Ignition wires

Those readings seem super high, search my posts, I had engine running problems that traced out to bad spark wires and posted a thread with my measurements old and new. New wire kit from GT car parts solved the problem and the numbers explained why.

 

Actually I dont know if yours are high or not, here’s my numbers:


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The original Cavis spark plug wires used in a TR have a tiny metal spiral wound wire around a kevlar filament core. The high voltage of an automotive ignition system will not damage the metal wire as the current flow is very low. The problem is that the wires are fairly delicate and can break due to flexing over time. The engine will still usually run on a broken wire, as the spark jumps the gap inside the broken wire. Still the broken wires can cause rough run/engine miss-fires. I always check the resistance of the wire sets during a major service from the distributor cap contacts to the spark plug connectors. The resistance of the wires will range from 1k ohm-2k ohms depending on the length of the wire, with coil wires just under 1k ohm.
Quite often the cause is a poor connection at the wire piercing connector screws at the distributor cap. If the resistance is only slightly high and changes when you flex the wire right at the cap connection, you can often shorten the wire 1/2" or so, reinstall the cap screw and the resistance will be fine. If the resistance of the wire is in meg-ohms or open circuit, then the wire is usually defective and needs replacement.
Going from a car with bad ignition wires to good wires makes a huge different in engine smoothness and emissions and is possibly the biggest factor outside of cam timing in making an engine run better during and engine-out service.
Always recheck the resistance of the wires from the cap contacts to the spark plug connectors after replacement, as the wire piercing screw sometimes does not make good contact with the little metal wire inside the ignition wire.

 

for what you need wires with resistance? only to have no noises/disturbances in the radio?
why not just use copper wires. this I did in my competition, but also I have an other ignition system in and still use the old coils but without the ignition moduls.
for older cars what had original resistance wires in ( vauxhaul, opel, renault, peugeot ) and had problems ( mostly when it was raining ) I always changed those to copper wires and never had problems

 

Many cars with electronic ignition systems will not run at all or if they do very badly with solid core wires due to the EMI they create. The Marelli systems are are particularly prone to this. I have even seen a mismatched resistance wire raise havoc with Digiplex and Microplex systems. Any car I touch for a running issue if it doesnt have Cavis or Magnecore wires of roughly 500 ohm/s foot they come off first. I have seen incorrect wires destroy the speedometer signal in 355's because of their proximity to the cable bundle carrying the speedo signal.

Modern cars are subjected to a lot of tests for electronic noise creating issues with onboard systems, never mind the stuff we drive by going down the road. Just put them back the way they were built. There isn't a reason in the world not to.

 

I listen to you Brian!

 

Wrong wire. It is a product no longer made. A friend bought the last couple of thousand feet they had.

Cavis is all I will use and yes I am familiar with the others.

I don't use aftermarket junk.

 

I´m a little confused now:
I know that some ignitions needs resistance wires, but the longer those wires are the higher is the resistance. why not put between the distributor cap and the sparkplug connector to all cylinders each 1 fix resistance from for example 1 K ohm or just put only 1 resistance ( 1 K ohm ) between the coil and the distributor? or why not just use a 1, 2 or 5 K ohm sparkplug connector?

I hate those resistance wires because always they make trouble and here in europe ( except UK ) those resistance wires are not popular and also very hard to get

 

what is/are rf interference?

 

That tiny little bit of resistance from the HT-Leads is negligible compared to the 0.7mm gap with 10 bar of air pressure in between on the tip of the spark plug. But that negligible amount of resistance does suppress all the necessary RFI & EMI. Electronics really don't like it, whether it is an electronic ignition or a tacho etc. etc. it can confuse many systems
With a powerfull ignition system you can almost broadcast to outer space if you don't use the correct suppressed leads.
In my opinion the 'low resistance cable' is only a marketing strategic, you can easily see that good quality cables like for example Magnecor are often 3K ohm/ft or even more.
If an ignition can't handle that, than it's so weak that the ignition should be investigated.

https://www.magnecor.com/magnecor1/truth.htm

 

By the way, I meant RF not EMI.

I asked today and Ferrari quit selling Cavis wire in bulk so as of now I'd have no idea where to get it. Not sure what wire the popular replacements set I see use. I though they were Cavis but it has been a long time since I had any in my hands. I do know some of the stuff out there is just a little bigger and nearly impossible to get inside the red silicone tubing.

 

It stands for Radio Frequency.

 

Actually I was talking about someone else. I thought Daves was a different brand. Whatever his is it is too large to put in the red silicone tubing. Once was enough to learn the error of that.

The good thing is I do not work on very many anymore with spark plug wires so it has not been an issue for a while.

 

thank you brian,
this is what I mentioned already in my post here No.6, but have not known the english word

what means EMI ?

 

Electro-Magnetic Interference