Computech Systems RaceAir Pro User manual

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v3b
QUICK START GUIDE
1. Make sure batteries are installed.
2. Press POWER ON/OFF key.
3. Press SAMPLE key to take weather sample.
4. Use left side black and red keys to access programs. Press ALT first for red programs.
5. Use down arrow (NO) key or up arrow (YES) key to move the display left indicator
arrow to navigate program menus.
6. Press ENTER to use program.
7. Answer program questions (?) to calculate result.
CONTENTS
COMPUTER PROGRAM CAPABILITIES Page 2
GENERAL INFORMATION Page 8
Power Requirements. Page 8
Keyboard Functions. Page 8
Program Access and Use. Page 9
Communication Port. Page 9
Program Updates. Page 10
Additional Instructions Page 10
COMPETITION WEATHER ANALYZER Page 10
Overview Page 10
Weather Terms. Page 10
Good Air / Bad Air. Page 13
Sampling Information. Page 14
Calibration Page 15
Specifications Page 15
Weather Analyzer Operation. Page 15

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COMPUTER PROGRAMS OPERATION Page 16
COMPUTER PROGRAM CAPABILITIES
This list is indented to show access menu levels. See Program Access and Use on page 9.
TUNE-UP key Page 16
1 Jetting Menu
1 Holley Page 17
This program will calculate the proper Holley carburetor jet to use based
on a change in weather conditions. It also allows the user to adjust the
air/fuel ratio to achieve the proper engine tune.
2 Prec Jets Page 18
This program will calculate the proper jet diameter, in inches or millimeters,
to use based on a change in weather conditions for any carburetor. It also
allows the user to adjust the air/fuel ratio to achieve the proper engine tune.
3 Mikuni Jets Page 18
This program will calculate the proper Mikuni carburetor jet to use based
on a change in weather conditions. It also allows the user to adjust the
air/fuel ratio to achieve the proper engine tune.
4 Keihin Jets Page 19
This program will calculate the proper Keihin carburetor jet to use based
on a change in weather conditions. It also allows the user to adjust the
air/fuel ratio to achieve the proper engine tune.
5 Injection Page 19
This program will calculate the proper continuous flow mechanical fuel
injection main jet (pill) to use based on a change in weather conditions
using jet and nozzle areas. It allows the user to adjust the air/fuel ratio to
achieve the proper engine tune. Additionally, a fuel rail pressure change
is calculated for use in adjusting a high speed lean out system relief
valve. See Important program information on page 21.
6 F/G Injection Page 20
This program will calculate the proper continuous flow mechanical fuel
injection main jet (pill) to use based on a change in weather conditions
without knowing the injector nozzle sizes. It also allows the user to adjust
the air/fuel ratio to achieve the proper engine tune. Additionally, a fuel rail
pressure change is calculated for use in adjusting a high speed lean out
system relief valve. See Important program information on page 21.
7 High Speed Page 21

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This program will calculate a bypass flow jet change for a continuous flow
mechanical fuel injection high speed lean out system. See Important
program information on page 21.
8 Square Area Page 22
This program will easily calculate the area of several nozzles or jets and
provide a single orifice diameter equivalent.
2 Blower OD Page 22
This program will calculate blower drive speed in relation to crankshaft speed
based on pulley tooth count or circumference.
3 Meth. Spec. Page 23
This program is used in conjunction with a hydrometer and thermometer to correct
the specific gravity of methanol when checking for moisture contamination.
4 Gas. Spec. Page 23
This program is used in conjunction with a hydrometer and thermometer to correct
the specific gravity of gasoline.
5 Nitro % Page 23
This program is used in conjunction with a hydrometer and thermometer to
determine the corrected nitro percentage of a measured sample.
6 EGT Correct'n Page 24
This program will correct the indicated or observed engine exhaust gas
temperature (EGT) for variations in engine air inlet temperature. The corrected
EGT value can be used as a tuning aid.
7 EGT Predict'n Page 24
This program will calculate the indicated or observed engine exhaust temperature
(EGT) from a corrected EGT and the current engine air inlet temperature.
DIAL-IN key
1 Standard Page 25
This program will predict an elapsed time (ET) dial-in, for 1/8 and 1/4-mile Drag
Racing, based on 1 previous good run and the change in horsepower correction
factor due to a weather change. Note: This program requires changing the fuel
selection in SET-UP, Program Setup, Fuel Setup when using methanol.
2 Density Altd Page 26
This program will predict an elapsed time (ET) dial-in based on 3 previous good
runs and the change in density altitude due to a weather change.

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T-STOP key Page 27
This program will calculate the throttle closed timer setting to produce a desired elapsed
time (ET) based on 2 previous runs, 1 faster than the index and 1 slower than the index.
The program capacity allows data storage for 3 different cars or 3 different indexes.
DRAG FORMULAS key
1 Gear Ratio Page 29
This program will calculate the vehicle gear ratio based on tire size, MPH, engine
RPM, and torque converter slip.
2 Trap RPM Page 29
This program will calculate the trap engine RPM based on tire size, MPH, gear
ratio, and torque converter slip.
3 Converter Slip Page 30
This program will calculate the torque converter slip RPM and percentage based
on tire size, MPH, engine RPM, and gear ratio.
CIR.TRK. FORMULAS key
1 Gearing/Tires
1 Engine RPM Page 33
This program will calculate the resulting engine RPM change with tire size
and gear ratio changes.
2 Gear Ratio Page 33
This program will calculate the proper gear ratio to compensate for changes
in tire size and desired engine RPM.
3 Tire Size Page 33
This program will calculate the proper tire size to compensate for changes
in gear ratio and desired engine RPM.
4 MPH Calc Page 37
This program will calculate the vehicle MPH based on engine RPM, gear
ratio, and tire size.
5 Tire Stagger Page 34
This program will suggest a tire stagger condition based on track
measurements.
2 Chassis

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1 Setup by Pct Page 34
This program will calculate the scale weights for each wheel from total
vehicle weight and requested front, rear, and diagonal weight distribution
percentages.
2 Setup by Wgt Page 35
This program will calculate the front, rear, and diagonal weight distribution
percentages from actual scale weights for each wheel.
3 Fuel Mileage Page 35
This program will calculate fuel mileage from pit stop measurements, predict when the
next fuel stop should be made, and calculate the fuel required to finish the race.
4 Liquid Wgts Page 36
This program will calculate the weight of water, methanol, and gasoline when the
quantity in gallons is entered.
ALT - AIR CORR. key Page 16
This program will calculate the horsepower correction factor, density altitude, air density
ratio (ADR), dry barometer, wet bulb temperature, dew point, partial vapor pressure, water
vapor grains, and pressure altitude from an input of temperature, relative humidity, and
absolute barometer. Use this program to calculate weather data when taking an actual air
sample is not desired (i.e. from logbook entries of temperature, relative humidity, and
barometric pressure or evaluating other than sampled conditions).
ALT - RUN COMP key Page 30
This program will estimate the 1/8 or 1/4 mile elapsed time (ET) and MPH for a run where
thethrottlewasclosed beforethe finish line. Theprogram uses informationfroma previous
full pass to predict performance.
ALT - DRAG PERF key
1 Full Run Std Page 30
This program will correct observed finish line elapsed time (ET) and MPH
performance to Standard Day weather conditions. This information can be used to
compare runs done on different days to evaluate vehicle changes or driving
techniques.
2 Intermed. Run Page 31
This program will correct observed 60', 330', 660', 1000', and 1320' elapsed times
(ETs) to Standard Day weather conditions. This information can be used to
compare runs done on different days to evaluate vehicle changes or driving
techniques.
3 Est. 1/8 HP Page 32

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This program will estimate the horsepower output required to move the vehicle to
the 660' track marker based on vehicle weight and elapsed time (ET). It will also
adjust horsepower corrected to Standard Day weather conditions.
4 Est. 1/4 HP Page 32
This program will estimate the horsepower output required to move the vehicle to
the 1320' track marker based on vehicle weight and elapsed time (ET). It will also
calculate horsepower corrected to Standard Day weather conditions.
5 Est. ET/MPH Page 32
This program will estimate the 1/8-mile elapsed time (ET) and MPH plus the 1/4-
mile ET and MPH from engine horsepower and vehicle weight.
ALT - ENGINE FORMULAS key
1 C/R Menu
1 Calc Ratio Page 37
This program will calculate engine compression ratio from cylinder bore,
crankshaft stroke, combustion chamber volume, and piston dome volume.
Piston deck height, head gasket volume, and supercharger boost pressure
are included in the equation.
2 Calc Chamber Page 38
This program will calculate the required combustion chamber volume from
cylinder bore, crankshaft stroke, and piston dome volume when a
compression ratio is specified. Piston deck height, head gasket volume,
and supercharger boost pressure are included in the equation.
3 Calc Dome Page 38
This program will calculate the required piston dome volume from cylinder
bore, crankshaft stroke, and combustion chamber volume when a
compression ratio is specified. Piston deck height, head gasket volume,
and supercharger boost pressure are included in the equation.
4 Pour Chamber Page 39
This program will calculate the engine compression ratio using the cylinder
bore, crankshaft stroke, and the measured liquid volume poured into the
combustion chamber of an assembled engine with the piston on top dead
center (TDC).
5 Pour Dome Page 39
This program will calculate the effective piston dome volume by measuring
the piston deck height, installing a clear plastic plate in place of the cylinder
head, and then measuring the poured liquid volume in the void.

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2 C.I.D. Menu
1 Calc C.I.D. Page 40
This program will calculate engine displacement in cubic inches and liters
from cylinder bore, crankshaft stroke, and the number of cylinders.
2 Calc Bore Page 40
This program will calculate the cylinder bore required for a specified
engine displacement when crankshaft stroke and the number of cylinders
are given.
3 Calc Stroke Page 40
This program will calculate the crankshaft stroke required for a specified
engine displacement when cylinder bore and the number of cylinders are
given.
ALT - SET-UP key
1 Program Setup
1 Fuel Setup
This program is used to set the fuel type (gasoline, methanol, or special)
in the Std. Dial-In, the Full Run Std, and the Intermed. Run programs.
The default setting is gasoline. Press the down arrow key to view the
other fuels then press ENTER to select that fuel. The proper fuel factor is
automatically set into the programs when gasoline or methanol is
selected. To compensate for other fuels or to use another factor, press
the down arrow key until Special is displayed then press ENTER. The
display will show Factor?. Press in the desired multiplication factor and
press ENTER. For example, a fuel factor that is 10% less than the
standard would be 0.90.
2 T-Stop Setup
This function is discussed in the Throttle Stop program. It only needs to
be done to predict throttle stop timer settings.
3 D.A. Setup
This function is discussed in the Density Altd Dial-In program. It is used
to determine the slope of run data for that program.
4 SAE HP vs. STD
This function changes the horsepower correction method from Standard
to SAE. The default setting is STD. When the SAE HP? NO line is
displayed, press ENTER to cause the cursor block to flash then YES to
change to the new SAE correction factor.
2 Factory Setup

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1 Set Clock
This program is used to set the date and time.
2 Show Calib.
This screen is for factory use to show the weather sensors calibration file.
3 Factory Reset
This program will remove the weather sensor calibration file from the
computer memory. DO NOT use this program without specific instructions
from Computech on how to save the calibration file.
4 Empty Recycle
This program can be used when the Loading User Memory…
Message remains on the screen for several seconds. Emptying the
recycle bin will speed up the computer operation.
5 Clr User Mem
This function is not normally used. Clearing the user memory will reset all
computer variables to 0. All set-up functions will need to be reentered.
Battery=
This line indicates the measured voltage in the computer circuit. When on
battery power, it can show when the batteries are getting weak.
3 Calculator
This program is a 4 function calculator (i. e. add, subtract, multiply, and divide).
The +key (YES) and the --key (NO) are used to add and subtract. To multiply,
press ALT then + or to divide press ALT then --. Press ENTER to see the answer.
Important: The calculator can be accessed from within any program by pressing
ALT then ENTER. The calculator function will remember the number from the
computer program line where the left indicator arrow is positioned. The calculator
functions can then be used with that number. The computer will insert the new
calculated value back in the program line by pressing ALT then ENTER again.
Dynamometer Horsepower Correction
The = Sampled Wthr = screen can be used to quickly correct observed dyno torque
and horsepower values. Press the SAMPLE key and place the RaceAir Pro near the
engine air intake. Allow the unit to finish sampling. Make sure the left side indicator
arrow is on the STD Corr= (or SAE Corr=). Press ALT then ENTER to transfer the
correction factor to the calculator. Press ALT then + (to multiply). Press in the observed
number (torque or horsepower) and press ENTER to see the corrected value. Pressing
ALT ENTER again will send the computer back to the = Sampled Wthr = screen. The
process can be repeated again for the next value. The same technique can be used for
previously recorded weather conditions using the AIR CORR. program.

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GENERAL INFORMATION
Power Requirements.
The RaceAir Pro uses 6 AA batteries. Note the polarity markings on the battery tray when
installing the batteries. The unit will automatically turn off after 10 minutes of inactivity. The
highest current draw on the batteries is the fan that comes on when the air SAMPLE key is
pressed. Use the display LIGHT only as necessary, to preserve battery life. The computer will
display a caution message when the battery voltage is too low for acceptable operation. If the
display stops responding to keystrokes, including the POWER ON/OFF key, it may be necessary
to remove and reinstall the batteries to restart the computer.
The computer may also be powered with a 12-V dc adapter through the upper connector provided
on the left side of the case. The 110-V ac to 12-V dc adapter is available from Computech
Systems, Inc. The unit may be safely powered by the adapter while the batteries are installed.
Keyboard Functions.
The keyboard has several multifunction keys. The YES key also functions as an up arrow key and
a + (plus) key. The NO key functions as a down arrow key and a -- (minus) key. To enter a
negative number into a program, press the number, press the minus key, then press ENTER. The
split black and red keys have 2 functions. When a black and red key is pressed the computer will
go to the function labeled in black. When the red ALT key is pressed then a black and red key is
pressed the computer will go to the function labeled in red.
The POWER ON/OFF key must be pressed and momentarily held to turn on the computer.
The ENTER key is discussed in Program Access and Use below.
The CLEAR key may be used anytime to exit a menu or program. CLEAR is also used to
backspace an incorrect entry.
When the computer is powered, pressing the red SAMPLE key will turn on the fan and take a
weather sample. The weather sampling process may be aborted by pressing SAMPLE again.
Several of the included programs use weather information in the calculations. When a program
asks for current weather information, pressing the IMPORT WEATHER DATA key will
automatically transfer that data. The RaceAir Pro powers up in the ==Live== Fan OFF mode. The
actual air data from the last sample may be viewed by pressing ALT then IMPORT WEATHER
DATA.
Program Access and Use
The COMPUTER PROGRAM CAPABILITIES list can be used to select a program. The list is
indented to show the access menu levels. The indicator arrow on the left side of the display may

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be repositioned in a menu or in a program screen by pressing the up or down arrow keys. The up
and down arrow keys will repeat or continue to move the indicator arrow when held. Pressing the
ENTER key will make the computer go to the item where the left indicator arrow is positioned.
An alternate quick program access method is to use the number shown to the left of a program.
For example - to access the Holley carburetor jetting program, press TUNE-UP, then 1 to access
the Jetting Menu, then 1 again to get to the Holley program.
When a program needs a user input a ? will appear at the end of a statement. A number from the
computer memory may appear after the ?. Either accept this number by pressing ENTER or press
in a new number on the keyboard then press ENTER. When an answer is presented, an = will
appear at the end of the statement. A blinking cursor block will appear on the right side of a
statement when the computer is expecting a user input.
Recalculate Function. The up and down arrow keys may be used to reposition the left side
indicator arrow to a program input line. Pressing ENTER will open that input and show a blinking
cursor block to accept a new entry. It is not necessary to restart the program from the beginning
to calculate a new answer.
Communication Port.
The lower of the 2 ports on the left side of the computer is for communication with a personal
computer (PC). The optionally available Computech Weather Pro software will interface with the
RaceAir Pro. When the communications link is established, the sensors in the RaceAir Pro send
information to the PC that is running the Weather Pro program. The Weather Pro calculates the
various air conditions, logs the information, and presents a graphic view of what the weather is
doing. A weather file is saved for future reference. The Weather Pro software, with the required
cables and power supply, is available from Computech Systems, Inc.
Additionally, the Comm port is used to update the RaceAir Pro program firmware. An interface
kit is available from Computech Systems, Inc. to perform these updates. The kit contains the PC
interface software, the PC to RaceAir Pro interface cable with serial adapter, and a power
supply.
Program Updates.
The RaceAir Pro program firmware is user updateable with the optional PC interface kit. The
latest version of the program will be posted on the Computech Systems, Inc. web site.
Downloads are free for the life of the computer. As changes or additions are made to the
program, new files will be posted on the web site. The RaceAir Pro may be sent back to
Computech Systems, Inc. for program updates, if desired.