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Re: Re: rotor for 20v turbo engine

I believe the position of the rotor has absoultely no bearing whatsoever on
when the ignition fires. If the rotor is totally out of position then the
spark may be sent to the wrong plug or to no plug at all. You could remove
the rotor and the ingition would still fire but the energy would be totally
randomly distributed to none, some or all of the plugs, most likely none or
one - whatever the path of least resistance in the cap was at that time.
The rotor serves as a mechanical 'switch' to connect the output of the coil
to the correct sparkplug lead and, we hope, at the correct time for that
plug. The spark sould occur in sync with the rotor passing by the contact
in the cap connected to the lead connected to the intended plug to be
fired.  It is not intended that the rotor 'delay' or 'time' the spark till
the rotor gets into position with the correct contact. The actual instant
in time of the spark is totally controlled by the ECU regardless of the
position of the rotor. The rotor must be in the correct physical position
at this instant for things to work well, if it's off a bit too soon or too
late then you will rapidly burn on the cap and rotor and get a very weak
spark at the plug, if you get a spark at all.


C1J1Miller@aol.com on 11/05/98 10:48:43 PM

To:   wallace@remdesign.com, owner-200Q20V@pdikeman.ne.mediaone.net
cc:   quattro@coimbra.ans.net, 200q20v@pdikeman.ne.mediaone.net (Glen
Subject:  Re:  Re: rotor for 20v turbo engine

In a message dated 11/5/98 11:29:44 PM, wallace@remdesign.com wrote:

>But that would be the fault of the ECU and/or the distributor itself,
>not the distributor rotor, as I see it. The job of the rotor is to make
>sure there's a good easy path to whichever plug is going to be fired; if
>you have a narrower rotor, you make that path a little more difficult in
>the case of extreme advance, but you don't succeed in preventing
>it--which, at any rate, would result in a misfire.

I'm not sure if we're talking about the same thing...
cheap ascii art follows:

 [-------]             [   ----   ]
    [     ]                    [     ]
    [  o  ]                   [  o  ]

10v rotor             20v rotor

As I understand a coil, it builds up the voltage, then discharges.  Not
instantaneous, but takes some time.  The longer metal piece (-) will get
to the spark plug wire before the shorter 20v rotor will and the spark will
occur first.

The ECU says to the coil when to fire; with the longer than expected 10v
rotor, the coil may fire to the cylinder before the ECU thinks it will.
ECU doesn't measure when the spark occurs, just knows when it _should_
It advances/retards ignition timing based on 3D maps in the computer
and on ignition knock, temp, rpm, load.  But it doesn't have an inductive
pickup for when the spark actually occurs.