Lancia Motor Club

I am having a little, no, make that a lot of difficulty in identifying the part number, spec.(micro-fahreds) etc for my Appia Berlina......
Can anyone say what part number, or specification I need to know.
I have one Intermotor 3391 ,I think?   that is rated for Fiat x1/9 , 127. 124. 128 .There is no marking, so I do not know the spec.
What is the harm in fitting other than the correct one, assuming it is 12 volt....There seems to be a lot of mystery regarding the capacitor/condenser.....

In general, there is no difference in 6 or 12 V systems in terms of selecting the condenser. Moreover, as long as the condenser is rated in the range 0.2-0.3 microFaraday, it will be OK for the Appia (and Fulvia). Check that its mounting is compatible with the distributor, though, Andrea 

The Appia Consortium has a big bag of brand new ones...

I was hoping to find a cross reference chart someplace!.....
I cant recall seeing the rating on the condenser that was fitted......also ,what determines the microfad
rating,is it the number of cylinders, the coil characteristics , the plugs.....the capacity of the engine..
Id like to understand this much more than just changing the condenser.
Thanks to you all for your replies.

Condenser/capacitor value is determined by the ignition system, mainly the coil. The common value on most cars is 0.22 mfd. but between 0.22-0.29 will work fine. If the value is too large/ small there will pitting on the moving point and a build up on the fixed contact and vice/versa. ( I can`t recall which way round at the moment but I have a note somewhere if you need to know.
It is there to prevent arcing across the contacts as they open and the magnetic field that is built up inside the coil collapses and oscillates between coil and condenser until it fades away. It`s the collapse of the magnetic field and the resulting inductive kick that causes the secondary high voltage spark across the plugs.

Thanks for all your replies....It seems it is as much about(well, all about) the coil fitted, that determines
the condenser needed....As a matter of fact my Appia came with a LUCAS SA 12....not a Marelli as fitted to Turin built cars,

Ian

So you need to "match" the coil with condenser, or do 12v coils differ hence need to match?

P

Hi Frank
Yes, the coils do differ on the ratio between the number of turns of wire between the Secondary and Primary systems inside the coil and also Primary resistance ( measured between the the 2 outside terminals). These are determined by the engine manufacturer. Generally a contact breaker system uses a coil with a primary resistance  around 2.0-2.5 ohms whereas an electronic system needs a lower resistance of 0.8 - 1.0 ohm.
Condensers aren`t super critical but usually have a value of 0.22- 0.29 microfarads . Too large a capacity will produce pitting in the moving contact of the points and under capacity produce pitting in the stationary contact.
Also they don`t need to match the fitting in the distributor particularly, because if you can mount it outside of the distributor, with the wire connected to the coil negative terminal and the the condenser body to a good earth, it will last longer as they don`t like too much heat. The most effective way is to buy a competition condenser from SWIFTUNE ( 01233 850843) They work with any engine and are very reliable. They cost around £30.00 but that`s better than breaking down and cheaper than recovery. ( I have no connection to the Company) They mount outside the distributor on the bulkhead or similar.

John

Very useful John, another day at school being on this forum!!!

P

On the subject of coils, on a car like a Fulvia or Aurelia running OE distributor + points, should the coil run cool or hot?
And if its hot, why is this?
Another lesson please John.
Chris

There are 2 generic types of coil c1.5ohm and c 3ohm. The former should be run with a "1.5 ohm ballast resistor". If not it will run hot. I generally run the DLB105 Lucas Sport coils on my Fulvias and Flavia. This is with either points or Luminition systems. The coil never runs hot unless the engine is not running and the ignition on (not to be recommended as the coil will burn out). John may be able to add that if the dwell angle is not correct then the coil does not have time to collapse and therefore will retain more energy than designed and this will generate heat.

Hi Chris

In my experience some coils run hotter than others, depending on the number of turns of wire internally. Essentially a coil is a transformer, converting 12 volts ( battery) to 200-300 volts on the low tension side to 30,000-40.000 volts on the high tension side to the centre of the distributor and in doing so will by its nature generate heat. Sports coils like a DLB105 as Tim is using are oil filled to dissipate the higher voltage produced.  We always position race car coils in the airflow if possible or on a metal plate as a heat sink.
Incorrect coil connections, bad plug leads and an internal fault in the coil can cause higher than normal temperatures, as will an incorrect resistance coil. ( Lower resistance = more current flow = more heat generated)
However if the car is running OK and the coil is hot but not enough to take your skin off, it should in my opinion, pose no problems.

Tim
I agree  the dwell angle needs to be correct otherwise if it is too short ( points gap too wide) then the coil doesn`t have sufficient time to build up the magnetic field and will cause a less powerful spark and also advance the ignition timing. Too small a gap increases the dwell angle and retards the timing and may raise the engine temperature.
P.S. In my earlier post about connecting an external condenser to the negative side of the coil I maybe should have clarified (Distributor side) as it depends whether you have negative or positive earth system.

Apologies for rambling on and I am happy to be corrected, we are all still learning, but hope it helps in some way.

John