Fw: [Diy_efi] OT - cap/rotor clearance

[Geoff Harrison]

I have heard about this theory. Lets take it to extremes. Lets make the gap 
at the rotor 15". The gap in the plugs 40thou. How much spark will we get at 
the plug?

The overall gap, i.e. that in the dizzy plus that in the plug can slightly 
effect timing. The more gap, the higher the voltage required to bridge the 
gap. So the spark occurs later. That's why the old series type timing lights 
weren't that accurate.

What may be a greater concern with the tighter gap in the dizzy, is extra 
loading on the ign coil.
I agree with your ref to resistance wires. This can be easily demonstrated 
by connecting 2 light bulbs in series. Say a headlight, and a parker light. 
Connect the lot to a 12v battery. Only the parker will glow. The headlight 
doesn't have enough current to develop sufficient power to glow.

That's why I use inductive wires, and not resistive.
The comment about the "voltage rise time" is half true. With more gap, the 
rise time will be slightly longer, and the voltage slightly higher. However, 
a higher voltage is required to bridge the gap. A good thing if it was 
inside the combustion chamber, a bigger flame front. Wasted energy inside 
the dizzy cap.

BTW, I started with electronics in the 60s, and engines in the 70s.

Regards, Geoff
----- Original Message ----- 
From: <cobraman at insightbb.com>
To: <diy_efi at diy-efi.org>
Sent: Wednesday, October 19, 2005 12:01 AM
Subject: Re: [Diy_efi] OT - cap/rotor clearance


> There is a theory that the plug gap is harder to cross then the rotor gap 
> as
> the pressure is higher, so the rotor gap should be "big" to decrease the
> voltage rise time at the plug - kind of a dam it up then let it go to. 
> Someone
> with an EE background might want to comment. Same with resistance wires. 
> TomS
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