Weather Stations & Computers:

ET Predictor II Computer

Description:
The ET Predictor II computer, will enable you to properly manage air/fuel ratios for the current air density, track vehicle performance or modifications, and accurately predict elapsed time and throttle stop settings according to varying weather conditions. Included are programs to calculate Air Density, Horsepower Correction, Density Altitude, Vapor Pressure, Water Grains, Engine Displacement, Compression Ratios, STP Corrected Elapsed Time, Run Completion, Corrected HP from MPH, HP Corrected Vehicle Weight, Throttle Stop Factor, and our exclusive Run Segment Analysis program. The next best thing to having an on-board computer. Comes with complete instructions, including sample log sheet and ET prediction hints and tips.

You enter the air conditions from your weather station or weather gauges into the program. We have many weather instruments and weather stations available here on the website.

For Gasoline and Methanol Fuel

Drag racing programs calculate:

ET Prediction (60, 330, 660, 1000, and 1320 foot)
Throttle Stop Prediction
Air Density Index
Horsepower Correction Factor
Density Altitude
Dew Point Temperature
Vapor Pressure
Water Grains Per Pound
Corrected Elapsed Time
Run Completion
Run Segment Analysis program, the next best thing to having an on-board computer!
Predicted 60' ET
Predicted 330' ET
Predicted 660' ET
Predicted 1000' ET
Predicted 1320' ET
Also:
Engine Displacement
Compression Ratio
Inches HG to Altitude
HP from MPH
Crossover Math

The ET Predictor software is the most accurate ET Prediction and Weather Station software available because it uses Horsepower Correction and does not predict from an average of stored runs. The ET Predictor provides a Horsepower Correction Factor (HCF) and Air Density Index (ADI) using a standard of 0 Elevation, 29.92 In Hg Barometric Pressure, 60 degrees F Temperature, and 0 percent Relative Humidity. Under these conditions, the HCF equals 1.0000 and the ADI will equal 100.0 percent. The HCF and ADI compensate for pressure, temperature, and relative humidity. Conditions that improve the HCF and ADI are cold air, high air pressure, and low humidity.

The program uses the Elevation, Barometric Pressure, Temperature, and Humidity, to calculate the current Horsepower Correction Factor (Current HCF), Air Density Index (ADI), and Density Altitude (DA), Dew Point, and Vapor Pressure. The formulas used in this program are the same ones used in our ET Predictor II hand-held computers, ET Predictor software, and RaceLog Pro software.

Elevation - Range: -3,000 to +26,000 Feet - Elevation is only used if you are using an altimeter or a corrected barometer. If you're using an uncorrected barometer reading absolute pressure, always enter 0 for the elevation. If you have an altimeter, calibrate it to 29.92 In Hg and enter the reported altitude as the elevation. If you are using an analog barometer and your altitude requires that you use a corrected barometer, then you should always enter the number of feet equal to the amount of correction when you calibrated the barometer. Digital barometers and altimeters measure absolute pressure, without any need for correction, so their use is preferred.

Barometer - Range: 12 to 35 Inches Hg - If you're using a barometer to obtain the air pressure, enter the barometric pressure from the gauge. When using an altimeter, always enter 29.92 for the barometric pressure.

Temp F - Range: 10 to 130 degrees F - Enter the temperature from a digital thermometer or other temperature gauge. From round to round, temperature changes are apt to affect performance more than any other variable. RH% - Range: 0 to 100 Per Cent - You can use a digital hygrometer to find the relative humidity. At low temperature, relative humidity has the least effect on performance. However, at high temperatures, the effect is much greater. For example, 50% RH at 60 F will result in a .01 loss in power, while at 90 F the addition of 50% RH equals about a .03 loss in power. Changes in temperature are also more critical under high humidity.

The following is more information on the resulting calculations:

Current HCF (Current HP Correction Factor) - The Horsepower Correction Factor is computed using the current weather conditions that you enter. In other words, the HCF equals the current elevation, barometer, temperature, and humidity. When the HCF is higher, less horsepower is produced, and the car will run slower. So, the lower the HCF is, the faster the car will run. You can use the HCF to determine the variance in horsepower or torque that is being produced under different weather conditions. For example, if your engine produces 400 horsepower with an HCF of 1.012, it will produce 404.80 horsepower at sea level conditions (STP) or 1.0000 (400 x 1.012=404.80).

Vapor Pressure - Vapor Pressure is the exact portion of barometric pressure that is present due to Relative Humidity, or moisture, in the air. Vapor Pressure is used in calculating the horsepower correction.

Air Density (Air Density Index) - The Air Density Index (ADI) is the computed ratio of the current density to that of STP with STP having an index of 100 percent. This factor is used to determine the correct jetting or pill size required under varying weather conditions. The higher the ADI, the more air there is available for combustion. Therefore, more fuel must be burned to maintain the correct air/fuel ratio. When using gasoline, a four (4) percent change in the ADI will usually necessitate a change in jet area in order to maintain the same level of performance. Holley jet sizes are about 4 percent apart in flow area. If the ADI goes up four (4) percent, for example 100.0 to 104.0, increase all jet sizes by one number. And, if the ADI goes down four (4) percent, for example 100.0 to 96.0, decrease all jet sizes by one number.

Density Alt (Density Altitude) - Density Altitude (DA) is the current air density expressed in feet of elevation. DA is also known as the corrected or relative altitude. DA is not scientific and is very inaccurate. Therefore we do not use this factor in ET Prediction. We only report this value for information purposes only.

Dew Point - Dew Point is the calculated temperature at which condensation (moisture) occurs based on the entered air conditions. Dew Point will tell the racer when the traction on the race track will worsen due to condensation. When the actual measured air temperature matches the Dew Point temperature, the race track will be wet.

Unsure about whose weather computer to buy? To find out the cold hard facts about weather computers, read our newsletter on this subject by clicking here.


We also reprogram SHARP EL-5500 computers to ET Predictor II specs for just $125.00. Give us a call!

Convert your Sharp PC-1270 to an ET Predictor II

Part # ET-PRAM ET Predictor II Program Card (V6.06)
Price: $165.00

Description:
With our Program Card you can convert any PC-1270 computer to an ET Predictor II. Program card comes with complete instructions, including sample log sheet and ET prediction hints and tips. We convert many other brands of prediction computers, that just don't work as well as our ET Predictor II. We can also reprogram your Sharp EL-5500 III computer to ET Predictor II specs. Call for information. Our prediction program has become the standard for the industry. There simply isn't anything better at any price!


Unsure about whose weather computer to buy? To find out the cold hard facts about weather computers, read our newsletter on this subject by clicking here.

We can repair and/or program all Sharp PC-1270 computers including:
Barry Grant
B&G
Computech
Magsearch
Nova

We also reprogram SHARP EL-5500-III computers to ET Predictor II specs for just $125.00. Give us a call!