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Rotor, without the 12 k-ohms resistance

.. Distributor rotors, without 12,000 ohms resistance

1) The original Bosch rotors, as recommended by VW, I believe had 12,000 ohms, or was it 6,000 ohms of resistance across the contacts... that being from the centre, out to the tip.

2) What I am finding these days (probably from China) is just a straight through conductor with zero resistance.

3) Would love to hear feedback on what harm might come using these newer type rotors built without the resistance.

4) I am guessing/hoping it would not overheat the coil, since the proper Bosch coils have their own built-in resistance/ballast in the primary windings to control the proper amount of primary current in the primary windings... and thus control the proper level of current in the secondary, going through the rotor. Secondary current is always proportional to primary current, since that is the only place the secondary circuit can get its electrical energy.

5) So I am hoping some of you might have some thoughts on these newer rotors being found in the market missing the 12,000 ohms, or 6,000 ohms of resistance.

6) Hope Speedy Jim is still on his computer since I know anything electrical is definitely his specialty.

Ross Virgin, Toronto, Canada ..

Reply to
rvirgin22
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Ross:

Resistors were added some years back to help reduce ignition noise in car radios. There were resistor plugs and resistor wires and resistor rotors.

Radio noise is much less a problem today and many feel that any resistance in the HI tension circuit degrades performance. That's probably why you're seeing rotors with the resistor omitted.

Some discussion here:

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Speedy Jim

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Reply to
Speedy Jim

WOW, Speedy Jim, WOW Great response! That exactly explains why my old (AM) Mororola Radio sounded so good years ago, staticy now.

Reply to
Cletus

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The rotor that you think is from China sounds similar to a rotor that Aircooled.net discusses in the following link. It says that if you have a high output ignition, e.g. a CDI, you can dig out the resistor and braze a piece of brass in its place. They also sell modified resistor-less rotors.

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the drop down box that says "Required Selection" choose "Modified Rotor, SVDA ..." for a further explanation of how the rotor is modified. They sell the most commonly used stock rotors. I emailed them in 2004 with the request: "Do you sell a rotor that has had the resistor replaced for use with a CDI? My distributor uses a Bosch 04 006 rotor." Their answer was: "You'd have to order that rotor from us and have us modify it ($15 more). We normally carry the 04-033 or 04-038 rotors in modified form.

John [Connolly]"

You can send your technical questions to them by clicking on the "contact info" link at the bottom of every one of their web pages.

-- Randall

Reply to
Randall

.. .. Speedy Jim and Randall

1) Much appreciate your informative replies.

2) If the resistance is just to stop radio interference, I definitely will not worry about that.

Ross Virgin Toronto, Canada .. ..

Reply to
rvirgin22

I would add that it is recommended that the resistor exist near the arc (spark plug). So, the resistor spark plugs are the best location for a resistor to suppress radio interference. Giving up the resistor(s) in the rotor and plug wires then using resistor plugs would seem to provide the best radio noise suppression.

Here's a good write up for anyone interested:

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Reply to
AshMan40

Did that on a 009 that had the resistor turn into a charred hole. Just dig out enough space to allow a bit of wire to be soldered across as suggested then put a layer of araldite to hold it in place. John

Reply to
John

If you normally required a 5 kohm resistor and switch to a lower resistance rotor you may notice a slight difference in engine firing. Compare the spa rk produced by the 5 kohm resistor in the first trace to the traces for a 1 kohm resistor and one that has had the resistor removed (0 kohm). The 5 ko hm trace has a very sharp fall from the peak voltage required to fire the s park plug, to the burn voltage level where the bulk of the current flows. T his results in the longest burning spark. As the resistance of the rotor de creases, the length of time it takes to fall from peak voltage increases an d the shorter the spark. Don't try to outsmart VW/Bosch: they knew what the y are doing when they specified which rotor to use.

Reply to
calvinlpms

Would have been interesting to see the CRO traces. With an inductive/resistive circuit the time constant is L/R so decreasing R makes time constant greater which ties up with your results. I wonder how a 0 ohm rotor with 10K spark leads compare?. For years I constantly adjusted the chokes on my T3 carbies. After many years I eventually realised the best way to adjust them seemed to be how the VW service manual recommended!. I also agree with your last statement!!! John

If you normally required a 5 kohm resistor and switch to a lower resistance rotor you may notice a slight difference in engine firing. Compare the spark produced by the 5 kohm resistor in the first trace to the traces for a 1 kohm resistor and one that has had the resistor removed (0 kohm). The 5 kohm trace has a very sharp fall from the peak voltage required to fire the spark plug, to the burn voltage level where the bulk of the current flows. This results in the longest burning spark. As the resistance of the rotor decreases, the length of time it takes to fall from peak voltage increases and the shorter the spark. Don't try to outsmart VW/Bosch: they knew what they are doing when they specified which rotor to use.

Reply to
John

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