Waste spark system??????

[sst1988]

No Spark Line, Open Spark Plug Cables. are parade and raster patterns with no spark lines. These are more examples of open-circuit conditions, which usually indicate disconnected or open plug cables.

Long, Low Spark Line, Few Coil Oscillations: Fouled Plug or Shorted Coil. are raster and parade patterns that show a long, low spark line and few oscillations for one coil. This usually indicates a badly fouled plug or plugs, or a shorted coil.

High, Short Spark Line: Lean Mixture or Wide Plug Gap. Figs. are raster and parade patterns that show a high, short spark line for one coil. This is a common sign of a lean mixture or very wide plug gap in one or both cylinders for that coil. If the problem is a lean mixture, it may be due to a vacuum leak that affects only one cylinder.
Mistakes To Avoid Jumping Spark Line. an unstable spark line for one coil. It appears to jump up and down at random. This is often caused by a sticking or worn valve in one cylinder that causes an uneven air/fuel ratio.

Upward-Sloping Spark a spark line for one coil that slopes upward as it ends. This is similar to the jumping spark line , but usually indicates sticking or floating valves if it appears at all speeds. It also can indicate burned valves, wide plug gaps or a vacuum leak that affects several cylinders.

False Trigger: Bad Crankshaft or Camshaft Sensor. is a raster pattern with a false trigger signal on the waveform for one coil. This may indicate a bad crank or cam sensor, and may appear randomly for various cylinders. Other causes may be a bad ignition module, radio frequency interference (RFI) with the ignition module, shorted sensor wiring or a dirty or bent trigger wheel for the sensor.

Check Waste-Spark on Parade

To close this report, we'll point out an extra feature of digital lab scopes that split the superimposed waste-spark DIS firing event. When a scope displays a waveform for each cylinder, you can compare the waste spark to the power spark for each cylinder. If the wastespark firing line seems higher than normal, or higher than the waste spark for the other cylinders by comparison, you're probably looking at high resistance in the portion of the circuit to that cylinder.

The problem might be an open or high-resistance plug wire or an accidental gap at the connection to the coil or the plug. Whatever the source, the high resistance can lead to a misfire. If you recognize this symptom, you're on your way to solving the problem.

[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

[art leong]

Thanks
this is what was happening to me. I had a Snap-On light, which I thought was bad. I just bought a new light a Equus-Inova.
Same thing
But I still get a different reading when I hook it up from number 1 to number 4 Number 4 seems like its right number one seems to bounce around.

[Pat Cook]

Art, just for giggles, does it do the same thing when checking 2&3? could it be there is some sort of "fly back voltage" on the wasted spark cycle? caused from a weak condenser or missing condenser?