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Author: WisdomAugust

Air Flow Meter – Hot Wire

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 Author| Post time 2020-2-10 08:01:42 | 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.

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.


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 Author| Post time 2020-2-11 07:37:32 | Show all posts
The voltage measured at the spark plug is the voltage required to jump the plug gap in varying conditions.
This voltage is determined by the 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 2020-2-12 07:59:20 | 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 2020-2-13 07:30:27 | Show all posts
Connect the oscilloscope
1. Plug an auto-ignition probe (HT25) into channel 1 on the DSO3064(A).
2. Clip the lead's crocodile clip on suitable earth.
3. Fit the HT clip on one of the engine's positively-fired plug leads.
If the live waveform is missing or upside-down, you have selected a negatively fired plug. Either choose a
different plug lead or load the secondary negative waveform from the drop-down menu.


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 Author| Post time 2020-2-14 07:40:00 | Show all posts
Warning: When attaching or removing secondary ignition pickups from damaged HT25 leads there is
a risk of electric shock. To eliminate this danger, attach and remove the secondary ignition pickup with
the ignition turned off.



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 Author| Post time 2020-2-15 07:42:08 | 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 2020-2-17 07:41:40 | 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 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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 Author| Post time 2020-2-18 07:53:04 | Show all posts
Lambda Sensor - Zirconia
The lambda sensor is also referred to as the Oxygen O2 sensor or a Heated Exhaust Gas Oxygen
(HEGO) sensor and plays a very important role in the control of exhaust emissions on a catalytic
equipped vehicle. The lambda sensor is fitted into the exhaust pipe before the catalytic converter;
cars using the new EOBD2 will also have a post cat lambda sensor.

The sensor will have varying electrical connections and may have up to four wires; it reacts to the oxygen
content in the exhaust system and will produce a small voltage depending on the Air/Fuel mixture seen at
the time. The voltage range seen will, in most cases, vary between 0.2 and 0.8 volts: 0.2 volts indicates a
lean mixture and a voltage of 0.8v shows a richer mixture. A vehicle equipped with a lambda sensor is said
to have 'closed-loop', this means that after the fuel has been burnt during the combustion process, the sensor
will analyze the resultant emissions and readjust the engine's fuelling accordingly. Lambda sensors can have
a heater element which heats the sensor to its optimum operating temperature of 600℃, this enables the sensor
to be located further away from the heat source at the manifold to a 'cleaner' location.


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 Author| Post time 2020-2-19 13:42:26 | Show all posts
The lambda sensor is essentially two porous platinum electrodes. The outer electrode surface is exposed
to the exhaust gasses and is coated in a porous ceramic with the inner coated surface exposed to fresh air.

The most commonly used sensor uses a Zirconia element, producing a voltage when a difference in oxygen
content is seen between the two electrodes. This signal is then sent to the Electronic Control Module (ECM)
and the mixture is adjusted accordingly. Titania is also used in the manufacture of another type of lambda
sensor that offers a faster switching time than the more common Zirconia sensor.


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 Author| Post time 2020-2-20 07:32:16 | Show all posts
The titania oxygen sensor differs from the zirconia sensor in the fact that it is incapable of producing its
own output voltage and is therefore reliant upon a 5 volt supply from the vehicle's ECU. The reference
voltage is altered according to the engine's air-fuel ratio, with a lean mixture returning a voltage as low
as 0.4 volts to a rich mixture producing a voltage in the region of 4.0 volts.

A constant high voltage output from the zirconia shows that the engine is running constantly rich and is
outside the ECU's adjusting range, whereas a low voltage indicates a lean or weak mixture.


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