[Diy_efi] About MAP sensing and it's jitter

steve ravet sravet at arm.com
Wed Jan 14 23:15:23 GMT 2004


"Tomas Sokorai Sch." wrote:
> On Wednesday 14 January 2004 14:57, steve ravet wrote:
> > There's an article on the gmecm page about how GM implements lag filters
> > for O2, MAP, etc.  It's always a good idea to filter based on your
> > sample rate.  In the case of MAP you can do it with a small orifice
> > restriction in the line to the MAP sensor, or electrically, or in
> > software.
> >
> > --steve
> 
> Thanks!, I'm already using a filter like that on the coolant temp. input. But
> it has a fixed filter coefficient (. I guess that to implement such filter on
> a signal with a sampling rate dependant on the engine speed, it could be a
> good idea to lower the coefficient proportionally with the RPM increase?

Sampling based on engine position complicates the filtering.  To keep it
simple you could filter based on the slowest sample rate (at idle),
unless that introduces too much lag.

--steve

-- 
Steve Ravet
steve.ravet at arm.com
ARM,Inc.
www.arm.com
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