Electronic Ignition System Condenser

[ramon.alban]

Your valued knowledge gentlemen, please?

Seen on the attached image of a period Rover Ignition Module fitted to various Cars including Rover SD1 Efi cars, is a condenser connected between the White wire "+12 Volt Feed/Coil +ve" and "Earth".

On other period systems (eg, where the ign amplifier is on the side of the Distributor) a condenser is earthed with the coil retaining strap and connected likewise to "Coil +ve".

I know of three possible reasons for this condenser.

1 - A Radio Frequency Suppressor

2 - To assist the Coil Voltage to collapse rapidly when the amplifier switches off the current thro' the coil thereby enhancing the HT discharge. IE - Fatter Sparks.

3 - To absorb the Back EMF generated by the coil and thereby protect the electronics circuits elsewhere.

Does any one know if all, some or none of these reasons apply, and if None, what the heck does it do?

Much obliged.

Ramon

 

[classic kev]

Your valued knowledge gentlemen, please?

Seen on the attached image of a period Rover Ignition Module fitted to various Cars including Rover SD1 Efi cars, is a condenser connected between the White wire "+12 Volt Feed/Coil +ve" and "Earth".

On other period systems (eg, where the ign amplifier is on the side of the Distributor) a condenser is earthed with the coil retaining strap and connected likewise to "Coil +ve".

I know of three possible reasons for this condenser.

1 - A Radio Frequency Suppressor

2 - To assist the Coil Voltage to collapse rapidly when the amplifier switches off the current thro' the coil thereby enhancing the HT discharge. IE - Fatter Sparks.

3 - To absorb the Back EMF generated by the coil and thereby protect the electronics circuits elsewhere.

Does any one know if all, some or none of these reasons apply, and if None, what the heck does it do?

An interesting question and one I have wondered about myself. I don't claim to know for sure but I would have thought it would be reason 2. I say this because I would have thought radio supression would have been more likely done with an in line suppressor on the power feed to the radio (if that is what you mean). Option 3 is obviously a possiblity but I would have thought a diode would have been used instead and as far as I know, the EFI and ABS relays have diodes in them for that very reason. So by elimination, the condenser is there to assist the speed of field collapse.

I'm sure you can correct me if I am wrong, but as I understand it, electronic ignition systems generally generate higher voltages and in part this is related to the speed they are switched at and that the field collapses at - I think

I have also heard that Rover V8's don't like high power coils and that they run best with relatively "ordinary" coils Does any of that make sense?