Calculate injector size and pump flow fast. Compare duty cycle, pressure, density, and margins easily. Build reliable fuel setups for stronger machine performance today.
| Application | Power (hp) | BSFC | Injectors | Duty % | Injector Need (cc/min) | Pump Need (LPH) |
|---|---|---|---|---|---|---|
| Compact diesel generator | 180 | 0.42 | 4 | 80 | 196.5 | 113.3 |
| Wheel loader retrofit | 320 | 0.50 | 6 | 85 | 214.2 | 184.9 |
| Concrete pump engine | 450 | 0.55 | 8 | 85 | 218.2 | 282.1 |
| High output site vehicle | 600 | 0.60 | 8 | 90 | 276.1 | 423.9 |
1. Total fuel mass flow:
Fuel Mass (lb/hr) = Target Power × BSFC
2. Injector flow needed at target pressure:
Injector Flow per Injector (lb/hr) = Fuel Mass ÷ (Injector Count × Duty Cycle)
3. Pressure correction:
Pressure Factor = √(Target Pressure ÷ Base Pressure)
4. Equivalent injector rating at base pressure:
Base Rated Injector Flow = Actual Required Flow ÷ Pressure Factor
5. Injector cc/min conversion:
cc/min = (lb/hr × 453.59237) ÷ (Fuel Density × 60)
6. Pump requirement with margin:
Pump LPH = ((Fuel Mass × 0.45359237) ÷ Fuel Density) × (1 + Safety Margin)
Fuel system sizing affects reliability. It also affects power stability. A small injector can force high duty cycle. A weak pump can reduce rail pressure. Both issues can hurt performance.
Construction engines often run under long loads. That makes fuel demand more important. Pumps, generators, loaders, and site vehicles need stable supply. This tool helps estimate that supply with simple inputs.
Target power tells the calculator how much work the engine must support. BSFC tells how much fuel is needed for that work. Higher BSFC means more fuel demand. Lower BSFC means a more efficient setup.
Injectors should not run at extreme duty for long periods. A safer duty limit leaves room for tuning changes. It also helps during heat and pressure loss. Many builders target about 80 to 90 percent.
Injector flow changes with pressure. More rail pressure increases actual flow. The increase is not linear. It follows the square root rule. This page includes that correction. That helps compare rated size and actual delivered size.
Pump flow should cover demand and reserve. Reserve helps with filter restriction, hot fuel, wiring loss, and future upgrades. That is why this calculator adds a safety margin. A margin can prevent lean operation under peak load.
You can also enter your current injector size and pump flow. The calculator estimates duty cycle and pump utilization. That helps you see if current parts are adequate, borderline, or undersized.
These outputs are ideal estimates. Real systems still need tuning and verification. Always confirm pressure, voltage, and actual fuel delivery on the machine. Use this tool to plan smarter before buying parts.
It estimates total fuel demand, injector size, pump flow, pressure correction, projected injector duty, and pump utilization. It helps compare your target with current parts.
BSFC means brake specific fuel consumption. It shows how many pounds of fuel are needed per horsepower per hour. Higher values mean greater fuel demand.
Duty cycle shows how hard the injector works. Very high duty can reduce control and safety margin. Keeping duty lower supports more stable fueling.
Injectors are usually rated at a base pressure. Real delivered flow changes when rail pressure changes. This tool corrects that difference with a square root factor.
Yes, as a planning tool. You must enter sensible BSFC and fuel density values for the fuel you use. Final validation should still happen on the machine.
A margin helps cover hot fuel, filter losses, wiring drops, and future tuning changes. It reduces the chance of a pump running too close to its limit.
Yes. After calculation, use the export buttons above the form. CSV saves the output table. PDF creates a clean report from the same result set.
No. They are engineering estimates. Always compare with manufacturer data, fuel pressure behavior, regulator setup, and real testing before final selection.
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.