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Registered
Join Date: Apr 2002
Location: Massachusetts
Posts: 438
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RPM-Limiting rotor wasn't limiting
So, a bit of a scary thing started happening. I use my car for autocross so I rely
on my rev-limiting rotor a lot more than most (2.2L E engine). Sometimes you need to just leave it in second at the limit for a short time. Well, it dawned on me that I never seemed to hit it last event, and then a quick check showed that it wasn't stopping at 7100. (I'm sure my valves springs can handle a bit more, but in general am saving crank etc at this limit). Basic check: use an ohmmeter, clip one lead to a good ground; pull dist cap and gently touch (don't poke with sharp lead) the rotor's grounding tab (the one that the spring-contact will eventually touch). If that is not basically a short, then guess what, it ain't gonna limit your engine. Reason: rust on the grounding piece; everything in the rotor is brass or something similar, but this piece is steel, and obviously not painted or protected. Rust on the contact area and/or the piece that touches the shaft is not good. The 2 rotors I have are no more than a few years old, too. ![]() This piece is removable; the white plastic clip comes out and it's otherwise a friction fit at the other end. In a pinch, I simply scraped the rust and put it back. However, for the long term, I'm trying to plate them (simple Eastwood tin-zinc electroplate kit). Here they are after plating: ![]() Here is what the rotors look like with piece re-installed. ![]() Hopefully this keeps the rust at bay. Check this yourself and maybe save an engine!
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Mark S. '70 914-6 |
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20kV usually does not stop when presented with a little rust, unless you want it to jump the gap in which case it won't. Nicely caught.
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1972 911T Coupe with a '73E MFI engine and 'S' pistons 10 year resto mostly completed, in original Albert Blue. ***If only I didn't know now what I didn't know then*** |
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this is why I love the "soft" rev limiter in a modern CDI. In addition to better spark that is.
You can easily set it where you want it, and it works every time. It also is a lot more gentle and you don't just stop the spark. I have mine set for 6500 in my car and just starts by missing a bit.
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RGruppe #79 '73 Carrera RS spec 2.7 MFI 00 Saab 95 Aero wagon stick 01 Saab 95 Aero wagon auto 03 Boxster 90 Chevy PU Prerunner....1990 |
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