S/S CDI

[gbravo]

Anybody knows if is possible to connect the S/S CDI module with two spark plugs (both spark plugs fire together), using only one hall sensor, connecting two coils to the CDI board or the sensor with two boards and two coils?

This application is for a two cylinders boxer model engine with Rimfire Viper spark plugs.
Thanks,
German

 

[Admiral_dk]

That's way to do it, is to have a ignition coil where both ends are "exposed", so they both are connected to a sparkplug - it's the way ALL older Japanese inline-fours are done - one coil for cylinder 1 & 4 and another coil for cylinder 2 & 3.

I haven't got a clue if S/S has such coils, but if not, then their competition has.

Per

 

[stevehuckss396]

Contact Roy directly on his website. He is a very nice guy and will respond. He really knows his ignitions and if what you want to do is possible, he will know how to do it.

http://www.cncengines.com/

 

[Dave G]

I purchased a waste fire system from Roy last year at Zaneville, It's the same system he normally sells but he uses 2 coils instead of one. I have yet to try it but have had good luck with all of his products in the past. Up until Roy having his systems available I would use a coil from a 2 or 4 cyl motorcycle as stated in the previous post. Dave

 

[gbravo]

Yes I have sent this question to Roy.
My engine is a replica of BWM R7 motorcycle engine with two cylinders in boxer configuration, for this I bought the CDI system from Cncengines, I connected both spark plugs to the coil included in the board, but despite you can see both spark plus firing, the engine don´t start, unless unplug one spark plug and run the engine with one cylinder only.

My original question was if anyone has used the system from Cncengines with two spark plugs and only a Hall sensor and how is the connection.

I like this CDI because the coil is very small and you can place it inside the upper part of the engine, where the coils and start engine is located in the original engine.

I hope you can understand me in my bad English.
Thanks,
GErman

 

[Dave G]

Hi German, If you are trying to fire 2 sparkplugs with one coil I think you are going to have trouble as the sparkplug under compression will be much more difficult to fire than the sparkplug that isn't under compression. Waste fire systems will either have two coils or one coil with two high tension leads coming from it. Both plugs will fire at the same time with one cylinder firing at the top of the compression stroke and the other cylinder will fire during the overlap of the valve timing events. This will only work if your engine is designed to fire the plugs at 360 degrees of crank rotation from each other. Roy's waste fire system only uses one hall effect sensor and one magnet to fire both plugs at the same time. Try to keep the magnet and sensor away from anything that conducts magnetism on installation and away from the high tension leads. I hope this helps and by the way, WE NEED PICTURES. Dave

 

[gbravo]

You wrote: "Roy's waste fire system only uses one hall effect sensor and one magnet to fire both plugs at the same time."

This is my doubt,
one hall sensor, one magnet, one board and two coils
or
one hall sensor, one magnet, two boards and two coils

I will prepare some pictures.

 

[Admiral_dk]

I've been looking at the S/S CDI site and he isn't showing ANY waste fire ignition sets as such ... :-( ... Except maybe : RCEXL TWIN CYLINDER CDI SYSTEM

There's a cheat way of trying to get it to run. Connect the high-tension lead from the ignition coil to one sparkplug and connect the center electrode on the other sparkplug to the ground part of the ignition circuit - remember NOT to connet the rest of the engine to the ignition circuit. This way one ignition coil with only one high-tension connection, will be able to fire two plugs. BUT it WILL generate a lot of EMI noise and is therefor NOT a permanent solution - that said, try it to see if you can make it run on both cylinders.

Oh .... and th_wwp I'm a Suzuki owner, but would very much like to see a small Beemer.

 

[Ken I]

Those "Waste Fire" coils are duplex - ie two HT windings about a single primary.

Using a single HT in one plug through the engine and out the other raises almighty voltages on the engine differential to anything else you might have bolted on to it - points - hall sensor etc.

See this thread - Allthumbs had a a lot of trouble starting his motor until he changed to a duplex coil.

http://www.homemodelenginemachinist.com/index.php?topic=11421.15

Regards,
Ken

 

[gbravo]

This is the replay from Roy:
" I have recently had two modelers successfully use one of our single spark CDI systems on twin cylinder waste spark engines. What I did was leave the ground wire off from the secondary back to the ground on the board. They used 2 spark plug wires, 1 on each of the spark coil terminals ( this does not use a ground wire ) to each of the spark plugs. The ground path is through the engine from one spark plug to the other. In both cases this worked very well on their engines"

I will try this connection and inform you about my results.
Also I will prepare some set of pictures for introduce my engine.

 

[Ken I]

All very well if you can keep you coil ground off the motor (or even close to it) but since this ground is likely to be common to other parts of your circuit mounted on the motor - even if "insulated" from the motor - will be subjected to differentials of 25kV - way more than most 12V insulation systems can stand.

It is certainly possible - but problematical.

Ken

 

[Admiral_dk]

Well I warned that it wouldn't be a final solution, but just a way to test if the engine will run on both cylinders and I'll wholeheartedly agree with Ken - DO NOT use it as a final solution !!!!

 

[gbravo]

I order another coil to cncengines.
How you recommend to connect the second coil (with the primary in serie or in parallel)?
German

 

[Ken I]

Connect the primarys in parallel.

Good luck.

Ken

 

[gbravo]

I purchased a waste fire system from Roy last year at Zaneville, It's the same system he normally sells but he uses 2 coils instead of one. I have yet to try it but have had good luck with all of his products in the past. Up until Roy having his systems available I would use a coil from a 2 or 4 cyl motorcycle as stated in the previous post. Dave

Dave,
The "same system he normally sells " mentioned in your post is the Wysiwyg Board with two High Voltage Spark Coils from Cncengines?