Rotor, without the 12 k-ohms resistance

[rvirgin22]

.. 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
..

[Speedy Jim]

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:
http://www.shoptalkforums.com/viewtopic.php?f=1&t=99137&start=0

Speedy Jim
http://www.nls.net/mp/volks/

[Cletus]

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

"Speedy Jim" <volks...@sbcglobal.net> wrote in message
news:hq0a8k$ohh$1...@news.eternal-september.org...

[Randall]

rvirgin22 wrote:
> .. 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.

--- <snipped> ---

>
> Ross Virgin, Toronto, Canada
> ..

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.
http://www.aircooled.net/new-bin/viewproductdetail.php?keyword2=IGR0002&cartid=
Under 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

[rvirgin22]

..
..
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
..
..

[AshMan40]

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:
http://www.oldcitypublishing.com/FullText/JAPEDfulltext/JAPED3.3-4fulltext/Klimiec.pdf

[John]

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

[calvi...@gmail.com]

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.

[John]

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



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