13. Glossary
The terms used in the guide, in alphabetical order. Screen names appear in bold.
| Term | Definition |
|---|---|
| Angular limit | Maximum pulse duration in crankshaft degrees, counting the dead time. The smaller of it and the window width applies. |
| Anti-windup | With feed-forward on, the limit of the accumulator of the PID integral term: the maximum integral term is Ki × Anti-windup. Not used without feed-forward. |
| Bank | Group of injectors (A, B or C). Each rail marks the banks it feeds. |
| Cam dependence | Makes the pump window follow the VVT deviation of the chosen cam. A retarded cam shifts the window later. |
| Camshaft degree | Degree measured on the cam, which turns at half the crankshaft speed. One camshaft degree equals 2 crankshaft degrees. |
| Closing | Lobe #1 closing angle: end of the pulse, near the lobe peak, not at the peak. By sweep, the value ends up a few crankshaft degrees before it. |
| Commanded pulse | Duration of the valve pulse, in ms, after all the ceilings. It is what is compared between maps. |
| Consumption | Average of the injection time, with dead time and corrections, of the marked banks. It is the basis of the feed-forward. |
| Control valve | Pump valve that the VCU turns on and off, once per lobe, to decide when the pump delivers. The VCU does not control the current. |
| Crank index position | Adjustment of the RPM signal: the tooth over the sensor with cylinder 1 at TDC. If wrong, all the pump angles come out shifted. |
| Crankshaft degree | Degree measured on the crankshaft: 720 per 4-stroke cycle, from the TDC of cylinder 1. The pump angles use this unit. |
| Dead time | See dead time (t0). |
| Dead time (t0) | Part of the pulse that does not deliver volume: t0 plus the curve by battery voltage. It only enters when there is demand. |
| Deceleration cut | With injector consumption below 0.3 ms and pressure 10 bar above the target, the VCU zeroes the pump pulse. Only with feed-forward. |
| DI1 and DI2 | Pressure sensor inputs of Rail #1 and Rail #2 (DI: direct injection). The channels DI Rail pressure #1 and DI Rail pressure #2 show the direct reading. |
| Duty | Commanded pulse divided by the window width, in %. It is 100 in the start routine and 0 with the rail off. |
| Effective window | Start and end of the real pulse, in the channels GDI - Rail 1 window: effective opening and GDI - Rail 1 window: effective closing. The effective opening is the start of the pulse, not the typed angle. |
| Feed-forward | Physical model that calculates the pulse from the injector consumption. With it on, the PID becomes just a correction, the trim. |
| Fill factor | Curve by rpm (Fill factor (RPM)) that enters as a factor in the calculation of W, before the G(W) curve. With 1.00 there is no effect. |
| Filtered pressure | Reading of the rail sensor filtered at the stroke frequency, used by the loop. It is not in the log: filtered = target − error. |
| Flex IO | FT470 pin that can be an output or an input. The pump pin stays as an output. |
| Full scale | The highest pressure the VCU can see: the last point of the sensor table. Only a guard set below it acts (except Guard 2 through the condition target plus 20 bar, with the release below full scale), and a target above it is never seen as reached. |
| G(W) | Capture curve: returns the crankshaft degrees of useful pulse needed to deliver the demand W. |
| GDI | Direct injection (gasoline direct injection). The direct injection injectors are fed by the high pressure rail. |
| Guard | Pump overpressure protection: see Guard 1 and Guard 2. |
| Guard 1 | Pulse limiter: above the entry level, the pulse is limited to a % of the window width. It exits 3 bar below. |
| Guard 2 | Overpressure latch: turns off the rail pump and only releases below the release level. It does not cut the injectors. |
| High pressure fuel pump (HPFP) | Mechanical pump driven by the cam lobes that takes fuel to the direct injection rail. The VCU controls only the pump control valve. |
| Injector lockout | At start, the marked banks stay without a pulse until the minimum pressure, the Engine running RPM (disengages lockout) or the timeout. Requires feed-forward and the cut on. |
| Kick | Short boost added to the pulse when the injector consumption rises fast. It only adds, limited by the Kick upper limit. |
| Kp, Ki and Kd | Proportional, integral and derivative gains of the PID. Kp and Ki are curves by rpm; Kd is a single value. |
| Latch | Lock that keeps Guard 2 active until the pressure drops below the release level or the VCU restarts. Stopping the engine does not release it. |
| Limp-home | Safe mode with the rail sensor declared failed. With feed-forward the pulse comes from the model only, without PID. Without feed-forward the pump turns off. |
| Lobe | Cam bump that drives the pump. Each lobe gives one stroke per cycle. |
| Lockout | See injector lockout. |
| Low rail pressure injector cut-off | Injectors of the marked banks stay without a pulse with the pressure below the limit and come back above the limit + 2 bar. |
| MAP | Manifold pressure. On the load axis of the target map it is in relative bar; vacuum is negative. |
| max Theta | Short name of the Angled window upper limit, used in the channel GDI - Angular upper limit (max Theta) rail 1. |
| Opening | Lobe #1 opening angle: the earliest start the pulse can have. Together with the closing, it defines the window width. |
| Phase sensor | Sensor that confirms the phase of the 720 crankshaft degree cycle. The function requires it: without it half of the pulses fall outside the lobes. |
| Phase sweep | Field experience: at a fixed steady state, move opening and closing together (the width does not change), 10 crankshaft degrees per step up to ±20, and keep the step with the smallest pulse in ms. |
| PID | Controller that corrects the pulse by the pressure error, with the proportional, integral and derivative terms. |
| Pressure error | Target minus the filtered pressure. Positive: the rail is below the target. |
| Pressurization (gain) | Adds time to the pulse when the target rises and removes it when it falls, limited to ±1.5 ms. |
| Pump stroke | Each pump delivery, one per lobe. The frequency is rpm × lobes ÷ 120 strokes per second. |
| Rail | The fuel rail: the high pressure line that feeds the direct injection injectors. The function accepts 1 or 2 rails, each with an output and a sensor. |
| Rail off | The VCU stops commanding the rail valve: invalid width, no sync, no RPM, Guard 2 or, without feed-forward, sensor fault. In the log, the effective window stays at 0/0. |
| Start routine | With feed-forward, between 50 rpm and the Crank out RPM the valve is held on (duty 100), at most until the timeout. |
| Sync | The VCU recognizes the wheel and, with a phase sensor, confirms the phase. Before it the RPM is 0 and the valve is not driven. |
| TDC | Top dead center. The pump angles count from the TDC of cylinder 1, like those of injection and ignition. It is not the lobe peak. |
| Trim | PID correction with feed-forward on, in ms, between the floor (PID minimum trim or Trim floor: feedforward fraction) and the PID maximum trim. |
| VCU | FuelTech control unit, FT700 or FT470, that controls the pump valve. |
| VVT | Variable valve timing (Variable camshaft (VVT)). With Cam dependence, the pump window follows the cam offset. |
| W (demand) | Consumption in ms corrected to 100 bar. Axis of the G(W) curve. The screen does not show the unit. |
| Window | Range of crankshaft degrees of lobe #1 between the opening and the closing. The width (closing − opening) is the pulse ceiling. |
| Window upper limit | Maximum pulse duration that the window width allows: width ÷ (0.006 × rpm). The signal GDI - Lobe window upper limit rail 1 indicates when it limits the pulse. |