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Injector Resistor Calculator

To aid the use of peak and hold (low-impedance) injectors
in saturated (high-impedance) fuel injection systems.

Injector Resistance (ohms)
Typically 0.8 to 8 ohms*

Operating Current (amps)
Generally 1.5 to 2 amps

Supply Voltage (volts)
±14 volts in "12V" systems

Calculated Resistors (ohms)
One resistor per injector

Resistor Watts
At 85% Duty Cycle

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NOTES: Speeduino does not require resistors with injectors of 8 ohms or more. As of the January 2016 code release, Speeduino systems have an approximate 85% duty cycle limitation. This calculator includes this limitation, and the Resistor Watts value is therefore 15% lower than systems that are capable of 100% injector duty cycle. If this calculator is used for other 100% DC systems, or if you are using Speeduino code capable of 100% DC, then multiply the Resistor Watts figure by 1.18 for a corrected value. While we make every reasonable effort to assist with helpful results it is your responsibility to verify what your system needs. Your system is yours, not ours, and we know nothing about it.