How could this device determine "cylinder power balance"?
IIRC, there is an inductive pickup on #1 spark plug lead and clips for coil + and -. It would short out the coil on the cylinder that you selected so the plug did not fire. "Balance" was simply checking for consistent RPM drop for each cylinder.
The real benefit was being able to look at the secondary voltage (pickup on the coil lead ?) and compare it to all of the others
(it had 2 display modes; 1 cylinder after another and "stacked"). Different parts of each cylinders wave form corresponded to different things happening in the ignition secondary. Peak coil voltage, distributor cap contact/arc health, plug wires and spark plug health. Good techs could spot a lot of issues.
Of course, does any production engine built in the past 10 years use a single coil/distributor ?
Is the unit in this video clip real, or just a film prop?
Not Sun. Different brand.