In most cases a naturally aspirated engine will have a B.S.F.C of .50. This means that the engine will use .50 lbs. of fuel per hour for each horsepower it produces. Turbocharged engines will want to be at .60 lbs. per hour or higher.

• Forced induction, estimate BSFC to be 0.6 to 0.7
• Naturally aspirated engines, estimate BSFC to be 0.4 to 0.5
• Nitrous engines, estimate BSFC to be 0.5 to 0.6
• Rotary engines, estimate BSFC to be 0.6 to 0.7
• For engines running methanol, double the
appropriate gasoline BSFC (e.g. a rotary engine running methanol has a
BSFC between 1.2 and 1.4)

Most injectors will max out at 80% duty cycle and this is the accepted industry standard. It is NOT recommended to run higher than 80% duty cycle.

B.S.F.C is brake specific fuel consumption - How much fuel you are using per horsepower per hour

•Some Important conversion factors & notes:

To convert cc / min to lbs. / hr. - Multiply by 10.5
To convert lbs / hr to cc / min – Divide by 10.5
To convert lbs. / hr to gal. / hr - Divide by 6
To convert cc / min to gal. / hr. - Multiply by .015873
Fuel Injector flow rates are usually rated at a flow pressure of 43.5 PSI (3 Bar)


•To find the Flow rate of an injector after a pressure change you will need to do the conversion in the following example. In this example we will be using a 240cc injector and determining what the flow rate of this injector will be if the fuel pressure is changed.


1. You will need to Divide the New Pressure by the Old Pressure.
2. Find the square root of the answer to step 1.
3. Multiply the square root by the OLD Flow Rate.
4. The answer will be the New Flow Rate of this injector at the New Pressure.


Lets do each step with some numbers so you can see the numbers in action. We will take this 240cc injector and determine the New Flow Rate at 50psi. Remember that injectors are tested / flow rated at 43.5 (or 3 Bar).

1. Divide the New Pressure (50psi) by the Old Pressure (43.5psi) = 1.1494
2. The Square Root of 1.1494 = 1.0721
3. The Old flow rate of 43.5 PSI multiplied by 240 (cc’s) =
4. 257.3cc’s