Bosch CDI and voltage regulation.

[Jonny H]

Bosch CDI and voltage regulation.

Hi All,

One of the shortfalls of the Bosch CDI is that it has no internal voltage regulation. The coil voltage decreases both with battery (alternator) voltage and also with RPM.

We have overcome this issue in CDI+ by employing a regulated power supply that offers a constant voltage to the coil under all RPM conditions and with battery voltages as low as 8 volts.

This means you get the same spark energy under all conditions. In fact, you get twice that of a Bosch CDI as we have two sparks back to back, typically at 400us intervals although it can be adjusted right down as far as the coil will allow, around 200us.

Here's a video I made of a Bosch CDI and a Classic Retrofit CDI+under the same test conditions which hopefully is self explanatory:

[mysocal911]

Originally Posted by Jonny H

Bosch CDI and voltage regulation.

One of the shortfalls of the Bosch CDI is that it has no internal voltage regulation. The coil voltage decreases both with battery (alternator) voltage and also with RPM.

Bosch was well aware of this when they designed the 3 & 6 pin CDIs. As long as the ignition coil's primary
voltage stays with as usable range, e.g. 250V - 350V for a spark voltage of 25K - 35K, the spark energy
is more than adequate. Remember, once the engine is running, the battery voltage is regulated for the CDI.
With regard to the Bosch's reduced output voltage as a function of higher RPM, the output voltage is still
within an adequate spark energy level for non-raced street engines, i.e. below 6.5K RPM.

Bottom Line: Few if any reports exit over the last 40 years where the Bosch CDIs have provided an
inadequate spark for street use!

[Jonny H]

Firstly, Bosch did not design the CDI unit, it was made under license. I'm sure Fred Winterburn can chime in here!

Bosch could not foresee a future where voltage regulator failure would be a pretty common occurance and that shoddy Brazilian made coils would short out the unit. Like most automotive parts it was designed to a price. Fine on a new car with all new parts.

As with all good aftermarket parts, the idea is to improve the design.

[mysocal911]

Originally Posted by Jonny H

Firstly, Bosch did not design the CDI unit, it was made under license.

Really? Where is proof of this? The Bosch design is unique, i.e. most CDIs use a DC to DC converter
that requires two transistors verses one for the Bosch. The Bosch CDI uses a flyback DC to DC.
Besides, the overall design is extremely simple for long term reliability. Do a patent search.

Originally Posted by Jonny H

Bosch could not foresee a future where voltage regulator failure would be a pretty common occurance and that shoddy Brazilian made coils would short out the unit.

Bosch was aware of potential regulator failures, but the probability of such was considered low
when weighed against reduced reliability of the additional parts for a power supply regulator.
Besides, the Bosch CDI has a unique design in that its flyback design of the DC to DC converter
has an inherent voltage regulation over an input of 10 -15 volts (constant capacitor voltage).
The Brazilian coils don't short-out, i.e. they typically become intermittent and don't damage the
Bosch CDI.

Originally Posted by Jonny H

As with all good aftermarket parts, the idea is to improve the design.

Or promote a product for "performance" or a marginal benefit with little to no real long term
benefit to the consumer.

[T77911S]

the theory of the CD has been around long before bosch used it.

the design is very similar to the pulse forming network in the transmitter for radar systems.

[mysocal911]

Originally Posted by T77911S

the theory of the CD has been around long before bosch used it.

the design is very similar to the pulse forming network in the transmitter for radar systems.

Yes, using a SCR and a capacitor to develop a high voltage pulse was established technology.
But Bosch's design was a unique design for an automotive ignition system as was the Bosch's
other CDI design used in the early Audi's and in the 8 pin CDIs used in the '77 930,
the 962s, & BMW M1s.

[Jonny H]

"Bosch bought the patent rights (US, German, French, British) from Winterburn as their own CD ignition was based upon the Winterburn design."

Just one of many sources:

https://www.linkedin.com/pulse/unsung-motor-industry-hero-fl-winterburn-his-capacitor-nicholas-gomez

I'm sure Fred can give us more details!

[Jonny H]

Originally Posted by mysocal911

Or promote a product for "performance" or a marginal benefit with little to no real long term
benefit to the consumer.

This comment from someone who has NO direct experience of our product?

How do you think PMO, SSI, Wevo, Elephant Racing, Rennline, Singer etc got started?

Well I can tell you most were enthusiasts first. They invented stuff, fitted it to their cars, made a tweak here, a tweak there, made an improvement. They showed their ideas to their mates and they said 'Hey, I like these, can you make some more?'.

And so it began and they got some interest from engine/car builders and some more orders and it became a business. So they thought they'd share it to a wider audience so that their fellow enthusiasts worldwide could benefit from what they had worked so hard to achieve.

After all, we're all in this hobby together and we want the best for our beloved Porsches right? But no, there is always the guy who wants to crap on it. It's always the same guy too.

P.s. I actually posted this for those curious about the constant voltage. I was going to post on another thread but some guy there says 'quit the sales talk - start your own thread'. So that's what I do and just get the same old crap.

I'm just about done with Pelican!

[RSTarga]

Electronics have come a long way from the 60's. I am sure there are many components that are now improvements and more reliable than they were back then.
I'm all for re-engineering.
I don't see anyone claiming that bullet fuses are better than the blades.

[mysocal911]

Originally Posted by Jonny H

"Bosch bought the patent rights (US, German, French, British) from Winterburn as their own CD ignition was based upon the Winterburn design."

Just one of many sources:

https://www.linkedin.com/pulse/unsung-motor-industry-hero-fl-winterburn-his-capacitor-nicholas-gomez

I'm sure Fred can give us more details!

The only patentable aspect for the Winterburn design is the use of the SCR, i.e. as other CDI
designs prior to Winterburn were used but lacked the SCR switching device developed by GE in 1957.
Winterburn's other key aspect, although really not patentable, was the use of an integrator circuit
to minimize noise triggering of the SCR.

Again, the Bosch design is unique, i.e. doesn't have any similarity to Winterburn, with design simplicity,
reliability, and 45+ years of use.

[mysocal911]

Originally Posted by RSTarga

Electronics have come a long way from the 60's. I am sure there are many components that are now improvements and more reliable than they were back then.

Not really, when it comes to the basic design of a CDI ignition, i.e. transistors, resistors, SCRs,
transformers, mylar capacitors are all produced as they were 40+ years ago using the same
manufacturing processes.

[Alfasrule]

From the outside!!
I've repaired ~ 8 CDI's 3 PIN at this point, had to rewind 2 transformers, and pretty easy. All the units I've repaired so far are working well today. The design is very simple and works great, so far as I incorporated these units in 2 of my ALFAs and they never ran better. Having ~300V go to the primary of a coil (Changed them) instead of 12V/6V gives my car quite the punch.
My 75 Race Car with NO Chokes 48mm webers starts better than it's never been, doesn't go any faster, but now starts right up!
My 75 Sedan has the best improvement. all original w/ SPICA injection, not only does it start right up, but there is a noticeable improvement in the performance.
Know it is OLD SCHOOL, but I still listen to music with Tube Amps.
The circuit is simple and works efficiently. Why add more semiconductors to complicate the system?
The 2 transformers, 1 transistor, 1 diode, 1uf cap and 82V zenor, now that's simplicity at it's best.
400V pulse at the secondary to charge the output cap, a thyristor to discharge the cap when the points close. Awesome circuit!
Bosch assumed the regulator in the alternator would compensate for the drift in the input voltage keeping a constant supply to the input.
You can take out the CDI and still run your Porsche without it. It's a 3 wire change. The CDI was put in the 911 and ALFA Montreal to give it a higher voltage at the plug to efficiently burn all the fuel, but the car can still run fine without it.

[Jonny H]

Originally Posted by mysocal911

Not really, when it comes to the basic design of a CDI ignition, i.e. transistors, resistors, SCRs,
transformers, mylar capacitors are all produced as they were 40+ years ago using the same
manufacturing processes.

Next you'll be telling us that integrated circuits are not reliable

I used to be a development engineer at Applied Materials. They design and supply most of the world's semiconductor manufacturing equipment. The changes needed to the manufacturing process to keep up with progression of technology from the likes of Intel, IBM and Motorola etc keeps around 15,000 employees constantly busy.

Semiconductor feature sizes have gone from 10um to 10nm in 40 years, that's 1000 times smaller! Production cleanliness and quality has changed dramatically.

To say that the process has not changed in 40 years is complete nonsense.

[Jonny H]

Originally Posted by Alfasrule

From the outside!!
I've repaired ~ 8 CDI's 3 PIN at this point, had to rewind 2 transformers, and pretty easy. All the units I've repaired so far are working well today. The design is very simple and works great, so far as I incorporated these units in 2 of my ALFAs and they never ran better. Having ~300V go to the primary of a coil (Changed them) instead of 12V/6V gives my car quite the punch.
My 75 Race Car with NO Chokes 48mm webers starts better than it's never been, doesn't go any faster, but now starts right up!
My 75 Sedan has the best improvement. all original w/ SPICA injection, not only does it start right up, but there is a noticeable improvement in the performance.
Know it is OLD SCHOOL, but I still listen to music with Tube Amps.
The circuit is simple and works efficiently. Why add more semiconductors to complicate the system?
The 2 transformers, 1 transistor, 1 diode, 1uf cap and 82V zenor, now that's simplicity at it's best.
400V pulse at the secondary to charge the output cap, a thyristor to discharge the cap when the points close. Awesome circuit!
Bosch assumed the regulator in the alternator would compensate for the drift in the input voltage keeping a constant supply to the input.
You can take out the CDI and still run your Porsche without it. It's a 3 wire change. The CDI was put in the 911 and ALFA Montreal to give it a higher voltage at the plug to efficiently burn all the fuel, but the car can still run fine without it.

Funnily enough I'm off to Alfaholics tomorrow.

[ischmitz]

I know chiming in here won't settle this to where everyone agrees. But what's funny is that I don't see that much of a controversy because everyone makes valid points:

- In the '70 when the Bosch (or Winterburn) units where designed there were no milli-ohm HEX-trench MOSFET devices available. It was Darligntons and BJTs. MCU where super-expensive. and clunky. In that regard the CDI circuit is a pretty ingenious design. Can it be improved or could it have been made more complex? Sure. Would Bosch have done it differently in hindsight if they had known at the time how it would survive. NO WAY!!!

- The performance, complexity, and integration density of semiconductors has gone up with Moore's law and the design rules shrank tremendously. Today sub-100nm is standard even for the simplest stuff and Intel is doing 10nm devices in production.

But this is a two-sided coin. Where yesterday only a simple junction would fail with a higher probability in a transistor today there are 10th of thousands of junctions and interconnects even in the most simple MCU and each one failing renders the chip and the box it is in non-functional. So yes reliability and packaging vastly improved but these devices are so much more sensitive.

I don't believe we have any good data on how a design from 2010 will do in 2050 because most consumer-grade electronics get replaced within 10 years at the most. So there is no incentive for any device maker today to design beyond that unless it's MIL-SPEC stuff. Where back in the days you had CER-DIP housings today plastic DIP is used. Same for SMD stuff - plastic only. Now expose that to the serious heat cycles in an engine bay and you have a recipe for housing failures, ingress of moisture and device failures. I have seen CDI boxes that must have been on the bottom of the ocean and still work. This isn't true for SMD electronics.....

That being said the longevity of the CDI boxes is pretty amazing. I have repaired probably more than 150 CDI boxes at this point and have a pretty good handle on what fails. There are only 2 components I am aware off that age. The SCR to some extend (starts to act more non-ideal) and the main capacitor (dries out and shorts). Everything else seems to go forever unless there are external factors (over-voltage, bad coil). I call that bullet-proof. I help improving current designs for our equipment (digital, mixed-signal, analog) and help repair modern electronics and these have very different failure modes.

I wonder what sort of HALT testing (highly accelerated lifetime testing) was done for the new CDI+units. That would be good data to provide if the rational is to improve reliability.

But then I really respect anyone taking on making or designing new products for what is arguably a very limited market. The NRI costs are tremendous and not everyone appreciates that. Let's just hope the CDI+ don't end up like the Permatune with a terrible track record of poor reliability.

Cheers,
Ingo

[mysocal911]

Originally Posted by Jonny H

Next you'll be telling us that integrated circuits are not reliable

I used to be a development engineer at Applied Materials. They design and supply most of the world's semiconductor manufacturing equipment. The changes needed to the manufacturing process to keep up with progression of technology from the likes of Intel, IBM and Motorola etc keeps around 15,000 employees constantly busy.

Semiconductor feature sizes have gone from 10um to 10nm in 40 years, that's 1000 times smaller! Production cleanliness and quality has changed dramatically.

To say that the process has not changed in 40 years is complete nonsense.

I only discussed discrete devices used in the Bosch CDI as having not been improved
significantly over the last 40 years. There was NO mention of integrated circuits as
none are used in it.

Please re-read:

"Not really, when it comes to the basic design of a CDI ignition, i.e. transistors,
resistors, SCRs, transformers, mylar capacitors are all produced as they were 40+
years ago using the same manufacturing processes."

[Fred Winterburn]

Jonny,
Actually the Bosch design has almost nothing in common with my late father's design. Bosch did track him down in the early seventies with the intention of buying up his European patents, (which they did). As far as I can tell Bosch was merely collecting patents and most probably wanted some intellectual control over its rival, Magneti Marelli. The Marelli Aec 101 CDi was related to my father's design but not executed very well and needed a special coil. Look up patent#3564581. If you really dig, you will find that 3 other people also patented essentially the same circuit in the USA, and one in Canada, but all of those patents were actually filed later and became invalid aside from some claims (which is absolute BS in how the system works). The final Winterburn patent took years to be granted because of another fellow who claimed to have invented first (I have found some evidence to prove it was first stolen in mid 1963 by three different parties, two Canadian and the American who claimed to have invented first). The litigation also held up the German patent because their patent office sat back and watched to see what would happen in the USA. What finally caught the American fellow is when they looked at the design claim that used a transistor that hadn't been manufactured until well after the period the fellow claimed to have invented the ignition. A liar and a sloppy one at that, but still it took years to catch him out on it, and then even longer for the patent office to do anything about it. By then, there were 2 other patents granted for the same circuit which shows just how sloppy the US patent office was back then. Sydmur and Delta were the major infringers back in the day. The Canadian patent office was no better as a Canadian army captain patented an almost exact copy of the circuit my father presented to DND (department of national defence) in 1962. The circuit had to be shown to have no military value and was scrutinized by a military officer with an electrical engineering degree in 62/63. This delayed filing the patent for over one year. That paperwork would have still been on file for a few years and been accessible. You can draw your own conclusions on that one!
I agree that voltage control is very important, but not just for performance. Having excess available voltage at low rpm only to have it drop off quickly as rpm rises is not a good way to provide sufficient spark energy. The other major problem with using that crude method is that it stresses insulation unduly and can lead to early failure of some external components, not to mention stress on the unit itself. Fred

Originally Posted by Jonny H

Firstly, Bosch did not design the CDI unit, it was made under license. I'm sure Fred Winterburn can chime in here!

Bosch could not foresee a future where voltage regulator failure would be a pretty common occurance and that shoddy Brazilian made coils would short out the unit. Like most automotive parts it was designed to a price. Fine on a new car with all new parts.

As with all good aftermarket parts, the idea is to improve the design.

[Fred Winterburn]

Jonny, That is impressive. I'd be lying if I said mine had such tight regulation. But then I am using a different older technology. A lot simpler too, but providing what you have is reliable and can take some high voltage hits without failing it sounds good to me. I noticed the sound your CD sparks make compared to the Bosch. A much deeper tone indicating a longer effective duration. MSD with the long separation gives it a squeaky sound because the ear can actually discern each short spark event. Yours come close enough together to sound like a single fat spark. I like it, Fred

Originally Posted by Jonny H

Bosch CDI and voltage regulation.

Hi All,

One of the shortfalls of the Bosch CDI is that it has no internal voltage regulation. The coil voltage decreases both with battery (alternator) voltage and also with RPM.

We have overcome this issue in CDI+ by employing a regulated power supply that offers a constant voltage to the coil under all RPM conditions and with battery voltages as low as 8 volts.

This means you get the same spark energy under all conditions. In fact, you get twice that of a Bosch CDI as we have two sparks back to back, typically at 400us intervals although it can be adjusted right down as far as the coil will allow, around 200us.

Here's a video I made of a Bosch CDI and a Classic Retrofit CDI+under the same test conditions which hopefully is self explanatory:

[Fred Winterburn]

Dave,
Yes the Bosch design is unique. Never forget technical hubris.
With regard to Lloyd Winterburn's trigger circuit, you are not being historically correct. SCRs were thought of immediately as a switching device for Cdi and some rather complex solutions were developed to make them work after a fashion. The Theodor Sturm patent that was filed only 3 or 4 days after my father's in 63 and became the first Permatune is an example of the complexity that some went to in order to make a Cdi triggerable by points. The first Delta Mark 10 'thunderbolt' worked by accident more than by design until they found a way to use my father's method without it appearing so to the layman.(They also built the Tiger later on and that trigger was a direct copy) And no, as simple as his anti-bounce method seems in retrospect, it hadn't been thought of before that in any application I know of. Recently I saw his patent referenced in a new patent for touch screens to prevent unwanted responses from jittery fingers. He was also the first to find an easy way to make a positive ground trigger for a CDi. At the time he starting designing an SCR based CDi for home use in 1959 or 1960, an SCR cost almost $20 and they all had sensitive gates, at least any that were suitable for Cdi. Fred

Originally Posted by mysocal911

The only patentable aspect for the Winterburn design is the use of the SCR, i.e. as other CDI
designs prior to Winterburn were used but lacked the SCR switching device developed by GE in 1957.
Winterburn's other key aspect, although really not patentable, was the use of an integrator circuit
to minimize noise triggering of the SCR.

Again, the Bosch design is unique, i.e. doesn't have any similarity to Winterburn, with design simplicity,
reliability, and 45+ years of use.

[Alfasrule]

Nice test fixture! Mine's not as complicated, but it's efficient. I still believe that the cars regulation system is efficient enough to give the CDI the proper voltage to operate the entire bandwidth.
My car is a constant 13.8V, Bosch Alternators are very efficient and robust. Maybe they counted on this?
Although my Race Car is a 4 and you are a 6, me race car does not suffer any degradation in performance even at high revs 6.5K is the most I go, but I only fire a 3rd of the time per revolution.
A friend of mine this summer through one on his Harley and he loved it. They are so easy to install and to integrate into any car with points.

As far as semiconductors, I been doing electronics for over 34 years and presently I'm an integrated circuit designer,specifically memory, and the new stuff is cool, but NOT better! I work on 20nm design platform.

But my motto has always been "Why mess with something that works fine in the first place?"

Engineering Hero's are a Dime a Dozen, they can tweek a circuit and write another Patient. Worked with a bunch of these idiots at IBM for 25 years. I evaluated Patents at IBM.

I just fix CDI's for fun. I just fixed 2 for a guy in IL and I will charge him for parts, but really don't care to get any money to repair them. I do this for FUN. It's me hobby! I wouldn't even known how much to charge?