Need help understanding breakerless ignition

gilach · gilach's Garage

hello all,
me not to swift with understanding electrical components. i did a search of the FAQ's, but didn't find a basic explanation and or advantage of the breakerless system. i just had plugs, wires, cap n rotor replaced, but did not have the timing set. with breakerless is timing set less often.

best, paul.

Howard M · 09-20-2006, 10:39 AM

Without points and a rubbing block to wear, the timing should not change on a point-less distributor. "Never" is a long time, but other than distributor shaft bushing wear, nothing should change your timing after it is properly set. We mid-year and older types have to check timing regularly, or change to a Pertronix magnetic points eliminator (as I did).

randywebb · 09-20-2006, 12:16 PM

to add... there is no mechanical contact; either a light beam is interrupted (photochopper - not sure they use that anymore) or a magnetic field is interrupted (usually in a clever way - Hall effect)

this gives the signal as to WHEN to fire -- it is NOT the high energy electricity that fires the spark, just a signal

Does that make sense? Ask if you have more questions.

cmcfaul · cmcfaul's Garage

Eliminationg points is BY FAR the best improvment one can make to their Porsche. Adjusting point and dwell is a nightmare. With Petronics or other means the car runs like it was just tuned all the time. Those with points understand exactly what I am talking about.

Chris
73 911 E

304065 · 09-20-2006, 03:15 PM

Except that only three guys in the country are still running Kettering ignition where the points actually wear and Dwell makes a difference.

The capacitor in the Bosch CDI charges at the speed of light and it's good for operation up to probably 600 Hz. For reference, when the engine is turning at 8000 RPM, that's three ignition events per revolution, or 400 Hz. With a dwell of 38 degrees of distributor rotation, or 19 degrees of crankshaft rotation, at 8000 rpm the points are closed for a total of 0.0004 seconds which is STILL enough time to charge the CDI.

randywebb · 09-20-2006, 03:42 PM

"speed of light" - this is artistic license, right?

gilach · gilach's Garage

ok guys, check this link out....

http://auto.howstuffworks.com/ignition-system.htm

very nice explaination....now i see the breakered distributor, now what's the deal w/breakerless? is the flow of current constant?

i'm pretty sure my 930 has breakerless system as does my R5 T2..though i could be wrong about the 930. i'm just trying to understand why the timing doesn't need to be set as frequently.

also, i thought that 930's had the 'heavy duty' oil cooler from factory, located in the front wheel well....any thoughts.

finally, by speed of light i think john means it in the same way that the millenium falcon could reach light speed :-)

best, paul.

randywebb · 09-22-2006, 12:08 PM

"is the flow of current constant?"

Which flow? Altho the answer is no, no matter what...

Eagledriver · 09-22-2006, 04:15 PM

CD systems dump large amounts of current through a coil for the spark event. This is true for points or no points. Old style ignition used the current through the points itself to run through the coil, when the points opened the magnetic field collapsed causing a large voltage to be generated in the secondary loop of the coil. Dwell is only important in these old systems not in CD systems. The old system had current running through the coil whenever the points were closed the CD system only has current when a firing event occurs.

-Andy