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Secondary ignition waveform diagnosis (Read 52,174 times)
fisher
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Re: Secondary ignition waveform diagnosis
Reply #15 - Jun 3rd, 2011 at 2:02pm
 
You get what I am asking? We have been saying that there is a voltage increase at primary shut-off. The scope pattern has been inverted  though. In actuality there is no such spike.
    When you open the primary circuit, you witness that drop in voltage if you have left the pattern alone to display as it shows uninverted. The scope is not lying.
Someone had a problem equating the voltage drop of coil turn off with the existence of the flame in the spark...their question was, "How can a lack of voltage create a spark?"
So the pattern gets turned over to make it look like there is a voltage increase -there is a spark , so, there must be power to create that spark; an increase in voltage...
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Donald Bruce Gamble  
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Mr. Bill
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Re: Secondary ignition waveform diagnosis
Reply #16 - Jun 3rd, 2011 at 4:06pm
 
fisher wrote on Jun 3rd, 2011 at 2:02pm:
So the pattern gets turned over to make it look like there is a voltage increase


Whether there is an increase or decrease doesn't matter. The scope clearly shows a potential difference, in other words voltage! A 20kv spike is a 20kv potential difference, the starting point doesn't matter but the difference from the starting point does.
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Randy H.
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Re: Secondary ignition waveform diagnosis
Reply #17 - Jun 5th, 2011 at 2:58pm
 
fisher wrote on Jun 3rd, 2011 at 2:02pm:
So the pattern gets turned over to make it look like there is a voltage increase

A voltage potential is a voltage potential, whether positive or negative polarity. Whether or not it is inverted is of no consequence.
There is no lack of voltage - there is a resistance across the spark gap which the energy(electrical charge) of the coil secondary wants to return to where it was created. To do this it must flow across the spark gap. So it creates a corona, ionizes(kv voltage), then turns to plasma, which lowers effective resistance across the gap. (this is the burn line)
Its just that simple.
Mr bill is saying exactly the same thing as I am. Wink
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Randy Hatton
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benmixmaster
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Re: Secondary ignition waveform diagnosis
Reply #18 - Feb 13th, 2012 at 12:49pm
 
Secondary osciloscope patterns can show the firing voltage needed to start and finish the current flow across the spark plug electrodes, which can be anylized to tell you much about what is happening inside the combustion chamber (like open plug wires, large plug gaps,high or low compression etc.). And this is the most important area of an internal combustion engine, the whole purpose of the engine is to produce power to push the vehicle and this is where that happens.
Primary scope patterns do not show the firing voltage level but do show burn time as the secondary does as well and this usualy is in proportion to firing voltage, the exceptions to this would be a fouled plug-wet or carboned up.
Sometimes it's easier to get at one or the other (primary or secondary) so having both capabilities is nice, also secondary can be deadly to your scope or computer, make shure you ground any leads used for secondary and dont hook directly to primary without an attenuator.

I would highly recomend the autonerdz training material, Mac vandenbrink www.datec.us he has some free downloads, as well as full powerpoint training you can purchase or bill fulton www.ohioautotech.com enhanced ignition system testing this is also available at auto-video. also great training at   www.auto-video.com they also have on demand online videos to purchase.

It's an awsome area of interest, pico/autonerdz has a secondary tool called mixmaster shows all cylinders and parades EI/DIS as well. I would buy it direct from them if I had it to do over again and get the support package, which is included in there scope packages last I knew. I also recomend at least 4 trace scope.

I have studied scoping ignitions for some time and your equipment will play a big role in this, definitely a book/video & hands on thing to learn! Each vehicle layout, Like fuel rail shape clogging injector inlets at ends or rail can showup in scope pattern as lean injector. get a propane tank enrichening tool so you can experiment richening and pull vacuum hose to lean it.

I should stop here, please excuse my grammar? If you want to know more ask on but too fully learn ignition anylization get training videos/books etc. 
Hope this was usefull, have fun!
Wow i just noticed how old this post was Oh well. mayby your still looking for replies.
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ben.bigelow1  
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Re: Secondary ignition waveform diagnosis
Reply #19 - Feb 13th, 2012 at 9:39pm
 
Never hurts to add some information Ben.
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Re: Secondary ignition waveform diagnosis
Reply #20 - Jun 6th, 2014 at 7:03am
 
Some more information
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Re: Secondary ignition waveform diagnosis
Reply #21 - Jun 6th, 2014 at 7:04am
 

Further evaluation
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Re: Secondary ignition waveform diagnosis
Reply #22 - Jun 6th, 2014 at 8:44pm
 
Please find attached a file of a capture of a BMW E46 with a M43 engine.

It has a coil pack mounted on the skirt with ignition leads to the spark plugs.

The car had a mis fire on acceleration that was infact a loos lead onto #4 spark plug, but there are clearly other issues.

We are yet to complete our diagnosis but I would welcome comment on the secondary capture.

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Re: Secondary ignition waveform diagnosis
Reply #23 - Jun 19th, 2014 at 4:04am
 
Logic thanks for the info!
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neildavy14  
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fisher
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Re: Secondary ignition waveform diagnosis
Reply #24 - Jun 19th, 2014 at 8:04am
 
Logic, is that a Beta version of PICO?
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Donald Bruce Gamble  
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Re: Secondary ignition waveform diagnosis
Reply #25 - Jun 20th, 2014 at 1:24pm
 
I think so, I opened it with the latest beta.
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