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Simple Test for Coil On "Wasted Spark" 2 Cylinder Engine

Started by Bret Cahill May 25, 2012
I suspected a CDI coil wouldn't put out enough voltage for the "energy
transfer" -- the worst misnomer ever -- system and suggested shorting
out the spark plug electrode on one of the 2 cylinders by pounding the
gap shut or stuffing it with a bit of foil.

The theory was instead of jumping two gaps it would only need to jump
one.  The lower effective resistance would give a better spark on the
remaining firing cylinder.  The al foil trick worked.  It ran on one
cylinder which seems to confirm my suspicions about the coil as well
as my test, which may or may not be original.  Googling is hard work.

Anyway the engine has two magnetos opposite each other, one for the
ignition and one for charging the battery.  The four magnets are
equally spaced on the flywheel.

The 2 low voltage magneto coils look about the same and both seem to
do the same thing to a volt meter when cranked -- admittedly not a
very scientific indicator.

It seems like it would be possible to just forget about charging a
battery and wire another CDI coil to the charger coil.

Even simpler would be to tap the plug gaps to half that recommended in
the specs.

Maybe the fuel efficiency would drop by 20%?  Maybe it wouldn't fire
at all?


Bret Cahill








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Bret Cahill wrote:

> I suspected a CDI coil wouldn't put out enough voltage for the > "energy transfer" -- the worst misnomer ever
That's 'the BEST misnomer ever'. A bad misnomer isn't doing a very good job of 'misnoming'. Those Latin types have a word for everything. nomenclature mike -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJPwt5/AAoJEDTMN7GV3zbXuQoH/254Rrt5lX2bg5uQFAaHkw0w G+FGnioZoN3O8tbnfMvGlBVA/aEcUOZ8I6WhwFxg26Ylw3x/vpZFTNcziqiFc5BW Sg/V4n2m5jRjDBfZ0MnmbvPAzbSIgMwg2JA0A8H96gjbTJhZrP/D4FYjGEphRqWB QUieq1+vFEmbMf1TFc0nlh3SpUIkqrDIvDZamzu1NFqk6i8GZscIfD8X+vaFrHlA Wec93IauWJYFUy7y5qFd5FyeqcWqTq8ZcMu3zTwZ/mqpSOIVEpu1BZJ/ipxYhqjT 28q2xMAlWOqGYBptthp5lO2CeXtAYJvgPGLjUoKLfnD86esgKGSfuVyeltfhcn0= =JWQ2 -----END PGP SIGNATURE-----
On Fri, 25 May 2012 16:40:43 -0700, Bret Cahill wrote:

> I suspected a CDI coil wouldn't put out enough voltage for the "energy > transfer" -- the worst misnomer ever -- system and suggested shorting > out the spark plug electrode on one of the 2 cylinders by pounding the > gap shut or stuffing it with a bit of foil. > > The theory was instead of jumping two gaps it would only need to jump > one. The lower effective resistance would give a better spark on the > remaining firing cylinder. The al foil trick worked. It ran on one > cylinder which seems to confirm my suspicions about the coil as well as > my test, which may or may not be original. Googling is hard work. > > Anyway the engine has two magnetos opposite each other, one for the > ignition and one for charging the battery. The four magnets are equally > spaced on the flywheel. > > The 2 low voltage magneto coils look about the same and both seem to do > the same thing to a volt meter when cranked -- admittedly not a very > scientific indicator. > > It seems like it would be possible to just forget about charging a > battery and wire another CDI coil to the charger coil. > > Even simpler would be to tap the plug gaps to half that recommended in > the specs. > > Maybe the fuel efficiency would drop by 20%? Maybe it wouldn't fire at > all?
This is a basic electRONICS group. Not a basic electRICS group. Certainly not a basic small engines repair group. Maybe if you took your off-topic questions to where they are _on_ topic, you'd get quicker answers. But, here's some theory for you: If it worked good from the factory, and you fix it back to factory specifications, it should work good. If the ignition works and the motor doesn't, the problem isn't the ignition. If the ignition has been "improved" by someone who has no clue how ignition systems work, and the motor doesn't work, then restore it back to factor specification and see the first sentence in this paragraph. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
On Fri, 25 May 2012 16:40:43 -0700 (PDT), Bret Cahill
<Bret_E_Cahill@yahoo.com> wrote:

>I suspected a CDI coil wouldn't put out enough voltage for the "energy >transfer" -- the worst misnomer ever -- system and suggested shorting >out the spark plug electrode on one of the 2 cylinders by pounding the >gap shut or stuffing it with a bit of foil. > >The theory was instead of jumping two gaps it would only need to jump >one. The lower effective resistance would give a better spark on the >remaining firing cylinder. The al foil trick worked. It ran on one >cylinder which seems to confirm my suspicions about the coil as well >as my test, which may or may not be original. Googling is hard work. > >Anyway the engine has two magnetos opposite each other, one for the >ignition and one for charging the battery. The four magnets are >equally spaced on the flywheel. > >The 2 low voltage magneto coils look about the same and both seem to >do the same thing to a volt meter when cranked -- admittedly not a >very scientific indicator. > >It seems like it would be possible to just forget about charging a >battery and wire another CDI coil to the charger coil. > >Even simpler would be to tap the plug gaps to half that recommended in >the specs. > >Maybe the fuel efficiency would drop by 20%? Maybe it wouldn't fire >at all? > > >Bret Cahill > > > > > > >
The wasted spark is derived from two series connected coils (connected at the low voltage side in series) or one coil with two secondary windings; the spark plugs themselves aren't in series. Think about it - that would take an engine block operating ~20 KV above ground unless you had spark plugs with two insulated electrodes. As for shorting one plug that might raise the voltage to the other by a small amount with two coils in series providing you have two primaries (two complete separate coils). With a two secondary coils wound on the same core, it would probably lower the voltage (acting as a shorted turn and causing the field to collapse slowly) Some years ago I built a 1KW induction coil (~13 miles of 32 AWG wire in the secondary - weighs 40 lbs). When the gap was opened to 4" or so the sound would be a crackling noise - but close the gap to a 1/8" and it made a hissing sound and the spark lasted longer. Repetition rate was ~20 cycles per second with a 4" spark (lot of iron and took time to charge). Visual/audible indication that a shorted turn (heavily loaded secondary in this case) causes more "hang time" with the spark.
> >I suspected a CDI coil wouldn't put out enough voltage for the "energy > >transfer" -- the worst misnomer ever -- system and suggested shorting > >out the spark plug electrode on one of the 2 cylinders by pounding the > >gap shut or stuffing it with a bit of foil. > > >The theory was instead of jumping two gaps it would only need to jump > >one. =A0The lower effective resistance would give a better spark on the > >remaining firing cylinder. =A0The al foil trick worked. =A0It ran on one > >cylinder which seems to confirm my suspicions about the coil as well > >as my test, which may or may not be original. =A0Googling is hard work. > > >Anyway the engine has two magnetos opposite each other, one for the > >ignition and one for charging the battery. =A0The four magnets are > >equally spaced on the flywheel. > > >The 2 low voltage magneto coils look about the same and both seem to > >do the same thing to a volt meter when cranked -- admittedly not a > >very scientific indicator. > > >It seems like it would be possible to just forget about charging a > >battery and wire another CDI coil to the charger coil. > > >Even simpler would be to tap the plug gaps to half that recommended in > >the specs. > > >Maybe the fuel efficiency would drop by 20%? =A0Maybe it wouldn't fire > >at all? > > >Bret Cahill > > The wasted spark is derived from two series connected coils (connected > at the low voltage side in series) or one coil with two secondary > windings; =A0the spark plugs themselves aren't in series.
There was only one high resistance between any two terminals in the ignition coil, 30K ohms between the two plug wires. The resistance between either plug wire and ground was infinite. The other two resistances were 3 and 0.75 ohms. Instead of a conventional ground for the secondary the other spark plug becomes ground. The "wasted" spark isn't a complete waste. It's necessary to complete the circuit for the firing plug.
> Think about > it - that would take an engine block operating ~20 KV above ground > unless you had spark plugs with two insulated electrodes.
> As for shorting one plug that might raise the voltage to the other by > a small amount with two coils in series providing you have two > primaries (two complete separate coils).
My first guess is it would double the voltage in the good plug, however, considering CDI has over an order of magnitude higher voltage in the primary, 2X may not be enough to do much. It may have just been coincidental that it finally fired when one plug was shortened out.
> With a two secondary coils > wound on the same core, it would probably lower the voltage (acting as > a shorted turn and causing the field to collapse slowly)
That's another reason why I'm sticking to the one secondary coil theory.
> Some years ago I built a 1KW induction coil (~13 miles of 32 AWG wire > in the secondary - weighs 40 lbs). =A0When the gap was opened to 4" or > so the sound would be a crackling noise - but close the gap to a =A01/8" > and it made a hissing sound and the spark lasted longer. =A0Repetition > rate was ~20 cycles per second with a 4" spark (lot of iron and took > time to charge). =A0Visual/audible indication that a shorted turn > (heavily loaded secondary in this case) causes more "hang time" with > the spark.
How linear was the output from the secondary compared to the input to the primary? Bret Cahill
On 2012-05-28, Bret Cahill <Bret_E_Cahill@yahoo.com> wrote:
>> >> The wasted spark is derived from two series connected coils (connected >> at the low voltage side in series) or one coil with two secondary >> windings; &nbsp;the spark plugs themselves aren't in series. > > There was only one high resistance between any two terminals in the > ignition coil, 30K ohms between the two plug wires. The resistance > between either plug wire and ground was infinite. The other two > resistances were 3 and 0.75 ohms. > > Instead of a conventional ground for the secondary the other spark > plug becomes ground. The "wasted" spark isn't a complete waste. It's > necessary to complete the circuit for the firing plug. > >> As for shorting one plug that might raise the voltage to the other by >> a small amount with two coils in series providing you have two >> primaries (two complete separate coils). > > My first guess is it would double the voltage in the good plug, > however, considering CDI has over an order of magnitude higher voltage > in the primary, 2X may not be enough to do much.
It needs a path to ground, but the plug on the wasted end has a lower breakdown voltage as it's not under pressure and once the arc forms the voltage is only a few tens of volts. So shorted is not likely to be a great improvement over wasted. -- &#9858;&#9859; 100% natural --- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---
On Mon, 28 May 2012 13:01:52 -0700 (PDT), Bret Cahill
<Bret_E_Cahill@yahoo.com> wrote:

>> >I suspected a CDI coil wouldn't put out enough voltage for the "energy >> >transfer" -- the worst misnomer ever -- system and suggested shorting >> >out the spark plug electrode on one of the 2 cylinders by pounding the >> >gap shut or stuffing it with a bit of foil. >> >> >The theory was instead of jumping two gaps it would only need to jump >> >one. &#2013266080;The lower effective resistance would give a better spark on the >> >remaining firing cylinder. &#2013266080;The al foil trick worked. &#2013266080;It ran on one >> >cylinder which seems to confirm my suspicions about the coil as well >> >as my test, which may or may not be original. &#2013266080;Googling is hard work. >> >> >Anyway the engine has two magnetos opposite each other, one for the >> >ignition and one for charging the battery. &#2013266080;The four magnets are >> >equally spaced on the flywheel. >> >> >The 2 low voltage magneto coils look about the same and both seem to >> >do the same thing to a volt meter when cranked -- admittedly not a >> >very scientific indicator. >> >> >It seems like it would be possible to just forget about charging a >> >battery and wire another CDI coil to the charger coil. >> >> >Even simpler would be to tap the plug gaps to half that recommended in >> >the specs. >> >> >Maybe the fuel efficiency would drop by 20%? &#2013266080;Maybe it wouldn't fire >> >at all? >> >> >Bret Cahill >> >> The wasted spark is derived from two series connected coils (connected >> at the low voltage side in series) or one coil with two secondary >> windings; &#2013266080;the spark plugs themselves aren't in series. > >There was only one high resistance between any two terminals in the >ignition coil, 30K ohms between the two plug wires. The resistance >between either plug wire and ground was infinite. The other two >resistances were 3 and 0.75 ohms. > >Instead of a conventional ground for the secondary the other spark >plug becomes ground. The "wasted" spark isn't a complete waste. It's >necessary to complete the circuit for the firing plug. > >> Think about >> it - that would take an engine block operating ~20 KV above ground >> unless you had spark plugs with two insulated electrodes. > >> As for shorting one plug that might raise the voltage to the other by >> a small amount with two coils in series providing you have two >> primaries (two complete separate coils). > >My first guess is it would double the voltage in the good plug, >however, considering CDI has over an order of magnitude higher voltage >in the primary, 2X may not be enough to do much. > >It may have just been coincidental that it finally fired when one plug >was shortened out. > >> With a two secondary coils >> wound on the same core, it would probably lower the voltage (acting as >> a shorted turn and causing the field to collapse slowly) > >That's another reason why I'm sticking to the one secondary coil >theory. > >> Some years ago I built a 1KW induction coil (~13 miles of 32 AWG wire >> in the secondary - weighs 40 lbs). &#2013266080;When the gap was opened to 4" or >> so the sound would be a crackling noise - but close the gap to a &#2013266080;1/8" >> and it made a hissing sound and the spark lasted longer. &#2013266080;Repetition >> rate was ~20 cycles per second with a 4" spark (lot of iron and took >> time to charge). &#2013266080;Visual/audible indication that a shorted turn >> (heavily loaded secondary in this case) causes more "hang time" with >> the spark. > >How linear was the output from the secondary compared to the input to >the primary?
Not linear at all if you mean voltage/turns ratio. I built it to work as both a step up 120 VAC transformer, or induction coil. The turns ratio is ~ 1:64 (67,800 turns secondary 1062 turns primary for 120 volt operation). The primary is in four layers of 354 turns each and can be switched into series or parallel to operate from 10-24 VDC or 120 VAC. The DC resistance of the secondary is 10,688 ohms. Turns ratio counts for less when operating as an induction coil - the speed at which the field collapses over time counts. AND the capacitor counts. The coil should "ring" when it fires. Shorted turns (or iron with thick laminations) impedes the collapse speed, as well as wasting energy. My coil rings at ~2,000 hertz As a step up 120 VAC transformer it produces 7,500 volts, as an induction coil from 24 volts, more like 50-80 KV (estimated). I found the secondary voltage was highest when the 10 amp relay I was using as an interrupter arced the least (with the wrong value the output voltage was lower and the contacts burned in short order) My first motorcycle ~1966, was a Gilera that used energy transfer magneto. One coil fed by a coil on the alternator - no battery. The lights were fed by their own coil with the exception of the brake light, it was in series with the low voltage ignition circuit when you stepped on the brake - and the bike would die if the brake light filament burned out and you used the brakes. (one of its many endearing idiosyncrasies) Honda motorcycles seem to favor transistor switched battery powered coils with two secondaries for each set of two cylinders. Johnson and Evinrude both use energy transfer magneto systems with dual secondary coils. Or my three outboards do (circa 1987 and earlier) If you need a coil like that - try a junked outboard.
> >> The wasted spark is derived from two series connected coils (connected > >> at the low voltage side in series) or one coil with two secondary > >> windings; the spark plugs themselves aren't in series. > > > There was only one high resistance between any two terminals in the > > ignition coil, 30K ohms between the two plug wires. The resistance > > between either plug wire and ground was infinite. The other two > > resistances were 3 and 0.75 ohms. > > > Instead of a conventional ground for the secondary the other spark > > plug becomes ground. The "wasted" spark isn't a complete waste. It's > > necessary to complete the circuit for the firing plug. > > >> As for shorting one plug that might raise the voltage to the other by > >> a small amount with two coils in series providing you have two > >> primaries (two complete separate coils). > > > My first guess is it would double the voltage in the good plug, > > however, considering CDI has over an order of magnitude higher voltage > > in the primary, 2X may not be enough to do much. > > It needs a path to ground, but the plug on the wasted end has a lower > breakdown voltage as it's not under pressure and once the arc forms > the voltage is only a few tens of volts. So shorted is not likely to be a > great improvement over wasted.
I never considered the effect of the differences in partial pressures and composition of the gases and vapors. Last I heard it was running on both cylinders so it probably was purely coincidental. I never was able to determine if a CDI ignition coil is actually any different in any respect than a low tension magneto / energy transfer ignition coil. The 2 look identical in all respects, not just bolt hole locations. Why waste a lot of wire and insulation material if it isn't required? Bret Cahill
> >> >I suspected a CDI coil wouldn't put out enough voltage for the "energ=
y
> >> >transfer" -- the worst misnomer ever -- system and suggested shorting > >> >out the spark plug electrode on one of the 2 cylinders by pounding th=
e
> >> >gap shut or stuffing it with a bit of foil. > > >> >The theory was instead of jumping two gaps it would only need to jump > >> >one. =A0The lower effective resistance would give a better spark on t=
he
> >> >remaining firing cylinder. =A0The al foil trick worked. =A0It ran on =
one
> >> >cylinder which seems to confirm my suspicions about the coil as well > >> >as my test, which may or may not be original. =A0Googling is hard wor=
k.
> > >> >Anyway the engine has two magnetos opposite each other, one for the > >> >ignition and one for charging the battery. =A0The four magnets are > >> >equally spaced on the flywheel. > > >> >The 2 low voltage magneto coils look about the same and both seem to > >> >do the same thing to a volt meter when cranked -- admittedly not a > >> >very scientific indicator. > > >> >It seems like it would be possible to just forget about charging a > >> >battery and wire another CDI coil to the charger coil. > > >> >Even simpler would be to tap the plug gaps to half that recommended i=
n
> >> >the specs. > > >> >Maybe the fuel efficiency would drop by 20%? =A0Maybe it wouldn't fir=
e
> >> >at all? > > >> >Bret Cahill > > >> The wasted spark is derived from two series connected coils (connected > >> at the low voltage side in series) or one coil with two secondary > >> windings; =A0the spark plugs themselves aren't in series. > > >There was only one high resistance between any two terminals in the > >ignition coil, 30K ohms between the two plug wires. =A0The resistance > >between either plug wire and ground was infinite. =A0The other two > >resistances were 3 and 0.75 ohms. > > >Instead of a conventional ground for the secondary the other spark > >plug becomes ground. =A0The "wasted" spark isn't a complete waste. =A0It=
's
> >necessary to complete the circuit for the firing plug. > > >> Think about > >> it - that would take an engine block operating ~20 KV above ground > >> unless you had spark plugs with two insulated electrodes. > > >> As for shorting one plug that might raise the voltage to the other by > >> a small amount with two coils in series providing you have two > >> primaries (two complete separate coils). > > >My first guess is it would double the voltage in the good plug, > >however, considering CDI has over an order of magnitude higher voltage > >in the primary, 2X may not be enough to do much. > > >It may have just been coincidental that it finally fired when one plug > >was shortened out. > > >> With a two secondary coils > >> wound on the same core, it would probably lower the voltage (acting as > >> a shorted turn and causing the field to collapse slowly) > > >That's another reason why I'm sticking to the one secondary coil > >theory. > > >> Some years ago I built a 1KW induction coil (~13 miles of 32 AWG wire > >> in the secondary - weighs 40 lbs). =A0When the gap was opened to 4" or > >> so the sound would be a crackling noise - but close the gap to a =A01/=
8"
> >> and it made a hissing sound and the spark lasted longer. =A0Repetition > >> rate was ~20 cycles per second with a 4" spark (lot of iron and took > >> time to charge). =A0Visual/audible indication that a shorted turn > >> (heavily loaded secondary in this case) causes more "hang time" with > >> the spark. > > >How linear was the output from the secondary compared to the input to > >the primary? > > Not linear at all if you mean voltage/turns ratio.
I meant "does doubling the voltage in the primary double the voltage in the secondary?"
> I built it to work > as both a step up 120 VAC transformer, or induction coil. =A0The turns > ratio is ~ 1:64 =A0(67,800 turns secondary 1062 turns primary for 120 > volt operation). =A0The primary is in four layers of 354 turns each and > can be switched into series or parallel to operate from 10-24 VDC or > 120 VAC. =A0The DC resistance of the secondary is 10,688 ohms. > > Turns ratio counts for less when operating as an induction coil - the > speed at which the field collapses over time counts. =A0AND the > capacitor counts. =A0The coil should "ring" when it fires. =A0Shorted > turns (or iron with thick laminations) impedes the collapse speed, as > well as wasting energy. =A0My coil rings at ~2,000 hertz > > As a step up 120 VAC transformer it produces 7,500 volts, as an > induction coil from 24 volts, more like 50-80 KV (estimated). > > I found the secondary voltage was highest when the 10 amp relay I was > using as an interrupter arced the least (with the wrong value the > output voltage was lower and the contacts burned in short order) > > My first motorcycle ~1966, was a Gilera that used energy transfer > magneto. =A0One coil fed by a coil on the alternator - no battery. =A0The > lights were fed by their own coil with the exception of the brake > light, it was in series with the low voltage =A0ignition circuit when > you stepped on the brake - and the bike would die if the brake light > filament burned out and you used the brakes. =A0(one of its many > endearing idiosyncrasies)
Sounds like a good safety feature got dove tailed in there.
> Honda motorcycles seem to favor transistor switched battery powered > coils with two secondaries for each set of two cylinders.
> Johnson and Evinrude both use energy transfer magneto systems with > dual secondary coils. Or my three outboards do (circa 1987 and > earlier) =A0If you need a coil like that - try a junked outboard.
It might not fit physically but would it work electronically? I just read where the CDI coil for a Honda 100 outboard was only 9K ohms between the two spark plug wires. The coil I have is 30K ohms between the two spark plug wires. If higher resistance =3D> higher voltage in the secondary this would seem to be closer to what an energy transfer system might require. Bret Cahill
<default> wrote in message 
news:cun6s7lvv6u9jp8oik2cg5d90td51b4c0u@4ax.com...
> On Fri, 25 May 2012 16:40:43 -0700 (PDT), Bret Cahill > <Bret_E_Cahill@yahoo.com> wrote: > >>I suspected a CDI coil wouldn't put out enough voltage for the "energy >>transfer" -- the worst misnomer ever -- system and suggested shorting >>out the spark plug electrode on one of the 2 cylinders by pounding the >>gap shut or stuffing it with a bit of foil. >> >>The theory was instead of jumping two gaps it would only need to jump >>one. The lower effective resistance would give a better spark on the >>remaining firing cylinder. The al foil trick worked. It ran on one >>cylinder which seems to confirm my suspicions about the coil as well >>as my test, which may or may not be original. Googling is hard work. >> >>Anyway the engine has two magnetos opposite each other, one for the >>ignition and one for charging the battery. The four magnets are >>equally spaced on the flywheel. >> >>The 2 low voltage magneto coils look about the same and both seem to >>do the same thing to a volt meter when cranked -- admittedly not a >>very scientific indicator. >> >>It seems like it would be possible to just forget about charging a >>battery and wire another CDI coil to the charger coil. >> >>Even simpler would be to tap the plug gaps to half that recommended in >>the specs. >> >>Maybe the fuel efficiency would drop by 20%? Maybe it wouldn't fire >>at all? >> >> >>Bret Cahill >> >> >> >> >> >> >> > The wasted spark is derived from two series connected coils (connected > at the low voltage side in series) or one coil with two secondary > windings; the spark plugs themselves aren't in series. Think about > it - that would take an engine block operating ~20 KV above ground > unless you had spark plugs with two insulated electrodes.
You'd be better off confining your replies to topics where you know what you're talking about. All the "wasted spark" coils I've seen are strung between the 2 plugs and have no chassis connection anywhere between the 2 HT leads emerging from the unit. If you had 2 HT coils sharing the core with the same LT winding; the one feeding the narrowest gap (inequality can happen no matter how good you are with feeler guages) would effectively clamp the spark voltage - one plug would have a good spark (sort of), the other plug would have a very weak or no spark!