Electronic ignition - Revisited after I gave up!

[Zedyone_kenobi]

Installed my 60 amp alternator today with custom plug. Could not be easier. Great instructions Arne!

Took the car out for a drive. MY old alternator was only putting out 12.4 volts, my new one gets 14.5 volts. Very strong. I am getting almost 13.89 volts to the hot side of the coil, versus 12.2 volts. Car runs liquid smooth now. I cannot make the car hiccup or bog, or pop or sputter. Ran strong all the way to 6500 and even was smooth under all combinations up to that magical 5000 rpm band. I am very pleased. I swear the extra juice makes the fan blow stronger, but it is probably my imagination. I do wonder if it will effect my headlights since my old alternator was so marginally charging.

[motorman7]

I swear the extra juice makes the fan blow stronger, but it is probably my imagination.

Increased voltage in DC motors makes them run faster. Increased amps improves available torque (assuming it's needed). It's not your imagination...assuming you are running an electric fan.

[Zedyone_kenobi]

I get the engineering behind it and all (BS in MCHE), I was alluding to the fact that I am not sure I can actually feel 1 extra volt.

[GreenZZZ]

It felt like I got 5-10% more horsepower after the alternator upgrade even though I didn't hit an RPM wall prior to the upgrade. I run 92-93 octane with an E31 head.

[Arne]

So today, not quite five months after I put it all back in, I took it back out again.

To recap - back in April (at 70,500 miles) I re-installed the Pertronix Ignitor and 3Ω coil, along with a good old-fashioned tune up. New plugs, wires, valve adjustment, cleaned and lubed the advance mechanism, and new wiring to the Pertronix. This seemed to work. For a while.

But as the Summer has gone by, I've noticed an increasing tendency for the ignition to washout. At first it was just a bit if I ran it up over 6000. So slight, and I run it that high so seldom, that I wasn't sure it was happening. Then I started noticing it over 5500. Recently, it became noticeable just over 5000 RPM.

So I went back to the used points and original 39 year-old coil. No other changes at all. Runs perfectly all the way to redline again.

So during the driving I have done this Summer, something has changed/worn just enough to cause a return of the problem. It's worth noting that I have driven it a total of 1000 miles since putting the Pertronix back in. That's not much wear. Perhaps I could fix it with another fresh set of plugs. But plugs every 1000 miles? I'd rather change points once every year or two.

I had hopes that doing it all correctly back in April would have been enough, and the initial results were encouraging. But in the end, it certainly appears that for whatever reason, my car is simply not a viable candidate for electronic ignition.

[alhbln]

This might be a problem with the Ignitor overheating, i had similar effects with an Ignitor installation where the engine would start to run rough above 5000 RPM, then gradually it got worse until i let the engine cool down, and everything would be fine until the engine heated up again. Did you notice the same issues with a cold engine?

The overheating issue seems to be a design fault with the Ignitor. The Pertronix Ignitor uses an IGBT transistor for driving the coil, which lowers the coil current for circuit protection when the temperature rises considerably.

Up to 150ºC internal temperature everything works nice, then the current drops progressively up to 175ºC where the available current is below 1A.

The round mounting plate of the Ignitor is the heat sink of the IGBT, but as the engine (and thus the mounting plate) easily heats up to 80-90ºC, the IGBT can't cool down and warms up even further, up to a point where the coil current is so low the ignition starts to cut out.

You could either use a points or Pertronix Ignitor setup to drive an external (robust) transistor ignition, as example a MSD 5900 or convert to an optical pickup and transistor ignition such as the Crane XR700.

Good luck,

Adrian

[Arne]

This might be a problem with the Ignitor overheating, i had similar effects with an Ignitor installation where the engine would start to run rough above 5000 RPM, then gradually it got worse until i let the engine cool down, and everything would be fine until the engine heated up again. Did you notice the same issues with a cold engine?

Not temperature related, same thing hot or cold. I still tend to think it has to do with voltage. If I make a change that reduces the resistance to spark (i.e. new plugs), or to decrease the resistance/voltage drop to the coil it gets better. I'm currently highly suspect of the wire to goes to (and then returns from) the early four-wire tach. Edited August 30, 2010 by Arne

[alhbln]

Sounds like the supply power wiring if its not temperature related, but then the symptoms would be the same when changing to a points ignition setup, as the supply wiring itself does not change.

The symptoms you mentioned could indicate a defect Pertronix coil. If there is a broken wire or short in the secondary (output) winding of the coil, the output voltage would be quite low and barely sufficient to create a spark, especially at higher RPM. You could run the factory coil and resistor with the Pertronix ignitor as a test, the combination is equal to a 3.2 Ohm coil.

[Arne]

Sounds like the supply power wiring if its not temperature related, but then the symptoms would be the same when changing to a points ignition setup, as the supply wiring itself does not change.

The symptoms you mentioned could indicate a defect Pertronix coil. If there is a broken wire or short in the secondary (output) winding of the coil, the output voltage would be quite low and barely sufficient to create a spark, especially at higher RPM. You could run the factory coil and resistor with the Pertronix ignitor as a test, the combination is equal to a 3.2 Ohm coil.

I've tried that. My notes tell me that it was much the same with the OE coil and ballast, better (i.e. higher RPM before it stops revving) with the stock coil and the resistor bypassed.

[alhbln]

That leaves the Ignitor, which seems to have gone bad, or the magnetic shim had a bit of play and started to vibrate at high speeds but i guessed you checked that already.

I don't think its a problem with the supply wiring as your points setup is ok and the Ignitor is merely an electronic version of the mechanical switch, so your wiring seems to be fine.

[soundmasterg]

In 2 years I've had three Pertronix units....one was my fault but the other two developed the same problem you mentioned Arne. I swapped them under warranty and the one I am using now is perfect and has been in there for over a year. The first one would get hot and the car would flat out quit, usually when idling. The second one got too hot also and would miss at high rpms. I found out that I needed a new gasket between the distributor and it's mounting point on the block. Just replacing that gasket reduced the heat just enough to where the new one has behaved fine. The third one that was my fault failed because I had it disconnected, and reconnected the wires backwards by accident. Woops.

Overall I am happy with the Pertronix as my distributor was a bit worn and didn't work well with points at all....cutting out about 5000 rpm. The Pertronix works fine up to the redline and the car is faster too. Eventually I am doing a turbo swap and will use coil packs and get rid of the distributor.

Good luck with yours!

Greg

[alhbln]

Eventually I am doing a turbo swap and will use coil packs and get rid of the distributor.

Speaking of coil packs :-) Looks not really out of place as the spark wires are coming from the same location.