This may have been a topic in the past, but I can't locate if it's been discussed. Sorry for ignorance, but can some one give me a high level expalaniton on what the main differences are in the 2 systems, pros and cons, how to test them, reliabilty, why / when Deere switchedover, etc.
Thanks for any hep ....
CDI versus Points Ignition
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guitardude081
- Posts: 989
- Joined: Sun Sep 11, 2005 12:00 am
- Real Name: Jack Durand
- Location: Brainerd, MN
CDI versus Points Ignition
--In the points ign. As the flywheel rotates over the coils, it generates a current. This current is stored for a short time in the condenser. When the points are closed, the current will travel to ground. When the points are open, the normal path of current is interupted, and the path of current will find a ground by traveling through the wires to the ignition coil where the current is then "stepped up" enough to travel through the spark plug wire to the spark plug where it creates a spark. There are 1 set of points per cylinder unless both cylinders fire simultaneously. (ET ign stator)
-- In the CDI ign. As the flywheel rotates over the coils, the four pole magnet on it generates an AC current. The exciter coil sends AC current to the CDI unit where it is converted to DC current and stored. The pulser coil signals the CDI unit when to release the stored DC current to the ignition coil. The ignition coil "steps-up" the electrical energy (DC current) to a level high enough to fire the spark plugs. Both plugs fire simultaneously.
The points system required a lot of adjustment to get it to work correctly, and the points would have to be replaced periodically. They would also wear or get dirty and would create a weaker spark. The points would have to be filed and set accordingly. The CDI system was capable of generating a better spark and was more reliable than the points system. A lot of the original JD CDI boxes would stop working if you looked at them wrong. I was told by a mechanic that the CDI boxes can just fail from sitting too long. They were still the better choice in his opinion.
*info taken from an old clymer condensed service manual. Circa 1988.
Points ign.: 1972-1974
CDI ign.: 1975-1984
There were various makes of both kinds of ignitions, I'm not 100% sure about what years and what were used.
I'm sure one of the tech gurus can really dig into the theories, and all of the pros and cons of the different systems and brands , but heres the basics. Hope I help a little bit.
~Jack
-- In the CDI ign. As the flywheel rotates over the coils, the four pole magnet on it generates an AC current. The exciter coil sends AC current to the CDI unit where it is converted to DC current and stored. The pulser coil signals the CDI unit when to release the stored DC current to the ignition coil. The ignition coil "steps-up" the electrical energy (DC current) to a level high enough to fire the spark plugs. Both plugs fire simultaneously.
The points system required a lot of adjustment to get it to work correctly, and the points would have to be replaced periodically. They would also wear or get dirty and would create a weaker spark. The points would have to be filed and set accordingly. The CDI system was capable of generating a better spark and was more reliable than the points system. A lot of the original JD CDI boxes would stop working if you looked at them wrong. I was told by a mechanic that the CDI boxes can just fail from sitting too long. They were still the better choice in his opinion.
*info taken from an old clymer condensed service manual. Circa 1988.
Points ign.: 1972-1974
CDI ign.: 1975-1984
There were various makes of both kinds of ignitions, I'm not 100% sure about what years and what were used.
I'm sure one of the tech gurus can really dig into the theories, and all of the pros and cons of the different systems and brands , but heres the basics. Hope I help a little bit.
~Jack
Owner, Durand Motorsports
1980 Trailfire 340 (Grandpa bought new)
1983 Trailfire LX
1982 Spitfire (Grandpa bought new)
(3)1974 295/S
1975 340/S
(2) 1978 Liquifire
2003 Ski Doo Renegade 600HO
1993 Polaris XLT Special with AAEN pipes
2020 Polaris Indy 600 XC 129 40th Anniversary Edition
1980 Liquifire (currently in pieces)
1980 Trailfire 340 (Grandpa bought new)
1983 Trailfire LX
1982 Spitfire (Grandpa bought new)
(3)1974 295/S
1975 340/S
(2) 1978 Liquifire
2003 Ski Doo Renegade 600HO
1993 Polaris XLT Special with AAEN pipes
2020 Polaris Indy 600 XC 129 40th Anniversary Edition
1980 Liquifire (currently in pieces)
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Rodimus Prime
- Posts: 738
- Joined: Sun Jul 24, 2005 12:00 am
CDI versus Points Ignition
one points were on jd machines in 75 not 74. prestolite cdi systems where then made standard on jd machines in 76 till 78, 79 kokuscan cdu11 cdi till 84. the cdu11 unit is popular on skidoos polaris articat yamahas so its not hard to find and the basic components are the same for all just wiring changes.
the point system is the simplest easiest system.. and when one considers age far more durable than the cdi units which are subject to cold solder joints and solderjoint failure from vibration damage.
while its true that the point system does require more skill to initally set its ususally good for a couple thousand miles of use before points wear out.
cdi units are supposed to generate a better spark...in theory in practice not. they can last for 2 minutes to 20 years. some cdi systems are more complicated than others. the first jd style used on ccw engines use a complicated stator assembly that is prone to damage. they second style used on the kawasaki engines is simpler and more durable it can also be used on the old ccw engines with a bit of work.
as for performance neither one is better than the other really points have float and the tolerances of electronic components in the cdi boxes dont help that much either unless you design and build your own or get a custom one.. Note in the faq section i posted a schematic and circuit layout of the cdu11
althought more techincal than needed there is currently a chip available that can be programmed to match an engines torgue/power curve better and is still NOT put in even current cdi boxes although the new ones have come a long way over the last 10 years.
the point system is the simplest easiest system.. and when one considers age far more durable than the cdi units which are subject to cold solder joints and solderjoint failure from vibration damage.
while its true that the point system does require more skill to initally set its ususally good for a couple thousand miles of use before points wear out.
cdi units are supposed to generate a better spark...in theory in practice not. they can last for 2 minutes to 20 years. some cdi systems are more complicated than others. the first jd style used on ccw engines use a complicated stator assembly that is prone to damage. they second style used on the kawasaki engines is simpler and more durable it can also be used on the old ccw engines with a bit of work.
as for performance neither one is better than the other really points have float and the tolerances of electronic components in the cdi boxes dont help that much either unless you design and build your own or get a custom one.. Note in the faq section i posted a schematic and circuit layout of the cdu11
althought more techincal than needed there is currently a chip available that can be programmed to match an engines torgue/power curve better and is still NOT put in even current cdi boxes although the new ones have come a long way over the last 10 years.
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Deere John
- Posts: 24
- Joined: Fri Oct 06, 2006 12:00 am
CDI versus Points Ignition
WOW .. you guys are awesome .... this is a lot to swallow, but it makes sense. Thanks so much!
Greg
Greg