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 Post subject: Re: 6 Volt CDI units?
PostPosted: Tue Oct 24, 2017 8:38 pm 
356 Fan

Joined: Wed Sep 13, 2017 6:31 pm
Posts: 42
Location: Ripley, Ontario, Canada
Anything is possible as far as an add-on converter is concerned providing it meets the required parameters, which probably requires a new design to run an ignition system successfully if paired to a modern CDI. Even if it works within the required specs and is reliable at a reasonable cost, it still amounts to band-aid electronics. It's better to have fewer components that do the same thing better (in my opinion) than stacking potential failures on top of one another with too many design compromises. There is no reason that other companies can't make a 6V CDI, although it is a little tougher to do than making a 12V unit. The reason nobody does so, is because the market is so very small. To date, I have only 5 on my waiting list for the next batch, which suits me just fine as this is simply a hobby. Fred

"Al Zim"]Perhaps I am naive in my thinking and certainly having degrees in Psychology do not qualify me as an electrical engineer but I would think that someone could easily design a power supply that would supply the proper voltage and amperage to operate a CD unit properly. On my desk I have a solid state 6 volt regulator in a Bosch black regulator box that was designed by the person that produced a lot of our electrical mechanisms he was not an EE but all his stuff worked and we are still selling it. al zim[/quote]


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 Post subject: Re: 6 Volt CDI units?
PostPosted: Wed Dec 06, 2017 1:20 am 
356 Fan
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I got the car fired up today for the first time with the Winterburn CDI units - it sounds good but I need to adjust the timing and check a couple of things before I take it out and see how much better it performs. This whole adventure was a bit more complicated than any of us expected but I can't tell you how much help Fred Winterburn has been through this whole process. His units perform better than I expected and he has been with me every step of the way as we try to solve some technical issues unique to the Carrera installation.

One of the issues inherent in the early 4-cam motors with the camshaft driven distributors is a variation in the spark timing between the left and right distributors due to a variety of possible reasons. As it turns out one of my distributors advance curve was lagging the other one by a couple of degrees. There is also the issue of backlash in the gear drive and inevitable variations in the point gap so that both plugs in the cylinder don't fire at exactly the same moment. I talked to some of the other 4-cam car owners at Amelia last year and they said the best solution is to fire both coils off of one distributor. They also said its a lot easier if the car has a 12 volt system. My car is still six volt which led me to the Winterburn CDI units. Fred was extremely helpful in designing a circuit with a bridge rectifier in it that we could use to trigger both CDI units using the points in the LH distributor.

I also had mismatched coils - with the help of members of the 356 fraternity I was able to round up a pair of the TK6A5 Bosch Blue 6V coils that came standard on Carreras - not entirely necessary for my application but a nice touch for the restoration. Another member was able to supply a new old stock pair of the capacitors used in the Carrera distributors - again not necessary but nice to have. The capacitors insert into a bore in the body of the distributors - the old ones had to be removed with a slide hammer and the bores had to be honed up a couple of thousandths to accept the new ones. It is also possible to insert the capacitors too far so the lead grounds out to the top of the bore - don't ask me how I know....

So a process that should have taken a few days stretched out over months as I had to find the parts I needed and assemble the pieces of the puzzle but once everything was in place the car fired right up this afternoon. With a little fine tuning I look forward to a much better running 4-cam (finally).

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 Post subject: Re: 6 Volt CDI units?
PostPosted: Tue Dec 12, 2017 6:15 pm 
356 Fan

Joined: Wed Sep 13, 2017 6:31 pm
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Location: Ripley, Ontario, Canada
Jack Thanks for that. What an interesting project and I enjoyed the testing. Just so people know, the bridge rectifier could have easily been replaced by two diodes in series with each of the green CDI trigger wires. The only reason for the diodes is to prevent SCR failure if one CDI is selected to STD (Kettering) in which case a high voltage pulse is applied to the gate of the SCR in the other unit still operating in CD mode. With my test rig, doing so blew the SCR. With a battery supply it would probably survive since the voltage spike would most likely pass hamlessly through the battery while my test rig uses a rectified power supply that will not provide that type of protection. In any case the rectifier is insurance. I have posted a rough sketch of Jack's setup. By the way, I have taken all of the orders I can fill for the next batch, hopefully available by the end of January. I still need to finish up units and build some tach adapters. Fred

Jack Walter wrote:
I got the car fired up today for the first time with the Winterburn CDI units - it sounds good but I need to adjust the timing and check a couple of things before I take it out and see how much better it performs. This whole adventure was a bit more complicated than any of us expected but I can't tell you how much help Fred Winterburn has been through this whole process. His units perform better than I expected and he has been with me every step of the way as we try to solve some technical issues unique to the Carrera installation.

One of the issues inherent in the early 4-cam motors with the camshaft driven distributors is a variation in the spark timing between the left and right distributors due to a variety of possible reasons. As it turns out one of my distributors advance curve was lagging the other one by a couple of degrees. There is also the issue of backlash in the gear drive and inevitable variations in the point gap so that both plugs in the cylinder don't fire at exactly the same moment. I talked to some of the other 4-cam car owners at Amelia last year and they said the best solution is to fire both coils off of one distributor. They also said its a lot easier if the car has a 12 volt system. My car is still six volt which led me to the Winterburn CDI units. Fred was extremely helpful in designing a circuit with a bridge rectifier in it that we could use to trigger both CDI units using the points in the LH distributor.

I also had mismatched coils - with the help of members of the 356 fraternity I was able to round up a pair of the TK6A5 Bosch Blue 6V coils that came standard on Carreras - not entirely necessary for my application but a nice touch for the restoration. Another member was able to supply a new old stock pair of the capacitors used in the Carrera distributors - again not necessary but nice to have. The capacitors insert into a bore in the body of the distributors - the old ones had to be removed with a slide hammer and the bores had to be honed up a couple of thousandths to accept the new ones. It is also possible to insert the capacitors too far so the lead grounds out to the top of the bore - don't ask me how I know....

So a process that should have taken a few days stretched out over months as I had to find the parts I needed and assemble the pieces of the puzzle but once everything was in place the car fired right up this afternoon. With a little fine tuning I look forward to a much better running 4-cam (finally).


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Porsche Carrera with two 6V Winterburn CDI units.jpg
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 Post subject: Re: 6 Volt CDI units?
PostPosted: Sat Jan 20, 2018 7:38 pm 
356 Fan
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Joined: Fri May 09, 2008 9:36 pm
Posts: 381
We finally got a break in the winter weather long enough to get the timing on the Winterburn ignition system dialed in. Ernie came over and said he's never seen a brighter flash from his induction timing light - even at cranking speed so we could tell from the beginning we were getting a much better spark from the ignition system. After a bit of wasted time with a battery that wasn't fully charged up and a bit of an issue with not one but three different starters that killed a few hours the car finally cranked right up and settled into a very nice idle with no popping and snorting. The timing is very stable and dead on with both coils. We tweaked the timing and the car runs much better than it has since we put the engine in. I didn't get a chance to drive the car since it's up on jack stands so I can clean the undercarriage. I think my ignition issues are a thing of the pass and look forward to a road test in the next week or two.

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 Post subject: Re: 6 Volt CDI units?
PostPosted: Tue Jan 23, 2018 7:11 pm 
356 Fan

Joined: Wed Sep 13, 2017 6:31 pm
Posts: 42
Location: Ripley, Ontario, Canada
Jack, I'm glad the CDI units are working like they should so far. I realised today after I read your post that the diode protection for the SCRs in case one CDI unit is selected to STD, also serves another purpose that is just as important. You can't see it in the sketch, but the power to each CDI trigger circuit is through an 18 ohm resistor. Without the diode protection, if one of the dash switches supplying one CDI were turned off, the corresponding CDI wouldn't be completely 'off'. That's because without the bridge rectifier in the circuit (two diodes would have sufficed but mounting a large bridge rectifier is easier) current from the CDI selected ON at its corresponding dash switch would back feed through its 18ohm resistor to the other CDI during the short time the points are open. There would be enough current to keep the CDI selected off at the dash, running well enough to provide a weak spark at low rpm. So the bridge rectifier really is not optional after all if those dash mounted switches are to work as intended. I should have thought of this immediately, but I was more concerned with protecting the SCRs. I really like it when a single component can have two or more purposes in a circuit. In the CDI internal circuitry there are 6 components that serve two purposes each. This helps cut down on the number of components needed. Fred

Jack Walter wrote:
We finally got a break in the winter weather long enough to get the timing on the Winterburn ignition system dialed in. Ernie came over and said he's never seen a brighter flash from his induction timing light - even at cranking speed so we could tell from the beginning we were getting a much better spark from the ignition system. After a bit of wasted time with a battery that wasn't fully charged up and a bit of an issue with not one but three different starters that killed a few hours the car finally cranked right up and settled into a very nice idle with no popping and snorting. The timing is very stable and dead on with both coils. We tweaked the timing and the car runs much better than it has since we put the engine in. I didn't get a chance to drive the car since it's up on jack stands so I can clean the undercarriage. I think my ignition issues are a thing of the pass and look forward to a road test in the next week or two.


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 Post subject: Re: 6 Volt CDI units?
PostPosted: Sun Mar 04, 2018 9:54 pm 
356 Fan
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Joined: Wed Nov 25, 2015 9:12 pm
Posts: 692
Location: Sunshine Coast Australia
I finally got around to fitting Fred Winterburn's CDI/6V on the 1600S. Very simple to do and with some random comparison of the starting on CDI and on (switchable) STD/Kettering, the difference is very noticeable. It always started pretty well but now it is instantaneous with large spark from the outset. Smooth through the rev range and no adjustment needed to the timing. Happy camper!

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 Post subject: Re: 6 Volt CDI units?
PostPosted: Sun Mar 04, 2018 10:26 pm 
356 Fan
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Joined: Fri May 09, 2008 9:36 pm
Posts: 381
The Carrera runs much better and starts almost instantaneously with the Winterburn CDI unit. It has a lot more noticeable power at low rpm and has no problem getting up my steep driveway now. I'm very pleased with how well it performs, no more skipping and popping.

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 Post subject: Re: 6 Volt CDI units?
PostPosted: Fri Mar 09, 2018 3:55 pm 
356 Fan
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Joined: Wed May 28, 2014 5:02 pm
Posts: 425
Location: Dallas, TX
What spark plugs are you using, Jack?

Chuck

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