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function be run for each vehicle so that the program can calculate an elapsed time versus density
altitude ratio. The program has memory for 3 different data sets.
The Dial-In is predicted from 3 previous runs that are entered into the computer memory during
the Dens Alt Setup program and a recent reference run. The reference run. on which the
prediction is based, is selected by the user. The reference run should be the most recent good
full run when the vehicle performed as expected. Runs that had tire spin, unusual 60 ft times, or
gusty wind conditions should not be used for the reference run. Change the run used as the
reference (old) run as the race day progresses. It is important to use the most recent good full run
as the reference. The most recent run will best represent the current traction and weather
conditions. Since this program utilizes runs from memory, it is compatible with whatever fuel being
used.
This program works best when the engine fuel/air mixture is slightly rich so the vehicle
performance will change appropriately with the weather changes. This may require periodic jet
changes during the race season. The benefits gained in consistency and predictability are well
worth the effort. If the vehicle runs quicker than the computer is predicting when the density
altitude is improving (getting lower) then the fuel/air mixture is probably too rich and should be
leaned slightly. Conversely, if the vehicle will not run as quick as the computer is predicting when
the density altitude is improving then the fuel/air mixture is probably too lean and should be
richened slightly. Efforts spent on getting the fuel/air mixture correct will be well worth the rewards
in increased predictability. See the Tune-Up Information section for more details.
DA DIAL-IN SETUP. It is likely that several runs will need to made to get 3 good runs for the
setup. Record the run data for all the runs, including the density altitude. The runs you select
should all be good, full runs with at least 100 feet of difference in density altitude between any
two runs. This will allow the program to calculate the amount of elapsed time change the vehicle
experiences in comparison to the respective change in the density altitude. The setup runs should
be made on the same day, preferably in the same lane so that the traction conditions will be
similar. Make sure the 60 foot times are within 0.01 seconds of each other. Also, verify that as the
density altitude gets higher, the vehicle slows down. Conversely, as the density altitude gets lower
the vehicle should go quicker.
The setup function may be run as often as you desire or whenever the accuracy of the program
is not up to par. The entire setup routine must be repeated for each vehicle.
Important: When any change is made that might affect vehicle performance the setup program
should be run again to assure accuracy. Remember, the Density Altitude Dial-In program
predictions can only be as good as the information put into the setup.
Press DIAL-IN, select Density Altd, select D.A. Setup then select 1 Car #0 to start this program.
Setup Display Example:
=Dens Alt Setup=
Car #? 228 (Enter car or combination ID number)
Run 1 DA? 862 (Enter density altitude for run #1)
Run 1 ET? 8.921 (Enter ET for run #1)
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