ignition condenser - revisited

i wrote here a few months back about how my civic had lackluster
performance, but this had been changed by replacing the condenser on the
distributor. well, i'd kinda forgotten the degree of difference this
change made, so when i revisited this situation again last weekend, i
was surprised to confirm the same effect.

long story short, after my last igniter failure, i'd been looking for a
spare distributor "just in case" so i could keep it in the trunk rather
than pay $300+ towing charges in the event of another breakdown.
finally, i managed to find a spare oem distributor [$10!!! thank you
craigslist!!!], tested it and put it on my car. it worked fine and the
car fired up immediately. /but/, performance was very ho-hum. double
checked the timing, no problems. put the old distributor [new
condenser] back on, checked the timing, and hey presto! back to driving
being a ripping good time again! this was /exactly/ the scenario i'd
experienced before.

the moral of the story: while i have no convenient means to measure
sparking performance or h.t. voltage output from the coil so can't
factually confirm by observation, a 16 year old condenser vs. a brand
new one seems to show a distinct degradation in performance. the
distributor with the old condenser works ok, no real problems, but
there's just no "pep" to the motor. the distributor with the new
condenser solves all that. in all other respects, my distributors are
identical. so, if your 88-91 civic lacks a little in the "pep"
department, consider condenser replacement - works for me.

 

++++++++++++++++++++++++++++++++++++++==
Call around to the electronic repair services. I bet you will find one
that has a Honda owner and teh equipment to measure the
charactorisitics
of that capacitor. Given how hot the entire assembly runs at, I
wouldn't
be suprised if the value shifted, the "dialectric absorbtion" shot up,
or the ESR increased. Any of these will result in less effective
capacitance.

Terry

 

wrote in

And less effective capacitance would result in what? A reduced spark?

 

yes, lower spark energy. this affects output - to a degree.

 

Would this condenser perform the same sort of role a Kettering condenser
would?

My '91 'Teg also has such a condenser. The factory manual even shows it,
but is totally silent on what it's there for.

 

thanks terry! i have a capacitance function on my cheapo dvm, and it
read the correct value cold. but i didn't check hot or at working
voltage [obviously]. guess that'll be another project some time.

 

yes, identical function.

if your car has plenty of pep to it, i wouldn't worry about it.
afterall, your climate is cold enough that you're still on your original
igniter, correct? heat is my suspicion for the condenser degradation on
my car.

 

++++++++++++++++++++++
Until Jim posted his experiences with the capacitor I wouild have bet
it was only for RF noise supresion. In the Kettereing system, it's main
prupose was to reduce pitting of the breaker points. And it went across
the points. I don'thave a diagram with me, but I think the cap in the
Honda Civic is across the +12 coming into the coil. I am going to have
to do some experiments and try to understand this. Perhaps, and this
is all theory, the capacitor charges between pulses and reduces the
effect of the inductance in the wiring. Kind of a stretch, but it
almost makes sense.
Capacitors have several failure modes.
The most common is a reduction the amount of capacitance.

Next is ESR, Effective Series Resistance. This is like
adding a resistor in series with the cap. A very common
failure mode for electrolytics.

And the last odd ball failure mode is Dielectric Absorbtion,
AKA "Capacitor Soakage". I am unfamiliar with this being an
issue with modern film caps. But cooking one for days on end
could change the charactoristics of the dielectric.

Loss of capacitance is the most common, and ESR is second.
Either will reduce the ablilty of a cap to sotre and release
energy.

Rereading this I see it might be possible for "noise" from the
ignition coil to get back to the ECM if the capacitor isn't there
to supress it. This could result in the ECM making wrong commands.
But I would expect such a gross error condition to produce back
firing as well a loss of performance. When the internal tansistor
switch turns off there is a heck of a back EMF induced onto the
12V power rail. I will have to look at it with a oscilloscope
adn see what, if any, amplitude pulses are created. I would expect
the noise to be effectivly surpessed by the lead acid battery.
But who knows. Fast rise time noise is more like RF then DC and
can do some very "funny" things.

Terry

 

Tegger, hey, hope you didn't miss this query from Jim. That would knock my
proverbial socks off if your 91 Integra were still on its original ignitor.

Is it?

 

Are you sure? It's in the line from ignition switch to coil, which suggests
to me that it's there to prevent back-voltage from getting to the ignition
switch.

Kettering condensers absorb primary voltage for a time to keep the coil
field from collapsing until the points are far apart, to prevent flashover.
Transistorized systems don't need that, do they?

Yep. Distributor internals are 100% original except for the rotor.

Electronics really hate heat, don't they?

 

It is. Completely original distributor assembly. I'm a bit surprised
myself, actually.

I'm of the opinion that my very diligent maintenance has played a big role.
HT voltage has always had a secure path to the plugs, so the coil and
ingiter have never been subject to unspecified loads.

Rotor, cap, and wires are replaced every five years. Plugs every one or
two.

 

wrote in

Not quite. It's installed BEFORE the ground point.

As the points open and resistance increases, the condenser takes over and
keeps the primary current flowing for a while so the points can open enough
to prevent flashover. As the condenser gets saturated, current flow stops,
at which point the field collapses and a spark is generated at the plugs.

A good page for that:
http://users.mrbean.net.au/~rover/ketterin.htm

It is. It's in the line from the ignition switch to the coil.

That would be nice. It's mostly over my head.

 

well, i'm deferring to terry here, but as i understand it, the
condenser, correctly chosen for the inductance of the coil it serves,
form the classic RC charge/decay partnership. if the decay rate is
"just right", it should be enough to form those nice fat high energy
sparks on the h.t. side of the coil, without them being too weak because
decay is too slow or too fast giving spikey & eratic transients. i
believe that to be the same as kettering. with kettering, [no
condenser] causes big transients, and transients cause flashover on the
points and rapid erosion.

plausible, but i think you can also argue it as condensers conducting
high frequencies, not d.c., hence conducting transients to earth. i'm
foggy on this stuff dude - it's been a long time. i'm sure it'll help
reduce load on the flyback diodes, but it doesn't appear to be essential
because my crx didn't have any condenser at all [it was a reconditioned
distributor]. i guess what i should try is disconnecting the condenser
and seeing if that makes any difference to performance. actually, when
i tested my igniter, i also rigged it to a coil and spark plug i had
lying about - nice big sparks, no condenser.

semiconductors definitely do.

 

A memory jog:
http://users.mrbean.net.au/~rover/ketterin.htm

 

oops, make that an LC partnership!

 

snip
+++++++++++++++++++
I checked my ancient engineering textbooks, from 1973 when solid
state ignitions were just begining to become viable, and they all
mention the capacitor is to prevent premature wear due to arcing
of the actual points. I do know that in the early 1960s I was given
an automotive ignition coil andwas disapointed to find out that
you had to constantly intrupt the current to get a continious spark.
My dad showed me how to wire a 12V relay as a very crude vibrator.
I burned up the contacts in less then a week so we placed his
capactiro substitution box across the "new" relay and tuned for
minimum contact spark. The output voltage was uneffected, or
the effect was so slight as to be unnoticable.

I have designed and built "snubbers", a capacitor and a resistor
that much be matched to reduce switch arcs under haeavy loads,.
There are some very nice formulae that don't produce acceptable
results.

Your comment,"> Kettering condensers absorb primary voltage for a
time to keep the coil > field from collapsing until the points are
far apart, to prevent flashover.", could mean the capacitor keeps
the filed form colasping by taking time to charge mimicking a
temporary "short" across the switch.

Transistors are almost certain generate much higher transients,
and transostors desinged for heavy indudctive switching have
a special internal structure to enabel them to cope without
being destroyed. A common solution is to place a zener diode
across the collector emitter junction to limit the peak
voltage spike. I am old enough that I have seen early transistor
switches had a resistor capactor snubber across them.
I would rate the modern, specialty transistors that are designed
to switch inductive loads a 100, a hefty transitor protected by a
zener a 80, and a "plain oold transistor" a 50. Now if we had
24V or 48V as our power rail, MOSFETs would be very usefull,
and very robust. I designed a door latch using an early power
MSOFET in ~1982. It operated from a 48V supply and it is still
working. Newer MOSFETs are much better from every charactoristic.

My favorite ignition system was the CDI, "Capacitor Dischage
Iignition",
system. I designed and built one for a marine application that was
killer. It tended to eat spark plugs, but you couldn't foul the thing
with 50% oil premix. If I was on a budget and my ignitor died I would
be very tempted to design and build a CDI for my Civic. My main
complant
about CDI systems is the nasty RFI they produce. Which I why I suspect
Honda and everyone else went to active "ignitors" A nice hot spark,
but not too hot.

Terry

 

interesting! particularly your comment on cdi. i remember when diy cdi
ignition systems were all the rage in the electronics mags, but never
got around to building one - because i wasn't old enough to drive.
looking at my bosch automotive handbook, it also comments that cdi
"generally remains impervious to electrical shunts in the high-voltage
circuit, especially those stemming from spark plug contamination". it
also goes on however to say that "for many applications, the spark
duration of 0.1 - 0.3 ms is too brief to ensure the air-fuel mixture
will ignite reliably". that accords with your fouling resistance
comment and i guess explains why it's not used today in low emission
engines.

 

No, as I think you and maybe Jim have figured out already. See below.

To be exact, the radio noise capacitor which Jim replaced is in parallel
with the igniter.

The modern igniter took the place of both the old Kettering points and the
points' condenser. The Kettering condenser was in parallel with the
Kettering mechanical points. The condenser minimized sparking across the
points (like you note below). That's not needed with the transistor system
that the igniter provides, because with a transistor, there is no mechanical
breaking of a circuit that would case arcing. (Like you also note below.)

My 1985-1995 Chilton's manual labels the capacitor Jim replaced as the
"Radio Noise Condenser." Is this the same drawing as the one in your Helm?
The UK site's ignition system schematics do not show it, for some reason.

I put up the schematic showing the radio noise condenser at
http://home.earthlink.net/~honda.lioness/id5.html .

I suspect its function is described in the following paragraph:
"The vehicle engine is a primary source of radio static, especially on the
AM band. Static suppression devices, called condensers, capacitors or radio
chokes, are sometimes installed at the factory to deal with the problem."
http://www.findarticles.com/p/articles/mi_qa3707/is_199609/ai_n8757761

Right. My reading supports this. I used:

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/ignition.html

http://users.mrbean.net.au/~rover/ketterin.htm (which Tegger suggested)

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

Jim, two questions:

Where'd you buy the new capacitor?

Where exactly is it located? I do have Graham's little drawing which I think
shows the physical shape and relative size of the thing, and I see one of
the black/yellow wires from the coil connects to it, so I reckon I can track
it down. Still clues are welcome.

I believe you wrote at your site that you are fastidious about maintaining
the high tension side of the distributor system (that is, plugs and wires).
Is there anything else you do, like, I dunno, take apart the whole
distributor periodically and clean all the electrical contacts?

 

http://users.mrbean.net.au/~rover/electron.htm seems to affirm this under
its answer to the question, "Why electronic ignition?"

 

Elle wrote:

In the above quoted para - please note that 'radio chokes' are not
capacitors but rather inductors used to raise the impedance of the
line at radio frequencies to stop the interference getting out.

I have 'cleaned up' the drawing somewhat - would you like a new copy?
It is labelled as a 'Suppresser' there.

Also to note that cleaning the insulating parts on the HV side will
improve the quality of the spark, too. My troubles arose from a dirty
film forming on the inside of the distributor cap and attracting
condensation which leaked away the spark energy to such an extent
that the engine would cough but not actually start!