gm 3barmapsenser

Hadi · Post by **Hadi** » Tue Feb 21, 2006 2:27 pm

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..

Post by **Spunkster** » Tue Feb 21, 2006 2:47 pm

If it is not the same as the Motec 3bar, then you will have to find the scaler from the manufacturer. I believe there are a few different GM sensors and this could be part of the problem. This is why we do not sell GM sensors.

alex · Post by **alex** » Fri Feb 24, 2006 10:19 am

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 is--can someone chime in?

I'm having the same "lopey" idle issues and it's pretty damn annoying.

Post by **Spunkster** » Fri Feb 24, 2006 12:14 pm

http://www.motec.com.au/drawings/x18.pdf

alex · Post by **alex** » Thu Mar 02, 2006 4:29 pm

right....so i guess I should just buy a motec sensor

Spanky · Post by **Spanky** » Sun Mar 05, 2006 5:32 pm

try 669 scalar and -334 offset.

Silverbeast · Post by **Silverbeast** » Mon Mar 06, 2006 2:43 pm

Spanky wrote:try 669 scalar and -334 offset.

How the hell did you come up with that?

Silverbeast · Post by **Silverbeast** » Mon Mar 06, 2006 6:40 pm

Doug, Matt, or Derek..

Can we get an explination of the offset?

Im curious....

Spanky · Post by **Spanky** » Mon Mar 06, 2006 9:17 pm

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

Silverbeast · Post by **Silverbeast** » Mon Mar 06, 2006 10:31 pm

The S300 map scaler looks like this... how does that equate to the Motec?

Silverbeast · Post by **Silverbeast** » Wed Mar 08, 2006 2:18 pm

Please someone verify the offset....

glosssiver · Post by **glosssiver** » Sat Mar 25, 2006 12:02 am

:( same here bumb for info

Post by **Spunkster** » Mon Mar 27, 2006 10:22 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.

crucian · Post by **crucian** » Thu Mar 30, 2006 3:08 am

Spanky wrote:try 669 scalar and -334 offset.

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/3-bar_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.

NAterror · Post by **NAterror** » Sun Apr 02, 2006 12:31 pm

crucian wrote:
Spanky wrote:try 669 scalar and -334 offset.
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/3-bar_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.

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.