Author Topic: MAXI-DWELL?  (Read 8712 times)

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Offline 754

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Re: MAXI-DWELL?
« Reply #25 on: December 15, 2011, 09:16:42 PM »
 Got some figures.....

 Stock point are like a rocker arm pivot to either end is approx .55 -.56 so I would say 14mm
 Delco points are different the rubbing block is between the pivot and contacts and a different ratio, ikt is .75 inch from pivot to rubbing block, and 1.25 from pivot to contact. So there is definitely a difference in the ratio and amoiunt of pivot angle. I would think thois changes dwell a bit. Stock points asre 1.3 inches long, Delco is 2.79 inches
 
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Offline thrutheframe

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Re: MAXI-DWELL?
« Reply #26 on: September 15, 2014, 09:10:10 PM »
I think it is .020 gap...

The Honda points cam supplies 195 degrees of dwell for the stock points gapped at .014" while at the cam lobe peak.  The lobe ramp position is then adjusted so that the points open at the specified time and then close 195 degrees later by cam lobe design profile.  If the gap is smaller, then the dwell or point closure time increases.  If the gap is larger, then the dwell time diminishes.

A larger gap changes the angle or distance between the cam ramp up and ramp down on the cam profile.  A larger gap closes later as it uses more of the cam ramp down, and then opens sooner as it encounters the ramp going up.  This diminishes dwell time.

Please note that the points and cam are part of a greater ignition system.
So, you can't simply look at dwell in isolation from the coils, which can be made or wound differently.  For example, low ohm coils charge much faster (drawing more current/power to do so), and may not even need to fully saturate before storing enough energy for the spark event  The spark gap and atmosphere between the electrodes determines the actual voltage needed to create the arc.  The coil secondary resistance determines how fast the coil can be discharged.  The dwell time is nearly unimportant at low RPM, as there is plenty of time between spark events to recharge the coil.  It is at High RPMs where the event durations become "interesting", because there is less time available to charge the coil back up before the next discharge event.

Each coil design will have an optimum saturation point and will not fully discharge as the spark event and current flow only last as long as the spark gap(s) has enough voltage to sustain the arc.

Other factors also come into play then, such as spark gap distance (larger gaps need more voltage to create the conductive arc), and added resistance in the coil output which can serve to limit the coil discharge depth.  The depth of coil discharge is then interactive with the charge time requirement or dwell of the next charge event. 

Hope this helps,


TT you're always spot on with your info.  Thanks.
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