Injector Slope (High/Low)

The flow rate of an injector in mass per millisecond of open time, with separate high and low pressure regions.

Injector slope is how much fuel (grams per millisecond, or lb/hr) an injector flows per unit of pulse width once it is fully open. Many tables list a high slope and a low slope because injector flow is not perfectly linear, and fuel pressure (especially on returnless and direct-injection systems) shifts the curve. Slope matters because it is the single biggest factor in whether commanded AFR matches delivered AFR: get it wrong and every fuel calculation is scaled off. After installing larger injectors you must enter their characterization data or the engine will run lean or rich everywhere. In HP Tuners VCM Editor the slope values sit under the Fuel Injector section, alongside offset and breakpoint. Always validate by logging a wideband across the load range; if trims or wideband AFR drift consistently with load, the slope is off, not the targets.