engine computer to adjust the ignition timing and fuel injection.
- Throttle Position Sensor (TPS): The TPS measures the position of the throttle plate. This information is used by the engine computer to control the amount of air that flows into the engine.
- Air Temperature Sensor (IAT): The IAT sensor measures the temperature of the air that is entering the engine. This information is used by the engine computer to adjust the ignition timing and fuel injection.
Common Problems with the Intake Stroke
There are a number of problems that can occur with the intake stroke, including:
- Vacuum leak: A vacuum leak can cause the engine to run rough and lose power. Vacuum leaks can be caused by a variety of things, such as a cracked intake manifold or a loose hose.
- Dirty MAF sensor: A dirty MAF sensor can cause the engine to run rich or lean. This can lead to decreased fuel efficiency and performance problems.
- Faulty MAP sensor: A faulty MAP sensor can cause the engine to misfire or stall. It can also lead to decreased fuel efficiency and performance problems.
- Faulty TPS: A faulty TPS can cause the engine to surge or stall. It can also lead to decreased fuel efficiency and performance problems.
- Clogged air filter: A clogged air filter can restrict the amount of air that can flow into the engine. This can lead to decreased power and fuel efficiency.
Additional Details about the Intake Stroke
The intake stroke is a relatively simple process, but there are a few additional details that are worth noting:
- The intake valve is typically opened by a camshaft-driven rocker arm. The camshaft is timed so that the intake valve opens just before the piston reaches the bottom of the cylinder. This allows the maximum amount of air and fuel to be drawn into the cylinder.
- The intake valve typically closes just after the piston reaches the top of the cylinder. This ensures that all of the air and fuel mixture is trapped in the cylinder for the compression stroke.
- The intake stroke is not the only time that air flows into the engine. A small amount of air also flows into the engine through the crankcase vent system. The crankcase vent system is designed to remove