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Ignition systems
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Circlotron:

--- Quote from: HighVoltage on October 01, 2021, 04:44:40 pm ---
--- Quote from: SeanB on October 01, 2021, 02:52:31 pm ---Going to guess that is for multipulse ignition, for ultra lean operation, so you will have enough spark to ignite the fuel mix, even if the plug area is transiently non combustible, you have enough high energy sparks that the lean mix will strike before TDC and complete combustion to a large degree.


--- End quote ---

Yes, Multi Pulse is another reason to have an ultra fast charge time.

To get the combustion more stabilized, the spark current must be increased.
Especially for lean burn mixtures, a higher spark current is required.

Spark duration has become secondary in modern systems and long spark duration are a relic in the past.

--- End quote ---
With older engines at least, long spark duration was considered desirable.
What size plug gap is your new coil meant to be used with, and what is present day thinking on this?
HighVoltage:

--- Quote from: Circlotron on October 02, 2021, 11:59:35 am ---With older engines at least, long spark duration was considered desirable.
What size plug gap is your new coil meant to be used with, and what is present day thinking on this?

--- End quote ---

Yes, you are correct, it was desired but why?
We always believed this myth. But University research out of the early 80s has shown that this is not correct.

The longest spark duration I had measured was 3 ms
Imagine an engine running at 6000 RPM = 100 Hz = 36 degree crank angle / ms
So, even a 1ms long spark would last for 36 degree crank angle.

Lets say that same engine has a spark advance of 30 degree before TDC
If you retard this spark advance only a few degree, the engine looses power dramatically.
Only the first few 100 us are responsible for a good ignition process.
You can force a long duration spark to stop at shorter duration and it makes no difference for the engine.

Even in the old days, with old style ignition systems it was the case.
Porsche had a stock CDI in some 911 engines with 500us spark duration and they had full power and no problems. At the same time, GM had the HEI with over 2ms spark duration.
I think the inductive system got stronger and stronger with higher currents on the primary and automatically the secondary windings and the secondary inductance increased. And because of the large secondary L, the long spark duration followed as a consequence.

On the new coils, the spark gab will stay at 0.8 mm.
One important aspect is the ion measurement across the spark gap and the analysis for each spark.
There is more software in a modern coil these days as hardware. :-DD
themadhippy:

--- Quote ---On coils....  however they claimed that on some bikes at least, they use different sized coils and power different things from each coil.

I'm just not sure how true this is or how common it is.
--- End quote ---
don't know about modern bikes,but it was certainly true on the  some of the bikes  i had in the past.On my ole z200 it came in handy to get the thing home when the cam bearing started to wear out,turning on high beam made the engine work harder,putting more tension on the timing chain.
Benta:

--- Quote from: themadhippy on October 02, 2021, 01:11:14 pm ---
--- Quote ---On coils....  however they claimed that on some bikes at least, they use different sized coils and power different things from each coil.

I'm just not sure how true this is or how common it is.
--- End quote ---
don't know about modern bikes,but it was certainly true on the  some of the bikes  i had in the past.On my ole z200 it came in handy to get the thing home when the cam bearing started to wear out,turning on high beam made the engine work harder,putting more tension on the timing chain.

--- End quote ---

??? Your magneto was on the cam shaft? What kind of bike was this? The ones I know of have it on the crank shaft.
themadhippy:

--- Quote ---Your magneto was on the cam shaft? What kind of bike was this? The ones I know of have it on the crank shaft
--- End quote ---
no,the cam bearing was worn,causing the timing  chain  that drove the points to go slack ,putting more load on the engine, by turning on the headlights , took enough slack out to get me home.I discovered the "cure" when i hit the indicators to pull over as the engine was dying and dam thing started running again,turning  off the indicators  and the engine started to die.
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