MAP Sensor Pressure Conversion Parameters
MAP Sensor Pressure Conversion Parameters
John at Japtrix needs a new MAP sensor for his Skyline. He wants to run 30+ psi of boost and his HKS MAP sensor maxes out around 24 psi. Thus, he is looking for at least a 3.5 Bar MAP sensor. After a bit of research, John and I found an AEM 3.5 Bar MAP sensor (P/N 30-2130-50) and an AEM 5 Bar MAP sensor (P/N 30-2130-75), both of which may be suitable for John's build. Unfortunately, the HKS ProWriter software does not have default Pressure Conversion Parameters for these sensors, nor were the parameters listed in the data sheet we downloaded from AEM.
The F-CON uses three Pressure Conversion Parameters, X, Y and Z, and the following equation:
P = (X/Y) x V + Z
where:
P = Pressure (mmHg)
V = Voltage (mV)
This equation seems pretty generic, so I assume it is used by other EMS systems, but I have not confirmed this. If it is, the following method can be implemented whenever the Pressure Conversion Parameters are needed.
The AEM data sheet lists output voltages for various pressure levels (psi). Below is how we used this data to generate the Pressure Conversion Parameters we needed. In this example, I’ll use the data from the AEM 3.5 Bar sensor.
1. Select two pressure levels and their corresponding voltages. We used the max. and min. values: 4.5 V at 35.3 psi and 0.5 V at -14.7 psi.
2. Convert voltages from V to mV by multiplying by 1000.
3. Convert pressures from psi to mmHg by multiplying by 51.71.
4. Enter the converted voltage and pressure for each data point into the equation above, resulting in the following two equations:
1825.4 = 4500(X/Y) + Z
-760.1 = 500(X/Y) + Z
5. Subtract the second equation from the first equation to cancel out Z, resulting in the following equation:
2685.5 = 4000(X/Y)
Dividing 2685.5 by 4000 gives: (X/Y) = 0.646375
6. Since (X/Y) is a constant ratio or each particular MAP sensor, any random value of Y can be selected, and then select a value for X that when divided by Y results in the constant. To keep things simple, I selected 1000 for Y, which gives a value for X of approximately 646. In other words, 646/1000 = 0.646, which matches the above value for (X/Y) when it is rounded off to 3 digits.
7. Plug the value for (X/Y) into any of the above equations to solve for Z. Using the first equation:
1824.4 = 4500(0.646375) + Z
Subtracting 4500(0.646375) from 1824.4 gives: Z = -1084 when rounded off.
The resulting Pressure Conversion Parameters for the AEM 3.5 Bar MAP sensor are:
X = 646
Y = 1000
Z = -1084
Using the same method, the resulting Pressure Conversion Parameters for the AEM 5 Bar MAP sensor are:
X = 970
Y = 1000
Z = -1245
If anyone knows whether any other EMS’s uses the same type of Pressure Conversion Parameters, please post here to let us know. I checked the Haltech website, but their new site appears to still be under construction so I couldn’t download their manual.
The F-CON uses three Pressure Conversion Parameters, X, Y and Z, and the following equation:
P = (X/Y) x V + Z
where:
P = Pressure (mmHg)
V = Voltage (mV)
This equation seems pretty generic, so I assume it is used by other EMS systems, but I have not confirmed this. If it is, the following method can be implemented whenever the Pressure Conversion Parameters are needed.
The AEM data sheet lists output voltages for various pressure levels (psi). Below is how we used this data to generate the Pressure Conversion Parameters we needed. In this example, I’ll use the data from the AEM 3.5 Bar sensor.
1. Select two pressure levels and their corresponding voltages. We used the max. and min. values: 4.5 V at 35.3 psi and 0.5 V at -14.7 psi.
2. Convert voltages from V to mV by multiplying by 1000.
3. Convert pressures from psi to mmHg by multiplying by 51.71.
4. Enter the converted voltage and pressure for each data point into the equation above, resulting in the following two equations:
1825.4 = 4500(X/Y) + Z
-760.1 = 500(X/Y) + Z
5. Subtract the second equation from the first equation to cancel out Z, resulting in the following equation:
2685.5 = 4000(X/Y)
Dividing 2685.5 by 4000 gives: (X/Y) = 0.646375
6. Since (X/Y) is a constant ratio or each particular MAP sensor, any random value of Y can be selected, and then select a value for X that when divided by Y results in the constant. To keep things simple, I selected 1000 for Y, which gives a value for X of approximately 646. In other words, 646/1000 = 0.646, which matches the above value for (X/Y) when it is rounded off to 3 digits.
7. Plug the value for (X/Y) into any of the above equations to solve for Z. Using the first equation:
1824.4 = 4500(0.646375) + Z
Subtracting 4500(0.646375) from 1824.4 gives: Z = -1084 when rounded off.
The resulting Pressure Conversion Parameters for the AEM 3.5 Bar MAP sensor are:
X = 646
Y = 1000
Z = -1084
Using the same method, the resulting Pressure Conversion Parameters for the AEM 5 Bar MAP sensor are:
X = 970
Y = 1000
Z = -1245
If anyone knows whether any other EMS’s uses the same type of Pressure Conversion Parameters, please post here to let us know. I checked the Haltech website, but their new site appears to still be under construction so I couldn’t download their manual.
Last edited by ttg35fort; May 2, 2009 at 10:08 AM.
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The HKS map sensor is able to run up to around 45psi. but i don't want to be close to peaking out a map sensor. Terry is awsome to help out as much as he has. The main reason i have been looking to swaping map sensors it that mine failed on me. and would rather go a little bigger. the plan is to max out the trubo and go for some BIG power
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