[Diy_efi] About MAP sensing and it's jitter

[Alexei Pavlov]

Hi,

I did not succeed to see you signal images. Even if you got better
signals afterwards I'd like to see the following:
The question is: do you want to see real pressure or do you
want to use average cycle pressure to manage the engine ?
Probably the second. In this case you need a correct sampling
of intake pressure oscillations. You must sample at a frequency
you've choosen and low-pass filter higher frequencies. 
Then the CPU will compute the average pressure of 1 engine cycle.

If you use higher frequency sampling you'll always get unstable
signal, as cylinders are all different and intake system has its
proper frequencies.

>From my experience with rather high overlap and very low overlap engines
I'd say you'll get more inter-cycle oscillations when WOT or at high
RPM.

tsokorai at xperts.cl wrote:
> 
> Hi!
> Anybody knows how much (KPa, inHg, etc.) should the MAP signal jump at idle
> with a totally stock 1975 Ford 302?. I know that engines with radical cams
> get heavy MAP jumping at idle, but I'm getting this after I installed my
> ignition project prototype on "datalog-only" mode (info about my project:
> http://www.sokorai.cl/camioneta/IGN_ECU_en.html) .
> I know that the signal is clean, as all the other sensors read OK (RPM from a
> hall pickup, battery voltage, and CTS), and when reading baro (engine not
> running) , it's very steady).
> I'm starting to worry engine valvetrain problems instead of my
> circuit's....  :(
> 
> TIA
> 
> --
> Tomas J. Sokorai Sch.
> Socio director, Gerente Proyectos Especiales
> Xperts Ltda. F: 63 244591, Valdivia, Chile
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> diy_efi at diy-efi.org
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