Primary and Secondary Ignition Patterns (WS8)

Primary and Secondary Ignition Patterns

I did testings on a Toyota 4A-FE engine. I set up a ignition oscilloscope with the engine warmed up and running and i recorded  firing voltage, burn time, burn voltage and dewll time.

Ignition Primary	CYL 1	CYL 2	CYL 3	CYL 4
Firing Voltage	300v	300v	300v	300v
Burn Voltage	40v	40v	40v	40v
Burn Time	1.4ms	1.4ms	1.4ms	1.4ms
Dwell Time	4.6ms	4.6ms	4.6ms	4.6ms

All readings look normal. The readings are constant for all cylinders. The engine is running smooth  without misfire and hesitation. Constant operation tells the engine is runnig efficiently.

A - Coil gets grounded which is the dwell period.

B - Coil is ungrounded, primary winding is open and the magnetic field collapses and voltage spikes up to 300V. This voltage is applied to the secondary windings.

C - this is the burn time, the duration of the spark.

D - Coil oscillation. The coil should display minimum of peaks(both upper and lower). If a loss of peaks in oscillation shows, coil should be substituted.

This is a stacked display showing each primary pattern for each cylinder. This is useful to diagnose faults with the engine by comparing each pattern for each cylinder.

When we increase the RPM on the engine the dwell time increases as it takes longer to saturate the coil and the burn time is longer to as the air fuel mixture is more and richer.

Secondary Voltage Patterns

I got the engine warmed up  and idling. I connected the ignition oscilloscope to view secondary ignition patterns. When i snapped the acceleration i recorded firing voltage and burn time.

Ignitiion Secondary	CYL 1	CYL 2	CYL 3	CYL 4
Firing Voltage (KV)	13KV	13KV	13KV	13KV
Burn Time (ms)	1.6ms	1.6ms	1.6ms	1.6ms

A - This shows the voltage required to jump the spark plug gap. The voltage has increased to KV voltage as there are more winds in the secondary and the voltage increases to kilo volts.

B -  This is the time the voltage is flowing across the gap after the voltage has jumped the gap

C - This is the burn voltage after jumping the gap the voltage stays constant to burn the fuel mixture.

D - The end of spark and the voltage drops down.

E - Coil oscillation.

Everything looks normal in the pattern. There are more winding in the secondary so the voltage increases to kilo volts to jump the spark plug gap. !3 KV was required to jump the spark plug gap but the voltage drops down to a constant voltage to burn the air fuel mixture.

As we increased the rpm the Firing voltage increases but quickly drops down as the burn time increases to burn more of the air fuel mixture. I could not upload the video on blogger so i uploaded it on you tube and here is the link - http://www.youtube.com/watch?v=Az7xEolJ684

The firing voltage increases due to a large plug gap or beak in the plug leads. If the mixture is also lean the firing voltage will increase. Worn out spark plugs will also cause a high firing voltage. 

The firing voltage decreases when the plug gap is small. Rich mixtures also have low firing voltage.

Then with the engine stopped  we disconnected Cylinder 1 spark plug lead and shorted it to the engine with a jumper wire.

By this testing we saw that that the firing voltage decreased for cylinder 1 as we had grounded that spark plug wire to the engine. But the spark duration increased a little bit.

Ignition Secondary	CYL 1	CYL 2	CYL 3	CYL 4
Firing Voltage (KV)	4kV	8KV	8KV	8KV
Burn Time (ms)	5.9ms	3ms	3ms	3ms

Then we stopped the engine an attached a spark plug tester to one of the spark plug leads and grounded it to the engine.

The the video keeps getting deleted off blogger so i uploaded it on you tube and hers the link - http://www.youtube.com/watch?v=Tx52mes4qG8

From this pattern we can see how the firing voltage increases to jump the gap but the burn time is very little. As the gap increases the firing voltage increases.

The we removed the spark tester and got the engine back to normal and the engine is runnig fine.