It is currently Tue Jan 16, 2018 9:03 am

All times are UTC - 5 hours [ DST ]


Forum rules


Please click here to view the forum rules



Post new topic Reply to topic  [ 48 posts ]  Go to page Previous  1, 2, 3, 4
Author Message
 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: 32
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]


Top
 Profile  
Reply with quote  
 Post subject: Re: 6 Volt CDI units?
PostPosted: Wed Dec 06, 2017 1:20 am 
356 Fan
User avatar

Joined: Fri May 09, 2008 9:36 pm
Posts: 318
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).

_________________


Top
 Profile  
Reply with quote  
 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
Posts: 32
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).


Attachments:
Porsche Carrera with two 6V Winterburn CDI units.jpg
Porsche Carrera with two 6V Winterburn CDI units.jpg [ 45.1 KiB | Viewed 58 times ]
Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 48 posts ]  Go to page Previous  1, 2, 3, 4

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: C J Murray, tim noble


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB® Forum Software © phpBB Group