Hi Alan,
My Understanding is That Electomagnetic Interference can Cause problems with the Electronics in the distributor,
the same thing happens on moderns with computers.

Just my view
Colin

Location: TINOPAI NZ

so, in practice, does that mean that adding one of these is unwise unless one has a perfectly overhauled dynamo, as well as posh leads? What are the main sources of such interference?

Ok. So what they have done is inadequately shielded the unit to cut costs?

Better shielding is probably the real answer, but would clip on ferrites fitted to cables -as commonly used on electrical home entertainment equipment prevent problems?


Steve V.

Location: Polegate, East Sussex, United Kingdom

The life of the unit being shortened by using copper leads? Often the case with aftermarket ignition modules unfortunately. The relatively high resistance and high frequency suppression of carbon string leads greatly reduces, but in my experience doesn't necessarily cure the dead electronics problem.

Whenever there's a spark at the spark plug, there will be a reflected high frequency pulse that goes back along your nice low resistance copper leads, then through the HT side of the coil, this is induced as a magnetic field in the coil's core, which in turn is induced as a high frequency pulse that goes back through the low tension side of the coil to the switch; the switch here is your aftermarket electronic gizmo.

OEM electronic units like GM or Lucas HEI have circuitry to effectively deal with the reflected pulse even when Copper leads are used (even though copper leads are not recommended with these systems). However, this is often not the case with aftermarket units _ I have learned this the hard way with two failures on my racing car; one of them as I was on the grid at Silverstone.

Location: N W Kent

Being a bit thick, I bought a cheap set of silicone leads, cut off the ends that go into the coil pack, trimmed the insulation back, poked the floppy wobbly silicone inner through the acorn and washer and tightened the leads as normal. All worked fine without the need for a spike. I didn't think there would be an issue...

I pulled the boot back from the spark plug end and it appears that the silicone core is folded back before the connector is crimped, just as you would with copper. I'd be surprised if you couldn't fit spade ends in the same way... still at £30 it's probably not worth DIY.

Location: In the garden

Until today... when a loss of power and a strange unbalanced chugging caused me to look for the reason for the missfire. Yup one silicone lead had come adrift at the acorn. A short strand of thin copper wire inserted in the centre and bent over, then normal service was resumed.

Location: Waiting for the bathroom