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PERTRONIX IGNITOR II ADAPTIVE DWELL CONTROL


Seventy911
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If you are using a pointless ignition system, I'd like to hear your thoughts and experiences please.

My 1970 2.2 came originally fitted with a Marelli distributor which the previous owner replaced with either a 0 231 169 001. (1968 2.0)  or 0 231 159 001 (1967) 2.0). I need to pull it to read the number clearly. I understand this is a common swap due to parts availability for Marelli's.

The car runs well in this configuration but I'm hoping for better response through the rev range for which the pointless conversion is a "simple" upgrade.

What are you using? Did you change the coil too? Curves for 2.0 and 2.2 are a little different. Any other distributor mods I should consider to get the most out of my current pairing?

many thanks!
 

 

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I used these MSD units in my early SC. They replaced the troublesome/expensive Bosch CDI box. It worked very well, I live in a hilly area and the improvement in low rev punch was appreciated. IMO the high-end MSD boxes are not needed for normal motoring (I took the garish stickers off to make them blend in better).

https://www.summitracing.com/parts/msd-5520

MSD Street Fire CD ignitions  offer capacitive discharge technology that fires a series of multiple sparks for 20 degrees of crankshaft rotation when the engine is running under 3,000 rpm. 

&

MSD Blaster High-Vibration Ignition Coil (if you bolt it to the engine).

https://www.summitracing.com/parts/msd-8222

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I assume the new distributor is a Bosch. Good stuff and better that Marelli IMO. A guy in Adelaide rebuilt mine to the original curve in his old Sun system for very little money. David Braham.

I also had the MSD AL6 IIRC.  It is a nice unit and adds reliability and a little torque at lower RPM. 
 

Most of the pointless systems lose voltage at the distributor, Petronics, etc. Fred Winterburn in Canada makes a marvellous CDI that only uses the points as a circuit breaker (they will last forever) and gives full voltage.

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17 minutes ago, Merv said:

Most of the pointless systems lose voltage at the distributor

I bet somebody that was selling you something told you that.

MSD stands for My Spark Died. And I have seen workshops full of dead MSD units. 

As for multi spark if you are relying on a spark 20degrees after it should have happened then you have other bigger issues to worry about. CDI ignitions are complex and highly stressed and are simply not necessary for anything other than extreme situations. 

The old Bosch 008 module (with self dwell control) when used with a hall sensor in the distributor is a good as it gets and is a near 25 year old device. 

Points have issues even with electronic modules such as follower wear and contact contamination. The changeover to a hall sensor is well worth the cost.

The next step up is a locked distributor with a programable curve ignition module but that is another thread.

 

 

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I did my own testing on 3 different systems such as the Pertronics (there are many US and Chinese copies) and each one showed the same significant voltage drop at the points on my 68 911 and on the 356.  The forums are filled with people pulling these off after a couple of years and unexplained failures.  Haggerty's did a useful review.  I did not test the MSD later fitted on the 911.  I agree on the Hall Effect in principle.  Getting rid of points and condensers was my aim at the time. On the 356 I retained the points with a (cheaper and reliable) bespoke CDI (above) and removed the need for a foil condenser (common fail point on older cars and the new ones are garbage - I tested many failed ones and found they used a cheap glue internally) and removed the 'heat' and wear from the points. On a 72, we fitted a rebuilt and curved Bosch distributor with a solid state condenser and an MSD with good outcome.

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2 hours ago, Merv said:

I did my own testing on 3 different systems such as the Pertronics (there are many US and Chinese copies) and each one showed the same significant voltage drop at the points on my 68 911 and on the 356.  The forums are filled with people pulling these off after a couple of years and unexplained failures.  Haggerty's did a useful review.  I did not test the MSD later fitted on the 911.  I agree on the Hall Effect in principle.  Getting rid of points and condensers was my aim at the time. On the 356 I retained the points with a (cheaper and reliable) bespoke CDI (above) and removed the need for a foil condenser (common fail point on older cars and the new ones are garbage - I tested many failed ones and found they used a cheap glue internally) and removed the 'heat' and wear from the points. On a 72, we fitted a rebuilt and curved Bosch distributor with a solid state condenser and an MSD with good outcome.

How are you measuring voltage drop at the points? The voltage here for an inductive ignition switched by the points has 3 phases. 
1) switched to ground and charging the coil.

2) Just after the points open there is the coil discharge phase where the voltage approximates the spark voltage/100 and will be around 20V

3) once the coil discharge is complete there is the idle phase where the voltage is the same as the 12V ignition. 

When installing a CDI the points are just a trigger signal to the electronics and have nothing to do with the volts/energy of the coil so using a multimeter to measure the points voltage and compare to points driving the coil directly is meaningless. 

All points ignitions use a series resistor to limit the coil current. This can be in the coil itself or a seperate resistor or a special resistor wire. When wiring a CDI this resistor must be bypassed or better still the CDI power wiring should be all new.

There is always an explanation for the failure and it is usually the failure of the main discharge device or capacitor charging device. Like I said CDI’s are complex and highly stressed and are nowhere near as reliable as a simple inductive transistor module. With a CDI reliability is proportional to the price paid and you will need 3K+ to get a good one and even then the reliability won’t be as good as a $150 inductive module. 

The points capacitor (called a condenser in the old days) is not required with a CDI and yep they are a failure point. There are many capacitors available that will do the job but they usually come in different form factors to the Classic tin can style and require some modifications to install. 

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Thanks Redracn (sorry I don't know your name). I don't have the time to be involved in yet another of the many long debates on this issue.

As I was advised, I measured the voltage drop from battery (quite direct as I used a relay to protect the IGN switch) to the switch side of the coil with Pertronics and two other US-made inductive units I had purchased.  It was of the order 1.5V which is quite considerable and asks a lot of the coil and of the distributor and affects eventual spark characteristics.  I worked with a couple of engineers on this issue. In principle, both CDI and magnetic inductive systems can work well and reliably.  It is about the quality of the device and the nature of its manufacture.  The forums are littered with failed inductive systems that finished up in the bin and the original Kettering system returned to (with its faults in points load and unreliable 'new' condensers/capacitors).  My final attempt to get a decent new condenser was to use a non-electrolytic capacitor 'potted' in the original Bosch aluminium 'can'.  It worked, but the CDI unit (under $500)  I obtained was a quality design including a feature to protect the coil from excessive current.  It works extremely well and most reliably. The difference in low RPM power was very noticeable especially on an early model Porsche.  The system was also instantly switchable, so at any time I could just go back to the original Kettering system. 

In the past I have used inductive systems, but like many others, they always let me down after a year or two, on the side of the road. I agree with you fully that quality is the key in both types of systems and this might have recently changed in the case of inductive systems.

You might find this interesting http://www.capacitordischargeignition.com

All the best

Merv

 

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1 hour ago, Merv said:

Thanks Redracn (sorry I don't know your name). I don't have the time to be involved in yet another of the many long debates on this issue.

As I was advised, I measured the voltage drop from battery (quite direct as I used a relay to protect the IGN switch) to the switch side of the coil with Pertronics and two other US-made inductive units I had purchased.  It was of the order 1.5V which is quite considerable and asks a lot of the coil and of the distributor and affects eventual spark characteristics.  I worked with a couple of engineers on this issue. In principle, both CDI and magnetic inductive systems can work well and reliably.  It is about the quality of the device and the nature of its manufacture.  The forums are littered with failed inductive systems that finished up in the bin and the original Kettering system returned to (with its faults in points load and unreliable 'new' condensers/capacitors).  My final attempt to get a decent new condenser was to use a non-electrolytic capacitor 'potted' in the original Bosch aluminium 'can'.  It worked, but the CDI unit (under $500)  I obtained was a quality design including a feature to protect the coil from excessive current.  It works extremely well and most reliably. The difference in low RPM power was very noticeable especially on an early model Porsche.  The system was also instantly switchable, so at any time I could just go back to the original Kettering system. 

In the past I have used inductive systems, but like many others, they always let me down after a year or two, on the side of the road. I agree with you fully that quality is the key in both types of systems and this might have recently changed in the case of inductive systems.

You might find this interesting http://www.capacitordischargeignition.com

All the best

Merv

 

Hate to say it Merv but it seems you have been given the internet run around with lots of rubbish information. Measuring the voltage from the battery to the points/switch side of coil(same cct) is not a measure of how the different systems are working relative to each other. Like I said with a CDI or inductive ignition the points only drive the electronics and have nothing to do with the coil. With inductive just stick to OEM modules from the likes of Bosch. How many modern cars do you see with dead inductive ignitions?
Now feel free to dismiss my advice but before you do I was a founder and chief engineer of an international company that designed and manufactured engine computers, ignitions, data loggers, power distribution and more for race cars and other applications. Even to this day many years after I sold up nearly all products the  company sells I designed. Porsche even factory fitted data loggers to GT3 Cup cars and the spiders and others. The equipment is also in use by the AUS military. I have designed CDI units for professional racing use and after 30years not much surprises me anymore when it comes to the internet experts and the rubbish information out there in relation to ignition systems. 

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Thanks Redracn (still don't know your name, sorry).  I have described my actual (not internet) experience with old Porsches and it seems that you are making the same point about quality that I was attempting to make. Hope you enjoyed the links.

Well done and good luck.

Merv

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1 minute ago, Merv said:

Thanks Redracn (still don't know your name, sorry).  I have described my actual experience with Porsches and it seems that you are making the same point about quality that I was attempting to make. 

Well done and good luck.

Hi Merv

After I sold up I was not allowed to use my name on any Internet forum. While that time has only just passed I avoid using it now so I don’t end up with endless requests for advice. I don’t mind helping out a fellow Porsche enthusiast but there has to be limits. 
I had a look at some Pertronic CDI specs and was not impressed. They are selling on bigger is better numbers which is common at the bottom end of the market and usually at the expense of reliable operation as they skimp on price and push the limits to get those (usually unnecessary) selling numbers. You don’t need 180+mJ of energy in your NA Porsche. A simple ultra reliable OEM  inductive module with matched coil at 70mJ  is way more than double what your original points system could manage. My Tarmac rally car with standard OEM system around 40mJ coil on plug has no issues with 30psi of boost and 7500 rpm.  One of the biggest problems is mismatching of the module and the coil. Coils have maximum operating voltages and the aftermarket likes to exceed them all the time. This can  dramatically reduce the life of the coil with its winding or terminal insulation breaking down. The CDI’s I designed had programmable output voltage so they could be properly matched to the coils.  

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