3.2 Ignition Coil

[TT Oversteer]

I'm troubleshooting a running issue with my 3.2 and considering the coil as a possible suspect. I'm currently running a MSD Blaster coil. Our host lists several different coils depending on whether it's a CIS or Motronic application. My car is a 77 911s with an 89 Carrera 3.2 conversion. Do these 12v coils differ in application? What's the best choice for the Motronic ignition system? Any higher performance options?

[TT Oversteer]

The Nology Pro Fire coil looks interesting and is recommended for the 3.2 Carrera. Has anyone used this with good results?

[wwest]

One of these would be BEST for CDI....

[JAR0023]

Used 3.2 coil just hit classifieds here. -J

FS: Misc used '84-89 parts

[304065]

get a used factory porsche 3,2 coil

[wwest]

Originally Posted by 304065

get a used factory porsche 3,2 coil

That would NOT be appropriate...

The '89 uses the old Kettering style inductive flyback ignition technique whereas Op is using the older CDI system that SHOULD be coupled with an "E & I" transformer type coil.

The Kettering system stores the spark energy in the coil's inductance PRIOR to initiating the spark whereas the CDI system stores the spark energy in the capacitor and then applies it to the "coil" primary to initiate the spark.

Op cannot switch to the 89 ignition absent the use of the '89's DME ECU and DME relay...a royal pain, that!

[wwest]

Oops...just ignore me.....

[TT Oversteer]

Scored the used 3.2 coil in classified and found this interesting info re: different coils

Bosch "Black" coil 0 221 102 006 8.5mH, pri res 2.1 ohms. Original SWB coil as above.
Bosch "Red" coil 0 221 119 030 8.2mH, pri res 1.3 ohms. Requires external ballast resistor.
Bosch "Blue" coil 0 221 119 027 12.8mH, pri res 3.2 ohms. This has an internal resistor.
Bosch "CDI" coil 0 221 121 001 1.8mH, pri res 0.2 ohms. This is for Bosch CDI only.
Bosch "Motronic" coil 0 221 118 322, 4.5mH, pri res 0.4 ohms. Original on Motronic cars.
MSD "High Vibration Blaster" coil 8222, 8.0mH, pri res 0.7 ohms, sec res 4.5k ohms, turns 100:1

As you can see there is a huge difference in Coil specifications over the years.

A few observations.

Points had a max current limit of about four amps. With a +12V nominal voltage at the coil, that meant that three ohms of resistance was necessary in the ignition circuit to keep the points from burning up. Hence the SWB 006 coil was used with an external resistor for normal operation, which resistor was bypassed during cranking when the voltage was lower anyway.

Same thing applies to the Red coil. This must be used with a 1.8 ohm external ballast resistor for points operation. That gets you 3.1 ohms, see above. For electronic ignition it's a different story, see below.

The famous "Blue" coil teaches us a lot. It has both an internal ballast resistor and a very high inductance. This will produce more ignition energy, but this coil's output will fall off dramatically as RPM increases. This coil would be fine for four-cylinder, low RPM motors such as the VW beetle, in which community the Blue coil is frequently found.

The CDI coil has very little inductance because in the Bosch CDI system, the coil does not store ignition energy, it's stored in a capacitor, which discharges through the coil. So the coil's purpose is to serve as a transformer only to step up the voltage from the 460V output of the CDI.

The Motronic coil is an interesting one. Looking at this, we see the tradeoffs made by Bosch and the Factory to get the right balance between ignition energy and high-rpm performance. Fairly low inductance and very, very low resistance-- this is due to the fact that the coil is switched by a transistor inside the Motronic unit, which can probably switch 10 amps or so. Having an onboard coil driver probably isn't great for the longevity of the control unit, however, which is probably why the Factory and Bosch started using external coil drivers with the 964 and 993.

[304065]

Originally Posted by TT Oversteer

Scored the used 3.2 coil in classified and found this interesting info re: different coils

Bosch "Black" coil 0 221 102 006 8.5mH, pri res 2.1 ohms. Original SWB coil as above.
Bosch "Red" coil 0 221 119 030 8.2mH, pri res 1.3 ohms. Requires external ballast resistor.
Bosch "Blue" coil 0 221 119 027 12.8mH, pri res 3.2 ohms. This has an internal resistor.
Bosch "CDI" coil 0 221 121 001 1.8mH, pri res 0.2 ohms. This is for Bosch CDI only.
Bosch "Motronic" coil 0 221 118 322, 4.5mH, pri res 0.4 ohms. Original on Motronic cars.
MSD "High Vibration Blaster" coil 8222, 8.0mH, pri res 0.7 ohms, sec res 4.5k ohms, turns 100:1

As you can see there is a huge difference in Coil specifications over the years.

A few observations.

Points had a max current limit of about four amps. With a +12V nominal voltage at the coil, that meant that three ohms of resistance was necessary in the ignition circuit to keep the points from burning up. Hence the SWB 006 coil was used with an external resistor for normal operation, which resistor was bypassed during cranking when the voltage was lower anyway.

Same thing applies to the Red coil. This must be used with a 1.8 ohm external ballast resistor for points operation. That gets you 3.1 ohms, see above. For electronic ignition it's a different story, see below.

The famous "Blue" coil teaches us a lot. It has both an internal ballast resistor and a very high inductance. This will produce more ignition energy, but this coil's output will fall off dramatically as RPM increases. This coil would be fine for four-cylinder, low RPM motors such as the VW beetle, in which community the Blue coil is frequently found.

The CDI coil has very little inductance because in the Bosch CDI system, the coil does not store ignition energy, it's stored in a capacitor, which discharges through the coil. So the coil's purpose is to serve as a transformer only to step up the voltage from the 460V output of the CDI.

The Motronic coil is an interesting one. Looking at this, we see the tradeoffs made by Bosch and the Factory to get the right balance between ignition energy and high-rpm performance. Fairly low inductance and very, very low resistance-- this is due to the fact that the coil is switched by a transistor inside the Motronic unit, which can probably switch 10 amps or so. Having an onboard coil driver probably isn't great for the longevity of the control unit, however, which is probably why the Factory and Bosch started using external coil drivers with the 964 and 993.

Yep, I wrote that over on early S, I am migrating a lot of these tech discussions over there.

[GH85Carrera]

OK, I am digging through old threads on coils.

I have a 85 Carrera and another coil has died. When the black goo is coming out the coil is dead.

What coil is available that is NOT the Bosch silver coil? My OEM black coil died after 28 years, the last coil only made it 6,000 miles. The MSD blasters seem to be OK for a SC but I have a Carrera and need the appropriate coil.

I have searched for the AC Delco E587A coil and I can't find one.

The Beru ZS109 is supposed to work but all I find is in Europe and I would really prefer to no have to deal with international shipping.

What coil can I buy for a 3.2 Carrera that is not a waste of time and money?

[GH85Carrera]

I was curious what Pelican sells. Of course the OEM Porsche and the same silver Bosch.

Pelican Parts - European Automotive Parts and Accessories - Porsche • BMW • Mercedes • Volkswagen • Audi • Saab • Volvo • MINI

There are 10 coils listed for a 1985 Carrera. Ain't no way they all could work. I just need to find the best one for my application.

[jlex]

It's obvious: go with the shiny one....

[Rodsrsr]

This is a problem for 3.2 owners. I researched this quite a bit as my original Bosch Black coil finally bit the dust. I was forced to get the Silver Brazil made replacement. So far so good, but I have it mounted vertically instead of the on the fan facing downward. The only other option would be a 964 type. They used the Bosch Black and usually sell as a pair, but you have to find a used set and now those too are getting quite old. It is a problem indeed. If anyone knows of a solution I'd love to hear it.

[Quicksilver]

Originally Posted by Rodsrsr

This is a problem for 3.2 owners. I researched this quite a bit as my original Bosch Black coil finally bit the dust. I was forced to get the Silver Brazil made replacement. So far so good, but I have it mounted vertically instead of the on the fan facing downward. The only other option would be a 964 type. They used the Bosch Black and usually sell as a pair, but you have to find a used set and now those too are getting quite old. It is a problem indeed. If anyone knows of a solution I'd love to hear it.

Doesn't really address anything. On a Motronic 3.2 the coil isn't mounted on the fan. It is mounted vertically on the driver's side of the engine bay. And in that position the silver Brazil coils are dying.

I'd call John Walker or TRE and see what they are using. They have to have a solution that will keep problems from coming back.

[GH85Carrera]

Originally Posted by Quicksilver

Doesn't really address anything. On a Motronic 3.2 the coil isn't mounted on the fan. It is mounted vertically on the driver's side of the engine bay. And in that position the silver Brazil coils are dying.

I'd call John Walker or TRE and see what they are using. They have to have a solution that will keep problems from coming back.

OK, I will call him.

One of the choices on the list of coils for a Carrera 3.2 from Pelican is the MSD Blaster part number 8222. I can tell you those are not any better than a Bosch silver coil. I mounted the MSD Blaster right before my 5,400 mile road trip. It was flawless for that trip but died two months later. The black goo started oozing out. I see it listed as a substitute for the stock coil but from what I am reading it is really a SC coil for use with a CDI ignition.

There is of course no CDI on a 3.2 Carrera. There just HAS to be some substitute out there. I don't want to drive around with 4 or 5 Bosch coils hoping one will get me back home.

[Pstallo]

WHATEVER you do. Do NOT get the silver Bosch coil!!!!!

I got one to replace my old black coil because I was just trying to replace potentially old parts. The silver one left me and my daughter stranded in the middle of the road. It just died while sitting at a red light and wouldn't start. Got a used black coil from Ebay and never had that problem again.

Afterwards, I read several posts recommending that I never use the silver Bosch coils.

[Rodsrsr]

Originally Posted by Quicksilver

Doesn't really address anything. On a Motronic 3.2 the coil isn't mounted on the fan. It is mounted vertically on the driver's side of the engine bay. And in that position the silver Brazil coils are dying.

I'd call John Walker or TRE and see what they are using. They have to have a solution that will keep problems from coming back.

Okay that makes sense. My car is a 76 with a 3.2 transplant so I think the coli was on the fan at one time. Once I turboed the car I moved everything anyway. I've had the Silver coil for about 6 months so far and all's good, but I would love to find a better alternative. The Black coil I had started and ran the car but produced a weak spark causing a misfire at high rpms. The new coil solved the problem but now Im stuck with a non reliable coil. The point is that an old Black coil may not always be the best answer.

[GH85Carrera]

I did a lot of on line searching and called some large shops. Either they are keeping the secret of coil replacement options to themselves or there are none. I came up with nothing but getting a new Bosch Silver.

Some places even said they had not had any issues with the Bosch Silver. I suspect that is the parts guy that sell parts putting his spin on it. I don't have access to the mechanic on the line that work on 30 year old air cooled cars. I suspect very few shops have them for customers.

So if any of you ever find a solid reliable replacement and a good source for that replacement please let me know. Until then I guess I will buy a three pack of coils to keep on the shelf in my garage.