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Posted by: dflesburg Mar 8 2010, 09:07 AM

we had a breaking throttle cable this weekend on the 2.0 four.

We did have a rev limiting rotor.

motor reved up to around 7000

not sure why?

do these rev limiters wear out?

Cut out is supposed to be like 5500

Posted by: pbanders Mar 8 2010, 10:43 AM

Could be the cut-out contact has gotten corroded. Did you pull the rotor and examine it?

Posted by: dflesburg Mar 8 2010, 11:58 AM

no but i will.

Posted by: kwales Mar 8 2010, 12:27 PM

The design is really simple-stupid to reduce likelyhood of failure. Is the limiter movement blocked? If it is, then the limiter can't move to create the dead short that kills the ignition.

Posted by: SirAndy Mar 8 2010, 12:32 PM

Posted by: Cap'n Krusty Mar 8 2010, 01:24 PM

Actually, there's no contact for "open" The rotor contains a spring loaded piece between the center and the rotor tip. When the revs rise to a set point, the spring is overcome and the connection is broken. Remember, too, that the rev limiter only affects the electrical system; If you downshift into the wrong gear, the engine will rev as high as the gearing wants it to go.

The Cap'n

Posted by: dflesburg Mar 8 2010, 02:08 PM

true.

but I am talking about the neutral condition.

so if the system works off a spring, it could stick.

Posted by: SirAndy Mar 8 2010, 02:19 PM

Yes. Post a pic of the rotor. They're usually pretty much fail-safe, unless it's heavily corroded or gummed up ...

Andy

Posted by: Cap'n Krusty Mar 8 2010, 02:53 PM

The "neutral" or default position is one of continuity. Until the RPM rises to the "break" point, the little coil spring is strong enough to hold the connection closed. Above that point, the spring can no longer maintain enough pressure to continue the continuity and the spark can no longer reach the tip of the rotor. Once the RPMs fall below the ability of the spring to hold the contact, the continuity is restored. I've never seen a "breaker" rotor so in need of maintenance that it failed to function, but then I inspect the ignition components of every car that comes through my shop for service every 3000-5000 miles (I lube the felt beneath the rotor, too). I suggest the failure mode of the rotor, other than actual physical breakage and tip corrosion, is a failure of continuity, NOT a failure to lose continuity.

The Cap'n

Posted by: pbanders Mar 8 2010, 02:58 PM

Thanks, hadn't looked at mine in a while, I got it wrong.

Posted by: pcar916 Mar 8 2010, 03:01 PM

In addition to the limiter issue, there's a more fundamental failure. A very dangerous one at that.

If you break a cable the throttle should close, not open. Could make you die.

Posted by: SirAndy Mar 8 2010, 03:03 PM

There should be a throttle return spring. Or better yet, two ...
Andy

Posted by: pbanders Mar 8 2010, 03:08 PM

That's how mine's set up (2). Isn't that the way it came?

Posted by: ME733 Mar 8 2010, 05:37 PM

........Well guys everythings been covered very well except......There are many different rev limiting rotor buttons of various RPM limits....just a few come to mind ..approx 4500-5200-5500-6200-6800-7200----If i remember correctly. the highest rpm limiter was for a 911,S I,m pretty sure.--They will all fit and work in the various 914/009/etc distributors...The rev limit of the rotor is usually cast in the (back side of the rotor).opposite the rotor contact point. They are all marked, designated in some way.........................Murray