Secondary Ignition scope analysis

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Technician
TwoWaves
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Secondary Ignition scope analysis

Post by Technician » Sun Aug 04, 2019 12:36 am

These are recorded from the Fiesta 1.4 SPJC engine after the rebuild.
Attachments
Ford_Fiesta_2012_Petrol_secondary ignition traces using 4 channels.psdata
(14.52 MiB) Downloaded 62 times

Iver
TwoWaves
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Re: Secondary Ignition scope analysis

Post by Iver » Mon Aug 05, 2019 3:58 pm

Secondary captures are of not much value at those speeds.

Technician
TwoWaves
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Re: Secondary Ignition scope analysis

Post by Technician » Mon Aug 05, 2019 5:07 pm

I did think about that at some point. What we saying 2500 rpm!
I'm interested in the cylinder 4 dwell period that looks like a problem, however I've been advised that leads crossing over could cause the same issue?

The other area of interest is the burn kv but not the duration. I have read conflicting information from different authors about this. Some authors appear to be saying that the burn kv line should be fairly straight without hash appearance, and others are saying that no hash present indicates that no fuel is being burned.I tend to believe the latter.

Iver
TwoWaves
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Re: Secondary Ignition scope analysis

Post by Iver » Tue Aug 06, 2019 6:10 am

the burn kv line should be fairly straight without hash appearance, and others are saying that no hash present indicates that no fuel is being burned
I wouldn't go with either for now. Test conditions first !
That dwell will be very precisely managed by the PCM. Much more could be gleaned from primary V & Current.
/
That dwell on #4 is going below 0v. Why ? How ?

Technician
TwoWaves
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Re: Secondary Ignition scope analysis

Post by Technician » Tue Aug 06, 2019 6:36 pm

Iver wrote:
Tue Aug 06, 2019 6:10 am
the burn kv line should be fairly straight without hash appearance, and others are saying that no hash present indicates that no fuel is being burned
I wouldn't go with either for now. Test conditions first !
That dwell will be very precisely managed by the PCM. Much more could be gleaned from primary V & Current.
/
That dwell on #4 is going below 0v. Why ? How ?
In short at the moment I've no idea, however the engine seems to run smoothly and no misfires etc.

Iver
TwoWaves
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Re: Secondary Ignition scope analysis

Post by Iver » Tue Aug 06, 2019 7:25 pm

In short at the moment I've no idea
AC & Polarity reversed aside

There is only one way we can see a minus reading on DC.

The Scope or Voltmeter measures potential voltage.

The formula for that is Vred Minus Vblack

Keep it simple with a voltmeter for now. Imagine it as 2 Voltmeters in one box taking voltage readings on both leads and then applying the formula above.

Now you can work out how it is possible to see a DC Negative Voltage. Of course in reality a Negative Voltage in DC cannot exist however when we see it WE SHOULD KNOW WHY & HOW.

The moment you see a Negative DC Voltage you are in Dangerous Misdiagnosis Territory.

You could have the best Nuclear Powered Meter or Scope but you are Donald Ducked !!
You are in a bad place
however the engine seems to run smoothly and no misfires etc
Then any test you do will Pass. Do a RPM calculation on CKP. Then you can know if you need to look at Secondary's. Probably wont.

Technician
TwoWaves
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Re: Secondary Ignition scope analysis

Post by Technician » Thu Aug 08, 2019 9:46 pm

I've not had the free time to look into those tests you advise, however I was advised to look at the secondary ignition waveforms again but this time looking at one cylinder at a time. Interestingly the scope trace on all four cylinders now looks normal. However I did recognize that the induced voltages through the coils when the PCM switches off are lower than they were previously. Looking at each cylinder when the ignition coil induces voltage into the secondary side the kv readings can be see to be as low as 4 kv and jump back to 15 kv. This did not show up on the last waveforms when tested. Looks to me like the wasted coil pack is at the end of its working life and could be ready for failing!
Attachments
Ford_Fiesta_2012_Petrol_ignition cylinder 4 test secondary.psdata
(13.11 MiB) Downloaded 14 times
Ford_Fiesta_2012_Petrol_ignition cylinder 3 test.psdata
(13.03 MiB) Downloaded 8 times
Ford_Fiesta_2012_Petrol_ignition cylinder 2 test.psdata
(13.02 MiB) Downloaded 11 times
Ford_Fiesta_2012_Petrol_Ignition cylinder 1 test secondary.psdata
(13.02 MiB) Downloaded 12 times

Iver
TwoWaves
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Re: Secondary Ignition scope analysis

Post by Iver » Fri Aug 09, 2019 7:04 am

've not had the free time to look into those tests you advise,
Your methods are Flawed to put it nicely !!

You have Minus Values in a DC system. Back to School or Back to Misdiagnosing - Your Choice !

Iver
TwoWaves
TwoWaves
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Re: Secondary Ignition scope analysis

Post by Iver » Fri Aug 09, 2019 7:10 am

've not had the free time to look into those tests you advise,
Your methods are Flawed to put it nicely !!

Facts are Facts. Like it or Not !!! You have Minus Values in a DC system. Back to School or Back to Misdiagnosing - Your Choice !

kona
OneWave
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Re: Secondary Ignition scope analysis

Post by kona » Fri Aug 09, 2019 8:46 am

Technician wrote:
Thu Aug 08, 2019 9:46 pm
.... can be see to be as low as 4 kv and jump back to 15 kv. This did not show up on the last waveforms when tested. Looks to me like the wasted coil pack is at the end ........
By changing the resolution you will get different voltage values. :shock:
The question is what voltage is real ? :?:
Attachments
2019-08-09_112054.gif
2019-08-09_112001.gif

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