resistor type plug: not to use?

[igdrasil]

I was talking to my new mechanic, has a nice background on racing experience and told me this:

A resistor type spark plug is not recomended for turbo applications. Why?

Because the resistor types are hard sparks and in the event of ping and detonation, the plug will hold strong and continue igniting the fuel, thus eventually the danger of damaging pistons is higher.

A 5,000-ohm ceramic resistor is built into the spark plug core to suppress spark-generated electromagnetic noise that can interfere with the car's on-board electronics.

Having the correct spark plugs with the proper gap is essential. In my opinion, it is good to pick up at least 2 sets of copper NGK ZFR7F-11 plugs. In theory the copper will help to protect your engine by melting or blowing off in the event of a bad tune that is too lean or with the timing too advanced resulting in detonation.

Does anybody wants to share their ideas?

 

[shinzen]

I hadn't heard this before.. Interesting theory, I would like to hear if anyone has experience with it.

 

[jersey_emt]

It makes sense, but I would like to hear from some of the experienced tuners here.

 

[igdrasil]

resistor feature

A 5,000-ohm ceramic resistor is built into the spark plug core to suppress spark-generated electromagnetic noise that can interfere with the car's on-board electronics.

This is true, Im using non-resistor (R5672A-8) heat range 8. And the only issue I find is...i hear a very faint ignition noise on the speakers. Not the high pitch, just the sparks ignition. Sometimes is loud.

Having the correct spark plugs with the proper gap is essential. In my opinion, it is good to pick up at least 2 sets of copper NGK ZFR7F-11 plugs. In theory the copper will help to protect your engine by melting or blowing off in the event of a bad tune that is too lean or with the timing too advanced resulting in detonation.

 

[JFW]

Melting point of copper in sparkplug 1981 deg F.
Melting point of aluminum pistons 1220 deg. F.

 

[igdrasil]

Melting point of copper in sparkplug 1981 deg F.
Melting point of aluminum pistons 1220 deg. F.

YFYI:

Our cars runs 1400F on WOT and I have reached 1650F with the probe on manifold, not inside the cylinder chamber where temps are higher.

And our pistons are oil cooled too.

So basically what you are saying is that all of the mazdaspeeds are melting pistons all the time.

My friends Eclipse runs 1800F on stock pistons!

 

[Little Beavis]

Melting point of copper in sparkplug 1981 deg F.
Melting point of aluminum pistons 1220 deg. F.

Do you happen to know the exact alloy they used on the piston? Heck, that's why it took some time for car makers to build aluminum engines. . .Quoting the melting point of "pure" aluminum doesn't really count.

Sorry, not trying to be a dick (but I guess I am), it isn't that simple.

 

[JFW]

Sorry, I should have elaborated.
The reason the Cu electrode melts is that it's mass in comparison to the mass of Al in the cylinder head and piston is much smaller. Therefore it heats up much more quickly when combustion chamber temperatures are so high that it cannot transfer that heat to the seat of the plug which would in turn transfer the heat to the head and then to the water jacket.
The problem being is that some spark plug reading charts I've seen mention melted electrode and siezed piston in the same sentence.

As far as meltiing points for casting Al alloys, alluminum alloy being defined as the base metal is 85% or more Al, your melting point is not going to go much higher than 1230 deg. F.
For more, cut and paste link.


http://www.efunda.com/processes/metal_processing/die_casting.cfm

 

[igdrasil]

true, but thats continous heat, pistons runs only 1 cycle of heat vs 3 of no heat, plus it gets oil cooled always.

The oil cooling feature is VERY VERY important for heat transfer, thats why you can run higher temperatures.

 

[LinuxRacr]

I just installed Denso Iridium plugs today (yesterday now). It has the 5K resister in it I believe. Hmmm.. Time for some research.