Correct condenser for SVDA dizzie?

Mike,

What's the number on your distributor?

Try this site:

Hope this helps,

Dane Tyler '69 Bug '63 Bug

Mike Rocket J. Squirrel Elliott wrote:

There's only one Bosch condensor, as far as I have been able to discern, although they have made them differently over the years. I once went thru a whole shop's worth of Bosch condensors, just to see if they all measured the same capacitance. They did.

OTOH, Bosch makes what appears to be a nearly infinite selection of Capacitor assemblies, which vary in the kinds of fittings they use and the length and type of wire and end connections.

Up thru about '71 VW used a condensor that had the retainer clip built into the condensor hold down clip. Starting around '72 they went to separate parts. You may find what you want if you go down a year or so. Look up a condensor for a '70 or '69 bus. It may come with the clip you're looking for.

It sounds like your distributor originally came with the separate clamp. This means that you have to either use an earlier condensor, or find the later clip, which was never supplied with the replacement condensors. I can dig one of these up if you really need it.

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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This makes sense, Jim. I should have said "condensor assmblies" since the capacitor itself doesn't need to be anything special other than reliable. It's not like there is any tuning or matching of capacitance to coil or points needed: it's standard procedure to stick a cap across contacts to prevent arcing and pitting when they are switching into an inductive load. Usually in the 0.1uF to 0.47uF is what I use on relay contacts when I need to do something like that.

I was addressing the mechanical fit issue: round vs square pegs, integrated retainer clips vs not. Cleaning up the shop table today I did stumble across a separate retainer clip. I reckon it's the part I need.

Thanks, Jim.

-- Mike "Rocket J Squirrel" Elliott

Hi ! do not take this wrong, but your statement:

"It's not like there is any tuning or matching of capacitance to coil or points needed: it's standard procedure to stick a cap across contacts to prevent arcing and pitting when they are switching into an inductive load. Usually in the 0.1uF to 0.47uF is what I use on relay contacts when I need to do something like that."

Is according to those in the know (read the old timers who actually knew/know the Kettering system) completely wrong..

The capacitor/condenser is tuned to the coil/complete system by frequence... Yes, I thought it bs too, but they are right..

Of cause you could get it to runn by applying "any" condenserbut milage would vary(SP?)

J.

Can you cite any references? What frequencies are we tuning for? If tuning for frequency is important then we'd use different capacitors with different coils, since the inductance of each type of coil is different and affects the frequency of the contact make/break ringing.

-- Mike "Rocket J Squirrel" Elliott

Mr.Rocket.

I'm to far from even remotely remebering the correct basics, look for (as in doing a "Google") (Yes, even being a forrrrrreigner I do realize the lingo is horrible) Kettering. I believe Mr.Hoover had a down to earth write-up on the Kettering system.

My biggest surprise was exchanging words with a Professor as in medicine...(I know the guy) He knew the Kettering system!!!::::

J.

Hi Mr. J -- I did a Google for "kettering ignition coil inductance frequency" and didn't find anything related to tuning by frequency.

A very nice tutorial (with excellent pictures) is at

If the condenser is too large, there is no spark, and if it is too small the points contacts will wear out soon due to arcing/pitting. But matching the value of capacitance to the inductance/resistance of the coil to produce a certain frequency of ringing doesn't seem like any part of ignition setup. In fact, minimum ringing would be best from the viewpoint of reducing emissions -- EMI or "electromagnetic interference" emissions, that is.

Those electronically-inclined might find this article detailing modeling and simulating the Kettering ignition with PSpice interesting:

Until then, I'm sticking to my original assertations that the sole function of the condenser is to prolong the life of the points by slowing down the collapse of the coil's magnetic field long enough to let the points open enough so back-EMF cannot arc across the gap between them; and that as long as the capacitance is neither so large that it slows things down to the point where there is no reliable spark, nor so small that it permits points arcing, it's the right value and dorking around within those two limits is a waste of time better spent enjoying the sunset or chasing girls.

-- Mike "Rocket J Squirrel" Elliott

Dammit, Chris -- now no one is going to want to follow /that/ act!!!

-- Mike "Rocket J Squirrel" Elliott

Try aircooled.net to be sure you get the right one. How about getting a Pertronix or Compufire for a SVDA from aircooled.net and do away with the points. The points rubbing block puts tension on the distributor shaft and helps cause distributor shaft wear. Your distributor will last longer when not usiong points. A Pertronix will last about 70,000 miles and your VW will be that much more high tech and run smoother..

I already got me a Compufire pointless setup sitting on the bench waiting for me to grind down the dizzie's rotor and to be popped in. I wuz just lookin' to see if there was some sort of explanation for my dealer's inability to find the right condenser for this dizzie w/ points.

This is both right and wrong.

The condensor together with the coil determines the resonant frequency. There are no 2 frequencies that need to be matched in some way.

But, the condensor does need to be chosen to give a rate of voltage rise at the points that is slow enough that the points won't arc as they open.

The system really doesn't care what frequency it rings at, but the rise time goes hand-in-hand with the frequency, so we really can't ignore it.

I'm impressed that Bosch manages to make all their coils work with the same capacitance, but that's probably a lot simpler than it sounds at first, since all their coils probably fall into just a very few groups electrically.

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Hello! I have a question : with a Compufire unit, do you need to keep the condenser?

Thanks!

You are taking the piss now??? If not the answer is no.

J.