plugs for road and competition

[sumplug]

Are single electrode better then double or triple ones?
What effect do they do to the charge?
Does it really matter to make sure single ones are lined up correctly?
How does heat range alter plug performance?

[SteveNZ]

Talking like for like plugs, double or triple electrodes are mainly used for longer service life.

You refer to "indexing" plugs. This can have some effect but it is small. Its not something to worry about on a street car. It seems common in the old school, but it is rarely looked at now.

The ground electrode can get in the way of the spark/ignition/flame which is not ideal. Indexing helps this. Multiple electrode plugs can also help this as the centre electrode is more exposed. There is some information about this on the NGK website.

Heat range does not affect performance afaik.

[sumplug]

My thoughts Steve is a big fat spark is better then a smaller multiple spark. Anyone got any ideas on this or above?

Andy.

[Julian]

One of the main points that runs alongside service life is consistency which also relates to indexing. By making sure all of the cylinders are providing the same results (by matching combustion chamber cc, porting, shaping, etc.) you are allegedly balancing out each cylinder in much the same way as you would go about balancing the moving parts of the engine.

Indexing is very much an "oldschool" technique but is all part of the quest to extract the very last few fractions of performance from the engine.

Given the somewhat chaotic nature of combustion, gas expansion and gas flow I would hazard a guess and say that it is largely a waste of time to index the plugs. There are going to be "better" positions and "worse" positions for the ground electrode to sit at but getting all of them exactly the same is practically impossible. In the case of 16v engines with a centrally positioned plug aperture I would even go so far as to say it is pointless as I don't see how you could hope to achieve any advantage.

I have seen some articles on the web (unproven as far as I can garner) arguing the case for "plasma" plugs that generate a sphere of plasma instead of a spark, the result would be a more even and cleaner combustion since no part of the plug is shrouded and the ignition is much more effective. Where you go about obtaining a set of these plugs seems to be a mystery (or was when I looked).

Heat range does not affect performance directly - the spark acts in exactly the same way *but* the lifespan of the plug is affected. Use the wrong one and the plug will not last very long or need a lot of cleaning. The "heat" range is describing the temperature at which the plug is self cleaning (trying to remember the exact details from reading through the NGK catalogues we had in my shop all those years ago). As such you select a plug to suit the performance of your engine, not the other way around.

[Julian]

My thoughts Steve is a big fat spark is better then a smaller multiple spark. Anyone got any ideas on this or above?

Andy.

Andy, the multi electrode plugs do not give multiple sparks unless the coil is giving multiple discharges. Which of those electrodes sparks is down to the individual gaps (which one is closest) and the gas filling the gap.

The actual situation is far more complex but in the end there is only one spark...

[Guy Croft]

Heat range see:
http://guy-croft.com/viewtopic.php?t=30

The spark goes from the sharpest electrode not the nearest. As for multiple electrodes, etc., no idea. If I put B9EGV in a StII-IV engine and out comes 80-100+ bhp per liter everyone's happy & I figure they must be working OK. Half my clients can't even set up a DCOE, so don't get time to dwell on glamorous things like that.



GC

[Julian]

See - even I get to learn something 8)

edited to add this:

A bit disgruntled now - NGK have a nice little flashy app on their website providing all sorts of information but nothing on what the temperature range means in detail. The site does confirm that it is the self-cleaning temperature range (makes me feel a bit better) and that it is the electrode requiring the lowest voltage to form the spark - they say the nearest one but I'm staying out of that argument. They also include information on the fouling range (usual diagnostics as to what the different types of fouling mean) and a general Q&A on what multi-electrode plugs do (and more imporantly do not).

http://www.ngkntk.co.uk/technicaltips/sparkplugs.asp

Will keep looking...

Edited again to add this:

http://www.ngksparkplugs.com/techinfo/s ... country=US

This pretty much sums up everything you need to know about spark plugs and heat ranges!

[Guy Croft]

yes,
sparks like sharp edges, prolonged use rounds them off and the spark wanders looking for the most 'attractive' place, sometimes not finding one and earthing thru the carbon instead.
It is for this reason incidentally that plug makers ceased to recommend the practice of beadblasting plugs many years ago, or so the former Manager of Champion Racing Div told me - right at the time Champion stopped selling their benchtop spark plug blaster.

GC

[SirYun]

this is something i have run across.

http://www.maxracesoftware.com/spark_plugs.htm.



Credit where is due : This is from Larry Meaux's site, He builds big dragracing V8's and markets software (cheap, as far a software goes. and it does seem to work well for a lot of folks..alas silly me uses a 5 port head) like Pipemax. Larry is often on the speedtalk board and seems a very standup guy that does give good replies.

[Guy Croft]

It's well put-across, very good photos and explanations, thanks.

GC