Mystery Bosch Box, 69 /912

[C. Clark]

Hello,
Back in June when I bought my 69 / 912 I discovered an item that I have yet to figure out. In the engine compartment on the voltage regulator side there was a aluminum finned box, rectangular, approximately 5" wide X 3.5" high X 2" deep. It had 3 cabled leads labeled A B C , and a male double plug in above the cabled leads. It has a Bosch stamped label with # 0227 200 001, 12 volts.
The device had obviously been disconnected for some time and the car ran fine. My guess is it may be one of those coiless ignition systems, but I'm really not sure, I've checked around a bit but have yet to get the answer. If anyone can help me out that would be great.
Thanks,
Chas

[69 Soft Targa]

Hello Chas,
As suspected, you are looking at a Bosch Capacitive Discharge Ignition. A stock item for a 911 but not a 912. Is everything else stock?

[C. Clark]

Bob,

Thanks for the reply, as you suspect, I agree, after looking through several Porsche catalogs I found what I believe is the identical piece. It was very expensive, $1400.00 if I am reading this correct.
The car had been stored shorty after the body was totally redone, 5 years ago,. the previous owner says. I believe the car is not stock, a friend who knows a great deal more than me about Porsche says it runs to strong for a stock 1600. The only obvious non stock stuff was the header and muffler. It sounded a little loud to me so I replace the exhaust with another system that turned out to be a mistake. The car ran terrible with the new system so I put the more throaty one back on, car runs strong. I do know that it was sold once by a Porsche restoration company in northern Cal, who know what they may have done. Why would a 911 item be in a 912 car? As I said before the wires were disconnected and the mounting bracket appears home made. Thanks again,
Chas.

[Roland Kunz]

Hello

The Bosch CDI was often used on other high performance engines on the aftermarked. The system will run with every normal breaker contact ignition.

Grüsse

[C. Clark]

Hello and thanks for the info,
Do you know where I could find the wiring directions?, or anymore info in general on the unit. I have no idea if the thing works or not, is there a test that can be done? What would be accomplished by running it on my 912?
Thank you,
Chas

[Roland Kunz]

Hello

You just need the transformator ( the coil ) and then you hook it up like on the Porsche 911 ( You can even use the 911 harness ).
You will find details about that on the 911 section.

Grüsse

[C. Clark]

Roland,
Thank you for the reply, by coil I assume you mean the Bosch Blue coil, I found a great deal of info at the the 911 site, thank for the help. CD's have generated a lot of 911 conversation.
Regards,
Chas.

[Roland Kunz]

Hello

No the Bosch CDI unit needs a special "coil" ( witch is only a transfomator as it doesn´t load cahrge ).
They had been delivered in Black and partillay in blue for other manufactorers ( I think the NSU had been blue )

Grüsse

[C. Clark]

Roland,
So the regular "Blue Coil" is not the corrrect one? who has the correct one or what do you ask for?
I ran a basic diagnosis on the CDI, it whines when you put 12 volts through the ignition contact and ground, from what I gather thats what it is supposed to do. What do you think of the "Permatune" unit?
Thanks for the info,
Chas

[Roland Kunz]

Hello

The problem is that Bosch sold high performance coils for the aftermarked and they where blue as well and used in many cars ( Volvo ). And they where coils for standard ignitions. As said before the Bosch CD unit has not a coil. The thing looking like a coil is only a transformator and has a slight different working process.

But those transformators where also sold in several colores. Most where black but early ones where also in blue and not to forget some units where orange ( depending on the car manufactorer, Maserati or Alfa had sometimes orange units ).

So don´t go for the color make sure the order# on the bottom is correct match. You also can go for the terminals. Most CD units have only terminal +, - or A, B while normal coil have 15, 4

Grüsse

[C. Clark]

Hello,

The Bosch CD has ABC male lead outs which the harness attaches to. I really don't understand concerning the coil, The Bosch blue has only + and - on the plugin end. I assume that is not the one you say works with the CD. I bet it's the $100.00 coil that is offered for the early 911's. The car runs good as is, but in my youth I discovered that special ignition could change the performance of a good performing auto noticeably, perhaps a "Permatune unit" would be the more prudent method rather than fooling with 30 year old capacitors. What do you think.
Thank you,
Chas

[Roland Kunz]

Hello

Yes the Bosch CD unit has the ABC out plus the seperate ground.
The Output from that Box is send to a "coil" and transformed from 500 Volt to 50000 Volt.

If you use a standard coil they mostly run on 12 Volt or on 9 BVolt ( High performance )

The system "might" work with a normal coil for a while but the CDI transformer will not work in combination with a normal ignition. I never tried it as the CD unit maybe will not survive it and this is to big $ to test it even on my own car.



To prevent people mix up the systems the contacts ( terminals ) have differnt markings depending on the system.

To make it simpler:

On the CD Box:

A is Voltage out to the A contact on the transformator
B is 12 Volt input on the Box
C Input from the breaker contact

On the Transformator:
A is the incoming spark from the CD unit
B is GROUND

It is absolue important that the CD box and the Transformator have good ground and it is important to have the A wire shielded with the ground to the CD box as 500 Volt with some Millijoule behind it can kill persons.

Grüsse

[C. Clark]

Hello,



I tried several test on the CDI, initially I did the 12 volt hook it up to a battery and ground and got the whine that it is allegedly supposed to do if working, second I hooked it up to the car taking care to connect all wires in the proper places, as you said the grounding is very important. I could get no spark from the unit, I did a resistance test over contact B and C and got a direct short, test from A to C seemed intermittent, so I guess the thing is faulty and was probably disconnected because it didn't work. I'm still interested in the whole CDI concept though, and as said before I will probably at some point get a modern version of the CDI unit. Thank you so much for all your interest and time spent trying to guide me through this process, it was greatly appreciated.

Frohliche Weihnachten,
Chas

[Roland Kunz]

Hello

Ups sorry

The Bosch CD unit is overkill for a normal engine. They where used on high performance engines witch have a wider spread field between runing far to rich and far to lean for normal Ignition systems.

A typical newer replacement unit will work well too.

Since 1965 the ignition hardware made some big steps and on a 912 you have 12 Volt with makes it easy useable.

But the stock 912 ignition is very capable to handle the thing.

Grüsse

[C. Clark]

Roland,
By "typical newer replacement unit" I take it you mean the "Permatune" type units that all the retailers sell? Performance Products and Stoddard advertise them for 912s. They get $200.00 for them and claim significant inprovement in ignition performance.
On a different note, what do you think is wrong with the guys Porsche that turns over hard? The "I don't get it " post on the 912 board.
Die Gedanken sind frei
Chas.

[Roland Kunz]

Hello

Ups sorry again somehow the replay loads not all threads.

The CD box is not direct the spark giving unit.

The benefit from the system is that it can handle very short duty cycles and the charge time isn´t direct relatet to the dwell angle.

So there is no ballast on your contact witch will not burn up as fast as on standard ignitions.

Grüsse