eli5: Difference between a throttle and a HP cock

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So a throttle is used to regulate the power to the engine by increasing or decreasing the flow of fuel. A HP cock is used to block fuel flow. Both of these things operate based on a turning mechanism that either lets the fuel flow or blocks it. So what is the difference between the two? Do they not just do the same thing?

In: 4

The throttle operates the throttle body which allows more air in the engine. The computer calculates fuel requirements based on air flow, load demand, etc..

A cock is used to stop fuel flowing to the engine. It’s an off switch for the fuel system.

A throttle is variable. It can be open a little, or open a lot, or opened all the way. It controls the speed of the engine. A throttle only controls fuel indirectly – the flow of air is what the throttle actually controls, and fuel is added to the engine (by fuel injectors or the jets of a carburetor) in response to the air flow.

tl;dr a fuel cock is either open or closed. A throttle is variable.

A throttle does not control the flow of fuel. The throttle increase the flow of **air** and then the sensors/computer in the car calculate how much fuel is required to make the proper air/fuel ratio.