springer3

Here are the properties that you need to match in an alternative coil - good luck:

1) Primary resistance (both directions)
2) Primary inductance (both directions)
3) Secondary resistance (both directions)
4) Secondary inductance (both directions)
5) Turns ratio between primary and secondary
6) Magnetic coupling between primary and secondary
7) Magnetic saturation for the iron core
8) Insulation level
9) Power consumption/efficiency (don't want it to overheat or burn out the ignition module)
10) Mechanical mounting
11) Electrical connections
12) Environmental (can it tolerate the vibration, heat and weather exposure in the 964 engine bay?)
13) Any other electronic components inside where you can't see them (resistors, reactors, diodes, MOVs...)?

Geoffrey

Yes, the above is true, however, there is a wide tolerance for these types of ignition systems. The Bosch ignitior in the 964, and dual ignitor in the 993 function the same way and come on a number of different vehicles with different coils.

Lorenfb

"can we use the 993 coils on our car"

Yes. I've tested those with the 964 modules and they are fine.
As mentioned by others, don't always assume that it's a coil
problem. Again, though, avoid the Bosch silver coils.

MassGuy

Dutchcrunch I need to look into your theory. You may have something there.
I know I have a few oil soaked wires on the right side.

How do I test the wires to see if they are ok?

Indycam

If you take the car to a shop with a ignition scope , they can look at the wires on the scope while the motor is running .

Indycam

Springer3
So I went down to the car parts store and asked about the Magnetic saturation for the iron core ,
and they looked at me funny . What should I do ?

springer3

LOL, there is good advice being given here. Stick to combinations that are proven. I think blind experiments with high-voltage will mostly end in grief. Pelican sold me two Bosch silver coils when I replaced mine a year and a half ago. So far no problems.

elbeee964

Springer, you're my new best friend/pathfinder! lol

Since Loren's stellar silver coil commendation, I feel as though I'm tip-toeing out into a (silver coil) mine field.
But now I got you -- a whole four feet out in front of me!

Keep goin', brother. I'm right behind ya!
-Lonnie

dfinnegan

I've got two shiny silver coils from Pelican, as well. Very nearly a year in. So far, so good. Maybe we should start a coil poll!

dutchcrunch

Hello Massguy,

how many miles on the wires?? replace the wires, you cna test them but its really a waste of time if they are aged. you can ohm them out and check for continuity, but you cannot test them like if you had a laod on them, dont even waste your time taking it to the shop to have it put on the scope, more than likely they are going to charge you 100 dollars and tell you the wires are bad.

not only can the the wires cause coil failure but if the plugs are worn with excessive gaps that can really cause the coil to work extra hard.

the coils need the the components down steam of it to be working correctly and be in good shape or failure will result. just if you left the coil wire disconnected , if the voltage cannot get to ground then the coil will have to absorb the load.

i may not be saying this in the best technical terms but the fact still remains that the components downstream have a problem.

as loren stated you can use the 993 coils too,


check the wires, cap, rotor and plugs. now if money is the problem and the same coil keeps going bad then you need to find witch ignition system the coil fires and deal with that one only if you need to.


also look for the clear coat on the distributor cap lugs. i made a post about it, nobody ever responded but i know i cannot be the only one that has this happen. these are bosch caps from the dealer. my car never did run one one coil at a time, one system did the other did not, after i removed the clear coat on the new cap, the car runs on either, no problem.

dutchcrunch

lets put it this way, when you get it corrected, you know that the ignition system is fuctioning correctly if you can run and start car on either ignition coil and idle smoothly. this is not to say that it 100 percent, if you did not replace everything, but if you cannot run or start on 1 coil something is wrong, dont let no one tell you other. i belive this is a good test to see if the ignition sytem is working as it should at minimum!!!!



i bought some new wires. i have not installed them yet. but i did just change the coil wires , 2 of them and the car has much more power when excellerating. it ran good before , it idles smooth, will start on 1 coil and idle smooth, but i alway suspected that some power was missing when accellerating, i was going to replace my black coils but i thought i would do the wires first, like i said i only replaced the 2 coil wires and what a difference.

Lorenfb

"Pelican sold me two Bosch silver coils when I replaced mine a year and a half ago. So far no problems."

Based on data from many DIYers AND Porsche shops over the last five years,
the Bosch silver coils have exhibited a higher probability of failure. This doesn't,
though, imply that ALL Bosch silver coils will fail, but only that they can increase
the likelihood of ignition problems in the long term.

parsecnc4

Loren,

If Bosch non-Brazilian coils are no longer available and the Bosch silver coils are unreliable at best, what would you use as alternative? Would like to know your thoughts on this. MSD, Jacobs, Nology, Accel, etc... or buy a couple spares and throw in the trunk like DME relay?

elbeee964

heh.



"Whatcha got, there, in the trunk?"

"Oh -- the usual -- spare DME, couple coils, slave cylinder, coil leads..."

parsecnc4

While you are at it... don't forget the fan/alternator/PS/AC belts. Maybe I can start a kit with all those parts and present them in a briefcase like one of those detailing kits