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Author: WisdomAugust

Air Flow Meter – Hot Wire

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 Author| Post time 2020-3-11 08:18:39 | Show all posts
Secondary-Distributorless (Positive Fired)
Technical information
Ignition coil is also referred to as a spark coil and used to transform lower voltages of power to the higher
voltages of power required to fire a system's spark plugs. It is similar to an electric transformer, consists
of primary and secondary winding circuits. Inside the coil's primary winding is the secondary winding.

This is coiled around a multi-laminated iron core and has approximately 20,000 to 30,000 turns.
One end is connected to the primary terminal and the other to the coil tower.


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 Author| Post time 2020-3-12 08:45:11 | Show all posts
The ignition probe(HT25) voltage is produced by mutual induction between the primary winding and the
secondary winding, with the central soft iron core intensifying the magnetic field between them.

The voltage measured at the spark plug is the voltage required to jump the plug gap in varying conditions.
This voltage is determined by a spark plug gap, rotor air gap etc.

The plug kilovolt (kV) requirement of older engines tends to be lower than that of the modern engine, as
the later designs run higher compression ratios, leaner air/fuel ratios, and larger spark plug gaps.


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 Author| Post time 2020-3-13 08:07:20 | Show all posts
The modern engine with Distributorless Ignition System (DIS) has all the advantages of a constant energy
electronic ignition system, but with the added bonus of the distributor cap, king lead and rotor arm being
removed from the system. Reliability problems from dampness and tracking are now almost eliminated.

DIS has its own drawbacks by having half of the plugs firing with an acceptable negative voltage, while
the other half are fired by the less acceptable positive polarity. This has the effect of increased plug wear
on the positive fired plugs.


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 Author| Post time 2020-3-14 08:21:40 | Show all posts
Connect the oscilloscope
1. Plug an auto-ignition probe (HT25) into channel 1 on the oscilloscope.
2. Clip the lead's crocodile clip on suitable earth.
3. Plug the Coil-on extension lead(HT308) into the engine's positively-fired plug of an air cylinder.
4. Fit the HT25 clip on the Coil-on extension lead as illustrated in Figure 6.5.1.





Figure 6.5.1


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 Author| Post time 2020-3-16 08:52:31 | Show all posts
Follow these steps:
1. Click “Vehicle->Diagnosis”, as illustrated in Figure 6.5.2
2. Click “Ignition->Secondary-> Secondary DIS (Positive-fired)”, click “OK”, as illustrated in Figure 6.5.3.

Figure 6.5.2

Figure 6.5.3


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 Author| Post time 2020-4-1 09:25:55 | Show all posts
Reference waveform
Figure
6.5.4


Example Waveform
Figure 6.5.5

Notes:
When the positive fired plug kV's are recorded on distributor less Ignition Systems (DIS), the voltage should
be as shown and not inverted, as this would suggest that the wrong lead has been chosen.

While the engine is running, the plug voltage continuously fluctuates and the display moves up and down.


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