Condensors

[2speed]

Can you eliminate the condensor and put a diode instead?

If the condensor is there to eliminate back emf across the points, couldn't you use a diode to do the same thing?

 

[LEROY POLL]

HELLO 2SPEED

....THE DIODE WILL FIRE TOO FAST TO INCREASE THE SPARK. A 100 VOLT ZENNER DIODE WOULD STILL FIRE TO QUICKLY TO HELP.

.... THE CONDENSER ACTS MORE LIKE A TANK TO HELP THE SPARK TO FIRE ON THE OTHER PATH TO GROUND...(SPARK PLUG). CONDERSERS ARE SLOW AND JUST FINE FOR THEIR USES. THE DIODE WILL REACT AND SWITCH TO GROUND IN MICRO SEC'S. EVEN AT VERY HIGH SWITCHING THE CONDENSER WORKS WELL. THE ONLY HELP IT WILL NEED, WITH POINTS, IS TO BE LARGER. THIS IS TAKING THE SPARK SURGE OFF THE POINTS WHEN THEY ARE AT A SMALLER GAP TO JUMP. THIS DELAY IN THE SPARK AT THE POINT GIVES A BIGGER SPARK AT THE S/PLUG. THIS WILL LEADS TO NO SPARK AT THE POINTS. IT IS ACTING AS A SUSPRESSOR AT THE POINTS.

.... IF THIS DOESN'T HELP AND YOU WERE THINKING OF SOMETHING ELSE, GIVE US WHAT YOU WERE THINKING.

LIVE IN GRACE

LEROY POLL

 

[Anonymous]

Hi, 2-speed;

The diode will clamp the negative EMF spikes, but not the positive. When I worked my way thru Electonics Engineering school, we played with this same thing on Hondas, as they were hard on their points. What we found was the diodes caused increased pitting of the points, building up the material on the moving point very quickly. We also discovered several other things that would probably translate to cars:

1. Required condensor capacity is directly proportional to coil current. A 4-amp coil, for example, needed about .25uF in the condensor to balance the point wear. A 2-amp current draw needed about .15uf, or about 50% as much. The highest-current test we ran was at 5 amps, which required a .33uF capacitor. If you had too little capacitance, the pitting caused the moving electrode to grow and the ground side to pit. Vice versa, too.

2. When we tried using diodes, the spark from the coil had an unbalanced output: the high-voltage swung wildly over the RPM range and was always below the voltage produced with a capacitor (condensor).

But, that was in the 60s, and you know what they say - "If you remember the 60s, YOU WEREN'T THERE!"