Nitrous Jet Size Calculator

A nitrous oxide system delivers a burst of power by injecting N2O and extra fuel into an engine — but the jet sizes must be precisely matched to hit your power target safely. Enter your desired horsepower gain, nitrous bottle pressure, fuel pressure at WOT, system type, target air/fuel ratio, and bottle temperature into the Nitrous Jet Size Calculator to get your recommended nitrous jet size and fuel jet size. Secondary outputs include N2O flow rate, fuel flow rate, and the calculated actual air/fuel ratio.

HP

Target horsepower increase from nitrous

PSI

Bottle pressure before run

PSI

Fuel pressure at WOT

:1

11.5-12.5 recommended for safety

°F

Affects pressure calculations

Results

Nitrous Jet Size

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Fuel Jet Size

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N2O Flow Rate

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Fuel Flow Rate

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Actual A/F Ratio

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Frequently Asked Questions

What air/fuel ratio should I target for nitrous?

Most experts recommend running slightly rich at 11.5-12.5:1 for safety. At 250hp and under, you can match your engine's normal A/F ratio. For higher power levels (450-500hp), run 11.5:1 as a safety factor.

How does bottle pressure affect jet sizing?

Higher bottle pressure increases nitrous flow through the same jet size. As the bottle cools during use, pressure drops and flow decreases. Start with a warm bottle (75-80°F) for consistent pressure readings.

What's the difference between wet and dry nitrous systems?

Wet systems inject both nitrous and fuel through the same nozzle, while dry systems only inject nitrous and rely on the fuel system to add extra fuel. Wet systems are generally safer and easier to tune.

How accurate is this calculator for real-world tuning?

This calculator provides a good starting point, but dyno testing with a wideband O2 sensor is highly recommended for final tuning. Engine combinations, altitude, and other factors can affect actual results.

Can I use these jet sizes for E85 fuel?

E85 requires different fuel flow rates due to its different stoichiometric ratio. You'll need approximately 30% more fuel flow with E85 compared to gasoline, so use a larger fuel jet.

What happens if my jets are too small or too large?

Jets too small will run lean (dangerous), while jets too large will run rich (power loss and fouled plugs). Always err on the rich side for safety, then fine-tune on the dyno.

How often should I check my nitrous system pressures?

Check bottle pressure before each run, and monitor fuel pressure regularly. Low fuel pressure is one of the most common causes of lean conditions and engine damage in nitrous systems.