Re: Dual-Plugging Question...
- Hi all, Just my 2 cents,but I have to agree with Swiss as in using a
Snap-On MT1665 Digital oscilloscope to veiw and measure secondary wave
forms and KV readings shows his ststement to be true(it may
never...).The KV reading per spark lead(sparkplug) should not exceed
40% of the rated coil voltage at any time,to insure proper spark under
all conditions.On Wasted spark normal systems(2 cylinders-1 dual plug
coil),the true firing KV is usually in the 6 to 14KV range and the
wasted firing is in the 0 to 4KV range.So,if you use a dual plug coil
on a single cylinder,the output of the coil will be between 6 to 14KV
on each sparkplug or a dual plug coil that needs to put out a total of
12 to 28KV.On a coil that can put out 40,000 volts,this leaves
anywhere from 28 to as low as 12KV in reserve.Voltage requirements
depend on a number of conditions and are as follows:Things that
require a High output:Eroded sparkplug electrodes;high secondary
circuit resistance;open secondary circuit;high primary
current;sparkplug gap wide;temperature of the electrodes being cooler
than normal;dull shape of the electrodes;polarity of the center
electrode being negative;retarded ignition timing;fuel mixture being
very lean or very rich;high compression;and cooler combustion chamber
temperature.Lower Voltage as follows:grounded secondary
circuit;primary circuit fault(resistance);narrow sparkplug gap;hotter
temperature of the electrodes;sharpe shape of the electrodes;polarity
of the center electrode being positive;advanced ignition timing;rich
fuel mixture;low compression;and hotter than normal combustion chamber
temperature.I hope this can help. Louis....
--- In mc-engine@y..., "Jim Schneider" <swissscf@c...> wrote:
> Understand that the spark jumps whenever it reaches the voltage and
> level that is required for the plug gap and the combustion chamber
> conditions. With a 30,000 or 40,000 volt coil, it may NEVER have to
> these kinds of volts to get the spark started. IF a dual output
> enough voltage available to spark a pair of parallel plugs, it will
> It IS better to have excess power available.
> ----- Original Message -----
> From: "Mike Wright" <mwright@g...>
> Subject: Re: Dual-Plugging Question...
> > 1. Using a twin output coil, is NOT recommended... I know others
> will nix
> > this.. but do the electronic math.. if you run a 40,000 volt twin
> coil, you
> > get 1/2 voltage to each plug (under compression).
> Ron (and others)
> Forgive what may be an amateur question, but electrical stuff has
> never made me very comfortable. What's the math for a Guzzi vtwin
> running dual plugged heads and 2 sets of points.
> Conventional "wisdom" in the Guzzi community says to run 2 twin
> output 3 ohm (I think) coils. If I wanted to run 4 individual coils,
> what's the best way to do that?
> Mike Wright
- Long ago in the dark ages before I had the Speedvision
channel with coverage of World Rally (my wife would
argue that the dark ages began AFTER I got
Speedvision), a high-school friend of mine had a well
used 4 door Subaru. Front wheel drive, naturally
aspirated, far from "sporty". However, because it had
a manual transmission, a somewhat interesting exhaust
note, and an owner who couldn't care less for the
condition of the car, it was used for all sorts of
on-road, off-road, and airborne adventures.
I will forever appreciate the fact that the Sube would
seem to take on any challenge and keep on chugging.
The job of the back seat passengers was to kick the
floor pans back down as they got hammered inward. The
car was finally done in by a taking a large puddle,or
small lake depending on your perspective, at high
speed and sucking water into the engine, knocking a
cylinder or two out of whack. We never did tear down
the engine to see the damage, and I regret it now. It
was limped into our school auto shop and donated as a
project car. I recommended sending it back to Subaru
with a list of accomplishments. It would have made a
great museum piece. Now, any time I watch World
Rally, I feel like "been there done that"
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