Injectors¶
Electronic valves that spray fuel. Their flow rate sets the engine's fuel ceiling; duty cycle and dead time set how precisely they meter at the extremes.
What it is¶
A fuel injector is an on/off valve held open for a measured pulse width. Three numbers describe it:
- Flow rate (cc/min) — how much fuel it passes when fully open. This sets the maximum fuel the engine can ever receive.
- Duty cycle — the fraction of each engine cycle the injector is open. As demand rises, duty cycle climbs toward 100%.
- Dead time (latency) — the brief delay between the ECU commanding "open" and fuel actually flowing. It grows at low battery voltage and is influenced by fuel pressure.
Why it matters¶
Injectors bracket fuelling at both ends:
- At the top end, when duty cycle reaches 100% the injector is maxed — it physically cannot flow more. The engine then leans out, which acts like a soft rev-limit. See Rev Limiter.
- At the bottom end, idle needs tiny pulses. If the injector is much bigger than the engine needs, those pulses approach the dead time, where metering is imprecise — idle mixture gets jumpy.
How to tune it¶
Size injectors to the power target with headroom, but no more. Bigger isn't automatically better: the larger the injector, the worse its low-pulse resolution at idle.
Rule of thumb
Pick injectors that run roughly 80–85% duty at peak power. That leaves a safety margin up top while keeping idle pulses long enough to meter cleanly.
Watch out
If the engine leans out and stops gaining power near redline, the injectors are likely maxed — not the engine breathing out. Confirm duty cycle before chasing the VE table.
In the game¶
Injector flow, dead time, and the live duty-cycle readout appear on the Fuel page. Watch duty cycle climb under load. (The hardware version is selected in Engine Setup → Fuel Injectors.)