Copyright © 2015  Grand Rapids Technologies, Inc.

Electronic Flight Instrumentation for Experimental Aircraft Since 1991

Specific Fuel Consumption

GRT is (to our knowledge) the only Experimental EFIS manufacturer to display this widely-accepted measure of fuel efficiency. It is a simple way to analyze the efficiency of your engine at a glance.




Percent Power and Specific Fuel Consumption (SFC)

A direct indication of engine efficiency, specific fuel  consumption (SFC) is a precise way to monitor fuel consumption and engine efficiency. SFC is defined as the number of pounds of fuel consumed for each horsepower generated for 1 hour. The lower the value, the more efficient the engine is operating.

To calculate SFC, the GRT EFIS requires an EIS with a calibrated fuel flow sender, a manifold pressure sensor, and performance values for your specific engine. SFC can be calculated and displayed on any GRT EFIS system.

To program the EFIS with the engine performance data necessary for SFC:

  1. Press MORE (or NEXT) > Set Menu and access the Engine Limits menu page.
  2. Scroll to Engine Performance and press the knob to access the Engine Performance table. An example for a 180-horsepower Lycoming is shown below.
  3. Enter the values for your engine based on the engine manufacturer’s documentation. The left side contains entries for the manifold pressure values representing 55% power and 75% power at sea level. The right side contains values for the change in horsepower for each increment of altitude. Estimated horsepower value charts for common engines are also located on the GRT EIS documentation web page. Use the engine manufacturer’s documentation whenever possible for the best accuracy.













   


SFC is displayed next to other measures of fuel efficiency, such as MPG, and trip data.

Viewing SFC Calculations on your GRT EFIS

On the HXr (right), SFC, Percent Power, and MPG, shown here highlighted in red, are permanently displayed in the center of the ENG/MAP page between the bar graph banks. They can also be displayed in a configurable data Box or dial for display on the PFD or Map screens.

On Horizon (WS/HS/HX) and Sport models, SFC appears on the Status Box in the center of the Engine screen. It is highlighted in red on the HX screenshot at right. To bring up the Status Box on the ENGINE page, press NEXT until the DATA softkey appears, and highlight STATUS.  

Once you learn the SFC numbers for your particular airframe/ engine/ propeller combination, it is simply a matter of observing the SFC to verify proper leaning and efficient operation of your engine.