Unofficial FAQ: Ignition corrections

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.

 

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.

 

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.

 

So I've read.

Terry seems to have determined that there is evidence of this.

 

So I've read.

Terry seems to have determined that there is evidence of this.

 

One more update:
http://www.tegger.com/hondafaq/igniter-operation/index.html

This has been a most interesting thread, I must say.

 

One more update:
http://www.tegger.com/hondafaq/igniter-operation/index.html

This has been a most interesting thread, I must say.

 

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

 

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

 

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?

 

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?

 

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.

 

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.

 

that would be most excellent!

 

that would be most excellent!

 

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.

 

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.

 

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

 

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

 

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