dizzy
Posted: Mon Jul 24, 2006 3:50 pm
i have points ignition and just wondering what sort of electronic ones r the best to use. 4.2petrol/gas gq. Ive been told there r two kinds one of them keep the points and one does not.
In a normal points set up the points control both the timing of the spark and the interruption of the primary circuit which creates the spark in the secondary (high voltage) circuit. When they open they actually interrupt the current flowing through the primary coil windings.
I think the two types you are referring to are:
1) The second task of the normal points system, the breaking of the primary circuit is taken over by an electronic switching unit. The points are merely used as a timing device to signal the electronic switch to open and close. Because the current in the points is much lower than previously the points last longer.
2) In the second type the timing role of the points is taken over by another device such as a trigger wheel, magnetic pickup coil or Hall Effect sensor. An example of this second type is the Pertronix Ignition which replaces the points with a Hall Effect sensor and electronic switching unit which fits inside the distributor.
In both these situations the ignition timing - advance and retard is still set by the distributor's mechanical and vacuum advance/retard and there is still a rotor to distribute the spark.
The next stage is to send the output from the sensor (or even the old points) to an electronic control unit which calculates the required advance and sends a spark-out signal to the electronic switching unit. The ecu can do a lot of other clever things such as switching off the current in your coil if you leave the ignition switch on accidentally! The Ford TFI system is an example of this type of ignition or you can use your own ECU such as the Megasquirt.
The final stage is to do away with the dizzy altogether with a waste spark system such as Ford's EDIS. There is a thread on this in the auto-electric section.
To answer your question you get a marked improvement over points by using such a system as the Pertronix. i.e. System 2 combing an electronic switching unit with a non-points pickup. I did this on my MQ and it revs much more freely at the higher revs (i.e 3000 rpm + for the P40 engine) as there is no points "bounce". Also the "points" never go out of adjustement so you are not forever fiddling around with dwell meters and feeler gauges. If you go with system 1 (retaining the points but using an electronic switching circuit) you will get a more intense spark than before and your points will last longer but you will have to adjust them as before but not so frequently. My son has just made such a system for his old Honda motorbike.
Sorry to be so long-winded but I hope this answers your question.
David