Which sparkplug wires/connectors for a race engine?

[stownsen914]

Hi all,

I'm putting new sparkplug wires on a 911 vintage race engine. What are you guys using for plug wires (and connectors, if not Porsche)?

The car currently has stock plug connectors (sparkplug end), and I'm trying to decide whether to buy supplies to replace the wires and coil/distributor connectors (I'd probably reuse the sparkplug connectors, which are standard 911), or just buy a set of Magnecor wires/connectors or similar.

Thanks!

Scott

[HawgRyder]

Depending on what ignition box you have....if the box needs resistance wires get the best you can find.
If the box does NOT need resistance...get solid core wires...8 or 9mm if possible.
The race car does not need to have a quiet radio!
Bob

[304065]

Clewett

[Walt Fricke]

Magnecors are nice. But for the vintage look, why not just stock wires? They will work fine.

[afterburn 549]

NAPA sells solid core under their marine brand.
Work your old SS braiding off and put it on these for a HUGE savings !

[stownsen914]

Thank you, gentlemen, for weighing in.

No radio, but I've heard some other electronics can be sensitive to solid core wires. This car has an older, multi-coil crankfire system similar to Electromotive, so I suspect I should play it safe and use racing-type resistor wires.

Good point by Walt about keeping the vintage look for this car. I though of this after I posted yesterday. This point may have swayed me in the direction of keeping the Porsche sparkplug connectors.

Out of curiosity, regarding the Clewett wires, does anyone know how they're different from Magnecor?

[turbo nut]

If you reuse your connector make sure and check the resistance with a dvom to make sure any don't need replaced.

[stownsen914]

Originally Posted by turbo nut

If you reuse your connector make sure and check the resistance with a dvom to make sure any don't need replaced.

Thanks for mentioning that. What reading should I look for?

[HawgRyder]

Don't forget...resistance of a wire depends on the ENTIRE length of the wire.
So....if you use a solid core wire...with a resistor type plug end...you end up with reduced current and therefore acceptable electronic reduction of spikes.
The bridging of the plug gap with a spark depends on Voltage.
The wider the gap the more voltage needed.
The more compression...the more voltage needed.
Current only takes a limiting place if the resistance is increased to a point where the voltage is reduced by current flowing through a resistor.(basic Ohm's law).
This gives you several options...so if your crankfire box is upset with induced interference...go with resistor wire..or plug ends...or even resistor plugs.
Hope this helps.
Bob

[stownsen914]

Originally Posted by HawgRyder

Don't forget...resistance of a wire depends on the ENTIRE length of the wire.
So....if you use a solid core wire...with a resistor type plug end...you end up with reduced current and therefore acceptable electronic reduction of spikes.
The bridging of the plug gap with a spark depends on Voltage.
The wider the gap the more voltage needed.
The more compression...the more voltage needed.
Current only takes a limiting place if the resistance is increased to a point where the voltage is reduced by current flowing through a resistor.(basic Ohm's law).
This gives you several options...so if your crankfire box is upset with induced interference...go with resistor wire..or plug ends...or even resistor plugs.
Hope this helps.
Bob

I was thinking about this after I posted and was wondering (with my very basic knowledge of electrical circuits!) whether it makes any difference whether the resistance is only in the plug connectors vs. spread all along the wire. I *think* it shouldn't matter, so I could use solid wire with my resistor plug ends and still not negatively impact my crankfire unit (assuming the resistance of the plug connectors alone is sufficient, of course). Does that sound right?

[HawgRyder]

Sounds right to me....and you are correct...resistance in any circuit is the TOTAL resistance.
Even wire has a resistance...not very much but measureable with special equipment.
Bob

[stownsen914]

Originally Posted by HawgRyder

Sounds right to me....and you are correct...resistance in any circuit is the TOTAL resistance.
Even wire has a resistance...not very much but measureable with special equipment.
Bob

I've done a bit of reading on this topic in the last few days. I found an ariticle on the Magnecor site saying that for unsuppressed wire you need to have resistors at BOTH ENDS of the sparkplug wire to effectively suppress EMI. This doesn't make sense to me, but again my understanding of electrical circuits and the like is pretty basic. Other sources seem to indicate that suppression at the sparkplug is sufficient (Porsche seemed to think so anyway). Is this just marketing fluff?

[HawgRyder]

There used to be a type of plug wire that had a coil of wire insulated and separated from the core wire wrapped around it.
I think Magnecore is this type.
It is not a resistor wire in fact...but it does have suppression capabilities.
They were fatter than stock...and sometimes difficult to install into the dist cap.
To the issue of resistors at both ends...useless in my opinion...the resistance of the wire is calculated from the over-all meter reading as applied to the ends of the wire.
The idea of resistor wire is only to reduce the CURRENT going through the wire....thereby reducing the radiated pulses leaking out of the wire.
One of the old problems in multi-wire sheathed (cable) was the one of "cross-talk" this is where the signal of one of the wires would induce a signal in some of the other wires in the cable.
Cross-talk gets worse with higher current...or...higher voltage signals.
This is why we use separators on the plug wires...and not run them in parallel for long distances...or you get "cross-fire".
If you have to cross over one wire with another...do it at as close to 90deg as you can to prevent this.
Bob

[stownsen914]

Thanks.

From reading on the Magnecor site, there is some mention of some sort of metallic core and spiral wound wire surrounding it. And they do have some pretty fat wires sizes (up to 10 mm). I'd understood that the current goes through the sprial wound wire, but I might have it backwards.

Having the resistor in the sparkplug connector as the 911 connectors do would argue for using solid core wires. I'm giving this a little more thought before pulling the trigger in case I hear or find information suggesting differently, but it seems like the way to go.

[BURN-BROS]

Hi Scott,

I use Solid core wires with Beru ends on all the engines I build.
Use resistor ends @ the coils.

This works well for all ignition systems....including MSD.

[HawgRyder]

Well...there is the definitive answer from Aaron.
Bob

[stownsen914]

Originally Posted by BURN-BROS

Hi Scott,

I use Solid core wires with Beru ends on all the engines I build.
Use resistor ends @ the coils.

This works well for all ignition systems....including MSD.

Thank you Aaron for your thoughts on this.

Can you shed some light on why it's important to have resistors on both ends of the sparkplug wire?

I poked around a little, and see that NGK makes some resistor terminals. Are you referring to something like this (though this seems to be for bikes, karts, etc.?
NGK Racing Wires

[911pcars]

Plug wires that contain metal conductors (copper, stainless steel) will last much longer than typical radio suppression wires (assume the insulation is high quality silicone or equivalent). Resistors on the end(s) offer more options for replacement, etc. I made up a set of silicone-jacketed stainless wires on my previous engine (2.0>2.7) and they were fine after 30+ years.

Sherwood

[KTL]

I've heard mention on this forum here that Kingsborne is a good source of ign wire goodies for our cars.

Kingsborne Wire Werks Inc - Spark plug wires, Automotive, RV, Motorcycle, Marine, Racing, Industry

[stownsen914]

Originally Posted by KTL

I've heard mention on this forum here that Kingsborne is a good source of ign wire goodies for our cars.

Kingsborne Wire Werks Inc - Spark plug wires, Automotive, RV, Motorcycle, Marine, Racing, Industry

Thanks Kevin. I see they sell the resistor connectors for the distributor/coil end of the wires. I'm still trying to figure out though why it's important to have resistors on BOTH ends of the sparkplug wires. I'm not finding consistent information on this topic for some reason!

Scott