600V DC from 12V DC Source

Thread Starter

MGPERF

Joined Jun 8, 2021
77
There are a lot of electronics magazines on this site:
https://worldradiohistory.com/index.htm
Have a look in particular at:
https://worldradiohistory.com/UK/Electronics-Today-UK/ETI-1976-Top-Projects-No-3-S-OCR.pdf
page 38.

These days, you could probably improve a few aspects of the design, quite possibly the step-up converter
There are a lot of electronics magazines on this site:
https://worldradiohistory.com/index.htm
Have a look in particular at:
https://worldradiohistory.com/UK/Electronics-Today-UK/ETI-1976-Top-Projects-No-3-S-OCR.pdf
page 38.

These days, you could probably improve a few aspects of the design, quite possibly the step-up converter

Thank you this was very helpful, I think page 40 would be what I would like to build as a complete setup I do not need a rev limiter so I can ommit that. Any suggestions for improvements to this with modern technology or components and how to simplify the circuit is greatly appreciated.
 

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shortbus

Joined Sep 30, 2009
10,045
From a hands on point of view, I can't see where CDI is worth the trouble. I don't think they are any better performance wise than a GM HEI. And the HEI is much simpler and available. When used with a HEI coil, the ones that look like a transformer with an E-I type core they give more than enough spark energy for just about any engine short of a top fuel dragster. They are good enough that aftermarket companies make distributors for non GM engines that use them.
 

Ian0

Joined Aug 7, 2020
9,667
When the coil is used in its normal manner, basically a flyback circuit, then the duration of the spark in inversely proportional to the output voltage - nice clean plugs will have a lower voltage drop, and the current will flow for longer. A smaller gap will give a longer lasting spark - a bigger gap will give a higher-energy shorter spark.
 

SamR

Joined Mar 19, 2019
5,031
That and the proper temp rating for the plug... Examining the tip of the plug can tell you a lot about how good the burn is.
 

Thread Starter

MGPERF

Joined Jun 8, 2021
77
For me it's about building my own reliable ignition system I can be proud of I'm more up for the challenge than anything else if it runs the same afterwards I'll be very pleased if it runs better I'll be ecstatic!
 

Ian0

Joined Aug 7, 2020
9,667
For me it's about building my own reliable ignition system I can be proud of I'm more up for the challenge than anything else if it runs the same afterwards I'll be very pleased if it runs better I'll be ecstatic!
Are you intending to take the timing from the points, or to use some sort of optical ("Lumenition") or magnetic sensor? What parts do you already have?
 

Thread Starter

MGPERF

Joined Jun 8, 2021
77
Are you intending to take the timing from the points, or to use some sort of optical ("Lumenition") or magnetic sensor? What parts do you already have?
The timing comes from a CB Performance Black Box it's a form of electronic ignition that is triggered by a ground signal from the told points. It has an input for a CDI box and has been used with winterburn and MSD etc. more often than not it is used with a CDI box. I have the car running with the Black Box and timed properly etc. regarding the CDI box I am starting from fresh I don't have any parts at the moment.
 

Papabravo

Joined Feb 24, 2006
21,159
For me it's about building my own reliable ignition system I can be proud of I'm more up for the challenge than anything else if it runs the same afterwards I'll be very pleased if it runs better I'll be ecstatic!
Aye - thar's the rub. You can't possibly compete with modern manufacturing, fabrication, and assembly techniques for a 'more reliable' system. Even if you could for a one off it will be fabulously expensive. Don't let me dissuade you from pushing large rocks up steep hills.
 

Thread Starter

MGPERF

Joined Jun 8, 2021
77
Aye - thar's the rub. You can't possibly compete with modern manufacturing, fabrication, and assembly techniques for a 'more reliable' system. Even if you could for a one off it will be fabulously expensive. Don't let me dissuade you from pushing large rocks up steep hills.
Building a well performing CDI box isn't out of the realm of hobbyists etc. being under the impression that whatever you get out of the summit/jegs catalog etc. has been dialed right in and shouldnt be touched is a bad mentality. My 1.8 liter MGB runs stronger than some v8 cars with horrific tuning.
 

Ian0

Joined Aug 7, 2020
9,667
The timing comes from a CB Performance Black Box it's a form of electronic ignition that is triggered by a ground signal from the told points. It has an input for a CDI box and has been used with winterburn and MSD etc. more often than not it is used with a CDI box. I have the car running with the Black Box and timed properly etc. regarding the CDI box I am starting from fresh I don't have any parts at the moment.
I've just realised how long it was since I built my Lumenition based circuit -
It worked very well, after I found the real problem after the vehicle in question refused to start at the petrol station. The coil insulation would break down when the coil was hot.
All this CB Performance stuff is new to me. In fact, I'd obtained the advance curves found a spare distributor and disabled the advance and was planning to build something similar myself, but never got round to it, or thought that the 8-bit processors available weren't up to the job, or couldn't find a suitable vacuum sensor. I thought that the points would be the weak-point of the system, and that an optical sensor would be the biggest improvement.
 

Papabravo

Joined Feb 24, 2006
21,159
Building a well performing CDI box isn't out of the realm of hobbyists etc. being under the impression that whatever you get out of the summit/jegs catalog etc. has been dialed right in and shouldnt be touched is a bad mentality. My 1.8 liter MGB runs stronger than some v8 cars with horrific tuning.
There is no accounting for extraordinary popular delusions.
 

Thread Starter

MGPERF

Joined Jun 8, 2021
77
I've just realised how long it was since I built my Lumenition based circuit -
It worked very well, after I found the real problem after the vehicle in question refused to start at the petrol station. The coil insulation would break down when the coil was hot.
All this CB Performance stuff is new to me. In fact, I'd obtained the advance curves found a spare distributor and disabled the advance and was planning to build something similar myself, but never got round to it, or thought that the 8-bit processors available weren't up to the job, or couldn't find a suitable vacuum sensor. I thought that the points would be the weak-point of the system, and that an optical sensor would be the biggest improvement.
The current doesn't flow through the points so point bounce etc. doesn't cause the spark output to decline there must be something in the sensor itself that only recognizes the first opening of the points. It really is a unique and fun system I had been looking for something similar for quite some time. My friends father told me about how he had cleaned, synched, and tuned the carbs on his 1967 gto tri-power over and over only to find out the hesitation/stumble was from his distributor not advancing. Ever since then I always look to the distributor first and at 28 years old tuning the MG with the laptop seems more natural. Let me know if you end up buying a CB Black Box I'd love to hear how it works for you. Can I ask what'd it be going on?
 

Ian0

Joined Aug 7, 2020
9,667
The current doesn't flow through the points so point bounce etc. doesn't cause the spark output to decline there must be something in the sensor itself that only recognizes the first opening of the points. It really is a unique and fun system I had been looking for something similar for quite some time. My friends father told me about how he had cleaned, synched, and tuned the carbs on his 1967 gto tri-power over and over only to find out the hesitation/stumble was from his distributor not advancing. Ever since then I always look to the distributor first and at 28 years old tuning the MG with the laptop seems more natural. Let me know if you end up buying a CB Black Box I'd love to hear how it works for you. Can I ask what'd it be going on?
Sunbeam Rapier fastback - bought by my grandfather in 1972 - he got a good discount because no-one in Wakefield, West Yorkshire wanted it in bright yellow.

I'd be very suspicious about running the points with no significant current through them, I would think it would suffer from oxidised contacts quite quickly - like using silver-oxide-contact switches for signals when you should use gold.
 

MisterBill2

Joined Jan 23, 2018
18,167
I used to run a Mallory dual point on a 350+HP 350CI chevy small block. I'd have to take the distributor to a speed shop with a Sun ignition analyzer to have them set up the mechanical advance curve (weights and springs) and adjust the pair of points to open and close sequentially correctly. If it has no current going through it the capacitor in the distributor died. It needs to be a genuine Mallory capacitor (and points) to handle the energy being cycled through it especially if using one of their hi voltage coils. It was a bear in wet weather due to hi voltage leaking all over the place even after lots of sprayed silicone and WD40. Lots of pretty little blue sprites dancing all about under the hood at night in the rain.
The dual point distributor was to increase the dwell time so as to have more spark energy. For adequate spark, back in about 1970-1971, I used a Delta Products Mark Ten CD system. It used a stock coil but it would deliver a long spark, a half inch or more.. And the rise time was fast enough to fire a fouled plug. So unless you are running a serious dragster, one with a blower and half inch fuel lines, or trying to run some non-combustible fuel, an old mark ten will serve you quite well. If you wanted a solid 625 volts DC you could get an old DM35 dynamotor, although they are not intended for a 100% duty cycle. It will draw 27amps running so it is a bit of a power hog. But very simple.
But if you try to depend on the rotor for switching the spark to each cylinder the engine will run like junk if it runs at all. Crossfire could be a problem with the Mark Ten if there was one weak plug wire.
The Mark Ten was a kit but assembling it so that it would live under the hood hard mounted to the rigid body is what made it my work. I did not design it but I did do the RELIABLE installation. Vibration and temp cycling in a car can be brutal. AND it will install on any caar while that GM HEI was made to only fit one brand of engine. Plus it cost a lot more.
 
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Thread Starter

MGPERF

Joined Jun 8, 2021
77
The dual point distributor was to increase the dwell time so as to have more spark energy. For adequate spark, back in about 1970-1971, I used a Delta Products Mark Ten CD system. It used a stock coil but it would deliver a long spark, a half inch or more.. And the rise time was fast enough to fire a fouled plug. So unless you are running a serious dragster, one with a blower and half inch fuel lines, or trying to run some non-combustible fuel, an old mark ten will serve you quite well. If you wanted a solid 625 volts DC you could get an old DM35 dynamotor, although they are not intended for a 100% duty cycle. It will draw 27amps running so it is a bit of a power hog. But very simple.
But if you try to depend on the rotor for switching the spark to each cylinder the engine will run like junk if it runs at all. Crossfire could be a problem with the Mark Ten if there was one weak plug wire.
The Mark Ten was a kit but assembling it so that it would live under the hood hard mounted to the rigid body is what made it my work. I did not design it but I did do the RELIABLE installation. Vibration and temp cycling in a car can be brutal. AND it will install on any caar while that GM HEI was made to only fit one brand of engine. Plus it cost a lot more.
I'd love to know more about the Mark 10 do you know where I could find a schematic for it? I'm wondering how they made the mark 10 able to create a spark duration long enough to work well with a 4 stroke.
 

MrSalts

Joined Apr 2, 2020
2,767
The HEI was made for GM engines. It can be installed on others, but why bother when an alternative is available cheaper and made to be universal??
Nope, not even close to true. "Cheaper" and "alternative" depends on what you are replacing. Not universal? Well, I have to ask, are you just making stuff up as you post?
 

Thread Starter

MGPERF

Joined Jun 8, 2021
77
Nope, not even close to true. "Cheaper" and "alternative" depends on what you are replacing. Not universal? Well, I have to ask, are you just making stuff up as you post?
Nope, not even close to true. "Cheaper" and "alternative" depends on what you are replacing. Not universal? Well, I have to ask, are you just making stuff up as you post?
My brother bought a knockoff HEI out of China for 60 bucks with the coil mounted on top for his CJ7. Did it work yah you instantly wanted the points back because it was noisy and had huge unexplainable dead spots. A good HEI costs the same as a dist. Msd/black box etc. and coil.
 

MisterBill2

Joined Jan 23, 2018
18,167
My brother bought a knockoff HEI out of China for 60 bucks with the coil mounted on top for his CJ7. Did it work yah you instantly wanted the points back because it was noisy and had huge unexplainable dead spots. A good HEI costs the same as a dist. Msd/black box etc. and coil.
When I wrote "alternative" I was referencing the Mark Ten CDI system. Sorry I was not clear on that point. The Mark Ten was much less expensive than the real HEI system.
 
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