[sst1988]

Most dial back timing lights will read DOUBLE the actual timing when using the dial back function on wasted spark engines. If you set the light to 0 degrees, it should read correctly though.

The reason they read double is that the timing light calculates the engine RPM from the igntion pulses and then calculates how long to delay the flash of light based off of RPM so that it takes the desired amount of timing out. What happens on a wastespark car is that since the coils are firing once per rotation instead of once every two rotations, (which is what the timing light is expecting to see) the timing light thinks the engine is spinning twice as fast as it actually is so that the delay time of flash is half as long as what it needs to be. The user then turns the knob more until the timing light lines up with zero, and the value on the timing light is then double the actual ignition timing.

Some timing lights come with wastespark adapters but if you don't have one, just make sure you take this doubling into account or have the light set to 0 degrees when checking timing.

I personally first saw this a couple years ago when I was dynoing a wasted spark engine which seemed to like to idle at 30 degrees timing, or so the timing light led me to believe, with a value of 15 degrees timing in the ECU. I then adjusted the offset in the ECU so that the timing light and ECU read the same timing at idle, like anyone would do. Then, when we began to do pulls, the engine seemed to be down on power unless I had a value of 37-40 degrees of timing in the igntion map. At this point, we knew something was not right so we mechanically checked the position of the crank and cam pickups and used a spare non-dialback light with additional marks scribed on the crank pulley. I then resynced the timing to the ECU and continued the dyno the engine. After that, everything seemed normal so we attributed it to a F'd up timing light.

Now, move forward a few months. Another engine for the same car with sightly different cam and headwork specs on the same exact dyno, with a new dialback light. Same thing happened again!! It was then and there that I had an idea of what was going on. This time I synced the timing with the dial back at double the value, 30 on the light and 15 in the ECU. I then checked it with the non-dial back light and it was spot on.

Looking back, I wish someone had told me about this as it would have saved quite a bit of head scratching and dyno time!!!



i hope this information helps.sst1988