gm 3barmapsenser
gm 3barmapsenser
hi i have an integra ls 95 turbo i tuned it on 12psi it ran good after that i put the gm 3barsenser and program it on s300 the result is unstabled idle the rpm goes up and down when i push on the gas pedle when its cold . it lost some power . its not stedy on any rpm range . i need to know the scaler . ofset setting for the gm3bar sens. and it will run at 17psi, help please..
For what this might be worth, I purchased a "gm" 3bar map sensor from lightning motorsports which is actually an MSD 3bar sensor. MSD gave me the following info:
5v @ 43.5psi and (of course) 0v @ 0psi
The slope would be 599.844 mbar/volt
While this is close to the Motec 3bar, i'm not sure about the other settings.
As far as the offset, neither the MSD tech nor I know what that iscan someone chime in?
I'm having the same "lopey" idle issues and it's pretty damn annoying.
5v @ 43.5psi and (of course) 0v @ 0psi
The slope would be 599.844 mbar/volt
While this is close to the Motec 3bar, i'm not sure about the other settings.
As far as the offset, neither the MSD tech nor I know what that iscan someone chime in?
I'm having the same "lopey" idle issues and it's pretty damn annoying.
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 Posts: 127
 Joined: Wed May 21, 2003 12:03 am

 Posts: 127
 Joined: Wed May 21, 2003 12:03 am
Here is how to calculate the scalar and offset.
1. Find the minimum and maximum voltage and absolute pressures.
2. Convert the pressures to mbar.
3. Subtract the minimum and maximum voltages to find the range, then do the same for the pressures.
4. Divide the pressure range by the voltage range to calculate the scalar.
5. Multiply the minimum voltage by the scalar to calculate the offset. Note that a positive voltage gives a negative offset.
So: for the 3 bar map. ( the aem 3.5 bar is pretty similar with a 431.25 offset)
0.5V @ 0 kPa (absolute)
4.94V @ 294 kPa (absolute)
2. 294 kPa = 2940 mbar.
3. Voltage range = 4.4V, pressure range = 2940 mbar.
4. 2940 / 4.4 = 668.2 = scalar
5. 668.2 x 0.5 x 1 = 334.1= offset
1. Find the minimum and maximum voltage and absolute pressures.
2. Convert the pressures to mbar.
3. Subtract the minimum and maximum voltages to find the range, then do the same for the pressures.
4. Divide the pressure range by the voltage range to calculate the scalar.
5. Multiply the minimum voltage by the scalar to calculate the offset. Note that a positive voltage gives a negative offset.
So: for the 3 bar map. ( the aem 3.5 bar is pretty similar with a 431.25 offset)
0.5V @ 0 kPa (absolute)
4.94V @ 294 kPa (absolute)
2. 294 kPa = 2940 mbar.
3. Voltage range = 4.4V, pressure range = 2940 mbar.
4. 2940 / 4.4 = 668.2 = scalar
5. 668.2 x 0.5 x 1 = 334.1= offset
"My other car is a camaro, but today I was in a hurry."

 Posts: 127
 Joined: Wed May 21, 2003 12:03 am
The answer has already been given.
The calculation can be found in the Help file of Smanager:
Here is how to calculate the scalar and offset for a MAP sensor.
1. Find the minimum and maximum voltage and absolute pressures.
2. Convert the pressures to mbar.
3. Subtract the minimum and maximum voltages to find the range, then do the same for the pressures.
4. Divide the pressure range by the voltage range to calculate the scalar.
5. Multiply the minimum voltage by the scalar to calculate the offset. Note that a positive voltage gives a negative offset.
Example for a 3.5 bar MAP sensor:
1. For a 3.5 bar data sheet:
0.5V @ 0 kPa (absolute)
4.5V @ 345 kPa (absolute)
2. 345 kPa = 3450 mbar.
3. Voltage range = 4.0V, pressure range = 3450 mbar.
4. 3450 / 4.0 = 862.5 = scalar
5. 862.5 x 0.5 x 1 = 431.25 = offset
So scalar = 862, offset = 431
Plug in the minimum and maximum voltages to check your work:
0.5V x 862.5  431.25 = 0 mbar @ 0.5v
4.5V x 862.5  431.25 = 3450 mbar @ 0.5v
If you have trouble then draw a graph and extrapolate the lines until they cross the pressure axis.
The calculation can be found in the Help file of Smanager:
Here is how to calculate the scalar and offset for a MAP sensor.
1. Find the minimum and maximum voltage and absolute pressures.
2. Convert the pressures to mbar.
3. Subtract the minimum and maximum voltages to find the range, then do the same for the pressures.
4. Divide the pressure range by the voltage range to calculate the scalar.
5. Multiply the minimum voltage by the scalar to calculate the offset. Note that a positive voltage gives a negative offset.
Example for a 3.5 bar MAP sensor:
1. For a 3.5 bar data sheet:
0.5V @ 0 kPa (absolute)
4.5V @ 345 kPa (absolute)
2. 345 kPa = 3450 mbar.
3. Voltage range = 4.0V, pressure range = 3450 mbar.
4. 3450 / 4.0 = 862.5 = scalar
5. 862.5 x 0.5 x 1 = 431.25 = offset
So scalar = 862, offset = 431
Plug in the minimum and maximum voltages to check your work:
0.5V x 862.5  431.25 = 0 mbar @ 0.5v
4.5V x 862.5  431.25 = 3450 mbar @ 0.5v
If you have trouble then draw a graph and extrapolate the lines until they cross the pressure axis.
When I enter these values, I get a voltage of 2.014v @ standard atmospheric pressure. The car also shut off when I entered those values. According to a graph I saw on http://hhscott.com/93tmv/3bar_map.htm , the voltage is supposed be 1.7volts. Someone correct me if I'm wrong. What I did was entered the 599.844 mbar/volt that "alex" posted and then use the scaler to get the standard atmospheric pressure as close to 1.7v as possible. All the rest of the numbers came close to what they were supposed to be. Car ran good. I don't know if that's how it's supposed to be done, but like I said it worked. I do most things by trial and error anyways.Spanky wrote:try 669 scalar and 334 offset.
OK, so what did you end up using for the offset? Since you said you used 599.844 for the scalar or did you? I was trying to help alex figure out the numbers, but we haven't been able to spend much time with it. Do to our schedules.crucian wrote:When I enter these values, I get a voltage of 2.014v @ standard atmospheric pressure. The car also shut off when I entered those values. According to a graph I saw on http://hhscott.com/93tmv/3bar_map.htm , the voltage is supposed be 1.7volts. Someone correct me if I'm wrong. What I did was entered the 599.844 mbar/volt that "alex" posted and then use the scaler to get the standard atmospheric pressure as close to 1.7v as possible. All the rest of the numbers came close to what they were supposed to be. Car ran good. I don't know if that's how it's supposed to be done, but like I said it worked. I do most things by trial and error anyways.Spanky wrote:try 669 scalar and 334 offset.
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