Bosch 3 pin cdi replacement

[dicklague]

I drive my 1973 911. It is not a Sunday morning car it is something I drive a lot. How much? Well about 10,000 miles a year. I have driven it over 120,000 since I acquired it. The chassis has a total of 230,000 miles and the engine over 120,000. I have a very nice 2.7 with MFI that was built by Mark Kinninger at Black Forest in San Diego.



My car in foreground......Bruce Meyer's RS behind. It is not a concours car, but it has had a full restoration 8 years ago.

Because it is a daily drive I have made changes such as better seats to make it more suited for my use. It is a valuable long hood, so I have not butchered of changed anything original on the car.

One of the things I did improve is the ignition system. I got tired of the points maintenance, and installed a Pertronix Ignitor II in the distributor. That was a great improvement and eliminated fiddling with points and dwell on a regular basis. I also added Nology wires and a Nology transformer type coil. Both of these items make a noticeable improvement ignition performance. I felt that I was getting stronger spark.




The Nology Pro fire coil......installed 10 years ago.

Over the years I keep looking at that oxidized Bosch CDI box and wondering if there is room for improvement there as well. Just like the Hall effect Petronix does a better job than points, maybe there is something that can do a better job than this 40 year old CD.



That Bosch box that is using technology from 50 years ago. 50 Years is a real long time in technology……heck, 5 years is a long time.

I would read Warren’s old posts on the Bosch and look at the photos and wiring diagrams and kind of scratched my head. It all worked and was quite serviceable, but it looked so basic and the components are so crude and basic in comparison to the new technology.

I guess it was very revolutionary at its time, and I certainly want to have a nice Bosch 3 pin on my parts shelf beautifully restored and repaired to put back in the car anytime, but I really want the best in performance and reliability in my daily driver 911. And I am convinced there is something better than the old 40 year old Bosch CDI.

This post is about my personal journey for a better ignition.

I have read many posts over the years about the MSD, and the Permatune. “my Permatune quit……the original owner put this thing in…..what do I do now?” Or ….”my MSD 6AL quit after a year and what do I do?” or …..”I can’t get the tach to work”

I am sure there are many installations of these products that are working well.




Electrical panel removed. A bit of messy add-on wiring. The small metal box is a 5vdc power supply for the map sensor that feeds into the AFR. Relay is for cold start solenoid [both of these will be redone in final install].


I finally decided to sink my teeth into the problem of what CDI is a good choice for my 911. I have to admit that the MSD stories have me worried a bit, and my Hot Rod and Bonneville friends are not reassuring on MSD. They seemed to trust Mallory.

Also MSD declared chapter 11 bankruptcy in December 2013, and was bought up by a private equity firm at the end of December 2013. Hard to say what this means. I am sure there is lots of product in the pipeline and they do need to keep generating revenue so product will surely be available. I just wonder what will happen to R&D spending and whether more product will be produced off shore somewhere.

I have to admit that I did have a bias going in. I have a Daytona-Sensors AFR instrument that has helped my sort out my MFI in a big way, and I love the quality and design of this unit. The execution is almost military spec and the quality with the latest surface mount components is outstanding, and it has worked well for 5 years.

I know one of the principals at Daytona-Sensors and like their engineering and quality attitude. Everything is built in the USA.

When they came out with their CD-1 ignition I was intrigued by the build quality and the features. Basically I wanted to investigate if this was a good solution to upgrading the CDI with a unit that would give good performance and reliability.

So if you guys are interested, I would like to take you along on my journey with this quest for a better CDI in my old 911.

[dicklague]

No comments.....and I know this is a tough crowd.....so will continue with my story of what I have learned in getting up to speed on CDIs to replace the old Bosch.

Why replace the old CDI at all? My reasons:

1. I know there is lots of improvement to be had in spark duration and intensity with more modern CDIs.

2. I would like to have a soft rev limiter that is electronic and adjustable rather than the 7000 RPM rotor mechanical version that sort of violently cuts off the spark. It would also be nice to set it lower if you like.

3. I assume that a quality CDI will be reliable. I have no complaints with the stock reliability, but maybe a new one will be more reliable than the 40 year old one.

4. I would like to have future growth possibilities like a shift light, and maybe programmable advance. Maybe data logging so I could see how the ignition is performing in use.


WHAT IS AVAILABLE ?

There are lots of CDI units that will work well in older 911s with a single distributor.

The MSD Street fire sells for less than $200 and has adjustable sort rev limiter, good output, multi spark, and can be used on points or magnetic sensor input distributors.




It has been installed by a few Pelicans with good results. I would recommend a good "E" type transformer coil to go with it so that you take full advantage of what it can put out. MSD openly admits that at this price it is made in China, but they do test all of them in the USA. I don't mean to be critical here, but it is built for a price.

there are other units in this price and feature range that probably would work as well.
Here are a few.

this is the Summit Racing CDI


Crane:


MALLORY:



How hard are they to install?

The wiring on most of these units is very similar. As a matter of fact lots of them use the same color coding for the wires.

Electrical connections strike fear in a lot of people, but these CDIs are not that difficult.

1 thick red and black wires go to +12 volts always on and ground.
2. Small Red wire to switched +12 volts
3. White wire for points trigger.
4. Grey wire for tach [12 volt square wave pattern]
5. black and orange bundled wire to the coil + and -

Wires #2 and # 3 can be plugged into the 3 pin plug at the red and black wires.

You will have to hook up the thick red to a constant source of 12 volts like the defroster fuse #3 in the back.

Mounting will vary, but some rubber lord mounts are recommended. The mounting may be the most difficult part of the install because the form factor is different from the Bosch, and there are considerations like being able to see the LED and reach the rev limit dials for adjustments.

The only connection that is new is the thick red +12 volt wire. The Bosch CDI uses switched 12 volts only, but these units need up to 10 Amps or so because they are much more powerful so they draw more power. It won't do to have this power go through the ignition switch.

Luckily there is a heavy wire in 911s that goes from the starter to the 14 pin connector, so you can pick this always on higher amp 12 volts there. Just be sure your 14 pin connector is clean and not corroded ( I found out the hard way!).

The most important connections for a reliable set that will work well and not damage the CDI are the +12 vdc wire and a very good ground. Make sure that you have a solid connection that is at least 10 gauge to the starter. The connection in the fuse box mentioned above is the minimum you should have. I have to say that I am nervous about this connection running through the 14 pin connector and will probably connect it downstream fro this connector with a new 20 AMP circuit breaker just to be sure.

Make sure that you have a good ground and connection the ground wire goes to the main ground on the left side of the engine compartment. There is a braided ground strap goes to the panel that comes from the main ground. Connect here or to the main ground on the other end.

The above are the simpler units. MSD and others produce a great variety of more expensive and complex CDI boxes. They basically work pretty much the same with more power and more features. The newest ones are programmable and have features like shift lights and boost retard etc.. The competitive nature of the market has made them decent values as well.

I will wrap this post by saying that a good CDI made an immediate and very noticeable change in the performance of my 1973. And I have been driving it for a dozen years with the old stock CDI box. Response is much crisper, idle is better and those rich portions of MFI running are less noticeable. And I love the soft rev limiter.

[Porboynz]

Nice post, have you verified the 10amp running current yourself? Seems an awful lot of heat to disperse, unless they are very efficient and turn all those watts into spark. (13V x 10Amps = 130 Watts.) Might be a consideration for an engine running a 55 Amp alternator once the headlights and wipers etc are on. Mind you, I have no idea how much the Bosch 3 pin draws.

[dicklague]

Originally Posted by Porboynz

Nice post, have you verified the 10amp running current yourself? Seems an awful lot of heat to disperse, unless they are very efficient and turn all those watts into spark. (13V x 10Amps = 130 Watts.) Might be a consideration for an engine running a 55 Amp alternator once the headlights and wipers etc are on. Mind you, I have no idea how much the Bosch 3 pin draws.

Most of these CDI units are claiming .7 amps per thousand RPM. Some may be a bit more. So you are looking at 3.5 amps at 5000 RPM and 7 amps at 10,000. Some MSDs draw 10 amps. Daytona-Sensors claims their CD-1 draws less than 5 amps at 8000 RPM due to their highly efficient switching power supply that they have patented.

I don't know what the Bosch CDI draws, but I will try to find out. I know these newer units have much more output so they draw more current. It is not unusual to see 120 or more mega joules out of these newer boxes. I will try to find out what the Bosch produces.

One thing that I have found very critical and is stressed in all installation instructions from the factory is a VERY good ground and a high capacity +12 Volt connection. Instructions state that you need to hook to the battery directly or to the starter wire that comes directly from the battery in the case of a 911. Don't compromise on this. In my case I hooked it to the wire that comes from the starter to the #3 fuse in the panel in the rear. I put a 20 amp circuit breaker in this line so as to not rely on an old open Bosch fuse in the panel. Again good ground and a high amp connection for the power feed line is VERY important.

My ground goes directly to the main ground behind the fuel filter.

The ideal would be a plug compatible connection to the 3 pin connector. But this is not realistic because the power wire in this plug is switched by the ignition switch. It would not be a good idea to try to draw that kind of amperage through the switch. So you can use the +12 vdc for the trigger or turn on connection, but NOT the main power feed. So you can use 2 of the 3 connections. Points wire (black) for input signal (usually white on the new CDI), and the red wire for the turn on connection (also red on the new CDI). The third wire in the 3 wire connector goes to the OE coil and is not used as these CDIs have their own pair of dedicated wires to the coil.

Plug compatible would be nice, but is just not an option for these CDIs.

On the other end of the system, the stock Bosch coil will work, but will reduce output. It is best to use a coil that will optimize the power of the newer CDI. Use and MSD recommended coil, like their Blaster or others. Some good systems like the Crane and the Daytona-Sensors come with a matching coil that is engineered for the system.

One last item, which has been discussed here on this forum often is the rotor. If you have a rotor with a resistor built in [recommended for the Bosch] , you will likely burn out the resistor. Use a non-resistor rotor. if you are using the CDI rev limiter then you should use a non rev limiting rotor.

[dicklague]

As I look at the old CDI posts here I can see where lots of Bosch 3 pins were replaced with aftermarket units because the cost of replacement was high and the availability of information and repair sources was not anywhere near what it is now.

For the purist the way to go is to replace or repair the Original Bosch. I even read one post the the owner left the Bosch in place and hid an MSD in the rear seat area and carefully wired the MSD so it looked like the Bosch was in use when it was not.

My experience has been that the Daytona-Sensors CD-1 has made a very noticeable power difference with my MFI 2.7. I would suspect that a carburetor equipped 911 will benefit a lot from a good CDI.

What is the difference between the Bosch and the more advanced systems? Several things.

1. One is stronger spark a good system will put out 130 or more Mjoules of power.

2. The spark duration can be as long as 20 degrees of crank rotation. MSD developed this idea and called it Multi Spark Discharge [MSD]. The patent on this system expired a long time ago and almost all system have this feature now. The long duration spark is active up to 3000 RPM. I does help idle and mid range on engines where the mixture can be occasionally too rich in some transients.

3. stronger spark at high RPM. The spark is strong enough that plug gaps of .045 are recommended.

4. Adjustable "soft" rev limiter. This is a great feature and works quite smoothly.

I have drive my 911 for over a dozen years with the stock CDI and have a good feeling for how the engine behaves. I feel I have my MFI well dialed thanks to posts here and a good AFR instrument. But MFI is not EFI and can present some really rich areas in some transients and RPMs even when well sorted.

I am really still setting the new CDI system up and will try bigger plug gaps in the near future, as I have to do a valve adjustment and that will include a plug change.

So I am a happy camper so far with the new Daytona Sensors CD-1. There are many features I have not yet explored, but it is working great and seems to be a very solid piece of equipment.

[Earlycar Fonzie]

Thanks for posting this information! I wanted to change my Bosch box to a MSD...but heard it from some purist. I have a 2.7 and want it to run the best that it can. The Bosch box will go in the garage incase I bring back to all stock.

[Porboynz]

If my Bosch 3 pin ever dies I plan to gut it and install an aftermarket kitset inside the case. Funny thing was when I bought the car about 20 years ago the CDI and coil was sitting in a box by the spare wheel as the previous owner had given up on it and gone back to points, condenser and coil ala original Kettering ignition). One day I thought I would try it out, connected everything up, removed the capacitor from the points and its been working fine ever since. Bizarre.

[gulf908]

I was at the Essen show last April and while at the Bosch classic stand I asked about the 911 3 pin CDI unit.
The Bosch guy said there was something on the way this year(2014) and to keep posted at my local Porsche spares outlet.
Without him saying too much I understood there will be a new tech unit in an old style casing to appear this year.
I will certainly put my hand up for one !

Cheers,
Dennis.

[dicklague]

Originally Posted by Porboynz

If my Bosch 3 pin ever dies I plan to gut it and install an aftermarket kitset inside the case. Funny thing was when I bought the car about 20 years ago the CDI and coil was sitting in a box by the spare wheel as the previous owner had given up on it and gone back to points, condenser and coil ala original Kettering ignition). One day I thought I would try it out, connected everything up, removed the capacitor from the points and its been working fine ever since. Bizarre.

Good decision on re-installing the CDI and happy it worked for you. I am sure one of the aftermarket circuit boards would fit inside. Maybe the MSD Streetfire would work. You also have a Sydney company M&W that made a small unit about the size of the Bosch maybe they have something M&W Ignitions

I love the performance of my Daytona-Sensors CD-1, but physical installation was more time consuming than the wiring. I did not want to modify the original pieces, so I was extra careful, but is all worked out well. I will post some before and after photos.

[dicklague]

Originally Posted by gulf908

I was at the Essen show last April and while at the Bosch classic stand I asked about the 911 3 pin CDI unit.
The Bosch guy said there was something on the way this year(2014) and to keep posted at my local Porsche spares outlet.
Without him saying too much I understood there will be a new tech unit in an old style casing to appear this year.
I will certainly put my hand up for one !

Cheers,
Dennis.

That is interesting! What a smart product that would be. There is plenty of room for a modern CDI circuit in there.

Coils could be a potential problem. Seems like the round oil filled coils are now not made in Germany and their quality varies. Also an "E" type transformer coil with proper matched windings would be needed for best performance. Maybe Bosch will market a matching coil and sell as a set.

I am looking forward to hearing more about this product.

[dicklague]

Old set up. The relay is for manual cold start set up for MFI. Metal box is a 5 VDC power supply for the AFR MAP sensor. The power supply will be removed because the CD-1 has a 5 volt out put for this purpose. Also the MAP signal will be sent to the CD-1 to be stored in the data memory for download later for evaluation. MAP sensor is at the far left. All that messy add on wiring will be cleaned up.



The CD-1 during installation. It is rubber mounted to the old panel. The OEM panel is rubber mounted as well I left all the stock wiring and added where I had to. I did not want to disturb the old stuff.

[Matt Monson]

I think the old distributors may be as much to blame as the CDI boxes. I've got a Mallory on my 914 and it is awesome. Coupled with a Crame fireball it has always run great.

Btw, I've got an nos 3 pin if any readers are in the market. Please pm me.

[dicklague]

I agree with you on the distributors.

I lived with adjusting points and dwell for years. One day the 911 just quit on the freeway. I had no idea what it was. Luckily it broke down near TRE and I had it towed there. Dave called the next morning and said the points were closed! That was it. I put in the Pertronix and never looked back.

I am not familiar with the Mallory, will have to check it out. I assume your 914 is a 4.

I like the Crane system as well. It may be more accurate than the Pertronix. Someone posted on Pelican some testing they had done and the magnets in the Pertronix plastic cap over the point cam were not precisely positioned and some were a bit off. I am not sure if it is off, or if that has any bearing on performance. The Pertronix has been good and reliable.

[Trackrash]

Awesome write-up. Have you considered a custom panel? Easy enough to make, and you could save your unmodified original with your old Bosch CDI.

[Matt Monson]

Pertronix was bought out of bankruptcy a few years back. Don't know if the product when they returned to market was the same or improved. I only mention it because a lot of the Pertronix problem threads predate their rebirth. Would be worth exploring before buying.

[dicklague]

Originally Posted by Trackrash

Awesome write-up. Have you considered a custom panel? Easy enough to make, and you could save your unmodified original with your old Bosch CDI.

I think a custom panel is a great idea. I worked really hard to make everything fit the old panel.

It would not be difficult to make. I guess the biggest problem would be the 14 pin and 12 pin connectors. I wonder if any one make a female portion that would be compatible so that you could use all the rest of the stock wiring harness. I will have to look into that. Maybe Mouser or some has some of those connectors.

[dicklague]

Originally Posted by Matt Monson

Pertronix was bought out of bankruptcy a few years back. Don't know if the product when they returned to market was the same or improved. I only mention it because a lot of the Pertronix problem threads predate their rebirth. Would be worth exploring before buying.

I did not know they had those financial troubles. My Pertonix has been in there 7 years or so.

On a similar note, MSD declared chapter 11 bankruptcy in September 2013 and was bought by a private equity firm in December 2013 El Paso's MSD Performance Group reorganized through bankruptcy court sale - El Paso Times

I wonder what will happen to R&D and quality. Maybe more off shore manufacturing? Hard to say.

[Matt Monson]

Yeah, I don't know about MSDs future. I'm just glad Trey bought Cobb Tuning back from them before they folded.

[dicklague]

Originally Posted by Matt Monson

Yeah, I don't know about MSDs future. I'm just glad Trey bought Cobb Tuning back from them before they folded.

I don't know much about Cobb......looks interesting from their website. I hope they continue to do well.

I assume MSD will continue on, I would just be concerned about support and continued development. They were the original innovators.

[Alfasrule]

I don't understand why you 911 owners feel it's important to change the Points. They have no current going through them. They should last forever! I own an Alfa Montreal which uses these units and I still have the original points from the factory in the car. The Bosch Box is the way to go. They are quite efficent and I can install one in any car that has points. I would believe over time the Box could not keep up with the RPM's generated, but I also fixed that issue by bumping up the Oscillator speed of the DC to DC converter, so the Box can keep up with the RPM's. I presently installed one in my Alfetta the car runs better than than ever.