This post for many might come with the response of “duh”. Surprisingly very few people really understand what makes a car engine rev. We have in the past posted about the 4 engine cycles of a standard car engine as well as what the difference between horsepower and torque is, but we feel like getting back to real basics. In a vintage car, the process of making the car engine rev when pressing down on the accelerator pedal involves more mechanical components compared to modern cars with electrics and computers controlling the engine or “drive by wire”.
Here is a step-by-step explanation of how a car engine rev:
Throttle Cable: In vintage cars, the accelerator pedal is mechanically connected to the throttle valve on the carburetor (or sometimes on the throttle body) via a throttle cable. When you press the pedal, the cable pulls on a linkage.
Throttle Valve: The movement of the throttle cable causes the throttle valve to open. The throttle valve controls the amount of air entering the engine’s intake manifold.
Carburetor: In cars equipped with a carburetor (common in vintage vehicles), the opening of the throttle valve allows more air to flow through the carburetor. The carburetor mixes this air with fuel in the correct ratio. As more air flows through, the carburetor increases the amount of fuel drawn into the airstream.
Increased Air-Fuel Mixture: The increased air and fuel mixture enters the engine’s combustion chambers. This mixture is then ignited by the spark plugs.
Combustion: The combustion of the increased air-fuel mixture generates more power. This increased power is transferred to the pistons, which move more vigorously.
Crankshaft Rotation: The pistons’ more vigorous movement causes the crankshaft to rotate faster. This increase in rotation speed is what causes the engine to rev.
Exhaust Flow: The exhaust gases produced from the combustion process are expelled through the exhaust valves and out through the exhaust system.
Finally
In summary, in a vintage car, pressing the accelerator pedal mechanically opens the throttle valve, which allows more air into the carburetor. The carburetor then increases the fuel supply to match the increased air intake, resulting in a higher air-fuel mixture entering the engine. The combustion of this mixture increases the engine speed, causing the engine to rev.
