Basics of the timing advance

Mika.J.Tuominen at nmp.nokia.com Mika.J.Tuominen at nmp.nokia.com
Wed Feb 28 08:08:39 GMT 1996


      Hi you there!

 I have been thinking about the principles of ignition timing advance.
I converted one timing diagram of mechanically adjusted distributor from=

degree-based to time-based graph, and noticed it has a peak in advance
just above idle speed. Obviously that is coming from 'two-phase'
adjusting mechanics in the distributor. Now I'm wondering is that kind
of behaviour needed or can I make it better if I make the advance to
follow engine speed linearly. =


 One other thing has also popped up when I was thinking my engine =

controller (at first only controlling ignition). Can I live with
two pulses per cranksaft revolution to make a timing good enough.
In 4-cylinder 4-stroke engine is needed two sparks per 360degs,
so if I place my sensor to cranksaft for example 30 degrees before
TDC I have enough time to calculate delay to correct spark time, and
speed I can derive from the delay between two pulses. Worst problem
which came into my mind is that can engine speed change so rapid that
I can't trust to speed counted from 180 degrees period. Any info
about teeths per round value in existing systems would be appreciated.
Easy place to find many teeths is starting gear, but I liked to keep
my CPU free for other jobs, than responding to interrupts.  =


    Thanks in advance, :)

    Mika

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 Mika J. Tuominen                    Internet: mitu at nmoy.nmp.nokia.com
 Nokia Mobile Phones Ltd. Address: P.O.box 86, FIN-24101 Salo, Finland
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