Multec 3.5 Fuel Injector Application Manual
Software
Delphi Energy and Chassis Systems
Revision:
11/05-1
5-5
M = Slope (grams/sec/msec)
X = Pulse-width (msec)
B = Y intercept (grams/sec)
Note
It is best if the slope and intercept are determined by flowing a fuel rail
assembly. This will then include pressure regulator effects (for a
recirculating fuel system) and rail pressure dynamic effects. Injector only
flow data can only be used for initial approximation.
Note
More sophisticated models of the injector flow curve can be developed
from the empirical flow data to include the non-linear nature of the curve
at very low pulse widths.
Figure 5-2 - Slope and intercept graph (Flow vs. Pulse Width)
The actual calculation process in the engine controller is as follows:
1. The offset is assumed to be zero and the desired injector pulse-width is
calculated from the inverse slope (msec/gram/sec). This is called the
intermediate Base Pulse-width (BPW).
2. For software sets including low pulse-width correction, if the BPW is
less than specification, then the low pulse-width correction is applied.
