MAP Sensor

Share

Attention: This example is for reference only. Do not just copy the values I have here. Program your ECM with the correct values for your MAP sensor and fueling requirements. Dyno tuning is highly recommended!

The Buell DDFI-II ECM is able to adjust fuel mapping for different manifold pressures, but the feature is not enabled from the factory. To enable and use this feature, you need a MAP sensor that covers the ranges of manifold pressures you want to adjust for and a program like ECMSpy or TunerPro to modify the ECM’s EEPROM.

To wire the MAP sensor to a Buell DDFI-II ECM, use pin 1 on the grey ECM connector for the 5 volt power source, use pin 7 on the grey ECM connector for the ground to the MAP sensor, and use pin 9 on the black ECM connector for the MAP sensor output.

These EEPROM locations are for a GB231 or IB310 ECM. You can read more about each of the locations functions at ECMSpy’s website. These instructions are geared towards using the Airbox Pressure feature to compensate for a forced induction setup. I include pressure values in kPa and my examples reference a GM 2 Bar MAP sensor, but you can use any units for pressure you like as long as none of the values go over 255 and you program each location using the same units. In the ECMSpy screenshots below, the highlighted areas are the values to change, and are programmed with the values in the examples. Notice that the table is displayed in Hexadecimal values, but you can use a hexadecimal converter to check each table value.

At location 00F0 in the EEPROM, change the value to 196 decimal. This is the configuration byte, which enables the airbox pressure feature and sets the input pin for Active Muffler Feedback to read the MAP sensor instead (pin 9 on the black connector).

At 00F3 and 00F4 set the value to 101. The ECM now thinks the base barometric pressure is 101 kPa. This simplifies the last table that is used for tuning the actual intended fuel correction for boost.

At 00F6 there is a table for the ECM to relate voltage from the sensor to an air pressure value. From the datasheet for the MAP sensor you can work out the analogue to digital counts, or ADC. The voltage output of the sensor divided by 5 and multiplied by 256 gives the ADC that the ECM uses. For example, at 101 kPa the MAP sensor gives an output of 2.38 volts if it has a 5.0V power supply. 2.38 divided by 5 multiplied by 256 gives 122, so the ECM sees an ADC value of 122 from the MAP sensor at 101 kPa. From any ADC value the ECM can work out the pressure in kPa. So this table starting at 00F6 basically tells the ECM the calibration of the MAP sensor. So you burn the values, beginning with the first ADC in 00F6: 122, 101, 149, 122, 176, 143, 203, 163, 248, 198 in that order.

ADC

kPa

122

101

149

122

176

143

203

163

248

198

The next table starts at 0100. This is for baro correction using a key-on read from the MAP sensor. The key-on sensor read was disabled in the config at 00F0. This forces the ECM to use the “101” value stored in 00F3 and 00F4. If baro correction is not needed, just make the numbers equal to stop any baro correction. We are using the airbox pressure feature, not the baro feature, but the baro feature needs to be turned on in the config byte at 00F0 in order to activate the airbox feature. The min and max baro pressure was set to 101 at 00F3 and 00F4 so the idea is this table only ever gets used for 101 = 101, therefore preventing any “baro” correction. So burn the values 70, 70, 80, 80 and so on.

Baro Pressure (kPa)

Baro Correction (%)

70

70

80

80

90

90

100

100

110

110

The last table is where you actually tune the fuel according to boost. The boost pressure values should be entered as a percentage of base barometric pressure. If you want to adjust fuel at 115 kPa (2psig), calculate the table value 115/101 = 114%. If the manifold pressure goes higher or lower than the highest or lowest value in the table, then the last value is used. Since the lowest value in this table is 101 kPa, the correction for off-boost conditions will always be 100%. But there is a danger at the high end, if you accidentally overboost more than the highest value in the table, the fuel correction will remain at the highest value in the table and you may go lean, so it is best to have a high kPA entry to cover that possible condition. The figures for this table are just an example. This table goes in the locations 010A to 0119. Both screenshots below are of the table.

Manifold Pressure %

Fuel Correction (%)

100

100

114

110

128

120

142

130

156

140

168

150

182

155

196

160


GM 2 Bar MAP Sensor Values:

Positive PSI

kPa

Volts

ADC

0

101

2.38

122

1

108

2.56

131

2

115

2.73

140

3

122

2.91

149

4

129

3.08

158

5

136

3.26

167

6

143

3.44

176

7

150

3.61

185

8

157

3.79

194

9

163

3.96

203

10

170

4.14

212

11

177

4.31

221

12

184

4.49

230

13

191

4.67

239

14

198

4.84

248

 

GM 3 Bar MAP Sensor Values:

PSI

kPa

V

ADC

0

101

1.62

83

1

108

1.74

89

2

115

1.85

95

3

122

1.96

100

4

129

2.07

106

5

136

2.18

112

6

143

2.29

117

7

150

2.41

123

8

157

2.52

129

9

163

2.63

135

10

170

2.74

140

11

177

2.85

146

12

184

2.96

152

13

191

3.08

157

14

198

3.19

163

15

205

3.30

169

16

212

3.41

175

17

219

3.52

180

18

225

3.63

186

19

232

3.75

192

20

239

3.86

198

21

246

3.97

203

22

253

4.08

209

23

260

4.19

215

24

267

4.30

220

25

274

4.42

226