No car issues at the moment just a technical question on wastespark/dis ignition systems that has come about from watching Paul's explanation of a 4 wire cop in the VW Passat video with the missing coil ramp, and it's really only because the small detail of it is annoying me.
Ok... I understand that the primary ignition coil is not connected to the secondary in these designs, and so what happens is you have field collapse from primary to the secondary. It then travels through the + side of the winding through the first plug electrode where it jumps the gap, goes through the cylinder head then jumps the gap back through the electrode to the - side of the winding. I understand that the - of the secondary is not the same as a block ground.
My question is this. What determines the + polarity once the field collapses into the secondary? And what stops the spark producing say another cycle before the energy form the field collapse dissipates. i.e another few sparks? I'm guessing heat?
I love when I have to dig something out my brain I was taught before most of you were born; yes is all ends up as heat an ignition coil is basically the same as an AC transformer. The coil oscillations at the end of the spark cause magnetic field reversals and every magnetic field reversal resuts in low level heating of the iron core of the transformer.
To quote from this site
www.electronics-tutorials.ws/electromagn...etic-hysteresis.html
"
Magnetic Hysteresis results in the dissipation of wasted energy in the form of heat with the energy wasted being in proportion to the area of the magnetic hysteresis loop. Hysteresis losses will always be a problem in AC transformers where the current is constantly changing direction and thus the magnetic poles in the core will cause losses because they constantly reverse direction "
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
I kind of knew that to be the case. It just seems very precise that a spark can jump through two plugs in a wastespark fashion and then dissipate that left over energy.
I'll stick to the black box approach. I don't need to know what's inside the box, I just need to know what's expected from it!
The energy usefully released by the coil is usually regarded as mirrored in the KV of the initial spark voltage + the MS time duration of the burn line however the way I see it the KV height of burn line also comes into it.
If the KV demand is increased then the spark duration is shortened.
Interestingly I have seen some really crazy coil oscillations with narrow spark gaps.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Do you scrutinise the kv height of the burn line during secondary diagnosis? That must differ greatly from vehicle to vehicle?
You know something, I never even gave a secondary waveform a thought when asking my initial question! I really need to get up to spreed with this stuff. It was over 20 years since I was in college!
Paul_Kilgour wrote: My question is this. What determines the + polarity once the field collapses into the secondary?
The north and south poles or direction of current flow through the primary winding is what determines secondary polarity.
Make sense?
Take a GM type ii ignition coil. They are identical but move one to the next coil over on the module and it's polarity changes.
It is much the same as a simple permanent magnet DC electric motor connect the wires, reverse the polarity and it runs backwards.
In the old days with DIS points ignition and old style coils all the books used to stress how important it was to connect the coil with the correct primary (LT) polarity I never saw it make any real difference to the running of the engine.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
I'm ok with dc motors and reversing the polarity. I demonstrated that exact principle on a lawnmower motor to my son last year during a repair.
I just needed a good visual in my mind as to what determined the polarity once the field collapsed into the secondary, and where the energy went after the second spark in a wastespark design. Not that it really matters for diagnosis, more that it's just one of those annoying questions that you just need an answer to! lol
Think of the coil oscillations after the spark as a bit like the springboard in the olympics diving after the diver bouces off the board the energy has to disispate somehow. When I listen to electrical guys about this they talk about "Back EMF" ie a voltage that opposes any change in current flow I never really could get my head around that concept.
Ignition system have changed a lot and from what I have read they are about to change a lot more. In the last few years it seems everytime we get the diagnostic methods perfected for one generation of ignition system a new one comes along that throws new obstacles into the ring.
The changes that evolved all the through all the generations of ignition systems over the last 100 years has the makings of a topic on its own in another section,
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
I'm just starting to get to grips with this scope stuff. I've been away from this stuff for over 20 years. Although I was still fixing the odd car here and there. Exactly what you've just said about the ever changing technology is the reason, partly, why I never thought I'd get up to speed. Then comes along this YouTube channel called 'Scannerdanner'. Then I had no excuses.
I did a lot of catching up last year when I was layed up for 6 months, Paul has made so many great videos perhaps some day I will manage to watch them all and of course there are the very select group of other Youtubers that contribute a great deal of quality learning to the collective.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
