Unofficial FAQ: Ignition corrections

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http://www.tegger.com/hondafaq/igniter-operation/index.html
Hopefully this is correct now.
Thanks to all for their help, especially Jim Yanik.

--
TeGGeR®

The Unofficial Honda/Acura FAQ
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TeGGeR® wrote:
http://www.tegger.com/hondafaq/igniter-operation/index.html
Hopefully this is correct now.
Thanks to all for their help, especially Jim Yanik.
-- TeGGeR®
The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ -------------------------------------- I think in the 1990 Honda Civic, the igniter also provides for for some PWM control. It senses the back EMF and kills the coil drive at the correct momment to insure a hot spark. I played with an ignitor and couldn't get it to because correctly until I connected to to a Honda igntion coil. As I varied the frequency of the drive pulses, all the same width, the output created wider pulse at higher "RPM".
Terry
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snipped-for-privacy@hotmail.com wrote:

interesting! i'd read that they did that, but just haven't had the time to sit down & test for it. thanks for the confirmation!
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"PWM" control?

Do you know the mechanism by which it sees the back EMF?

So how come my news server has this message, but not Terry's?
And yes, that's one of the very nice features about electronic ignition versus Kettering. With Kettering, the very moments you need a fat spark are the very moments you get a weaker and weaker spark since the system has no way of increasing dwell time to compensate for RPM.
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TeGGeR®

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TeGGeR® wrote:

as the magnetic field decays inducing a current into the secondary [high voltage] coil, the same is going on with the primary coil, but smaller. just need to measure it. presumably the chips we see in graham's photos either have a map or even calculate "dwell" based on what they measure. but i'm guessing, i don't know for sure.

ah! news servers! fickle things.

which is why people used to experiment with dual plugs and dual ignition systems occasionally. total pains in the rear and highly unreliable, but it was a stab in the right direction. but you're right, once electronic ignition came in, and it wasn't unreliable or expensive, suddenly, it was ok to go electronic with everything. and that's been a good thing up until recently. i don't see current chip technology physically having the longevity we've been so far used to. and of course, with increasing reliance on mysterious black box electronic componentry, how do you know whether a manufacturer caves in to the temptation to program in an end of life? that already happens with ink jet cartridges, regardless of their fill state.
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wrote:

Pulse Width Modulation.

I suspect the IC inside the igniter controls coil current,by means of varying the pulse width(that PWM). I haven't looked for any IC app notes to see exactly what they're doing,though.If anyone has a URL for an app note for these Ics,I'll go look.

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Jim Yanik
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That is probably what the IC in the igniter does.(control PW.) The ECU merely provides the trigger at the proper time.
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Jim Yanik
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Jim Yanik wrote:

so where does it adjust pulse width - has to be on the front end, right? if it was on the rear, the timing would be off. or maybe the ecu already knows what the igniter's timing characteristics are and adjusts accordingly?...
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wrote:

I think the ECU holds ground on Terminal 4 for the appropriate length of time, which keeps the igniter driving the coil until ground is removed. Once ground is removed from Pin 4, the IC switches off coil drive and the field collapses.
The ECU decides when to apply ground and break it based on the inputs of various sensors, such as the Crank Angle Sensor. It needs to know current RPM, cylinder position and crank angle.
Terry is also indicating that the coil is allowed to charge for a longer time at high RPMs to ensure a fatter spark under harsher conditions.
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TeGGeR® wrote:

yes, but that longer time seems to be determined by the igniter, not the ecu, if i understand jim yanik correctly. it kind of has to be because only the igniter is set up to meter the actual flyback, and that is itself a function of the health of the system.
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wrote:

I do not believe this,as the IC inside the igniter monitors coil current.

Yes,coil current has to reach some preset point before the IC shuts off the Darlington. That's the job of that IC.
The only way we will truly know for sure is to get a look at the IC's app sheet,or scope the ECU signal to the igniter and see if it's pulse width increases.If it does,then it controls the PW,not the IC.
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Jim Yanik
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wrote:

So I've read.

Terry seems to have determined that there is evidence of this.
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Jim Yanik wrote (in part):
Yes,coil current has to reach some preset point before the IC shuts off the Darlington. That's the job of that IC.
The only way we will truly know for sure is to get a look at the IC's app sheet,or scope the ECU signal to the igniter and see if it's pulse width increases.If it does,then it controls the PW,not the IC.
-- Jim Yanik ---------------------------
I have several "systems" pulled from cars to be crushed. I rigged a 1990 ECM and sensors, with igniter to try and figure out what was going on.
I am after a simple way to monitor the on time of the FIs.
I was kind of suprised to see the ignition pulse width incrase with engine speed. I used a dual channel oscilloscope and the output from the ECM stayed the same.
I experimented using a HP pulse generator to drive the igniter by itself and found the same thing to be true. In my celica the PW is directly controled by the ECM. I am asuming the IC monitors the delta V, or rate of change and integrates the data to determine PW.
I will try to test my 1991 Civc this weekend. I have brought most of the ECM outputs and inputs via 1K isolation resistors to a breakout box for testing.
I think it will be very usefull to measure on ratio of the FIs to squeeze every erg from the fuel for best MGP.
I can say that in many ways the ECM doesn't work the way I thought. There are odd actions during the warm up period.
One important point is that it looks like Honda skimps on teh heat sink compound. Of course the engine runs hotter then the igniter, so I am not at all sure that adding more thermal coupling will help. I have thought of adding a "heat pipe" tp remove heat from the igniter. I now consider the igniter a subsystem that is doomed to failure. It simply operates too hot for prolonged life.
Having said that, a friend's 1990 Civic has ~200K and is still on the original igniter. Somewhere I have a motorola "designing for long life of Si devices"(something like that) that says that for every 3 degree rise in temp over 20C, the life will be cut in half. But based on that the ~90 degrees C engine temp the igniter ought to fail in the first 100 miles. There are many things I just don't understand here.
But I now carry a spare ECM and igniter "just in case".
Terry
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snipped-for-privacy@hotmail.com wrote in

My '91 Integra has 248K miles and the interior of the distributor is entirely original, except for the rotor which I change every few years.
I wonder if maintenance might be a factor in igniter longevity the way it is with coil longevity. Since the igniter is doing a lot of monitoring as well as current carrying, might a large enough deviation from design spec in ignition system characteristics overload the igniter?
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It might be related to spark plug wire condition,and spark plug condition;if your wires are breaking down,it would place a greater load on the coil,and if the plugs were gummed up,slagged,or carboned,that would affect the coil voltage. IMO,igniters fail because of transients and migration of metals in the Darlington and IC.
One could conceivably use an electron microscope and examine failed igniter semiconductors and see why they failed,but it would be an expensive undertaking,unless you're a college student with access to an e- microscope,and doing a thesis or paper.
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Jim Yanik
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Jim Yanik wrote:

there are two "migration" mechanisms - first is solid state diffusion. that's where the bit about the life halving every 3 degrees comes in.
the other is a mass transportation effect at high current densities.
unfortunately, high current leads to heat, and semi conductors have high current densities, so the only real way to know for sure about the failure mechanism, as you say, is microscopy.

of the two igniter types tegger shows, the second is designed more for a high temperature environment from what i can see. the small scale circuitry in the components of the first igniter have much smaller diffusion paths. the larger scale thick film device has, for semiconductors at any rate, truly massive scale features. these are bad for speed, but even at 10,000 rpm, that's only 166Hz, not exactly a high frequency challenge.
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snipped-for-privacy@hotmail.com wrote:

that would be most excellent!

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I don't think the heat is too great for the ignitor. There apparently aren't any electrolytic capacitors in it, and those are the big heat sensitive worries.
The vulnerability of transistors to heat is related to junction temperature and to collector voltage. When the collector junction gets hot enough, the reverse voltage across it can make the dopants migrate and "blur" the junction. That spot gets hotter and eventually melts, leading to the device being shorted.
But the heat required to melt the junction without the voltage stress is much higher than your engine compartment - the melting point of silicon is over 2500 degrees F. The silicon chips are typically soldered to the heat sink internally, and I have personally soldered a UHF power transistor to a large copper heatsink with an acetylene torch.
Mike
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Michael Pardee wrote:
I don't think the heat is too great for the ignitor. There apparently aren't any electrolytic capacitors in it, and those are the big heat sensitive worries.
The vulnerability of transistors to heat is related to junction temperature and to collector voltage. When the collector junction gets hot enough, the reverse voltage across it can make the dopants migrate and "blur" the junction. That spot gets hotter and eventually melts, leading to the device being shorted.
But the heat required to melt the junction without the voltage stress is much higher than your engine compartment - the melting point of silicon is over 2500 degrees F. The silicon chips are typically soldered to the heat sink internally, and I have personally soldered a UHF power transistor to a large copper heatsink with an acetylene torch.
Mike -------------------------------------- Yes, but you didn't put power to it until after it cooled down, and I bet you moved a lot of air across that heatsink to keep it cool. In service the transisotr is switching at least 5A. I have the exact value in my notes, and yes it is a fast switch, the transistor is driven completly and rapidly into full conduction so the Vec is about .5V for ~2mS every few 10s of aMsec. Not a haeavy duty cydle by any means, but it runs, with "perfect" heatsinking to the block at ~195F. Those I measured actualy ran about 210~220F.
Somewhere I have the leakage versus temp from motorola and at +200F we are getting too darn hot. I saw a Ducati pointless ignition system that used a flip flop to switch between 2 transitor to cut the Pd in half. But that system was expossed directly to the airstream. Of the people I know who have had igniter failurs, Honda or Toyota, it has always been in >90F weather, most frequently in stop and go traffic on the way home. Except for one that failed in ~-25F weather on startup. I can't prove it, but I suspect if we could reduce the temp 20 or even 10 degrees F, the failure rate would drop "way down". Another failure mode that is only slightly heat related is the piezo effect on the junction when it switches. I had a early JBL switch mode power amp that ate switching transistors at fairly regular intervals. I had built, and still have, a ultrasonic down converter and you could plainly hear the transitors screaming at 40KHz. I supsect that heat, plus current stress, plus the piezo effect could explain most igniter failures. One could always attempt to place it remotly, in front of the radiator to breath cool air, but I suspect the lead inductanc would kill you and the RFI would be "interesting".
When I needed to align my R2000 SW I needed an "ignition like" noise source "with harmonics extending up too beyond 30MHz" I pulled my 1991 Civic under my "long" wire antenna, and adjusted the noise blanker. Worked much better then the puilse generator at the shop where I work.
Terry
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snipped-for-privacy@hotmail.com wrote:

no proof required - it's true. google for fick's laws and the arrhenius equation. i too have considered cooling options for my civic's igniter, even remote mounting in a location where it's not in the air stream heated by the exhaust or getting thermal conduction from a nice warm cylinder head, but so far, i've just not had an appetite for the work involved. i'm also worried about electrical noise. electrically, it makes so much sense to have the igniter mounted in close proximity to the coil - nice clean signal, faster switching, etc. but the reality is that the igniter is kept so toasty warm located where it is, it's always going to fry in short order, unless you live up in the frozen north of course, [tegger]. i now carry a spare.

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