options for dead CDI?
 

Driving along yesterday, I suddenly lost power and after coasting to the side of the road with suspected fuel pump/relay issue and getting towed to my shop it turns out I had a no spark issue - being stopped next to a busy road makes it difficult to hear a CDI whine. My mechanic says no replacement CDIs are available any more and recommends a Permatune with matching coil.

Car is a 83 SC (145k milew)- everything is bone stock and original down to the paint and I am not a big fan of aftermarket as a rule

What is the hive wisdom? Get my CDI repaired via our host, Permatune, or MSD? Too bad points didn't come with these cars - simple and always work :-)

I had Bob Ashlock send me a like-new unit and added a new coil for good measure. I couldn't send him my old one as a core because it had been "potted" in the past. Great result!

I had Kurt at modernize mine and refurbish the exterior. I am very happy with it. You have to put the two words together since speech is limited here. Parts Klassik

I have an MSD but if I was after a stock look this looks like a really nice option

911 CDI+ (6 Pin) - Classic Retrofit

You can have yours rebuilt for a reasonable price by Ingo, Ischmitz screen name, Ingo Schmitz, located in Santa Barbara CA

I've very recently installed the Classic Retrofit CDI+ on my '78 SC. A plug and play solution, which will give you complete electronic ignition control and dual-spark (with matching coil). Very noticeable difference in my car. I have no affiliation, this is just a very nice product.

What's the warranty like on these new replacements ?

You have lot's of option out there as other mentioned: They basically fall into rebuilding your box ($), or going aftermarket($$ - $$$). If you chose the latter there are lots of different offerings out there. Do a search here on the board and you will find basically two aftermarket routes:

- the standard, old-fashioned aftermarket offerings (Permatune, MSD) ($$)
- Highly programmable aftermarket units with completely different topologies ($$$)

Before the flame wars begin let me throw this out: Of course the MSD is also sort of programmable (rev limit). But to get a real ignition curve done you need something different.

So in the end it comes down to $ and whether you want original equipment or traditional aftermarket or modern aftermarket. When it comes to discussing performance benefits and reliability there are lots of heated discussions out here already and I won't go into details. Some swear it's night and day while other see little to no benefits for performance.

For reliability I do have this to offer: Most Bosch CDI boxes lasted 20 - 30 year on average, some even longer, before needing a repair. This is outstanding and exceptional in the world of electronics. The same can't be said for any of the newer designs because they are simply no out there long enough and in high enough quantities. However, keep in mind they are build with the same components that make other consumer good fail after 5 - 10 years.

Cheers,
Ingo

I'm always a fan of a better mousetrap. Can you expand a bit on the electronic ignition control and dual spark?

Flash drives vs Hard drives, one may be the latest greatest thing and super fast, but when they crash, uh, buh bye. Our server rooms are filled to the brim, the old hard drives keep on chugging, the ssd's fry like no other.

I recommend reading on Welcome to Classic Retrofit

The MSD provides a "double spark" until 3000rpm. The CDI+ provides double spark the entire rpm range. Wether that contributes to improved torque or hp - is another heated debate. Do a search.

What is more interesting (to me anyway) is the programmable ignition control. I'm now running 5 BTDC at idle and currently 32 BTDC at WOT on 99 RON octane. Impossible with original SC ignition. This essentially means you can fine tune the otherwise very conservative SC ignition curve to match your specific engine and present day fuel quality. That may account for the 10-15HP gain.

Classic retrofit

Thanks for the reply.

I read the info on Classic Retrofit's website, but I'm not clear on how it controls the advance curve. I thought that happened in the distributor? Perhaps that's different in a '78 than it is in my '73?

Yup thats correct. The dizzy advances the ignition timing by a complex system of springs and weights. But this way, the timing curve is always the same. Example: You want WOT timing to be further advanced than the stock 24-26 BTDC. You would have to advance the timing at idle as well (or have the dizzy re-curved).

There are 3 ways to use the CDI+:

1. Plug and play - dizzy is still in control. What ever benefit (if any) is from the "double" ignition and much more powerfull spark.

2. Set the dizzy too advanced and let the CDI+ electronically retard the timing. This is what I do at the moment. If the CDI+ didn't retard timing, I would be running 10-15 BTDC at idle - and the car would not idle or start very well.

3. Lock the dizzy out at fully advanced and let the CDI+ completely control the timing. My next step - and go to a dyno to set the optimal timing.

My CDI died last year and I went the MSD box, tach adapter and coil route with a gizmo that replaces the points in the distributer. Also replaced the plug wires. It was pretty spendy, about twice what it costs to just replace the MSD with a rebuilt one including labor. But if you can do it yourself (I couldn't) it's comparable to a rebuilt unit.

+! for Bob Ashlock. He offered to buy my fried MSD for a nice price and he rebuilds them. His name is his forum handle.

Tom

Since you have joined the Pelican Parts Forum and will benefit from Porsche tech info in the future,
you can send your Bosch CDI to Pelican Parts for rebuilding and also support Pelican Parts.

Yes, for whatever reason this subject tends to draw out emotion. I'm going to let that sleeping dog lie but there is someone (who has yet to comment on this thread edit: never mind) that appears to have an ulterior (read: financial) motive. Let's just leave it at that.

Here's my view.

1) I would not replace with a PermaTune. There are too many other good options.

2) I don't think you could go wrong with a rebuild with Ingo or the CDI+ from Jonny. Both, I believe, are solid guys. There may be other solid people (and I'm sure there are), I'm just speaking from my interactions with them. Disclaimer: I have never done business with either.

3) I did the MSD StreetFire in my '83 when the replacement PermaTune of the original Bosch unit failed. Requires changing plug wires to braided (Clewett, Magnecor or similar), a little DIY know-how to make up a connector with the right pin outs (two are reverse of normal) and to add a dedicated line to the starter, installing resistor-less rotor and resistor-less plugs. It is an economical solution but doubtful it is the 'best'. I definitely feel it was an improvement over the PermaTune. If you care about originality 'look', this is not the path for you.

4) I like Jonny's CDI+ for the programmability and the ability to lock the dizzy and control the advance. Had this been available at the time my CDI failed I would have given this serious consideration. A buddy of mine just installed one in his rebuilt '76 and loves it.

5) There are other good options. There are a couple of people who have used other CDI units and seem to be having good experiences. The point is, I think there are a range of very good options other than PermaTune so I disagree with what your mechanic told you -- what you decide is going to depend on what is important to you and that's all that matters. If you just want plug and play and originality at the lowest cost, go with a rebuild. If you want to 'upgrade' or you like to DIY, there are very good alternatives.

Thanks for this great explanation. Cool stuff...

Thanks for all the input. I decided to use the Permatune to get myself back on the road - and for the fact it looks more original and don't have to find a place to hide the larger MSD. I'll get my Bosch rebuilt / have it made into a CDI+ and keep it as a spare.