Injector Offset / Dead Time

The latency between the ECU commanding an injector open and it actually delivering fuel, varying with voltage.

Injector offset, also called dead time or latency, is the time an injector takes to physically open and close after being commanded, during which little or no fuel flows. The ECU adds this offset to the calculated pulse width so the intended fuel mass actually reaches the cylinder. Dead time rises as battery voltage drops, so it is stored as a curve against voltage rather than a single number. It matters most at small pulse widths (idle, light cruise) where the offset is a large fraction of total open time; a wrong offset makes the engine lean or rich at idle and during cranking, and can make trims swing with electrical load. In HP Tuners VCM Editor the offset/voltage table sits in the Fuel Injector section beside slope and breakpoint. Enter the injector vendor's dead-time table, then verify idle and low-load AFR on a wideband, since commanded fueling assumes this offset is accurate.