DIY_EFI Digest V5 #380

John Hess jhess at austin.rr.com
Sat Nov 11 10:11:06 GMT 2000


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----- Original Message -----
From: "DIY_EFI Digest" <DIY_EFI-Digest-Owner at diy-efi.org>
To: <DIY_EFI-Digest at lists.diy-efi.org>
Sent: Friday, November 10, 2000 5:42 PM
Subject: DIY_EFI Digest V5 #380


<SNIP>
> ----------------------------------------------------------------------
>
> Date: Fri, 10 Nov 2000 08:48:31 -0500
> From: Rodney_L_Wiggins at keybank.com
> Subject: Re: Ignition only
>
> I'm having trouble understanding the concept of firing the second plug
> backwards.
> After the spark jumps the gap on the first plug, isn't the "path of least
> resistance"
> going to be head-block-chassis instead of trying to jump the airgap of the
> second
> plug?? (compressed or otherwise). I'm probably missing something basic
here.
>
> TIA
> Rod
> 944 turbo (+NOS and big Turbo)
> only 7000 RPM so 1 coil 1msd. (sufficient??)
>
>
>
>

Actually, it doesn't fire "backwards."  the dual terminal coil has a single
primary and a dual secondary.  The polarity remains the same for both
terminals.

> >0ne difference I didn't see mentioned is that waste spark systems
> >fire one plug "backwards". (Normally the hot center electrode is
> >negative, since it's electrons being emitted that actually start
> >things off, as in vaccum tubes.) This probably means that the plug
> >gap in those cylinders cannot be as large as in a "forward"
> >cylinder, but I'm not sure if this is a meaningful difference or
> >not.
>
>
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