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Join Date: Nov 2003
Location: Yokosuka, Japan
Posts: 500
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964 ignition advance
All,
I was in discussion with a friend about electronic ignition (ala Motronic) units that still use the traditional looking cap and rotor. From doing a search of the site I understand that the weights used in a 964 rotor ONLY control rotor phasing as per the DME's ignition map. Question... -How does a set of weights and springs in the rotor phasing unit have enough fidelity or control to match the DME's ignition maps? Or, put another way, how does the rotor, operating on a set curve, "know" how to phase the rotor in conjunction with the DME's wishes? Please help...my brain hurts... R/ Dustin |
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09-27-2004, 12:36 PM
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Join Date: Jun 2003
Location: Camarillo, Ca.
Posts: 2,418
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I would venture to guess that the mechanical advance places the rotor close and the DME then decides to energize the ignition at the specific degree it is programmed for.
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Aaron.  F.S. 1965 Solex engine w carbs/cleanerBurnham Performance https://www.instagram.com/burnhamperformance/ |
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09-27-2004, 01:06 PM
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Join Date: Dec 1999
Location: Novato, CA
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Fidelity?
WTF...the rotor face/width itself allows at least 10 degees of slop either way to keep things lined up enough on the cap. It only needs to follow the advance curve within those rather loose limits. Joe |
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09-27-2004, 01:24 PM
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Location: Yokosuka, Japan
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Joe,
Sorry if the term "fidelity" for this usage bothers you...CTFD. I would take it then, that the rotor phasing mechanism and the DME are ALWAYS within +/- 10 degress of each other? When I think of counter weights and springs in this scenario it seems like a very crude system that is coupled to very precise measurements from the DME computer. R/ Dustin |
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09-27-2004, 01:55 PM
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Join Date: Jul 2002
Location: Sydney, Australia
Posts: 2,477
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i put one on a dizzy graphing machine and, from memory, it had 16 degress of mechanical advance
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Cheers, Ryan 1969 911E (historic racer) 911ST replica (tarmac rally) |
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09-27-2004, 02:54 PM
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Join Date: Dec 1999
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R/
Dustin, Didn't mean to offend you with my rather crude off the cuff remark but if I did, my appologies. Just trying to keep it light and have some fun. Cheers, Joe Last edited by stlrj; 09-28-2004 at 02:42 PM.. |
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09-28-2004, 02:37 PM
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Join Date: Nov 2003
Location: Yokosuka, Japan
Posts: 500
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Joe,
Of course, no hard feelings...I do appreciate the reply though. It just makes me scratch my head when I think about it....akin to measuring with a laser and cutting with a chainsaw.... R/ Dustin |
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09-28-2004, 05:32 PM
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Join Date: Dec 1999
Location: Novato, CA
Posts: 4,740
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R/
Dustin, Well, at the very least, they are very precise where it counts and where precision is not needed, it hardly makes any difference nor does it really bother me. Cheers, Joe |
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09-28-2004, 05:55 PM
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