The high performance formula for these calculations was devised and tested by some of the leading teams. Properly used, the results should allow you to start your day ready.
Just enter the local air temp and pressure and TrakData will suggest the correct performance jetting.
If you don't have access to a barometer or weather station, a 'get-out-of-jail-free-card' would be to calculate your local pressure using the Mean Sea Level pressure given by weather forecasts, and adjust it according to your circuit height (rule of thumb is about 1mb per 10m height). TrakData gives access to BBC weather (which is updated every 2 hours) by tapping:
Circuits > Weather Forecast > 'More detailed weather' link bottom left hand corner > 'Humidity, visibility and pressure' link halfway down the page.
HUMIDITY: In testing, we found this not to be particularly influential in choosing initial jet size. Rule of thumb is that a very humid day (say above 80%) you might consider using 1 jet size leaner, and a very dry day (say less than 20% humdity) you might try 1 jet size larger than suggested by the TrakData calculator. However, we found at this level of accuracy, you are more likely to be influenced by other racing factors and so we decided to set the calculator at an average uk day 0f 65%.
Datum for the needle/position is K98/pos 2.
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