This is more of a theoretical question. I'm not looking to troubleshoot, just learn more about the bikes. How does the ignition system know that the engine is under load?
Hmm a trick question?
An ignition trigger can know about RPM due to the frequency of its triggering. I don't think it does know about developed engine power.
There is a lot I don't know about the Boyer Brandson ignition. Got a schematic reference to post?
It's possible it may draw more power at higher switching speeds. The switch device inside may have slow on-off or off-on switch times. Or worse asymmetrical switch times, that can effect the duty cycle of the power used. Like if it turns on fast but turns off slow. The effective duty cycle then changes with frequency.
Contrary to previously posted misconceptions, duty cycle (ratio of on to off states) should remain constant throughout frequency changes. It doesn't matter if you flip your light switch every two days or two hours during a given month, at the end of a 30 day billing cycle you will be charged for 15 days of lighting power.
Does the Boyer Brandson still use the mechanical advance? By counting the pulses per unit of time, it's possible for a unit to change the pulse timing start and duration in a relational manner. IE, electronic advance curves, and ignition coil charge durations.
A while back, I popped the main fuse under high load, twice going up steep hills. Why would an extra load on the engine cause a spike in alternator amperage (I'm assuming that must be what popped the fuse).
Sounds like troubleshooting, you sly trickster.
Be aware that assumptions can interfere with good troubleshooting practise. The alternator can only provide more amperage if the load demands it. Also, be aware that the charging system is NOT fused between it and the battery. The main fuse is situated between the battery and the bikes load devices. Also, consider that your fuse issue may not be related to the ignition system.
I notice increased vibration with high power settings. I also imagine the battery will be closer to the 14.5V charging cutoff point while the engine is reving for awhile.
A couple more things I don't know:
1. The main fuse rating. What is yours?
2. The total electrical load going through the main fuse. Do you know?
Have you made any electrical load changes to the bike besides the ignition module? Halogen headlight? Brighter bulbs anywhere else?
Did you increase main fuse rating to correspond to with lighting energy consumption increases?
Why do I ask?
The resistance load of the bike does not change with engine power. However, its current usage can change with voltage. If the bike is using say 13 amps at 13 v system voltage, ohm's (R=E/I) law says that the resistance of the bike electrical components is 1 ohm. Raise the voltage to 14.5 and the current will be 14.5 amps (I= E/R). What's your fuse rating?
The fuse is designed to melt at about 120% of its current rating due to the heat created in the fusible material. Running the fuse close to its rating still heats the fuse metal. The heat makes the metal softer and it becomes more susceptible to damage from vibration. Such as the what comes from the power pulses of the engine under heavy power.
If I recall correctly, fusible links are usually selected by the circuit designer to operate at about 60% of their rating, assuming some kind of air cooling around it to exchange the heat generated within. A 15 amp main fuse shouldn't have more than about 10 amps flowing through it under normal circumstances.
I know your Boyer brandson unit draws more power than points do. But, I've no data to know how much more. Do you know what your total current draw through your main fuse is?
It's just a theory.
Cheers,
