DCondensers for distributer type ignition

[jimmystratos]

Do the capacities (in microfarads) of condensers vary much between cars, or is it more the connections? I'm trying to match a 5 microfarad condenser for a 1930s Rolls.

[Trooper2]

You might try giving these folks a shout. Maybe point you in the right direction anyway.

http://partfinder.smpeurope.com/index.html?p=155&a...


The website also has a cross reference search as well.

[Pigeon]

Five microfarads? Are you sure it's not .5? Not only does a whole five sound unfeasible from an electrical point of view, a five microfarad capacitor capable of withstanding a few hundred volts and built using 1930s technology would be sodding huge in terms of physical size.

Modern ones are I think almost universally either 0.22uF or 0.47uF but I can't remember which. If as I suspect you do have a decimal point missing, you could replace it with either any old modern one or two modern ones in parallel. Or you could buy a 0.47uF non-polarised capacitor rated at 400V or more from an electronics supplier.

[GreenV8S]

Been far too long since I had to deal with inductive circuits but I'd expect the HT voltage is going to be similar (maybe 20kV?) in order to produce a spark, the current is unlikely to be higher than a modern electronic ignition system so the capacitance requirements would be similar. If the old capacitor was physically a similar size to the modern ones then I'd guess they're a similar order of magnitude in capacity.

If you go too small I think the main effect would be burning out the points. Too large and it won't spark. So you should be able to tell quite quickly whether the capacitance is about right. I think in this application 'about right' probably means within a factor of 2, and I doubt you need to get it better than that. If you want to experiment you could always try doubling (parallel) and halving (series) the capacitance and see if it goes better.

[tvrolet]

Dunno if it's any help, but the 'standard' condender on a Mallory ignition setup (as on my small block chevy) is .28 microfarads. Ok, it's not on a 30's engine, but a small block on points, condenser and coil ain't that far off! Real Steel on 01895 440505 do the Mallory stuff in the UK...

[Steve_D]

looked through a pile of old Haynes and general figure is about 2.2.

Found these guys in Google
http://www.vintagemotorspares.com/phdi/p1.nsf/supp...

Steve