Lambdaλ

Injector size calculator

What injector do you need for the power?

Get the required flow in lb/hr (and cc/min) for your target HP, fuel and boost — sized to stay under a safe duty cycle so you don't run the injectors out of headroom.

How injector sizing works

Required flow scales with power and how thirsty the fuel is. Lambda uses flow = (HP × BSFC) ÷ (injectors × duty): BSFC (brake-specific fuel consumption) is higher for boost and for ethanol/methanol, and duty cycle is capped at a safe ceiling (85% by default) so the injectors keep control. Output is lb/hr (and cc/min) per injector — round up to the next available size.

Injector sizing

Max duty cycle target85%

85% is the common safe ceiling — above it you lose injector control.

You need (per injector)
88.2 lb/hr
≈ 895 cc/min
Total flow
300 lb/hr
BSFC used
0.60
Duty target
85%

Sized so 4 injectors stay at or below 85% duty at 500 HP. Round up to the next available injector size. Estimate only — an undersized injector runs lean and can damage the engine; verify against your fuel system and a wideband.

Injector duty cycle (IDC)

Pro

Check whether your injectors stay in control at your pulse width and RPM. Over ~85% duty they can't keep up and you lose fueling. Pro unlocks the IDC validator.

Go Pro — $29/yr