No, no election coverage here… we’re talking amps!

I’m surprised that I didn’t remember to do this until last night, namely measure the current draw of various components of the system.

For each measurement below, I first started and ran Buzz until warmed up, mostly so he’d idle without fiddling. Then I shut him off, pulled the fuse feeding the measured equipment and bridged the fuse connection with my ammeter probes. I started the engine and noted the values at idle, while reving and while holding the speed steady at what is currently the highest at which he’ll run smoothly, about 3200 RPM.

As expected from the start, the fuel pump may be the largest draw, coming in at 3.7 to 3.8A. This is also a fairly steady draw, since so long as the engine is running, the fuel pump is on.

The next big draw is the ignition system, coming in at 700mA at idle and 1.6A at speed. I suspect this value will climb at higher RPMs due to the nature of an ignition system. It’s essentially a PWM signal in which the pulse width stays about the same, but since the frequency increases, the apparent percentage gets larger, thus the current draw will go up.

Everything else is almost trivial, but may not be exactly accurate because the low range fuse on my ammeter is apparently blown.

The fuel injector rails draw 70mA each at all speeds. This will probably go up a little as RPMs get higher for similar reasons that the ignition system will draw more, but proportionally, it will still be a low value. Even at 100% duty cycle, each injector would draw a little less than 1A and with this small an engine, 100% duty cycle would pretty much be a hydrolocking degree of flooding.

The ECU itself appeared to draw about 30mA, but that seems low according to the documentation. I would expect it more like 100-200mA. The final measured value is the FIDLE output. One day, I will have a solenoid there, but for now it’s just an LED. The 10A range on my meter would probably not show it, but since the engine was warm, it wasn’t lit anyway so no reading.

All this measuring of current draw made me take note that the headlight was pretty dim while the engine was running. I checked the battery voltage and it was 11.58V, unchanging when either revving the engine or shutting it off. That is extremely unusual. With no charging system, I would expect the voltage to raise a bit when shut off, the load having been removed. If the charging system were working properly, it should raise when reving. I didn’t even see it change with my external charger connected. Hmmmmm

In any case, Buzz is to the point where I can begin tuning the engine in other RPM ranges, though I now also need to get this electrical issue resolved. No juice, no go.