Accurate measurement of very short time duration (millionths of a second) in which the Model T coil operates was not feasible back in the days of the Model T. The venerable Hand Cranked Coil Tester (HCCT) relied on average RMS coil current, which could be accurately measured, as an indirect approximation of coil dwell time to fire spark and coil current variation as an indirect indication of coil firing consistency. The HCCT coil adjustment was a break through achievement in Model T ignition performance that worked remarkably well provided all four coils exhibited similar electrical and physical characteristics. This was despite the fact the HCCT operated at hand cranked speed represents abnormally slow engine speed (60 - 120 RPM) with abnormally low magneto output voltage (3 - 4 Volts) in which the coils were adjusted but never operated in the car. Coils were also never permitted to rest in between firings since the HCCT lacks a timer function. The resulting coil current displayed is averaged over hundreds of sparks rather than the average of the first spark responsible for engine combustion.
Engine performance will suffer when the HCCT is used to adjust coils with differing electrical and/or physical properties such as coil inductance and/or presence of point arcing. Coils with differing coil inductance adjusted for exactly equal average coil current of 1.300A guarantees the coils will have differing dwell times to fire spark and hence, impose ignition timing variation. Similarly, mis-adjusted coil points that exhibit intermittent point arcing and associated ignition timing variation may not be apparent because the coil current is averaged over time. Yet HCCT adjusted coils have been deemed the accepted standard of for satisfactory engine performance for over 100 years.
Today, digital electronics permit highly accurate measurement of current as well as very short time duration and digital memory easily keeps track of measured data. The ECCT utilizes digital electronics and a fast Magneto pulse to directly measure coil peak current and dwell time to fire the first spark responsible for combustion. It does so at high simulated engine speed where ignition timing is most critical and keeps track of each coil firing history to display the coil firing consistency. All 4 coils can be precisely adjusted for equal and consistent firing time of the first spark from rest regardless of coils having differences in electrical or physical properties. ECCT users well know there is a Huge difference between a Model T engine that "runs" and one that runs well. The difference really is akin to a sundial versus digital clock when all other ignition and engine parameters are in good working order. Experience is believing and what made the ECCT the New Standard for Testing and Adjusting Model T Coils.
Judging ECCT Adjusted Coil Performance
The ECCT operates completely different from the HCCT. Do NOT be tempted to judge ECCT adjusted coil performance by testing them in a HCCT. It is like comparing apples and oranges! The only thing that really matters is how well ECCT adjusted coils make your Model T engine perform in your car on the road.