[Diy_efi] pic based afm -> maf conversion

[Ashley Evans]

Hi all,

Just thought some of you may be interested in my current project.  a afm 
-> maf conversion using pic based DAC -> ADC to map the signal.  It's 
for a motronic car, specifically an e30 bmw, but it should be suitable 
for any 5v system.  I plan to make the fuelling "mappable", probably a 
one off mapping with rolling road and exhaust probe o2 sensor.

I'm hoping to implement a cruise lean-off system to save fuel on light 
load cruising.  it will be based on average air volume over time, but 
the details are yet to be finalised as it's a secondary goal.

Currently I've set up my dev environment am about to record idle to 
red-line datalogs of voltages for both afm and maf, to build up the 
map.  using a picoscope adc-10 to take the datalogs.

the adc on the pic is a 10bit device, but according to the book I have 
it can only be trusted for 8bit accuracy.  There's no onboard dac on 
this particular pic so I may have to look at other devices at some 
point.  Hopefully the 8bit resolution will be good enough.  I think that 
gives me steps of ~19.5mv, so hopfully that's enough, if not I'll be 
looking at the extra bits in the 10bit adc, or another device alltogether.

I'm using the pickit1 starter kit as this is my first pic project (and 
I'm more of a computer guy than electronics)

Anyway, just thought some of you guys may be interested.  Comment and 
criticisms  welcome.

ashley