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[Count Johnny]

Hi Frank. For reason I shan't bore you with, I run my Enfield batteryless with a Boyer Power Box so - ahead of some night runs in the summer - I am trying to optimise my electrical systems, on paper. The only electrics that I run are a headlight, stop/tail light and (obviously) ignition - which is a Boyer Micro Digital unit and standard coil. My stop/tail light is now an LED unit that draws a maximum of 0.27amps but - until Classic Dynamos come up with their H4 replacement LED light (that actually uses the parabolic reflector and lights the road (which all of the other H4 LED replacements do not) - I am going to have to run a 35 watt H4 bulb. I'm in the process of upgrading to the higher output alternator, which I suspect will put me on the right side of things, but I like to know have a handle on things in advance. My reason for asking why ignition amps might reduce as engine speed increases is merely because, having been told that something is true (as Boyer have) I like to know why.

[Frank]

Well I think it's been shown why it draws less when it is running but I can't see why it decreases further with engine speed, unless the Boyer is altering something such as the switching period according to revs. One thing is sure though, you won't eliminate that drain unless fitting a set of pedals is another mod on your list!

[Count Johnny]

Heh, heh...I'll certainly consider your pedal suggestion, Frank. But right now (at 1000rpm) I reckon I'll get 7.63 amps from the alternator, with a current draw of (say) 1.5 amps, ignition; 2.92 amps, headlight; 0.21 amps, stoplight; giving me a balance of 3 amps - even if I ride everywhere on full beam with my foot on the brake. When I've got it all hooked up and running in the real world, I'll run some tests and post them up here.

[Dennis C]

"ignition - which is a Boyer Micro Digital unit and standard coil."

That is a whole different ball game from the standard points system and a lot that has been said on this thread is irrelevent and relates to points systems.

The Boyer system draws current from the moment it is turned on but the coil draws none whilst the engine is stationary regardless of crank position as the coil is switched by pulses from the Boyer which give the required momentary AC pulse and the coil only draws current with the engine spinning, due to the Boyer design it is quite possible that the dwell angle varies causing a variation in current draw as revs increase. You need to talk to Boyer for info on this.

[Count Johnny]

Hi Dennis. As I think I mentioned, earlier, my initial entry into this subject was based upon an article that related to a coil and points set up, on a motorcycle, which stated that the coil was drawing "[static, ignition on]... 2.5 amperes of current. At idle, average current flow was 1.4 amps, and at 4500rpm, flow was 1.2 amps". All of this seemed counter-intuitive - to a dunce like me - hence my question. I have, you'll be pleased to hear, been troubling Boyer on this subject who tell me that "...with the standard coil on a micro digital system the coil current is around 3 amps on first turn on and then around 1 amp running. The unit turning off after a few seconds if not triggered". In case it's of any use to anyone, they also told me the following about their Micro Power system with their matched coil "...the coil is only 0.6 ohm but first pulse will be around 6-8 amps and then the computer gives it very short pulses with average of around 1.0 amp when running. The electronics draw around 50mA".

[JTL]

Dennis C .. after re-reading the thread I noticed your comments on hot sparks and plugs. I get your point on not seeking too hot a spark to prevent pitting the piston; even holing it. All the tech comments on coil current is very interesting, but above my understanding of electrics at the moment. So they will be printed for future studies... But I still have questions about spark quality. I will start another thread on sparks and plugs. Hope you will take the time to share your knowledge... Jacob