Technical Spar kplug wires

[jte]

Hi,
I bought Mageneti Marelli plug wires for my 2006 Grande Punto 1.4 8V engine.
I measured resistance and they were: 9.5 Kohm, 7 Kohm, 14 Kohm and 8 Kohm.
Are these ok?
My MK2 punto Magneti Mareiili wires were about 1kohm and they were twice as long.

 

[bugsymike]

Hi,
I bought Mageneti Marelli plug wires for my 2006 Grande Punto 1.4 8V engine.
I measured resistance and they were: 9.5 Kohm, 7 Kohm, 14 Kohm and 8 Kohm.
Are these ok?
My MK2 punto Magneti Mareiili wires were about 1kohm and they were twice as long.

It shouldn't be a problem, when testing HT leads I have found the longer the lead the more "carbon suppressed string" so higher resistance.
If in good order they should work fine.
The reason I was testing them was where a misfire occurred when car under load pulling up hills or on a damp day and it was where there was open circuit, (no Ohm reading) as what was happening was the spark plug was working under no load with the spark/high voltage jumping the break in the lead, but due to the extra voltage caused by the gap then the spark was more likely to short to somewhere else rather than jump the spark plug gap.
The HT leads break because people pull on the leads rather than at the plug cap and it breaks the carbon string internally.
The resistance/suppressed leads etc. are for radio interference, so of no benefit to the engine performance.
When I used to race karts in the late 1960s we used to keep off any resistance in the HT circuit.
Around that time I used a Krypton garage diagnostic machine and found that the same ignition coil could fire a spark plug that was non resister type and using copper HT leads etc. would happily supply a far lower voltage of around 5Kv and engine would run well, but if using resister spark plugs, resister/suppressed HT leads etc. it needed around 14Kv which the same coil could supply (yes I know modern HT coils can supply much higher Kv) the point being if any weakness in the HT circuit, damp, dirt, a scratch in a Distributor cap or top of coil etc. it would cause a misfire as the electricity took the easiest route.

 

[GrandePunto PL]

"M-M" wires/leads have bad reputation (they work, until they don't). Try different brand, doesn't have to be expensive. For example "NGK" works fine (better than Magneti). Or "Champion". Both have lower resistance (possibly even under 1k) and all 4 wires will be pretty equal. Use some dielectric grease (regular silicone grease - not labeled "for high voltage" etc. - will do, PTFE filled or not), to avoid rubber boot sticking to the sparkplugs (that's how you damage the leads, by pulling).

For high voltage wiring like that (working in "pulses" = it's a "radio transmitter", AM range mostly), the resistance in kilo-ohms is not a big problem (you actually don't "waste" much energy - this is not like DC or low freq. AC circuit), in theory. But values should be similar, I mean equal between the 4 "cables" (how much is a different story, is it 1k, 5k, 10 kilo). Old-school books (this is from 1970's) say, that about 5 kilo is already enough to suppress radio stuff (and our spark plugs for Grande have 5 kilo resistor inside, so you don't need to double or triple that).

By the way. Energy lives outside (but very close to) the wires (inside, when it's a coaxial cable for example), we need metal wiring "only" to guide it (both regular cables and antennas must be conductive, for same reasons). Electrical Engineering basic stuff, 100+ years old. But now "controversial" and viral on YouTube (last 2-3 years).