Search

[Adrian Mansell]

Hi All,

I finally got around to measuring the ignition timings vs rpm of the YS CDI ignition and the RCExl ignition supplied by Just Engines (which I believe to be exactly the same unit just badged differently and with a different plug cap).

Measurements were made using a test circuit in place of the magnet sensor, allowing the CDI to be triggered at a known RPM without having to have an engine or motor whirling round.  A scope is then used to monitor the trigger pulse to the CDI and (by ground lead pick-up) the point at which the CDI sparks.  Once you know the RPM and the delay of the spark from the trigger point, you can work out the timing in degrees.

As you can see, the two units are (accepting a bit of measurement error) identical in timing.  Below about 500rpm, the unit has a constant spark delay of about 9.3ms from the trigger.  This is why you set the static timing to the most advanced you want, because when you are slowly rotating by hand 9.3ms is negligible.  Above 500rpm the unit gradually reduces the delay to give a roughly linear increase in advance vs rpm.  By 4200rpm, the unit is at its minimum spark delay of about 6us, which it maintains as the rpm is increased further.

Cheers,

A

[Andy Prime]

Hi All,

I finally got around to measuring the ignition timings vs rpm of the YS CDI ignition and the RCExl ignition supplied by Just Engines (which I believe to be exactly the same unit just badged differently and with a different plug cap).

Measurements were made using a test circuit in place of the magnet sensor, allowing the CDI to be triggered at a known RPM without having to have an engine or motor whirling round.  A scope is then used to monitor the trigger pulse to the CDI and (by ground lead pick-up) the point at which the CDI sparks.  Once you know the RPM and the delay of the spark from the trigger point, you can work out the timing in degrees.

As you can see, the two units are (accepting a bit of measurement error) identical in timing.  Below about 500rpm, the unit has a constant spark delay of about 9.3ms from the trigger.  This is why you set the static timing to the most advanced you want, because when you are slowly rotating by hand 9.3ms is negligible.  Above 500rpm the unit gradually reduces the delay to give a roughly linear increase in advance vs rpm.  By 4200rpm, the unit is at its minimum spark delay of about 6us, which it maintains as the rpm is increased further.

Cheers,

A

Very talented actually I'd say!............................seriously, thanks for sharing Adrian!