Ignition updates to the Unofficial FAQ

jim beam > wrote in
:


>
> i too was under the impression that the igniter handled dwell because
> i know that happens with some other ignitions, but it seems that with
> the honda, all that's taken care of by the ecu. #4 is the for the
> ecu's output signal. the igniter just switches as soon as it gets
> signal.
>
> but that said, i do have the gear to test that properly this time...
> i have a spare working igniter - i'll do some more homework.


That would really be appreciated, thanks.


--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

TeGGeR® wrote:
> Kevin McMurtrie > wrote in news:mcmurtri-
> :
>
>
>
>>There's a lot more in the Ignition Control Module than a darlington
>>pair.
>
>
>
> True. And I see that in these photos.
> http://www.gcw.org.uk/rover/igniter.htm
>
> Here's another page to critique:
> http://www.tegger.com/hondafaq/ignit...adigniter.html

looks like a good summary. obviously, as graham's pics show, there's
more to the igiter than the darlington, but what you show is a good
interpretation of the result. it's also worth mentioning that in both
my igniter failures, there's been no code. terminal 4 is behaving as
per normal, [hence no ecu] but the igniter output is failed hard "on"
and switching the input makes no difference to output.

i think it's also worth showing the condenser & mentioning its role too.
it's a $25 part & a pita to replace, but mine failed with a near dead
short so even before the igniter failed, my car had been chronically
weak & the exhaust way sooty because there was no strenght to the spark.

>
>
>
>>As I see it:
>>
>>1: Tach output
>
>
>
> It's there.
>
>
>
>>2: Coil output
>
>
>
> It's there
>
>
>
>>3: +12V
>
>
>
> It's there
>
>
>
>>4: TDC pickup
>
>
> According to the diagrams I'm seeing, such as
> http://www.tegger.com/hondafaq/misc/rov-ign.jpg
> #4 goes directly to the ECU. I think the TDC pickup goes directly to the
> ECU as well.
>
>
>
>>Case: GND
>
>
>
> Yes, but not really nesessary to show in this context.
>
>
>
>
>>The TDC sensor produces a curved waveform. Integrating the form
>>(high-pass) can produce the advanced timing needed for dwell.
>>
>>
>>
>>>>And yes, the ignitor gets flyback voltage too. Some electronic
>>>>ignition systems still need the condenser because the flyback voltage
>>>>on the primary side otherwise rises extremely rapidly. It can rise
>>>>faster than some high voltage transistors can turn off and it can even
>>>>rise before the spark plug discharges the energy.
>>>
>>>
>>>So how would I show that in the graphic? If there's a cap somewhere to
>>>blunt the flyback, I'd like to have that shown.
>>
>>Maybe Jim Beam can take a photo of his o-scope. My new Honda has a coil
>>on top of each spark plug so I'm not sure I can tap into the primary
>>coil. I have a circuit that drives coils but it's not quite the same as
>>a car ignition. Want a picture of that trace?
>>
>
>
>
> Sure! Thanks.
>
>
>

Kevin McMurtrie > wrote in
:

> In article >,
> "TeGGeR®" > wrote:
>
>> After a long passage of time and much dithering, I've finally
>> finished two big updates.
>>
>> 1) New section on igniter function
>> http://www.tegger.com/hondafaq/ignit.../howworks.html
>>
>> 2) Coil failure
>> http://www.tegger.com/hondafaq/start...s.html#badcoil
>>
>> Any critical advice is welcome. I'm not an electronics engineer, so
>> there are surely mistakes somewhere.
>
> A little adjustment to the graphics:
>
> The darlington pair is the switch. Pin 3 would be the pulses from the
> ECU or magnetic pickup. The tach connects either to the primary
> winding (which makes radio interference) or to whatever drives the
> transistors.
>
> And yes, the ignitor gets flyback voltage too. Some electronic
> ignition systems still need the condenser because the flyback voltage
> on the primary side otherwise rises extremely rapidly. It can rise
> faster than some high voltage transistors can turn off and it can even
> rise before the spark plug discharges the energy.
>

I looked up the Darlington transistor that is depicted on the Honda
igniter,and it has an internal diode to shunt the flyback voltage around
it,to protect the Darlington.

--
Jim Yanik
jyanik
at
kua.net

Jim Yanik .> wrote in
:


> I looked up the Darlington transistor that is depicted on the Honda
> igniter,and it has an internal diode to shunt the flyback voltage around
> it,to protect the Darlington.
>


Got a URL or a pic? I'd like to add that diode.

The pics I found showed resistors, but no diodes.

--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

TeGGeR® wrote:
> jim beam > wrote in
> :
>
>
>
>>i too was under the impression that the igniter handled dwell because
>>i know that happens with some other ignitions, but it seems that with
>>the honda, all that's taken care of by the ecu. #4 is the for the
>>ecu's output signal. the igniter just switches as soon as it gets
>>signal.
>>
>>but that said, i do have the gear to test that properly this time...
>>i have a spare working igniter - i'll do some more homework.
>
>
>
> That would really be appreciated, thanks.
>
>
probably not for a couple of weekends.

as a footnote to the condenser replacement, as i said before, both the
failed condenser & the condenserless crx distributors produced no r.f.
interference on the car stereo. but, if i was on the [hands free] cell
in the car, people always used to complain about static, even though i
couldn't hear any myself. tonight, [shows how bad it used to be that
i'd not bothered with the cell in the car for this long] i had to make a
call & i'm told it was completely clear! so the condenser /does/ make a
difference, even if the car stereo itself is sufficiently well filtered
to not be susceptible. this totally confirms kevin's rise rate explanation.

In article >,
jim beam > wrote:

> TeGGeR® wrote:
> > jim beam > wrote in
> > :
> >
> >
> >
> >>i too was under the impression that the igniter handled dwell because
> >>i know that happens with some other ignitions, but it seems that with
> >>the honda, all that's taken care of by the ecu. #4 is the for the
> >>ecu's output signal. the igniter just switches as soon as it gets
> >>signal.
> >>
> >>but that said, i do have the gear to test that properly this time...
> >>i have a spare working igniter - i'll do some more homework.
> >
> >
> >
> > That would really be appreciated, thanks.
> >
> >
> probably not for a couple of weekends.
>
> as a footnote to the condenser replacement, as i said before, both the
> failed condenser & the condenserless crx distributors produced no r.f.
> interference on the car stereo. but, if i was on the [hands free] cell
> in the car, people always used to complain about static, even though i
> couldn't hear any myself. tonight, [shows how bad it used to be that
> i'd not bothered with the cell in the car for this long] i had to make a
> call & i'm told it was completely clear! so the condenser /does/ make a
> difference, even if the car stereo itself is sufficiently well filtered
> to not be susceptible. this totally confirms kevin's rise rate explanation.

Cellphones operate at frequencies hundreds of times higher than the rise
rate of the primary coil. What probably happened is that the rise rate
was faster than the transistor could turn off. In some cases you can
induce crazy RF oscillations if a digital circuit is forced into an
analog mode. That kind of oscillation roasts a transistor in a hurry
too.

The radio noise I mentioned is in cars like the older Toyotas where
there was a long meandering wire between the primary coil and the ECU
and tach. The 350V ignition pulses bled into everything. Aftermarket
component stereo equipment needed braided shields over the interconnects.

"TeGGeR®" wrote:
>
> Got a URL or a pic? I'd like to add that diode.
>
> The pics I found showed resistors, but no diodes.

I have looked long and hard at the photos of the ignitor. The darlington
device is definitely from STM (http:/www.stm.com). The part number is
hard to decipher, but I am quite certain the first line of the part
number is BUxy41. I can't for the life of me see if "x" is actually a
character or just picture noise. The "y" looks like an "8" or a "9". The
second line of the part number almost certainly is "ZT". This is
consistent with "BU941ZT", which is an actual STM part number with a
package type like the one in the ignitor photo. The description is "HIGH
VOLTAGE IGNITION COIL DRIVER NPN POWER TRANSISTOR". See
http://www.st.com/stonline/books/ascii/docs/5288.htm for details. The
data sheet is at http://www.st.com/stonline/books/pdf/docs/5288.pdf. The
data sheet shows the diode between emitter and collector.

The IC in the photo looks like it has part number U2226B, and a good
guess is that the TFK in the first line stand for Telefunken, a German
semiconductor manufacturer later renamed TEMIC and eventually bought by
Vishay. I have not found any data sheet for the U2226B, but I believe it
is an opto-coupler.

Here are oscilloscope traces of an ignition coil with and without a
capacitor:

http://www.pixelmemory.us/Photos/Nerd/flyback/

Kevin McMurtrie wrote:
> Here are oscilloscope traces of an ignition coil with and without a
> capacitor:
>
> http://www.pixelmemory.us/Photos/Nerd/flyback/

awesome! that one without capacitor is /real/ ugly...

In rec.autos.makers.honda jim beam > wrote:
> Kevin McMurtrie wrote:
>> Here are oscilloscope traces of an ignition coil with and without a
>> capacitor:
>>
>> http://www.pixelmemory.us/Photos/Nerd/flyback/

> awesome! that one without capacitor is /real/ ugly...

It reminds me of my Mazda rotary with points. I could see the dwell begin
to take up too much time as the RPM got higher.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5