[Diy_efi] Re: Minimalist micro based EFI ?

[Mike]

At 03:34 PM 3/12/03 +0800, you wrote:
>> Yeah yeah :) Realise that - I was focussed on the comparative issue
>> and wanting a rationalisation of the issue re bits for range of power
>> out as someone made a generalisation not immediately substantive
>
>The output resolution is more significant in that respect than the
>ability to measure inputs to a great accuracy.  e.g. the ability to
>accurately meter injected fuel quantity is more important than being
>able to get the MAF resolution better than 8 bits.

Yeah sure, but one would expect to get most of the way there without
needing feedback most of the time to adjust fuel qty from Lambda
sensor. Especially since my ecu only goes closed loop under cruise
and then only if warm and ten only after a minute and goes out of
closed loop at the drop of hat. Open loop at idle, high load and WOT.

I expect there are a heap of stability issues why thats the case,
which means I'd like to get as close to the tuned figure by having
enough resolution in say the top 50% CFM range of the AFM and this
has me considering that 10 bits wont be enough *unless* its really
well tuned up at the time and checked fairly well quite often...

I have a draft of a system that might do this, send an 8 bit DAC
out a simple resistor network from a SPI port, differential back
to AFM input - effectively adding (allowing for linearity) about
4 bits - so without much hassle I can extend the existing CPU
10 bit resolution to 14 but will need to do a bit of juggling,
but thats where all the fun is ;)


Rgds

Mike Massen
Mb +61 (0) 438 048961
Perth, Western Australia
Some power/auto stuff here:-  http://www.iinet.net.au/~erazmus
Some auto stuff http://members.iinet.net.au/~erazmus/car_accessories/



_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi