Fuel System Calculator

The Dub Shop - Fuel System Calculator v1.1

Estimate fuel flow, pump capacity, injector size, and power by BSFC from displacement, RPM, VE, AFR, and boost. The pump comparison chart will update automatically.

Engine & Air Inputs

Display Units

Units

Starting Preset

Engine

Engine Displacement

Target RPM

Volumetric Efficiency

Target AFR (you type it)

Lambda (λ)

Air & Boost

Units

Ambient Pressure

Input Mode

Boost / MAP Value

Ambient Temp

Manifold Temp (IAT)

Ambient Air Density

Ambient density auto-calculated from Ambient Pressure & Ambient Temp (dry air).

Assumptions: 4-stroke. VE is NA breathing efficiency. Boost packing via ideal-gas PR×TR.

Fuel & Injectors

Fuel Type

Fuel Density

Fuel Rail Pressure (psi)

Injector & Duty

AFR is gasoline-equivalent (constant λ). We convert internally using each fuel’s stoich.

Results

Total Air Mass Flow

— —

Total Fuel Mass Flow

— —

Total Fuel Volume Flow

— —

Injector Sizing (@ duty)

Per-Injector (mass)

— lb/h

Per-Injector (volume)

— cc/min

Pump Capacity (min)

Recommended Pump

— — · — —

~20% headroom included

Estimated Power (BSFC)

Estimated Brake Power

— HP · — kW

BSFC & Preset

lb/hp·h

Output

BSFC mode uses the selected lb/hp·h. Output shown as Brake.

Note: Power is adjusted based on AFR. Extremely rich or lean mixtures will correctly reduce the estimated power output.

Pump Comparison

Chart Options

Chart Voltage

Chart Units

Select Pumps

Pump	Flow @ 12V	Margin @ 12V	Flow @ 13.5V	Margin @ 13.5V

TI/Walbro and Bosch data provided from the official datasheets. Use with real system testing.

Method

Intake volume (4-stroke): V̇ = Displacement × (RPM/60) / 2 × VE.
Boost correction: ρ_man = ρ_amb × (MAP_abs/P_amb) × (T_amb,K/T_man,K), with ρ_amb auto from P_amb, T_amb.
Air mass flow: ṁ_air = V̇ × ρ_man.
Gasoline-equiv AFR: AFR_eff = AFR_in × Stoich(fuel)/14.7, λ = AFR_in/14.7.
Power estimate: BSFC only; Wheel = Brake × (1 − Loss%).

Rev: v1.1 · The Dub Shop

Use for estimation only.