Jetting Calculations

So you want to maximise the horsepower produced by your carbureted engine? Well it’s not as hard as you may think when you have a PerformAIRE Eclipse Weather Station in hand.

The PerformAIRE Eclipse Weather Station includes a jet mode that will automatically calculate the required jet size based upon the current weather conditions.

Here’s how it works….
With the PerformAIRE Eclipse Weather Station you create a database for each vehicle you have. You set the database to jet mode and enter an initial base setting. The base setting includes the air density ratio (ADR), a jet type and size.

The ADR can range from 0.7 to 1.2, with 1.0 representing sea level.You can then select the jet type based upon the following defaults:

• Holley
• Mikuni
• Keihen
• Custom (Custom drilled jets, enter diameter of jet orifice. Example 0.042)

Once the database is set up, you can then calculate your true base settings. When you are in the dyno room or you are tuning the engine and you established the correct air/fuel ratio, sample the current weather conditions from the main menu. This will give you the current ADR. Now you can reconfigure your base settings with the appropriate ADR and the correct jet size.

At the track….
When you are at the track you sample the current conditions and the weather station will display the current ADR (A) and the appropriate jet size (B) - refer to the example screen shot. It’s a simple as that!

Features…
In addition to the jet size calculation, the PerformAIRE Eclipse Weather Station also has the following great features:

• Displays temperature, relative humidity, barometric pressure, grains of water, vapor pressure and dew point.
• Calculates density altitude and the horsepower correction factor.
• ET and throttle stop predictions for drag racing.
• Rechargeable LI-ION battery.
•  Large backlit LCD display.
•  Ultra quick, fan aspirated and auto stabilising