Re: rotor for 20v turbo engine

[Wallace White <wallace@remdesign.com>]

C1J1Miller@aol.com wrote:
> If you think about the distance between the 5 points on the cap, and the width
> of the rotor tip, the wider rotor tip will allow the spark to travel to the
> next cylinder before the narrower tip would.  In other words, the timing would
> be advanced to that cylinder.  Now, put in high rpm, modified computer, high
> temps...

I suppose, but the spark will jump across a pretty big gap anyway, as I
can say since my distributor rotor was so corroded that it had to jump
more than a 1/4". (Yes, it runs much better now with a new one!)

> The ECU could be advancing the spark pretty far for more power, especially in
> the modified computer; then consider the wider rotor tip advances the spark
> even more than the ECU expects (actually to a point where the piston is still
> moving up to compress the gas/air mix). If the spark happens _enough_ before
> top dead center, you could get ignition and combustion forcing the piston
> _down_ when it should be moving _up_.  This is preignition, and can blow or
> seriously damage an engine.

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. 

> That's my theory, anyways.

And this is just my theory, too. Please correct me if I'm wrong.

- Wallace
  '87 5kcstq 150k, big fat distributor rotor

> HTH chris miller, windham nh, c1j1miller@aol.com
> http://members.aol.com/c1j1miller/index.html