calculating GPH fuel consumption

How do I calculate GPH fuel consumption (gallons Per Hour) from fuel injector / pressure and pluse width?

anyone have a online calulator link for this?

You can estimate the engine's fuel requirements by multiplying flywheel HP x brake specific fuel consumption (BSFC, in #/HR/HP). BSFC for a normally aspirated engine will range from 0.45 #/HR/HP for a well tuned performance engine, to 0.50 #/HR/HP for a "stockish" setup. That will give you #/HR, and you need to convert that to GAL/HR using the fuel density in #/GAL... typically 6 #/GAL for pump gas.

Example:

(500 HP) x (0.50 #/HR/HP) = 250 #/HR

(250 #/HR) / (6 #/GAL) = 41.6 GAL/HR
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OR..........

Starting with the injector pulse width and the injector size requires additional data. You have to have the injector pulse width and RPM for several data points near you peak HP level. Calculate several points, to find the highest demand.

Injector duty cycle expressed as a decimal = ((pulse width, mSec) x (RPM)) / 120,000

Injector flow as a function of pressure = (Flow rating, #/HR) x ((pressure at which the injector is operating, PSI) / (pressure at which the injector is flow rated, PSI))^0.5

Total Injector flow = (injector flow rating, #/HR) x (duty cycle) x (8 injectors)

(Total flow / 6 #/GAL) = total flow, GAL/HR

Example:

Assumed Data you might get from your data log: Pulse width = 18.0 mSec @ 6000 RPM

((18.0) x (6000)) / 120,000 = 0.90 duty cycle

Example injector size = 30 #/HR, flow rated @ 43.5 PSI, but operating at 50 PSI:

Corrected flow rating = (30 #/HR) x ((50 PSI) / (43.5 PSI))^0.50 = (30) x (1.1494)^0.50 = (30) x (1.072) = 32.16 #/HR

Total actual fuel flow = (32.16 #/HR) x (0.90 DC) x (8 injectors) = 231.6 #/HR

Total actual fuel flow = (231.6 #/HR) / (6 #/GAL) = 38.6 GAL/HR

To convert to Liters/HR, multiply by 3.78

38.6 GAL/HR = 145.9 Liter/HR

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Let me verify all those numbers when I get a chance.... I just typed that off the top of my head. Yoiu would have to correct the density of the fuel (#/GAL) since actual fuel specific gravity varies widely. Remember also that the injector is really a volumetric flow device, and you are attempting to calculate that based on an injector flow rating that is in mass units. To be more correct, you would start with the injectors volumetric flow rating, e.g. cc/min

wow that is a rocking complex reply

very awsome! :bow: