> -----Original Message-----
> From: Alan Gorham [SMTP:alan@MICROTIMA.CO.UK]
> Sent: Monday, May 20, 2002 1:16 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [EE]: Update 2 - Spark ignition for model engines
>
> Hi
>
>
> >Based on this I think I would have tried moving the firing to closer to
> TDC,
> >say a couple of degrees after TDC.
>
>
> I would have tried this, but I wanted to check if it was sensible first.
> How does this explain the 'backfiring' behaviour I observed at the
> retarded
> ignition point
> and how will advancing the ignition slightly cure this?
>
I suspect you were slowly filling the exhaust with fuel during your attempts
to start it.  With very retarded ignition, the mixture is still burning when
it exits the exhaust port, which ignites the fuel stored within.  The result
is a backfire, quite an impressive one on a full size engine :o)

Regards

Mike

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