Innovate Motorsports LogWorks 3 - Manual (Page 140)

LogWorks3_Manual_1.01.doc - 140 -
15.2 Using external MAP sensors
Many people use GM or other brand MAP sensors. These sensors output a linear 0..5V voltage
when supplied by 5V.
Typically these sensors have 3 pins. One is 5V supply, one is output and one is ground. The
sensors come in different ranges. Very typical are 1 bar (for normally aspirated engines) and 3
bar (for boosted applications).
15.2.1 Calibrating a 3 bar (or more) MAP sensor
Use a good tire pressure gauge to measure the air pressure in your spare tire. Remember, tire
pressure gauges use gauge pressure. Lower the pressure in the tire to about 29 PSI (3.013 bar
or 3.072 kg/cm^2).
Connect the tire valve to the sensor’s input port and note the output voltage. Also note the current
atmospheric pressure in inHg or millibar (from a weather station or barometer).
Next measure the sensor output at normal atmospheric pressure.
For LogWorks the two points needed to set up a MAP channel (absolute pressure), calculate the
absolute pressures as follows:
For PSIa:
PSIa = atmospheric pressure (in inHg) * 0.491 + measured pressure (in PSI)
For kPa:
kPa = atmospheric pressure (in millibar) * 0.1 + measured pressure (in bar) * 100
or
kPa = atmospheric pressure (in millibar) * 0.1 + measured pressure (in kg/cm^2) * 98.07
15.2.2 Calibrating a 1 bar MAP sensor
Calibrating a 1 bar sensor is a little more difficult than calibrating a 3 bar sensor because a
convenient vacuum source is usually not available to the average user. If you have or can borrow
a good vacuum gauge, it is easy.
Connect the vacuum gauge with a T connection to the manifold of the engine. Connect the MAP
sensor also to this T. Run the engine at idle and note the vacuum and voltage.
Then switch the engine off. The MAP sensor will measure atmospheric pressure. Note the current
atmospheric pressure in inHg or millibar.
Vacuum gauges typically measure gauge pressure in inHg or mmHg (or Torr).
For LogWorks the two points needed to set up a MAP channel (absolute pressure), calculate the
absolute pressures as follows:
For PSIa:
PSIa = atmospheric pressure (in inHg) * 0.491 - measured pressure (inHg) *0.491
For kPa: