How does the ignition system work? (And understanding how it's wired)
08-19-14, 03:50 AM
#1
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How does the ignition system work? (And understanding how it's wired)
I have an '84 gsl 12a. I'm trying to wire my ignition system, but first I'd really like to understand what I'm actually doing. So basically, how does the entire ignition system work? Like I know the black/white wire is powered by 12v when the ignition switch is on the ign position. So how does it work from there? What exactly do the igniters (on the distributor) do? How are they wired, and how do they know when to work? Same for the coils, how are they wired and how do they know when to work? Etc for the whole system. Sorry if it sounds dumb i've just never really worked with ignition like this. I looked at the wiring diagram but it's a little confusing and I want to know exactly why it's wired like that and how it works. Thanks!
08-19-14, 09:29 AM
#2
HowStuffWorks "How Automobile Ignition Systems Work"
Main diff on a first gen is that there are essentially two of these systems, built for two plugs each and separated by ~20 degrees of shaft rotation; one system for leading spark, one for trailing.
The rotary needs two systems because physics limits how fast the coil can charge, & the tight timing between leading and trailing spark at high RPM doesn't allow enough time for the coil to reach full charge.
Early rotaries (like the 10A) actually had two small distributors; in the 12A they were combined mechanically but are still isolated electrically. The one cap and rotor actually has two separate distribution circuits in it.
Main diff on a first gen is that there are essentially two of these systems, built for two plugs each and separated by ~20 degrees of shaft rotation; one system for leading spark, one for trailing.
The rotary needs two systems because physics limits how fast the coil can charge, & the tight timing between leading and trailing spark at high RPM doesn't allow enough time for the coil to reach full charge.
Early rotaries (like the 10A) actually had two small distributors; in the 12A they were combined mechanically but are still isolated electrically. The one cap and rotor actually has two separate distribution circuits in it.
08-19-14, 03:27 PM
#3
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Thread Starter
HowStuffWorks "How Automobile Ignition Systems Work"
Main diff on a first gen is that there are essentially two of these systems, built for two plugs each and separated by ~20 degrees of shaft rotation; one system for leading spark, one for trailing.
The rotary needs two systems because physics limits how fast the coil can charge, & the tight timing between leading and trailing spark at high RPM doesn't allow enough time for the coil to reach full charge.
Early rotaries (like the 10A) actually had two small distributors; in the 12A they were combined mechanically but are still isolated electrically. The one cap and rotor actually has two separate distribution circuits in it.
Main diff on a first gen is that there are essentially two of these systems, built for two plugs each and separated by ~20 degrees of shaft rotation; one system for leading spark, one for trailing.
The rotary needs two systems because physics limits how fast the coil can charge, & the tight timing between leading and trailing spark at high RPM doesn't allow enough time for the coil to reach full charge.
Early rotaries (like the 10A) actually had two small distributors; in the 12A they were combined mechanically but are still isolated electrically. The one cap and rotor actually has two separate distribution circuits in it.
On an FD the leading spark plugs fire at the same time correct? So im guessing that this isnt the same on this type of ignition system since the distributor cant push power to 2 spark plug wires at the same time?
08-19-14, 04:36 PM
#4
The ignitor is an electronic amplifier; it provides a high-speed and high-current-capacity connection to ground to collapse the coil primary's magnetic field, which induces high voltage in the secondary. The distributor connects that high voltage to the appropriate plug.
You could use a beefy relay instead of the ignitor, except that 1) big-enough relays really aren't fast enough, and 2) the relays contacts would burn out quickly from the arc discharge. The points on an older-style ignition really are just a cam-operated switch, or mechanical relay.
I'm not an FD guy; I don't know their ignition systems. Looking at a diagram for one, it appears that they are distributorless and do fire both leading plugs off one coil. Probably a pretty expensive coil, as it has to saturate twice as fast as the trailing coils do yet still achieve full spark.
You could use a beefy relay instead of the ignitor, except that 1) big-enough relays really aren't fast enough, and 2) the relays contacts would burn out quickly from the arc discharge. The points on an older-style ignition really are just a cam-operated switch, or mechanical relay.
I'm not an FD guy; I don't know their ignition systems. Looking at a diagram for one, it appears that they are distributorless and do fire both leading plugs off one coil. Probably a pretty expensive coil, as it has to saturate twice as fast as the trailing coils do yet still achieve full spark.
08-19-14, 04:53 PM
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Divin is correct about the FD, there is no cap, so it just uses a double ended coil to fire both plugs at the same time.
the FD in principal works the same, except the magnetic pick up goes to the ecu, and the ecu switches the ignitor, according to an rpm x engine load table.
the really odd duck is the FC trailing, it has one signal that fires every time there is a trailing event, and then a second to switch between the different plugs. the JC cosmo is even weirder, as it has a toggle signal for each of the 3 rotors. no other car on the planet that i know of works like that. the FD just has 3 outputs, and a 3 channel ignitor. one for Leading, and then T1 and T2.
the FD in principal works the same, except the magnetic pick up goes to the ecu, and the ecu switches the ignitor, according to an rpm x engine load table.
the really odd duck is the FC trailing, it has one signal that fires every time there is a trailing event, and then a second to switch between the different plugs. the JC cosmo is even weirder, as it has a toggle signal for each of the 3 rotors. no other car on the planet that i know of works like that. the FD just has 3 outputs, and a 3 channel ignitor. one for Leading, and then T1 and T2.
08-20-14, 06:38 PM
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08-21-14, 08:48 AM
#8
Waffles - hmmm good
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dual fired leading plugs and wasted spark all at the same time. Its a great way to
give the rotary ignition a boost. Just search on DFIS or look at the link in my sig.
08-21-14, 10:24 AM
#9
Clarification: Stock first gen ignition fires Leading1 & Leading2 spark plugs 180 shaft degrees apart, not 'at the same time.' Distributor sees to this.
Trailing for each rotor follows the leading by 20* (12A) or 15* (13B)
This is why swapping L1 & L2 plug wires will stop a 1st-gen from running (as I know all too well ). On an FD, it likely wouldn't matter as both are fired at the same time.
One more first-gen twist; on the SA's sold in Cali (& I think Fed in 80), the trailing ignition is shut down entirely under certain engine conditions, to improve smog characteristics. This was needed with the Thermal Reactor style emission controls to provide a rich enough exhaust to keep the TR hot & working well.
When the 81's were switched to catalytic converters, the need to do this went away. That's why 81 dizzys were able to do away with the ignitor control box on the shock tower & just mount the ignitors right on the dizzy. Made for a much simpler and reputedly more reliable system.
Trailing for each rotor follows the leading by 20* (12A) or 15* (13B)
This is why swapping L1 & L2 plug wires will stop a 1st-gen from running (as I know all too well
). On an FD, it likely wouldn't matter as both are fired at the same time.One more first-gen twist; on the SA's sold in Cali (& I think Fed in 80), the trailing ignition is shut down entirely under certain engine conditions, to improve smog characteristics. This was needed with the Thermal Reactor style emission controls to provide a rich enough exhaust to keep the TR hot & working well.
When the 81's were switched to catalytic converters, the need to do this went away. That's why 81 dizzys were able to do away with the ignitor control box on the shock tower & just mount the ignitors right on the dizzy. Made for a much simpler and reputedly more reliable system.
08-21-14, 02:07 PM
#10
Waffles - hmmm good
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Clarification: Stock first gen ignition fires Leading1 & Leading2 spark plugs 180 shaft degrees apart, not 'at the same time.' Distributor sees to this.
Trailing for each rotor follows the leading by 20* (12A) or 15* (13B)
This is why swapping L1 & L2 plug wires will stop a 1st-gen from running (as I know all too well ). On an FD, it likely wouldn't matter as both are fired at the same time.
One more first-gen twist; on the SA's sold in Cali (& I think Fed in 80), the trailing ignition is shut down entirely under certain engine conditions, to improve smog characteristics. This was needed with the Thermal Reactor style emission controls to provide a rich enough exhaust to keep the TR hot & working well.
When the 81's were switched to catalytic converters, the need to do this went away. That's why 81 dizzys were able to do away with the ignitor control box on the shock tower & just mount the ignitors right on the dizzy. Made for a much simpler and reputedly more reliable system.
Trailing for each rotor follows the leading by 20* (12A) or 15* (13B)
This is why swapping L1 & L2 plug wires will stop a 1st-gen from running (as I know all too well
). On an FD, it likely wouldn't matter as both are fired at the same time.One more first-gen twist; on the SA's sold in Cali (& I think Fed in 80), the trailing ignition is shut down entirely under certain engine conditions, to improve smog characteristics. This was needed with the Thermal Reactor style emission controls to provide a rich enough exhaust to keep the TR hot & working well.
When the 81's were switched to catalytic converters, the need to do this went away. That's why 81 dizzys were able to do away with the ignitor control box on the shock tower & just mount the ignitors right on the dizzy. Made for a much simpler and reputedly more reliable system.
also cut down on crosstalk issues and noise on the dizzy signal wires. That and
they reshaped the reluctor wheel to generate a better signal as well. FB dizzies
are better for triggering HEIs too!
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