Carrera Spark Plug Wires?

[scarceller]

I'm looking to build (or buy) a aftermarket hi-perf set of spark wires for a 84-89 Carrera. I have a few questions I thought someone may be able to help with:

I know the early cars like the SC cars use different cables but they seem to only differ because of the connectors at the distributor. The SC cars use Male while the Carrera uses Female type connectors. Other than this difference are the cables similar? If they are you can find SC cables at much lower cost than the Carrera cables, so could you simply change the distributor connectors? Would this work?

Thanks in advance.

[bklyn]

I just purchased a set of Clewett wires for my 1987 Targa 3.2 and installed this past saturday. They were reasonable from our host. I am very happy with the quality the fit and the cost. Take a lookat them.

[scarceller]

Originally Posted by bklyn

I just purchased a set of Clewett wires for my 1987 Targa 3.2 and installed this past saturday. They were reasonable from our host. I am very happy with the quality the fit and the cost. Take a lookat them.

Yes they are very reasonable, do you know if they have resistors on the connectors or is the wire simply resistive per foot? Meaning, if you measure the ohms on the shortest wire is it lower resistance than the ohms on the longest wire?

The 3.2L Motronic ignition needs about 3000 Ohms in each wire to meet OEM specs, this is why the stock wires have close to 0 ohms on the wire and then have 3k ohm on each Beru connector.

If the wires have very low resistance (less than 500 ohms) it COULD damage the coil.

Hope this makes sense.

[wholberg]

I put magnecors from our host on my car. They work just fine.

[Barrpete]

I put a set of Clewetts on last spring and have had no problems - although that doesn't really answer your question. From their website it implies that the wires are resistive per foot.

"Clewett Engineering High Performance Ignition Wires are 8mm, with a 2 layer silicone jacket, inside a 1200 degree protective sleeve. This Spiral Core, resister conductor wire provides EMI/RFI suppression for all ignition and engine management systems. These wires are a great choice for racing or street applications."

[vanwyk4257]

I know at least a couple people running the magnecor wires on their carreras and they haven't had any problems. Those are probably what I will go with unless I build my own.

[JeremyD]

I have megnecors

[white85carrera]

+1 Magnecors from PP. FWIW-I sliced one in half and had to deal direct with Magnecor and they were great to deal with.

[MarkRobinson]

OEM wires by Beru are solid core stranded: 0 resistance. The necessary resistors are in each of the spark plug ends: this is how Beru/Bosch worked to get the wires with identical resistance. Though Magnecors work on many Porsche's if you have any electrical ignition issues, it could be the source of your issues as it was on one of my 928's.

FWIW, I bought into Beru & make spark plug wire leads for you to reuse your stock connectors, which basically never fail. I've sold a few hundred sets, though none to Carrera owners: most are to 993/964/928 owners.

does anyone know if the standard 3.2 carrera wire ends unscrew from both ends of all 7 wires??

Mark

[DCinVA]

I used the Magnecores on my car. Only minor issue was they are a bit beefier than the stock wires, so that when you route them through the stock securing devices, they are a snug fit. They seem to send a spark to the plugs just fine, and they are a nice blue color. They are the only thing in my engine compartment that look new and shiny.

[911pcars]

"If the wires have very low resistance (less than 500 ohms) it COULD damage the coil."

Not for electrical interference?

Where did you learn this? Inquiring mind wants to understand.

Thanks,
Sherwood

[richemj]

I've had some really good results with Nology Hotwires on my '84 3.2L. No RF interference like some have reported with similar capacitor-ground-type wires

[scarceller]

Originally Posted by 911pcars

"If the wires have very low resistance (less than 500 ohms) it COULD damage the coil."

Not for electrical interference?

Where did you learn this? Inquiring mind wants to understand.

Thanks,
Sherwood

Sherwood,

First notice I said COULD, but I base this on electrical theory 101, simply with near 0 ohms resistance the flow of current from the coil is uncontrolled and the coil will discharge much more quickly than with 3000 ohms resistance. Allowing a coils secondary windings to discharge very quickly will produce more internal heat within it and reduce it's life span.

Here's the worse case to think about, what if the secondary coil discharge circuit had 0 resistance and a very small air gap at the plug? I think this COULD cause the coil to fail due to heat.

This is simply an educated quess and something to think about.

The stock setup has the following component resistance:
- the rotor has 1K ohm resistance
- the stock spark plug end plugs have 3k ohm
- the wires also have some resistance can't recall how much.

Bottom line is the stock setup has > 3K ohm resistance to each plug

Altering this resistance to some lower value COULD damage the coil.

[MarkRobinson]

Simply look at the Beru rubber spark plug wire terminals at each end: they have a resistance moulded into the plastic: Distributor cap connectors are usually 1k, and spark plug terminals are 3k, for a total of 4k across the wire, as the wires are commonly solid core stranded copper or tin-covered copper. This applies (that I've verified & sold countless wires for) to:
85-95 928's
All 944s/turbo/S2/968
965's
993's (all)
964's.

Mark

[911pcars]

Originally Posted by scarceller

Sherwood,

First notice I said COULD, but I base this on electrical theory 101, simply with near 0 ohms resistance the flow of current from the coil is uncontrolled and the coil will discharge much more quickly than with 3000 ohms resistance. Allowing a coils secondary windings to discharge very quickly will produce more internal heat within it and reduce it's life span.

Here's the worse case to think about, what if the secondary coil discharge circuit had 0 resistance and a very small air gap at the plug? I think this COULD cause the coil to fail due to heat.

This is simply an educated quess and something to think about.

The stock setup has the following component resistance:
- the rotor has 1K ohm resistance
- the stock spark plug end plugs have 3k ohm
- the wires also have some resistance can't recall how much.

Bottom line is the stock setup has > 3K ohm resistance to each plug

Altering this resistance to some lower value COULD damage the coil.

I don't want to be too anal about this, but accuracy should prevail in a tech forum.
Due to the nature of the coil, a step-up transformer, the current in the secondary winding is quite small relative to the voltage generated as a result of the winding ratio between primary and secondary circuits. Current levels are higher in the primary windings since this is connected to source voltage, and thus affects coil temperatures more than secondary current. Faraday's Law provides an explanation of the relationship of voltage and current in primary and secondary coil windings. Here's a more detailed forum discussion about this:

http://www.physicsforums.com/archive/index.php/t-187441.html

and Wiki on the subject:
http://en.wikipedia.org/wiki/Electrical_transformer#Induction_law

As far as resistance in the high voltage secondary circuit, the air gap created by the spark plug provides more resistance to current flow than the relatively puny 3000 ohms created by the plug wires or connectors (mainly to reduce electrical interference to nearby electronic devices).

To summarize, high voltage and low current in the secondary circuit is directly proportional to the input voltage/current in the primary circuit.

Sherwood

[scarceller]

Originally Posted by 911pcars

I don't want to be too anal about this, but accuracy should prevail in a tech forum.
Due to the nature of the coil, a step-up transformer, the current in the secondary winding is quite small relative to the voltage generated as a result of the winding ratio between primary and secondary circuits. Current levels are higher in the primary windings since this is connected to source voltage, and thus affects coil temperatures more than secondary current. Faraday's Law provides an explanation of the relationship of voltage and current in primary and secondary coil windings. Here's a more detailed forum discussion about this:

http://www.physicsforums.com/archive/index.php/t-187441.html

and Wiki on the subject:
http://en.wikipedia.org/wiki/Electrical_transformer#Induction_law

As far as resistance in the high voltage secondary circuit, the air gap created by the spark plug provides more resistance to current flow than the relatively puny 3000 ohms created by the plug wires or connectors (mainly to reduce electrical interference to nearby electronic devices).

To summarize, high voltage and low current in the secondary circuit is directly proportional to the input voltage/current in the primary circuit.

Sherwood

Sherwood,

Thanks for the insight. I was only trying to say that when you stray from specs you need to think, that's the only point I wanted to make.

So what you are saying is that even if we take the secondary current path to 0 ohms you won'y damage the coil because the air gap is more than enough resistance. If this is the case then I guess we can use any low ohm wires we wish?

Once again thanks.

[scarceller]

Sherwood,

If I recall I think coils being used as transformers and those being used as storage device (Such as Ignition coils) may behave differently.

Any feedback on this?

[911pcars]

Sal,
Yes, within the limits of reducing radio/electrical interference with modern electronics. Aftermarket suppliers of spark plug cables seem to emphasize the power-producing capabilities of their product.... all for a premium price. With the exception of the quality of the spark plug connectors, resistance wire is an issue not worth the money most charge for them.

Have a good day,
Sherwood

[scarceller]

Originally Posted by 911pcars

Sal,
Yes, within the limits of reducing radio/electrical interference with modern electronics. Aftermarket suppliers of spark plug cables seem to emphasize the power-producing capabilities of their product.... all for a premium price. With the exception of the quality of the spark plug connectors, resistance wire is an issue not worth the money most charge for them.

Have a good day,
Sherwood

Sherwood,

This has nice write up
http://www.magnecor.com/magnecor1/truth.htm

I think I get it now, the resistance of the wire really does not matter but the EFI suppression does. I also now understand that the air gap is the main resistive device during the firing cycle. But what I did take away is that you need to be very careful of lo-ohm wires and how they are created, because if they simply are a simple wire then EFI levels are very high and could cause issues with EFI and DME boxes. Seems the wires that are lo-resistance but wound have the best life expectancy and for this reason may be worth the price.

Thanks for helping understand how the wires function.

[911pcars]

From the Magnecor page:
"Solid metal conductor wires cannot be suppressed to overcome EMI or RFI without the addition of current-reducing resistors at both ends of wires."

From the standpoint of longevity, solid core metal conductors are the best (given an equally long-life conductor jacket). Early Porsche connectors already have a resistor built in. Manufacturers realized that producing suppression wire in bulk (without costly metal), is more cost effective than supplying special connectors with built-in resistors.

My plug wires are stainless steel core with a silicone jacket. So far, they've lasted about ...... almost 40 years (including the 16 years the car was on stands ).

Sherwood