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

[Bret Cahill]

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

[m II]

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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






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[Tim Wescott]

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

[default]

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.

[Bret Cahill]

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).  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.

How linear was the output from the secondary compared to the input to
the primary?


Bret Cahill

[Jasen Betts]

On 2012-05-28, Bret Cahill <Bret_E...@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;  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.

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to ne...@netfront.net ---

[default]

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.

[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.
>
> > 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

[Bret Cahill]

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.  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)

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)  If 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 => higher voltage in the secondary this would seem
to be closer to what an energy transfer system might require.


Bret Cahill

[Ian Field]

<default> wrote in message
news:cun6s7lvv6u9jp8oi...@4ax.com...

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!

[m II]

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Ian Field wrote:

> 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.

Except for the engine block metal in between the two plugs. That is
part of the series circuit.....

'coil end 1'...plug...metal...plug...'coil end 2'

mike






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[Ian Field]

"m II" <C...@in.the.hat> wrote in message news:jq97de$i3p$1...@dont-email.me...

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> Hash: SHA1
>
> Ian Field wrote:
>
>> 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.
>
>
> Except for the engine block metal in between the two plugs. That is
> part of the series circuit.....
>
> 'coil end 1'...plug...metal...plug...'coil end 2'

I assumed that would be obvious to all but the very thickest of dumbasses.

[default]

On Wed, 30 May 2012 16:26:17 -0700 (PDT), Bret Cahill
<BretC...@peoplepc.com> wrote:

>I meant "does doubling the voltage in the primary double the voltage
>in the secondary?"

Not in the standard Kettering, or any system that depends on the
collapsing magnetic field to produce the voltage spike.

With more voltage you could saturate the iron faster so the "dwell"
time could be less (translates to a hotter high RPM spark).
Eventually you run up against iron saturation as the limiting factor.
Higher voltage increases the ampere-turns and magnetic field strength.

You are thinking transformers and applying that to induction coils -
two different animals.

Now something like a CDI where you operate the coil like a pulse
transformer would seem to benefit from increased primary voltage.

>>the bike would die if the brake light
>> filament burned out and you used the brakes.  (one of its many
>> endearing idiosyncrasies)

>Sounds like a good safety feature got dove tailed in there.

As far as letting you know the light is out - a resounding YES, but
it wasn't easy, or safe, to drive very far that way, particularly in
traffic on hills.

>> 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.
>
>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 => higher voltage in the secondary this would seem
>to be closer to what an energy transfer system might require.

I don't think you can put too much trust in DC resistance values. A
high secondary resistance might suggest a lot of turns of very fine
wire, and that would probably be a Kettering system coil where
inductive collapse is the means of producing high voltage. If the
system is run as a pulse transformer, turns ratio would seem to count
for more - that is a relatively few turns in the primary and lot in
the secondary (something all systems have but I'm talking an order of
magnitude fewer primary turns, so they might use larger diameter
secondary wire with fewer turns)

When all is said and done, it is the energy in the spark that
initiates ignition, not the voltage. A high current spark of 4,000
volts may outshine a low current 30 KV spark.

Did you also measure from the coil secondaries to ground? My Honda
coils have a bare wire that runs from the molded epoxy housing to the
core iron and it is painted black along with the iron - secondary is
center tapped to ground (at least when bolted to the frame).

And Honda calls it "CDI" but it runs from the battery and the modules
that do the switching aren't very large - they are ~1" X 1-1/4" X 3/8"
and it is obvious that most of the room inside the things are potting
epoxy and large diameter wires (relative to the size of the module).
It seems way too small to actually step up voltage to charge a cap to
fire the coils.

Here is a url for a site that may help a little...
http://gardentractorpullingtips.com/ignition.htm


http://www.cx500.50webs.com/
"How to Build a 1980 Honda CX500C CDI Module"

with schematic

[default]

Obviously you've never seen a BMW motorcycle ignition or a Honda with
a grounded twin secondary coil? Pull one coil wire loose and the four
cylinder engine runs on three cylinders - not two.

[default]

On Fri, 01 Jun 2012 12:38:32 -0400, default wrote:

>
>
>http://www.cx500.50webs.com/
>"How to Build a 1980 Honda CX500C CDI Module"
>
>with schematic

After looking at it ... I'm wondering if they are using the inductive
kick of the coil primary to charge the capacitor to a higher than
battery voltage.

[Bret Cahill]

> >http://www.cx500.50webs.com/
> >"How to Build a 1980 Honda CX500C CDI Module"
>
> >with schematic
>
> After looking at it ...  I'm wondering if they are using the inductive
> kick of the coil primary to charge the capacitor to a higher than
> battery voltage.

At least some CDIs step up from 12 V to 400 V in the CDI module. If
it's 12 V DC then there's an inverter as well which is why DC CDIs are
often larger than AC CDIs.

The coil we're using is only slightly small than the original and
there 30K ohms between the two plug wires. A CDI coil might be
significantly smaller and have lower resistance.

Is there any difference between a "pulsar" and a low voltage magneto?
It might be easier to omit the points and go to CDI.


Bret Cahill

[Jamie]

Interesting blog here.

A few years ago, I assisted a person that was restoring an old car.

I gave him a circuit that involved using a 555 timer with a few other
components to current sense and trigger the coil. He was using the
standard auto transformer style of collapsing the field. If you monitor
the current (Dwell Time) in the circuit, you can pretty much dictate the
level of spark you need. Putting in a PTC also helped to lower the spark
level when the engine was hot.

Monitoring the current in the primary side of the coil will allow you
to adjust your dwell time and thus when design properly will also give
you timing control, all in one..

Jamie

[default]

I don't know what a pulsar is - some manufacturer's name for
something?

If you read that URL for small engines he shows how to adapt various
car type solid state ignitions with pickup coils to old points type
small engines. Nothing looks too easy (to me) but that might all
depend on what type engine you have.

Briggs and Stratton did, and probably still do, have a retro-fit for
magneto coils so that the points are solid state. I haven't messed
with it myself.

[Ian Field]

"Jamie" <jamie_ka1lpa_not_v...@charter.net> wrote in message
news:kr7yr.30447$x11....@newsfe21.iad...

At various times I've tried all kinds of circuits for transistor assisted
contactor - every single one failed due to the lack of "wetting current",
oxide, tarnish or whtever insulated the points faces before I got as far as
the end of the road.

The most successful version to date used a high voltage MOSFET (from flyback
switcher PSU in 19" monitor) used in basically grounded base mode.

The coil lead was removed from the points abd connected to drain, the gate
was connected to +12V and the source connected to the points. A suitable
capacitor was found to put directly in parallel with the LT winding and a
zener was added to clamp the G/S voltage.

With the conventional coil/points arrangement, the points capacitor slows
the Dv/Dt so the spark quenches sooner as the points part, but the spark
still lasts long enough to waste significant energy - with the grounded gate
MOSFET the points voltage never exceeds 12V. Grounded gate is the fastest
configuration so the coil current is interrupted orders of magnitude faster
(you do need that capacitor!).

Not sure what the usual practice elsewhere, but on kettering ign honda
motorcycles, they usually wind the LT coil with wire having a strong PTC. A
sample coil drew 8A when connected to a 12V battery, but the reading sank
steadily untill it levelled out at 4A as the coil became warm - where
motorcycle coils are mounted gets a good airflow once underway, so they're
well cooled at normal commuting speeds.

[m II]

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Ian Field wrote:

> I assumed that would be obvious to all but the very thickest of
> dumbasses.

I should have realized this was just another of your many, ill-formed
personalities. Feel the pity.

mike










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[Jim Thompson]

On Fri, 01 Jun 2012 20:54:45 -0600, m II <C...@in.the.hat> wrote:

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>
>
>
>Ian Field wrote:
>
>> I assumed that would be obvious to all but the very thickest of
>> dumbasses.
>
>
>I should have realized this was just another of your many, ill-formed
>personalities. Feel the pity.
>
>mike
>

Ian Field is a Larkin boot-licker... behavior just as you'd expect.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

[Ian Field]

"Jim Thompson" <To-Email-Use-Th...@On-My-Web-Site.com> wrote in
message news:34fks7le7odmg9b93...@4ax.com...

> On Fri, 01 Jun 2012 20:54:45 -0600, m II <C...@in.the.hat> wrote:
>
>>-----BEGIN PGP SIGNED MESSAGE-----
>>Hash: SHA1
>>
>>
>>
>>Ian Field wrote:
>>
>>> I assumed that would be obvious to all but the very thickest of
>>> dumbasses.
>>
>>
>>I should have realized this was just another of your many, ill-formed
>>personalities. Feel the pity.
>>
>>mike
>>
>
> Ian Field is a Larkin boot-licker... behavior just as you'd expect.
>
> ...Jim Thompson

JT is a bitter twisted old nut job who's taken to ripping on me any chance
he gets - just ignore him and hope he goes away.

[dsdieboldt...@gmail.com]

The problem is the load, the empty cylinder is not the load, the system is also + and - (single platinum plugs with only the anode or cathode coated installed wrong cause crazy issues and created dibble plats) the system also works on standard i=r/o iirc on voltage needed to bridge the biggest resistance will generate voltage when the field collapsed and set amps and volts for proper heat.

To increase the voltage in the furring cylinder the waste cylinder has to have resistance higher. Then you run two resistance in a series formula. You also need to know the polarity on the leads and electron flow to determine which gets voltage first and if it should be modified for resistance.

Also ignition coils are a field collapse system and only supply voltage based on the need of the resistance. So it might say it’s a 80kv coil but if only 12kv is needed then that’s all it supplies. At 7k rpm in Death Valley 50k might be generated.

[default]

I'm having trouble understanding what you are doing, but wasted spark
systems do work and have been around a long time. It sounds like you
want to run one coil to fire two plugs? That won't work.

You either need two 6 V coils in series or a 12V motorcycle coil which
has two high voltage windings.

[Bret Cahill]

I vaguely remember wasted spark and 2 magnetos but it's like out of one of those REM dreams that make you want to get out of bed in the morning.

I'm going over everything that I was doing back then but I cannot remember the engine that prompted the OP.

The question is always there: Is there a "normal" or "correct" state of mind?


Bret Cahill


"What a feeble thing is human reason. A thing is either true or false. Before I was poor and now I am rich. Changing my lifestyle is OK, but please, leave my judgment alone."

-- Tocqueville

"The errors of great minds are more fruitful than the truths of little minds."

-- Nietzsche

[default]

On Mon, 26 Feb 2018 20:59:58 -0800 (PST), Bret Cahill
<bretc...@aol.com> wrote:

>I vaguely remember wasted spark and 2 magnetos but it's like out of one of those REM dreams that make you want to get out of bed in the morning.

Early BMW motorcycles used a magneto with two high tension windings,
and a wasted spark.

Small planes use two magnetos firing two plugs per cylinder through a
distributor(s).

>
>I'm going over everything that I was doing back then but I cannot remember the engine that prompted the OP.
>
>The question is always there: Is there a "normal" or "correct" state of mind?
>

Can't help you with the existential ruminations... Most folks just
pick a religion and allow themselves to be led by the nose through the
morass of philosophical cogitation.

[Abandoned Trolley]

> ---
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Wasted spark coils are as common as muck these days. Ford have been
using them on Mondeo and Focus models for at least 20 years. The "coil
pack" has 2 separate primary windings and 4 secondary windings (for 4
cylinder motors)

I would be surprised if other mass market car makers have not followed
suit, and I have a feeling that they are even more common on motorcycles.

and ... technically speaking the Briggs and Stratton single cylinder
motor on my lawnmower has a wasted spark. The cam for the contact
breaker is direct on the crankshaft - even though its a 4 stroke motor.

Also, using 2 distributors to fire 2 plugs per cylinder is not confined
to planes - in the distant past both Alfa Romeo and Aston Martin have
fitted systems on road cars. Ferrari have also had a crack at it, but I
am not sure if the vehicles involved could be called road cars.

Long story short ... if you look in the local scrapyard you should be
able to find plenty of material to experiment with.


Have fun ...

AT