manx

So I have been doing a bit of tuning with Mihnea's help and the aid of a voltage remapper from Split Second. I have gotten a fairly large, 4" inlet 3.5" outlet hot plate monometer to work on my car very well.

In doing so I have been monitoring MAF voltages unmolested and molested by my voltage mapper. I think that I have found some interesting things, at least some things that I didn't realize, but maybe should have.

The RS2 maf is appropriately sized to full scale on a basically stock RS2, at 320 hp I basically see full voltage out of the maf. This makes sense because they want to use all the voltage to get the best resolution. So all of us running over 320hp you will see that the maf voltage maxes out and past that the motronic in it's infinite wisdom relies on other things I suspect to calculate load.

I suspect that this poor hot wire monometer that is being given all the voltage it can and in Hap, MLP and old Edwins case starting at a very low rpm, it is no surprise the old thing get's ripped out, although this is not the case for these three people/cars anymore they have all moved on in one way or another..

So moving on to a larger maf my thought was always to copy the RS2 voltage map and enjoy the benefits of a lower delta P across the maf, and hopefully the intake track. But my realization that I would be running into full voltage at 3k or so meant that it would make more sense and with Mihnea help to first correct the maps to RS2 then to re-scale the maps to basically fatten up the maps so that I could lower the voltage offset, or lower the voltage offset and put in bigger injectors. This way instead of full scale at 3-4k I am full scale at or near full hp. My though is this will lead to more accurate load mapping and hopefully more average hp depending on conditions, also a bit more safety, I think.

So I am wondering when you put a resistor in place to scale the maf, I am speculating here so feel free to chime in, if you are in fact just hindering the benefit's that it might have given to have "more accurate" load calculations if you allowed it to represent it's true full scale to the motronic, instead of trying to get it to mimic the RS2 to enable tuning to be easier, at least this is how I think it is being done, someone correct me.

zVMAP

Putting a resistor or a resistor divider on the output is definetly not advisable and is a passive technique.

The issue with this technique is that you now have lowered your full scale output voltage swing.

I have seen this on some modified MAP sensors and find it quite amusing. Actually it is adjusting the scale to reasonable levels all the way till the output saturates.

If you reduced the output with a resistor divider by 20% you also reduced your full scale output by 20%.

Asssuming full scale is 5 volts now the maximum voltage swing is 4.0 volts ... so it works well up until 4.0 volts. If you write the code so the Analog to Digital convertor does not need to convert values that exceed this value it will work.

Best regards,
Feico van der Laan<ul><li><a href="http://www.moreboost.com">http://www.moreboost.com</a</li></ul>