This is part two of the MAF formulas thread. In this thread, I'll be explaining a theory that I have. I'd like to know if it makes any sense.

In Part I, I showed a way of finding MAF voltage by only knowing the airflow. Taking this a step further, I've come up with the following table highlighting rows 5 and 6 of MAF table #2, scalar 48. Sorry about the table's format; it got a little screwed up. Hopefully you can make it out.

row volts TBL gm/sec
5.00 1.92 198 37.13
5.01 1.92 199 37.23
5.02 1.93 199 37.34
5.03 1.93 200 37.45
5.04 1.93 200 37.56
5.05 1.93 201 37.66
5.06 1.94 201 37.77
5.07 1.94 202 37.88
5.08 1.94 203 37.99
5.09 1.94 203 38.10
5.10 1.95 204 38.20
5.11 1.95 204 38.31
5.12 1.95 205 38.42
5.13 1.96 205 38.53
5.14 1.96 206 38.64
5.15 1.96 207 38.74
5.16 1.96 207 38.85
5.17 1.97 208 38.96
5.18 1.97 208 39.07
5.19 1.97 209 39.18
5.20 1.97 210 39.28
5.21 1.98 210 39.39
5.22 1.98 211 39.50
5.23 1.98 211 39.61
5.24 1.99 212 39.72
5.25 1.99 212 39.82
5.26 1.99 213 39.93
5.27 1.99 214 40.04
5.28 2.00 214 40.15
5.29 2.00 215 40.26
5.30 2.00 215 40.36
5.31 2.00 216 40.47
5.32 2.01 216 40.58
6.00 2.01 217 40.70

There are 32 steps between rows. Because of this, the voltage increases 0.002727273 volts per step. The TBL increases 0.575757576 per step. Rounding the values off yields the number that the ECM can use (did I round to the correct place?). As you can see, there are some steps that contain the same voltage and the same TBL. This might account for some MAF inaccuracies, but I'm not completely sure.

Assume that at 39.50 gm/sec you're reading lean and you need to increase that value 2%. Since you can't adjust the values directly in each step, you have to indirectly change them by adjusting the boundary values. I've come up with a formula to do this, but I don't want to post it just yet. I'd like to get some feedback on this logic first. Am I on the right track?

 

all i can say is Good work. even if you can predict the boundry values they will always need just a bit of rinse and repeat to get right.

the reason values are redundant is becuase GM limites the bandwidth of the sensor.

 

Here's the math for calculating the boundary values if a "step value" needs adjusted. In this example, we'll be adjusting the LOWER boundary value.

Let's say that at step 8 we want a gm/sec of 39.

Find the TBL of the gm/sec you want.
(256 * 39 gm/sec) / 48 = 208

Find how many individual TBL values there are from the top row's value.
208 - 198 = 10

Find the TBL value over X steps (8).
10 / step 8 = 1.25
1.25 * 33 = 41.25

Add that to the top row's value.
41.25 + 198 = 239.25

The lower boundary value would need to be changed to 239 to ensure that step 5.08 reads 39 gm/sec. Now, that obviously upsets every value between rows 5 and 6, and also infringes on row 6 because 239 is much higher than the TBL of row 6, which is only 217. Keep in mind that this formula only works for changing the LOWER boundary value (in this case, the value of row 6). Some slight formula reconstruction would be needed if you wanted to change the UPPER boundary value.

I currently don't have the capability to play with the MAF tables and see how all of this affects changing them. It may just be easier to find boundary values on the scanner and change those, rather than mess with the values between rows.