Ignition coil questions...

[DCUK Martin]

DC resistance is important. It sets the current when the "points" remain closed.

The ballast resistor and the coil's parasitic resistance does that. Measuring the DC resistance of the coil doesn't tell you the inductance of the coil and therefore how it will behave to a unit step... (which looks like an open circuit initially).

[sean]

I have never "predicted the failure of your ignition system" I've simply recommended other people not copy you because your reasoning for changing the stock system is rooted in your own ignorance.

Sometime it's not ignorance but rather he does not wish to deal with hard things. Take for example his view on fuel pump covers which he now suggests owners leave off and install a water dam because:

Pump covers suck. They are a PITA to install, they shrink with time, and they crack.

taken from Farrar's blog thread

[Bitsyncmaster]

The ballast resistor and the coil's parasitic resistance does that. Measuring the DC resistance of the coil doesn't tell you the inductance of the coil and therefore how it will behave to a unit step... (which looks like an open circuit initially).

Yes the inductance will change a lot when the current is changing but that is only for a very short time. The rest of the time it is DC resistance. Now if the input was a sine wave that would eliminate any DC resistance importance because the current would always be changing.

I think our cars used two resistors because they could not find a coil with the proper characteristics. It would be better to use one resistor for starter bypassing with the proper coil.

[content22207]

I think our cars used two resistors because they could not find a coil with the proper characteristics. It would be better to use one resistor for starter bypassing with the proper coil.

Read up on the history of the Bosch Blue coil. It debuted in the late 1960's, when most ignitions were still breaker point. The Bosch Blue coil was designed to produce optimal spark from the ~6 volts primary that was then the industry standard (6 volt Volkswagen owners -- that's 6 volts car voltage -- couldn't buy them fast enough).

Fast forward to 1981. By then, the Bosch Blue coil was looking very dated indeed. Nearly every manufacturer had upgraded primary coil voltage to at least 10 volts. Nearly manufacturer was running ~.05" plug gaps that higher voltage coils made possible.

It cracks me up when owners claim that DeLorean ignition was optimized for performance. Quite the opposite -- it was dumbed down for the coil.

Bill Robertson
#5939

I've simply recommended other people not copy you because your reasoning for changing the stock system is rooted in your own ignorance.

Actually, my reasoning for changing the stock system is rooted in increased performance.

Bill Robertson
#5939

Sometime it's not ignorance but rather he does not wish to deal with hard things.

Nothing quite like impartial and objective moderation, eh?

With all due respect, it is less hard (easier) to leave a stock ignition in place than it is to do the research and make the changes necessary to upgrade ignition to 1981 standards, much less 21st century standards.

Bill Robertson
#5939

[sean]

Nothing quite like impartial and objective moderation, eh?

It truly rocks!

[ramblinmike]

Regardless of everyone's position on the stock vs. modified coil/ignition, everyone should at least agree that the stock plug gap is pretty small.

As the years went on every car manufacturer has found a way to increase secondary voltage and with it the plug gap.

A stock system works well. That has been proven through millions of real-world miles cars with a similar setup have put on the road. What I don't understand is why a car company would base their 'new' electronic ignition around the use of an off-the-shelf coil. If they were putting the money into developing this new system why not develop a new a new coil to take advantage of the breakerless ignition?

Bosch wasn't the only one to do this. Ford did the same thing over here. I just don't understand why they would stop at 6-8v at the coil. They knew in the 60's that increased primary voltage was the way to go for performance and economy. They wouldn't have resorted to dual-point distributors (and the associated headaches) if they didn't.

[content22207]

In the 1970's Ford used 10.5 volts primary (Duraspark breakerless ignition). Plug gaps were .044".

Bill Robertson
#5939

[ramblinmike]

In the 1970's Ford used 10.5 volts primary (Duraspark breakerless ignition). Plug gaps were .044".

Bill Robertson
#5939

Here's where I found the info I was basing my statement:

http://www.autozone.com/autozone/rep...00c15280077d43

From the above troubleshooting guide:
"If no spark occurs, measure the voltage on the battery side of the coil.

Less than 6 volts - Repair the wire carrying current to the battery terminal of the coil and repeat test.

If voltage is 6-8 volts - Substitute, but do not install, a known good module and repeat the test. If spark then occurs, reconnect the original module to verify its being defective. Replace as required. Refer to step 10 if the battery voltage is present."

This is not a Ford document FWIW.

[Bitsyncmaster]

Automotive coils need to switch 5 to 10 amps to work. It does not mater if it takes one volt or 100 volts to get that current in the primary. The output voltage is produced when the the current is switched off (open points) so at that time your + side of the coil will be 13.5 volts no mater if you have no resistor, 1 ohm or a 1000 ohm resistor.

[DCUK Martin]

Actually, my reasoning for changing the stock system is rooted in increased performance.

Give me detail - how much performance did you gain? Put your money where your mouth is....