Braiding on sparkplug wires, why?

S2GART · S2GART's Garage

Just curious as to why the factory wires are steel braided. Is it to protect the wires from rubbing each other, or is it to "ground" the wires. I will be replacing my original wires on my SC and noticed in the parts area that there are both braided and non braided wires.

azasadny · azasadny's Garage

The shielding was supposed to prevent electrical interference. It probably helps keep the wires from rubbing, etc...

SP2 · 02-03-2007, 06:13 PM

I thought it was the ground. I thought the hot wire is the core.

arbita1 · arbita1's Garage

I've read it was to prevent the wires from cross firing which was a cause of the "exploding air box". In 84 they got rid of the the ss covering and used the regular Beru black wires. But I think they spaced them further apart.

Jk369 · 02-03-2007, 06:45 PM

I was told by a porsche mechanic that iwas for preventing cross firing. I thought this to be odd, nothing else I have does this but I went with the ss anyway

madkow · 02-03-2007, 06:52 PM

Actually it was to keep interference to a minimum, on early Blaupunkt radios.

movin · 02-03-2007, 11:54 PM

Same reason early Corvettes did, reduce radio interference.

afterburn 549 · 02-04-2007, 12:40 AM

Remember, they have a solid wire core.................

RoninLB · 02-04-2007, 01:45 AM

Quote:

Originally posted by movin
Same reason early Corvettes did, reduce radio interference.

i bought a new 1969. Glass bodies allowed more radio static. There was even a metal box around the dizzys.

hcoles · 02-04-2007, 05:47 AM

I read somewhere that it was put in to prevent cross firing, it was later determined to not help or cross firing was not the issue and took the brading off

Bill Verburg · Bill Verburg's Garage

For all 10 yrs of it's life in a 911 CIS intake manifolds were susceptible to small explosions(those that have experienced one have found it to be very expensive and unnerving). There were many suspects as to the cause.

One of them was thought to be cross firing plugs. The solution was the ss braided sheath around the wires. SP2 is correct the braids are all connected to ground. I suppose that a secondary effect would be RFI shielding, but the primary RFI suppression is derived from the resistance in the plug connectors.

Owners of '73 to ~'75(purhased new) recieved a recall letter to have the shielded wire retrofitted, by '76 it was standard(at least it was on my C3)

Early_S_Man · 02-04-2007, 09:07 AM

Attempting to eliminate the exploding airbox problem is the primary reason. The engines already met German VDE regulations [more stringent than FCC regs at the time] without the braiding. The 1974 brochure showed production line pics of CIS 2.7 engines with green shrouds and early-style unshielded Beru spark plug wires.

S2GART · S2GART's Garage

Soooooo, I guess everyone is saying stay with braided wires? It would look nice with shiny stainless steel versus what is there now.

Early_S_Man · 02-06-2007, 07:40 PM

Do you have a pop-off relief valve installed in your airbox?

If so, you can safely install early-style non-shielded wire without fear, or rebuild your existing wires [replace the wire portion only] as I describe in your other thread.

dtw · 02-06-2007, 08:20 PM

Warren, I've got a fresh CIS 2.7 in need of plug wires - and I was sure hoping to drop $100 on early wires and not $200+ on the braided wires. Thanks for the info. (Pop-off valve is installed).

SP2 · 02-06-2007, 08:33 PM

I got the braided Beru OEM wires and they look sooooo nice when they are new.

safe · safe's Garage

Stupid question maybe, but when do you know when you need new wires?
Is there a test or just when you have ignition problem?

stlrj · 02-07-2007, 01:03 AM

Quote:

Is there a test or just when you have ignition problem?

When you have an ignition miss that only gets worse when your ignition cables get wet.

Navaros911 · 02-07-2007, 06:52 AM

Quote:

Originally posted by Bill Verburg
One of them was thought to be cross firing plugs. The solution was the ss braided sheath around the wires. SP2 is correct the braids are all connected to ground. I suppose that a secondary effect would be RFI shielding, but the primary RFI suppression is derived from the resistance in the plug connectors.

I'm by no means an expert, but the braiding would just pull the current away to the ground if the current manages to escape through - a crack of - the rubber, no?

In that case wouldn't the root of the issue be one/more badly isolated cables?

FWIW I went with the braided on mine two years ago...

Paulporsche · 02-07-2007, 07:08 AM

What I've heard is that , while the braided wires were originally intended to help prevent airbox explosions, they in fact didn't achieve this, since most airbox explosions were found to be the result of a too lean mixture.

FWIW about a year and a half ago I switched to MSD wires to go with their CD and coil. They work fine.