Friday, October 11, 2013
How to Calculate an Injector Flow Rate
Internal combustion engines are precise machines designed to exacting specifications to maximize power and fuel efficiency. To attain this, a specific fuel injector must be used that introduces fuel into the pistons for combustion at a precise rate as determined by characteristics of the engine. So long as these properties are known with certainty, the needed injector flow rate can be found with simple arithmetic.
Instructions
- 1
Multiply the engines horsepower by its brake specific fuel consumption (BSFC). The latter is a constant that measures between 0.4 and 0.7 for gasoline-powered systems. For naturally aspirated engines, estimate BSFC to be 0.4 to 0.5. Use 0.5 to 0.6 for nitrous engines. For forced induction and rotary engines, use 0.6 to 0.7 in the equation. Use a value between 1.2 and 1.4 for methanol-fueled systems.
2Divide the result by the number of injectors in the engine.
3Divide this new number by the injectors duty cycle. This is usually approximately .80, but never more. The result is the injectors flow rate in lbs. per hour per injector. Multiply the end result by 10.5 to convert this into cubic centimeters per minute (cc/min).
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