Date: Sat, 13 May 2000 23:13:51 -0400
Reply-To: Mark Rokus <marokus@VOYAGER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Rokus <marokus@VOYAGER.NET>
Subject: Re: dwell
Content-Type: multipart/alternative;
To add even more trivia to a beat to death subject:
Yes, Pertronix are Hall effect based. A hall sensor turns on based on the strength of the magnetic field that they see, thus, it is logical to conclude that you can effect the dwell by changing the distance from the collar (with the magnets in it) and the sensor. ie... the closer the pick-up is to the collar (magnets) , the longer the sensor will see it. Obviously, if you get too much of a gap, the pulse will be shorter.
Personal experience: Don't get you hand anywhere near the business side of one of these (coil output). Not only does the module decide when to fire the coil, it gives it a sustained spark. It hurts lots more than when you get hit by points. I ran one in a beetle that I circle track raced for years and it brought home more than one trophe. It later went into a '73 bus and ran fine. In case it matters, I also carried a set of points and a condenser in the bus just in case.
Mark Rokus
'87 Syncro (wifie's)
'87 Syncro Westy: Mine :-)
'81 Westy
'82 Diesel Rabbit
'72 Karmann Ghia
----- Original Message -----
From: jeff crane
To: vanagon@GERRY.VANAGON.COM
Sent: Saturday, May 13, 2000 10:54 PM
Subject: dwell
Yes dwell angle is still a factor in transistorized ignitions. It is no longer adjustable but through software it is possible in distributorless ignitions, but no the service tech cannot do so.
Dwell is expressed in degrees of distributor shaft rotation. 30*dwell on an eight cylinder engine would leave 120* of cumulative rotation for the coil to be off charge and therefore cooling somewhat. 45* on a four cylinder engine would leave 180* to cool, and 180* to charge the coil cumulatively. Simply because the distributor shaft rotates 360* of course. If you have a transistorized ignition, breakerless whatever, you can still measure the dwell angle. If the system is weak chances are you will find a shorter dwell angle when you test it. I have done this and I know it works. In fact, transistorized ignitions can and do have variable dwell periods factored into the circuitry on some applications. In reality the hall effect sensor is simply a switch and not the conductor that all current must pass to charge the coil and this leaves you many possibilities.
To understand this best it is best to realize that dwell exists even in distributorless ignitions, though it is often ignored, it is a percentage of time in a given engine revolution. That doesn't matter but that it is important to realize that without contact points you do still have a dwell angle.
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