Honda Mileage: VID constants

This provides a little background on the calibration constants used by the VID

Fc-----Fuel Constant

As we have already discussed, Fuel Injectors are sized according to how many cc (cubic centimeters) of fuel they spray per minute of full-on operation. For example, the fuel injectors I use, emit 240 cc per minute of operation. What does that mean to people who think about gasoline in terms of gallons:

240 cc/min is the number used by for just one cylinder. For the total amount of gasoline consumed by the engine we multiply this by the number of cylinders. Again, in my case, that number is 240 * 4 cylinders = 960 cc/min/engine.

960 cc/min/engine * 60 min/hour = 57600 cc/hour/engine

1 gallon of any liquid contains: 3785,51 cubic centimeters

Therfore: 57600 cc/hour/engine * 3785 gallon/cc = 15.217 gallons / hour / engine

To eliminate the decimal point, the number the VID uses internally is :
15.217 * 100 = 1522

Therefore Fc = 1522

Dc ----Distance Constant

Typically, vehicle Speed Sensors (VSS) change logic state (counts) between 4000 and 10000 times per mile (5280 feet) of travel. My vehicle happens to send about 4000 counts/min (PPS).

The VID, however, prefers the number be in another form:

So... to create that constant the program first divides the

PPM by 5280 = 4000/5280 = 0 .757575.

Fps_mph = 88 fps / 60 mph = 1.46666

Then, it multiplies Fps_mph * 0.757575 = 1.111

Therefore : Dc = 1111 = (1.111 * 1000)

Dc = 1111

The three numbers required by the VID are :

1. Pulses per mile PPS

2. Fuel Injector cc/ minute

3. Number of Cylinders