Wednesday, November 27, 2013
How to Determine Carburetor Size
Many modern engines no longer use carburetors. Instead, they use electronic fuel-injection systems, which forcibly spray fuel into air rather than just letting air and fuel mix. Carburetors still run in older vehicles, however, and in other engines such as chain saws or lawn mowers. In all applications, the carburetors size depends on the engines size. An engine needs a larger carburetor if it displaces more air or if its crankshaft rotates with a greater speed.
Instructions
- 1
Multiply the engine displacement, in cubic inches, by the engines maximum speed, in revolutions per minute (RPM). If your engine displaces 300 cubic inches with each stroke and works at up to 3,200 RPM: 300 x 3,200 = 960,000.
2Divide your answer by 3,456. 960,000 / 3,456 = 277.78.
3Divide your answer by the engines efficiency, which is typically close to 85 percent. 277.78 / 0.85 = 326.8. This is your required carburetor size in cubic feet per minute.
