Spark energy and duration

[FredWinterburn]

What Modok said. With an inductive system the vast majority of spark energy and power comes within the first 100µS. The rest of the energy probably won't do much ignite fuel unless the spark is blown out and a second powerful but less energetic spark forms with whatever energy is left in the coil. On the topic of zeners to simulate a spark gap, I really don't think it tells you much except for comparison purposes between inductive ignitions. The zener string will prolong the apparent spark duration by holding the voltage up, thus limiting the current. Definitely it would make a better scope trace for measuring energy, but otherwise the scope image will be very misleading because it does not simulate a real spark profile. Fred

How do I figure out how much spark energy I actually have in the spark if I know the system voltage and the dwell time?

Only knowing system voltage and dwell time is not enough information. I have measured coil energy using 1500 volts worth of zener diodes to simulate the voltage drop of a spark, and got my scope to display the integral of the voltage x current during the arc time. Not all scopes have that function. Somewhat similar method to what I used is detailed below.

http://dtec.net.au/Ignition%20Coil%20En ... esting.htm