Ignition updates to the Unofficial FAQ

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.

 

:

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/igniter-operation/badigniter.html

It's there.

It's there

It's there

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.

Yes, but not really nesessary to show in this context.

Sure! Thanks.

 

:

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/igniter-operation/badigniter.html

It's there.

It's there

It's there

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.

Yes, but not really nesessary to show in this context.

Sure! Thanks.

 

That would really be appreciated, thanks.

 

That would really be appreciated, thanks.

 

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.

 

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.

 

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.

 

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.

 

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

The pics I found showed resistors, but no diodes.

 

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.

 

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.

 

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.

 

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.

 

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/

 

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...