Plan injector flow for safe fueling under load. Adjust pressure, BSFC, duty cycle, and density. Get consistent sizing results with clear engineering reference outputs.
Enter your target horsepower, fuel assumptions, and injector system details. Results appear above this form after calculation.
This estimates the engine’s total fuel demand with a reserve margin included.
Duty fraction is the duty cycle percentage divided by 100.
Fuel density is entered in kg/L, which is numerically equal to g/cc.
Differential pressure equals rail pressure minus manifold pressure. Higher differential pressure increases injector flow.
This gives a practical pulse width limit per injection event for a four-stroke sequential setup.
| Scenario | HP | Fuel | Injectors | Duty | Pressure | Required Catalog Size |
|---|---|---|---|---|---|---|
| Street turbo four-cylinder | 300 hp | Gasoline | 4 | 85% | 3.0 bar | 492.45 cc/min |
| Six-cylinder performance build | 450 hp | Gasoline | 6 | 85% | 3.5 bar | 510.63 cc/min |
| High-output forced induction V8 | 650 hp | E85 | 8 | 82% | 4.0 bar | 684.25 cc/min |
These examples are reference values based on the same formulas used by the calculator. Final tuning should always be validated with real fuel pressure, injector characterization, and wideband data.
Injector flow is the volume or mass of fuel an injector can deliver over time. It is usually listed in cc/min or lb/hr at a stated differential pressure.
Duty cycle shows how long the injector stays open during each cycle. High duty leaves less control margin, increases heat, and can reduce consistent fuel delivery at peak demand.
BSFC links horsepower to fuel mass demand. Naturally aspirated, boosted, and alcohol-fueled engines often need different BSFC assumptions, so injector sizing changes with engine efficiency and fuel choice.
Differential pressure is fuel rail pressure minus manifold pressure. Injectors respond to the pressure drop across the nozzle, not simply the rail gauge number by itself.
A safety margin helps cover tuning changes, transient enrichment, fuel temperature shifts, aging components, and real-world uncertainty. It reduces the chance of selecting an injector that is barely adequate.
Sometimes, but only within safe system limits. More pressure raises flow by the square-root relationship, so gains are modest. Pump capacity, injector behavior, and regulator stability still matter.
Candidate comparison shows whether an injector you already own can support the target power at the chosen duty cycle, pressure, and fuel assumptions before hardware changes.
No. It is a sizing and planning tool. Final injector selection should also consider dead time, voltage compensation, spray pattern, minimum controllable pulse width, and measured fuel pressure behavior.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.