What does Ignition Module actually do??
03-30-2004, 12:01 AM
#1
Three Wheelin'
Thread Starter
What does Ignition Module actually do??
The IM on my S2 died the other night - stranding me.
It was quickly diagnosed and fixed by a great little local shop. Thanks to GTi Tuning here in Toronto.
But it got me thinking - what does the ignition module actually do? And why do only the 16V cars have one?
Thanks for any insight!
RK
It was quickly diagnosed and fixed by a great little local shop. Thanks to GTi Tuning here in Toronto.
But it got me thinking - what does the ignition module actually do? And why do only the 16V cars have one?
Thanks for any insight!
RK
03-30-2004, 12:09 AM
#3
Three Wheelin'
Thread Starter
$130 CDN and it takes moments to install.
Apparently they fail with some regularity. Might be prundent for the 16V crowd to have a spare on hand. Unlike the DME relay - I'll bet you can't fabricate a bypass with a couple of bits of wire and three spade plugs!
RK
Apparently they fail with some regularity. Might be prundent for the 16V crowd to have a spare on hand. Unlike the DME relay - I'll bet you can't fabricate a bypass with a couple of bits of wire and three spade plugs!
RK
03-30-2004, 12:17 AM
#5
Three Wheelin'
Thread Starter
Sorry man! But they are SO easy to swap - it's RIGHT THERE behind the drivers side headlight - that it would be a shame to be stuck like I was for want of one. I think between those and the DME relays - you'd be prepared for 90% of no-start situations.
RK
RK
03-30-2004, 12:09 PM
#6
Drifting
Join Date: Feb 2003
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My old car went though 2 or 3 in a matter of a month when I upgraded my coil in the car. Not sure how hard on a porsche but on my Pontiac Fiero gt it was easy, just 2 screws and a connection.
03-30-2004, 12:21 PM
#7
Burning Brakes
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I think all 944s have them. But on the 8-valve cars, and the 968, they're in the ECU.
I think that the all-too-common 8-valve ECU failure is in this stage of the ignition. And since it's part of the PCB in the ECU, you have to buy a whole new ECU. I thing Bosch either discovered this problem after the 944 had been out for a couple years, or suspected it might happen, so at the time of the 16-valve engine management re-design (knock sensors and stuff integrated), they decided to move it out of the ECU and to just about the furthest point from the ECU they could find.
Then after a few more years, Bosch solved whatever the issue was with putting the igniter module back in the ECU, and put it back. So the 968 has the igniter module back inside the computer.
I'm not sure what it actually does, though. It does "something" to the signal from the ECU to the coil.
Bryan
I think that the all-too-common 8-valve ECU failure is in this stage of the ignition. And since it's part of the PCB in the ECU, you have to buy a whole new ECU. I thing Bosch either discovered this problem after the 944 had been out for a couple years, or suspected it might happen, so at the time of the 16-valve engine management re-design (knock sensors and stuff integrated), they decided to move it out of the ECU and to just about the furthest point from the ECU they could find.
Then after a few more years, Bosch solved whatever the issue was with putting the igniter module back in the ECU, and put it back. So the 968 has the igniter module back inside the computer.
I'm not sure what it actually does, though. It does "something" to the signal from the ECU to the coil.
Bryan
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03-31-2004, 02:27 AM
#8
Three Wheelin'
Thread Starter
Bump - I still really want to know what it does - anyone - Bueller?
(although thanks for the interesting history on the ECU, Bryan! Never knew any of that!)
RK
(although thanks for the interesting history on the ECU, Bryan! Never knew any of that!)
RK
03-31-2004, 05:30 AM
#9
Race Director
It's an amplifier to switch a high-current load using a small-current drive signal. Basic darlington transistor circuit. The DME sends out a low-power signal (200-500ma) that switches on & off the transistor in the ignition-amplifier (also known as ignitor). The transitor then switches on & off a high-current (10-15amps) signal to charge and dump the ignition coil.
Another reason to relocate the ignition box is that the high-current and high-frequency also tends to cause interference in the other low-power circuits in the DME box.
With the newer cars the entire ignitor & coil assembly is situated directly over the individual plugs themselves to keep the length of the highest interference wires (the high-voltage spark-plug wires themselves) to a minimum.
Another reason to relocate the ignition box is that the high-current and high-frequency also tends to cause interference in the other low-power circuits in the DME box.
With the newer cars the entire ignitor & coil assembly is situated directly over the individual plugs themselves to keep the length of the highest interference wires (the high-voltage spark-plug wires themselves) to a minimum.
03-31-2004, 10:02 AM
#10
Three Wheelin'
Thread Starter
Wow - amazing - thanks for that - very cool to finally know.
So all electronic ignition systems mus thave this circuit in some form - no? I vaguely remember them being an expensive replacement item on my RX-7 turbos - IIRC.
RK
So all electronic ignition systems mus thave this circuit in some form - no? I vaguely remember them being an expensive replacement item on my RX-7 turbos - IIRC.
RK
