Throttle body and throttle plate

What is a throttle body and throttle plate?

A throttle plate in a carbureted engine

In older carbureted engine, the throttle plate is a

Carburetor throttle plate

circular disc that sits in a circular passage and regulates the amount of air coming into the engine based on the driver’s accelerator pedal. When the driver presses on the pedal, a cable running from the pedal to the carburetor rotates the throttle plate. The air passing through the carburetor venturi creates suction which pulls gas from the carburetor bowl through metering jets and into the engine.

At idle, the throttle plate is cracked slightly open to all enough air and fuel to enter the engine to maintain idle speed.

Throttle plate and throttle body in a throttle body injection engine

The throttle plate in a throttle body injection engine does the same job as in a carbureted engine by regulating the flow of air into the engine. However, unlike in a carbureted engine, fuel isn’t drawn from through a venture; it is injected into the engine with one or more fuel injectors located in the throttle body.

At idle, the throttle plate is cracked slightly open to all enough air to maintain idle speed.

Throttle Body Fuel Injection

Throttle plate and throttle body in a port injected engine

The throttle plate in a port injected engine also regulates air into the engine based on the driver’s input from the accelerator pedal. However, the fuel is delivered directly to the intake manifold above the intake valves by fuel injectors. NO FUEL TRAVELS THROUGH THE THROTTLE BODY in a port injected engine!

At idle, the throttle plate in a port injected engine is completely closed!. The air needed to keep the engine running is supplied by an idle air bypass valve and a passage the runs from in front of the throttle plate to behind the throttle plate. is cracked slightly open to all enough air to maintain idle speed. See this post to learn more about idle air bypass valves.

Electronically Controlled Throttle Body

An electronically controlled throttle body works like an

Electronic throttle body and accelerator pedal position sensor

ordinary throttle body for a port fuel injected engine except that it is not operated by a cable connected to the accelerator pedal. Instead, it is controlled by electric signals from an electronic accelerator pedal. A motor opens and closes the throttle plate. Idle air is provided by cracking the throttle plate open slightly by the motor. No IAC valves are used on an electronic throttle body.

©, 2018 Rick Muscoplat