Uprated condensers and electronic ignition aside I was recently looking at the range of condensers used on contemporary Fiat cars. The manual for a 500 states the capacitor value as 0.15 - 0.20 microfarads and 0.25 for the 126 range. So in my electronically uneducated state this leaves me to believe that any condenser within those values is acceptable. A whole range of other Fiats use 0.20 & 0.22 microfarads so I am thinking these are good alternatives for 500 & 126 engines. Any thoughts?
Technical Don’t give a Farad !
- Thread starter Toshi 975
- Start date
Currently reading:
Technical Don’t give a Farad !
the hobbler
Distinguished member
- Joined
- Jul 25, 2012
- Messages
- 4,082
- Points
- 1,013
That is interesting to be aware of David. The 2 reasons that I always reccomend the "Swiftune" condesnser are (1) they are built to a high standard (for racing) and, (2) due to the fact that they have a long earth lead as well as a long 'live' lead, they can be fitted remote from the distributor---up by the coil, well away from the hot 'cooling' air-flow from the engine. However, I would not argue tha fact that they are expensive (about £31), so if a QUALITY, less expensive alternative can be found, all well and good.
Thanks for the reminder about the “swifty” Tom. It does not even start to answer my question but you did win me a fiver 
Basically I was asking what effect variations in capacitor/condenser values would have on the ignition and spark?
Basically I was asking what effect variations in capacitor/condenser values would have on the ignition and spark?
- Joined
- Sep 27, 2020
- Messages
- 299
- Points
- 139
I believe (this knowledge coming from when I was researching the same subject for 2 stroke motorbike engines) that along as you're within the realms of normal for a cars condenser, that if the condensers capacitance is either too big you'll see pitting on one side of the points and material transferred onto the other, and if the capacitance is too small you'd see the same thing but the pitting will be on the opposite side of the points.
Ah-ha, just googled about it while typing this and found this site which I think I came across before, with some good condenser theory:
www.themagnetoguys.co.uk
And interesting that they are reccomending an actual capacitor as a replacement for the condenser. After all the condenser is just an old-fashioned capacitor...
Ah-ha, just googled about it while typing this and found this site which I think I came across before, with some good condenser theory:
Magneto condenser theory
Most of the work we do involves magnetos as fitted to Veteran, Vintage and Classic machines. This includes all types of Stationary Engines, Tractors, Boats, Motorcycles and Cars ranging from the most simple generator sets through to exotic racing machinery. Customers include individual owners...
And interesting that they are reccomending an actual capacitor as a replacement for the condenser. After all the condenser is just an old-fashioned capacitor...
Hey thanks for that, just what I wanted to knowI believe (this knowledge coming from when I was researching the same subject for 2 stroke motorbike engines) that along as you're within the realms of normal for a cars condenser, that if the condensers capacitance is either too big you'll see pitting on one side of the points and material transferred onto the other, and if the capacitance is too small you'd see the same thing but the pitting will be on the opposite side of the points.
Ah-ha, just googled about it while typing this and found this site which I think I came across before, with some good condenser theory:
Magneto condenser theory
Most of the work we do involves magnetos as fitted to Veteran, Vintage and Classic machines. This includes all types of Stationary Engines, Tractors, Boats, Motorcycles and Cars ranging from the most simple generator sets through to exotic racing machinery. Customers include individual owners...
And interesting that they are reccomending an actual capacitor as a replacement for the condenser. After all the condenser is just an old-fashioned capacitor...
I had read a number of things but seemed to be going round in circles. So seems to me that a 0.22 microfarads condenser is a good option and just keep an eye on the points over a period of time.
vexorg
Prominent member
- Joined
- Aug 14, 2021
- Messages
- 1,829
- Points
- 564
That makes no sense from an electral point of view.
The condenser is just a capactitor nowaday, plain and simple.
It's job it to help control the point gap from re-arcing across when they open. If you open the points without a condenser then it'll just spark back across immediately as the coil will drive the arc that's drawn out.
You want the smallest value that will stop the extra arcing.
Going larger will slow the current and magnetic field collapse in the coil, leading to a lower voltage on the HV side.
The actual value will depend on the coil resistance/inductance for the optimum.
- Joined
- Sep 27, 2020
- Messages
- 299
- Points
- 139
Yup with you there, thats the basic theory. I should have been more clear in my first reply but as Toshi was talking about replacing the 0.15uF-0.2uF factory condenser with a 0.22uF condenser from another Fiat, not replacing it with something several times bigger or smaller, I glossed over it.
Regarding the pitting/material transfer, I can only say that I've read about it in a couple of places when researching into motorbikes and passed on the info and a link to a site where I read about it.
