Page 342 - Understanding Automotive Electronics

2735 | CH 9 Page 329 Tuesday, March 10, 1998 1:24 PM

AUTOMOTIVE INSTRUMENTATION 9

Figure 9.27
Trip Information
System
FPO

The system computes a particular trip parameter from the input data.
For example, fuel economy in miles per gallon (MPG) can be found by
computing
MPG = S/F
where
S is the speed in miles per hour
F is the fuel consumption rate in gallons per hour
As operating conditions Of course, this computation varies markedly as operating conditions vary. At a
change, the values pro- steady cruising speed along a level highway with a constant wind, fuel economy
vided by a trip informa- is constant. If the driver then depresses the accelerator (e.g., to pass traffic), the
tion computer may also fuel consumption rate temporarily increases faster than speed, and MPG is
change. reduced for that time. Various averages can be computed such that instant fuel
economy, short-term average fuel economy, or long-term average fuel economy
can be displayed.

UNDERSTANDING AUTOMOTIVE ELECTRONICS 329