Saturday, 21 May 2011

WS8 PRIMARY AND SECONDARY IGNITION PATTERNS


To analyse primary ignition patterns we connected the oscilloscope between negative side of the primary coil and solid ground. To set up divisions on vertical axis we accounted on the generally accepted several hundred volts for the primary coil. To calculate time frame for the horizontal axis we can use simple calculation: RPM=1000; 4-cylinders engine;
P(period in sec)=1/(4cyl*(RPM/60sec*2))=1/(4cyl*(1000rpm/120))=30 ms from this figure we can pick up division per scale much easier to register a signal.
First experiment is on the Image#1 and in the table below:
PRIMARY AND SECONDARY IGNITION PATTERNS

CYL1
CYL2
CYL3
CYL4
PRYMARY IGNITION
400 V
400 V
400 V
400 V
Firing Voltage
40.7 V
40.7 V
40.7 V
40.7 V
Burn Voltage
1.05 ms
1.05 ms
1.05 ms
1.05 ms
Burn Time
5.85 ms
5.85 ms
5.85 ms
5.85 ms
Dwell Time








A-B is DWELL TIME, period in which circuit is completed via igniter to ground.
B-firing time at which igniter is disconnected from ground and magnetic field collapses in a fully saturated primary coil.
B-C- FIRING VOLTAGE, this shows us what does it takes to push the electron trough the high tension leads and spark plug gap to create sparking
D- burning voltage we spend keep sparking to burn fuel mixture.
E- oscillations in the coil. They occur due to mutual influence between primary and secondary coils by means of EMF. It takes time for the magnetic field it creates to die out.
So that, experiment underlined that using oscilloscope we can analyse the process in details. From this we can read a picture of current condition and functioning of each component of the ignition system. Moreover, if use raster and patterns parade, we can compare all the cylinders and by doing this localise the fault. Thus, oscilloscope is the main tool for this purpose, especially because we are looking at milliseconds and tiny fluctuation in the signal readings.  
SECONDARY VOLTAGE PATTERN
CYL1
CYL2
CYL3
CYL4
SECONDARY IGNITION
5.2
5.2
5.2
5.2
FIRING VOLTAGE(KV)
1.28
1.28
1.28
1.28
BURN TIME(ms)
7
7
7
7
SNAP ACCELERATION






Secondary voltage parade almost repeats the primary one. I said almost, because we cannot read dwell time. At this part of the horizontal axis we can watch only small fluctuations which occur due to mutual influence between coils. This is how emf acts. The voltage output produced by spark plugs of each cylinder can be compared and assessed.
Performance of the secondary part of the ignition system allows analysing the working condition of particular cylinder high tension lead and spark plug. All these aspects I mentioned are very important for diagnostics.
VOLTAGE PATTERN WITH SHORTED SPARK PLUG WIRE #2
CYL1
CYL2
CYL3
CYL4
SECONDARY IGNITION
5.1
3.5
5.1
5.1
FIRING VOLTAGE(KV)
1.33
----
1.33
1.33
BURN TIME

The firing voltage of the cylinder#2 express in figures that it takes less energy for the spark to jump across the small resistance aria.
 
VOLTAGE PATTERN WITH ATTACHED SPARK TESTER
CYL1
CYL2
CYL3
CYL4
SECONDARY IGNITION WITH SPARK TEATER
6
5.2
19
5.2
FIRING VOLTAGE (KV)
2
1.98
1.2
1.98
BURN TIME(ms)


SPARK GAP VARIATION 2mm-25mm
In this part of our experiment we assessed what is the influence of the spark plug gap on the firing voltage. It’s clear that the bigger gap the higher voltage it takes to push the electrons through it. With relation to this the burn time changes. The so-called string theory is very useful to analyse this process.
Video is attached to watch the experiment and compare how voltage and time changes. 
video





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