Ignition only

[Programmer]

Good question--we never really measure current, except the supplied
"current" to the ignition coils (current ramping 101). Firing voltage and
burn time are the more two important measurements.

Lyndon.

-----Original Message-----
From: Chris Conlon <synchris at ricochet.net>
To: diy_efi at diy-efi.org <diy_efi at diy-efi.org>
Date: November 9, 2000 11:55 AM
Subject: Re: Ignition only


>At 08:41 AM 11/9/00 -0700, Programmer wrote:
>
>>>The same current flows across both spark gaps - this must be the case
>>>unless we're losing or gaining electrons somewhere. The high voltage
>>
>>
>>Measure it on an ignition scope sometime...it's not the same kV
>>required to fire the waste side as it is the power side. That's
>>correct about the gap to "some" degree--other than the rotor to
>>tower gap and the plug gap is always on the power side. Not so
>>with DIS. The power side on DIS may be 8-10 kV, where
>>the waste spark side is 1-2kV (measured).
>
>He's talking current, and is correct. You're talking voltage, and I
>presume you're correct too. The current should (in any likely case)
>be equal, the voltages may be very different.
>
>
>
>At 10:21 AM 11/9/00 -0600, don.broadus at exeloncorp.com wrote:
>
>>would the difference in the kV voltage on the waste spark side have to do
>>with the lower cylinder pressure  or  possibly ionized exhaust products. ?
>>Just wondering
>
>The breakover voltage (the peak just before the spark fires) depends
>mainly on the gas density in the cylinder, and (in the case of the
>wasted spark) the fact that the gases are fairly ionized. (This
>lowers the breakover voltage). High temperature also lowers breakover
>voltage somewhat. The gap voltage during the spark event depends
>mainly on ion loss, either as ions drift out of the gap, or as non
>ionized gases drift into the gap. If everything is uniformly ionized,
>current flows easily, the gap voltage is low and little power is
>dissipated in this half of the circuit. If there is a lot of
>unionized gas, current flows less easily, gap voltage is high, and
>more power is dissipated in this half of the circuit. This is a
>*good* thing, because only power *dissipated* in the spark gap can
>help ignite things.
>
>
>One 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.
>
>
>   Chris C.
>
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