Small Ignition Coil Drive Question

[scottyp]

Has anyone used a coil like this one? It is used on small Honda motorcycle engines and are easy to find on ebay. I would imagine it is tailored for CDI use, and it may not work well with basic points/condenser driving it? It has a 1.2 ohm primary and a 2K ohm secondary. A more standard automotive coil I have here has a 2 ohm primary and a 14K ohm secondary. Opinions, info and ideas?

 

[doc1955]

Not sure they are the same but I used coil packs before I started winding my own coils to reduce the size down to the size of a letter D battery. Here are the ones I used with very good luck at 6v but they are 12v.

https://www.ebay.com/itm/8-Ignition...687899?hash=item3d631a86db:g:dRoAAOSwij5bmGwe

 

[earlwb]

Those small motorcycle or scooter or moped coils do work OK. But with CDI systems, they may be applying a higher voltage such as 40v or 80v even to drive the ignition coil. The main limitation is the voltage needed and the size and weight of them. for stationary or display engines or boat or cars, it is not a problem of course. if you were going to use it in a flying airplane model it might be a issue. It depends on the size of the engine and airplane and whether it can handle the weight or not. Most small motorcycle or scooter coils or moped that used regular non-CDI small coils use 6v DC or 12v DC to run them. You can try 6v DC and see if it works with it or not and bump up the voltage to 12v DC if it doesn't.

I would suggest getting a CDI unit intended for Radio control gas engines. RCEXL comes to mind, but there are other brands too. They run off of 5v to 8.4v depending on the unit specs. They use a hall effect sensor for the timing. You just attach a small magnet as appropriate and set the sensor up close to it.

 

[andrewh]

I’m not fully up to date with current (sorry) small Hondas but when I knew them they used a similar looking coil driven by an LT flywheel magneto, so the applied voltage was probably 2 to 20 volts approx. I have used the C50 coil for many applications, 6, 12 V and several random flywheel mags ( including the dreaded Villiers) with complete succes.
Try it with a small battery and spark plug. Break the circuit and see if you like the size of the spark.

I’m pretty sure that little engines of the world are too cheap to use electronic ignitions in any form

 

[bluejets]

I wrote a complete "how to" using these coils and another readily available "control box" , all available for less than $20.00 but all I received were negative comments.
It does work though and it's in here somewhere.

Try here.......

Model engine CDI easy and cheap
Start at post #1.

 

[earlwb]

I wrote a complete "how to" using these coils and another readily available "control box" , all available for less than $20.00 but all I received were negative comments.
It does work though and it's in here somewhere.

Try here.......

Model engine CDI easy and cheap
Start at post #1.

I missed your previous thread until now. I like your thoughts and ideas.

 

[rutzen]

I found these on eBay. Will this work for a small hit and miss engine?

 

[earlwb]

maybe it would, but it looks more like a magneto kind of a ignition device to me though. So I am not sure. I would go with no it is not suitable unless you are going to use it like a magneto setup. I would need more information about it.

Something like the EMGO 6v ignition coil would be the more traditional approach for ignition. It uses a make or break contact system that could use hall effect sensors too. They are selling 6v and 12v ones on Ebay and in different sizes.

 

[scottyp]

Sorry guys, I was busy yesterday with other things. Thanks for the input. I think I remember seeing bluejets thread but didn’t and haven’t gotten through all of it yet. I hope to do a bit of experimenting later today.

 

[scottyp]

So, for the coil in question, I connected a buzz drive circuit to it and at 12 volts, it really didn't have any spark, I ran it at ~25 volts and had a spark, but is was not very strong. I'm with Earl and Blue that this coil wants to be driven via a CDI module. I was just hoping that I would get lucky and be able to use it as it is since it is nice and small. Doc's coil suggestion looks good, I may give that a try also.

 

[bluejets]

Has anyone used a coil like this one? It is used on small Honda motorcycle engines and are easy to find on ebay. I would imagine it is tailored for CDI use, and it may not work well with basic points/condenser driving it? It has a 1.2 ohm primary and a 2K ohm secondary. A more standard automotive coil I have here has a 2 ohm primary and a 14K ohm secondary. Opinions, info and ideas?

Has anyone used a coil like this one? It is used on small Honda motorcycle engines and are easy to find on ebay. I would imagine it is tailored for CDI use, and it may not work well with basic points/condenser driving it? It has a 1.2 ohm primary and a 2K ohm secondary. A more standard automotive coil I have here has a 2 ohm primary and a 14K ohm secondary. Opinions, info and ideas?

These GY6 coils are strictly CDI (around 300-400V primary) and will not work in any way on a set of points.
Friend of mine tried it before he asked me about it and burnt the guts out of the coil before he could blink.

Doc had a Ford BA Falcon type coil which he used a resistor bank of somewhere around 3.5Ohm and 5W to run it on a 6v battery and points or electronic switcher.
His electronic unit was a trembler but no different to using points and a condensor as per standard kettering system.
I tracked down a second hand one and tried it and it will run on a 3.7v LiPo cell (18650 type) without the use of any resistor bank quite well.
Never managed to get around to trying it on an engine though.
Ignition Coil Fit For Ford Falcon Fairmont Fairlane LTD BA BF XR6 Territory SY SX 6pcs

I believe the DC type 4 pin CDI boxes I used originally are still available on Ebay etc. although price is slightly higher now.
You may have to ship around for a good price.
4 Pin CDI DC Fired High Quality CDI CDI Box Replacement for Bikes for Scooters | eBay

 

[earlwb]

I remember a number of years ago measuring the voltage driving a GY6 type coil and I was seeing 135v pulse levels. That was on a Chinese scooter with a 250cc engine Linhai copy of the Yamaha engine at the time. Plus I got the same thing on a Chinese Roketa 150cc scooter using a copy of the GY6 motor too.

Anyway, it would be easy to just get a scooter/motorcycle CDI unit and use it with the Gy6 coil.

But one could simply get a RC model gas engine CDI unit. it has the coil built in . The current new models are really small too. The current ones uses 4.8v to 8.4 volts. You have a power in servo plug connector and another connector for the hall effect sensor. One could use it with mechanical points by making a transistor circuit to shape the pulses for it. These come in several types, depending on the spark plug size you want and whether you want a straight or angled spark plug cap.
For example:
https://www.ebay.com/itm/Rcexl-Sing...879306?hash=item43fe37cf8a:g:sMEAAOSwTuJYojVw

 

[Cogsy]

I remember a number of years ago measuring the voltage driving a GY6 type coil and I was seeing 135v pulse levels. That was on a Chinese scooter with a 250cc engine Linhai copy of the Yamaha engine at the time. Plus I got the same thing on a Chinese Roketa 150cc scooter using a copy of the GY6 motor too.

Anyway, it would be easy to just get a scooter/motorcycle CDI unit and use it with the Gy6 coil.

But one could simply get a RC model gas engine CDI unit. it has the coil built in . The current new models are really small too. The current ones uses 4.8v to 8.4 volts. You have a power in servo plug connector and another connector for the hall effect sensor. One could use it with mechanical points by making a transistor circuit to shape the pulses for it. These come in several types, depending on the spark plug size you want and whether you want a straight or angled spark plug cap.
For example:
https://www.ebay.com/itm/Rcexl-Sing...879306?hash=item43fe37cf8a:g:sMEAAOSwTuJYojVw

I've used the cheaper clone of this sort of ignition with points without any modification on an engine I built for my father. I'd have to have another look at it to see exactly how I wired the points in place of the hall sensor but I definitely didn't use any other hardware (transistors, etc). I also forget how I found out that you could use points...

 

[earlwb]

yeah, one can use points. You can use 5v for powering it. The Hall effect sensor device is basically a transistor with a open collector output. The CDI unit typically has a pull up resistor built into it. Thus with a RCEXL unit one ought to be able to simply run the red wire to the contact points, the black wire would be to ground on the points. Other types of CDI units would likely be the same. The transistor circuit was to clean up the signal to make it more like nice electrical pulses for the CDI unit. But one may not need it.

 

[bluejets]

But one could simply get a RC model gas engine CDI unit. it has the coil built in

Not for less than $20.00 which is what the DC Cdi unit and GY6 coil can be from some suppliers.
More like the $80 to $90 mark for the Rcexl.
As for the hv levels, I imagine your measurement depends on how you measured the 135v.
Most systems this is insufficient energy for firing under compression and I'm guessing it was an average reading.

 

[earlwb]

That was a 135v pulse applied to the primary coil of the ignition coil. yes some coils do use a higher voltage pulse. The higher the voltage the smaller the coil can be made. With modern cars the coils are actually individual for each cylinder and spark plug and the coil is really small so it can fit down into the engine head on top of the spark plug.

 

[doc1955]

I was looking back at some of my old videos and here is one that I am using a 6v battery on a auto coil pack and the spark I get out of it. lol

 

[earlwb]

Yeah those old 6v motorcycle/moped/scooter coils are lots of fun. I used one in a buzz box for starting pulse jet engines.

 

[doc1955]

Yeah those old 6v motorcycle/moped/scooter coils are lots of fun. I used one in a buzz box for starting pulse jet engines.

The coil used was a Ford 12v coil pack.

 

[Misterg]

Not for less than $20.00 which is what the DC Cdi unit and GY6 coil can be from some suppliers.
More like the $80 to $90 mark for the Rcexl.

Not <$20, but less than $80 or $90

$34.83 Delivered

Generates a huge spark (20mm+ in air) and works in my little hit and miss engine (although I did kill one Hall sensor).
They also deliver to UK / Europe (it is £28.21 delivered to the UK).