my rotor is bigger than your rotor

Brandon Hull Hull at
Tue Jun 11 10:35:55 EDT 2002

I guess it's part of the nature of email lists that issues are raised and recede in their seasons, leaving behind vestiges of institutional memory and articles of faith.  It's worth a reminder of the origins of the "narrow rotor" doctrine.

So:  circa 1997:  Jeff Donnelly's famous "dragon wagon" was a fire breathing track animal with a 400HP 3B engine built for him by Lehman, via Hoppen motorsports.  He suffered a catastrophic engine failure which Lehman traced back to a distributer-caused misfire.  They shipped the engine back to germany, rebuilt it at their expense, sent it back to Jeff with the stern warning to never use anything but the factory distributer and ignition wires.  At about the same time, Alex Neckas was dealing with misfire issues on his very modified 3B installed in his 4Kq racecar.  He came to the same conclusions, namely that at high rpm, the later rotor was just wide enough to cause a spark to arc to the next ignition terminal prematurely.  Depending on what the cylinder was doing at the time, this could be a Bad Thing.  (eg exhaust stroke, no prob; compression stroke? V.Bad)

So, as for me and my house, we will use the narrow rotor...

Brandon H

> Don't quite agree, Brett:
> First of all - Audi/Bosch never really intended the
> distributor rotor on
> the 3b be replaced on it's own - the whole unit is supposed
> to be replaced
> - plastic gear and all.
> Replacement distributors come with the narrow rotor - which
> challenges your
> line of thought, too - if there was no difference, then
> Audi/Bosh would
> then have stopped making the additional part
> variation just
> increases costs for suppliers and manufactures
> Scott Mockry recommends the narrow, rotor, too.
> You are probably correct in that a mildly tuned engine can
> run with the
> "wider" rotor - however - for the relatively minor price
> difference - I'm
> not willing to risk it...I'll look for $ savings elsewhere.
> -Peter
> At 03:17 PM 6/10/2002 -0400, you wrote:
> >At 10:17 AM -0400 6/10/02, Peter Schulz wrote:
> >
> >>  but of course the rotor was the wrong type ( wide
> >>contact)  luckily I ordered a few of the correct rotors
> from ROd at TPC.
> >
> >The whole wrong versus right rotor is a bunch of horse
> whooey...IMHO :-)
> >
> >I've been running the "wrong" rotor for several years and around 60k
> >miles, with two different chipped ECUs...and I flog the bejezus out
> >of my car.  Running stage III+ now, pretty aggressive chip.
> >
> >There's the real-world evidence; the thinner rotor has been (for the
> >most part) "unavailable" for years....and there are probably hundreds
> >200q20v's running the "wrong" rotor...again for years(I would guess
> >that a survey of the list would find the majority, at least 2/3rds,
> >have the wider rotor installed.)  3B engine kabooms are pretty
> >rare...the only one I've heard of was Sarge, and there were other
> >issues involved the clouds of smoke on startup for a
> >couple days before the engine chewed itself on the highway.
> >
> >Personally, I'll be following the Bosch guidelines...I see no point
> >in spending the extra time, money, or effort on finding the "thin"
> >rotor.
> >
> >Besides, "Wider is Better", right? :-)
> >
> >Brett
> >--
> >----
> Peter Schulz
> 1990 CQ
> 1991 200 20v TQW indigo mica
> 1991 200 20v TQW titanium grey
> Chelmsford, MA USA
> peschulz at
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> 200q20v at

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