Primary & Secondary Ignition patterns

Primary Voltage Patterns

in this exercise i set up an oscilloscope to look at the primary ignition pattern of my engine while it was idling and warmed up (closed loop)
i rigged this oscilloscope up by putting the positive feed from the scope onto a pin which was inserted on the input down the connector of the distributor, i then put the negative/ground wire on a good common earth.

below is a table of the recordings i collected from the ignition patterns:

Cyl 1	Cyl 2	Cyl 3	Cyl 4	Primary Ignition
248v	248v	248v	248v	Firing Voltage
55.6v	55.6v	55.6v	55.6v	Burn Voltage
1.48ms	1.48ms	1.48ms	1.48ms	Burn Time
6.2ms	6.2ms	6.2ms	6.4ms	Dwell Time

HTML Tables

volts per division = 50v              milli seconds per division = 2ms


if we follow the line across the screen (left to right), when the line drop, this is called the DWELL TIME, this is when the circuited is grounded.
when the line is at its peek and goes all the way up, this is called the FIRING VOLTAGE, this is the voltage that it takes to push through the high tension leads and to spark plug.
when the line drops down and slightly scribbles across, this is the BURN TIME, this is the time we use to keep sparking the so we can burn all fuels in the combustion chamber.
when the line goes back down but oscillates, this is because the magnetic field is taking time to release.

The raster and stacked display you can put the patterns on top of each other, this helps to to compare times better and makes it more clear to see the length of things.


Secondary Voltage Patterns

in this exercise i had to set up an oscilloscope to the secondary ignition. i did this by attaching a belt around the distributor, this would sense the voltages through the distributor cap, i also rigged up a common earth.

i then let the engine idle at operating temperature and recorded my reading and put them into a graph.

Cyl 1	Cyl 2	Cyl 3	Cyl 4	Secondary Ignition
5.4kv	8.2kv	5.9kv	6.2kv	Firing Voltage (killer volts)
0.75ms	0.87ms	0.65ms	0.71ms	Burn Time (milli seconds)
9.8kv	8.4ms	9.8ms	9.0ms	Snap acceleration

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this waveform is the same as the primary waveform, the only difference is that the secondary pattern does not have a dwell time..
 the results from this test are all good and within specifications of the engine type (4A-FE)
when i snapped the accelerator i expected the burn time to be longer because it had more fuel inside the combustion chamber to burn, therefor the burn time needed to increase so it could burn all of the gasses .



Shorted Secondary

Cyl 1	Cyl 2	Cyl 3	Cyl 4	Secondary ignition
5.4kv	3.2kv	5.9kv	6.2kv	Firing Voltage (killer volts)
0.75ms	____	0.65ms	0.71ms	Burn Time (milli seconds)

HTML Tables

in the above table i have shorted number 2 cylinder to ground and it has a lower firing voltage because it has less resistance to make it fire.

Below is the waveform drawn from the oscilloscope:

the peek firing voltage says 10 volts but it is really 3.2kv

there is only a firing voltage on the graph because there is not any burn time to read on the oscilloscope because the plus is not in the cylinder.



Spark Tester

the spark plug tester is like a spark plug that goes on the end of a HT lead, this lets us know if the spark plug in engine is faulty or the plug gap is too large or too small

if the gap was too big, the burn voltage would be a lot higher and if the gap was too small the burn voltage would be a lot smaller. this happens because it takes more voltage to push the electricity across the spark plug gap if it is bigger. if it is smaller it takes less voltage.