Ignition Timings

nacelp nacelp at bright.net
Mon May 22 19:31:38 GMT 2000


I can't comment on the code end of it,  but, I can say I'd rather work with
a look up table, then say just using a slope for advance over a particular
rpm.
  The spark duration varies alot.  I've seen some cars carry a 2msec spark
duration at idle, and some less then .5, then all of them shorten as RPM
increase.
Grumpy


> I didn't see any replies to this but find it very interesting.  If there
> were any follow-ups, forgive me.  So, why do we think this timing is
> constant?  Is it simply the amount of time it takes for the plugs to fire?
> It clearly isn't related to piston position.
>
> Inquiring minds...
>
> Mike Diehl,
> MR-2, '87na
>
>
> > -----Original Message-----
> > From: Corner Paul [mailto:Paul.Corner at icl.com]
> > Sent: May 17, 2000 3:34 AM
> > To: 'diy_efi at diy-efi.org'
> > Subject: Ignition Timings
> >
> >
> >
> > Hi All
> >
> > I've been messing about with the ignition side of my ECU,
> > writing new code
> > and grafting it to the fuelling software....
> > Working out the initial advance tables from the original
> > advance curves. I
> > noticed that when the data is converted from degrees/RPM to
> > mSec before TDC,
> > it remains fairly constant from tickover to 4500 RPM.
> > Question is - can I use this time constant up to, say 6500
> > RPM, rather than
> > messing around with look up tables etc. Perhaps, at a later
> > stage, when the
> > engine is running and the hardware has been tested, the
> > software can be
> > rewritten to use look up tables. It really depends on how
> > much advance is
> > required above 4500 RPM.
> >
> > Regards, Paul.
> >
> >
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>
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