Spark plug orientation/position

[daverclasper]

Hi. Have been reading that may affect combustion a bit, depending on where the outer electrode position is in relation to fuel/air direction is coming into the head.

Not after fractions of better  performance etc (apparently some folk use the triple electrode  plugs for this) , though could this affect plug colour readings,  bit Richer/Weaker,when 

I, look to determine basic mixture settings by plug colour.

Thanks, Dave    .    

Edited December 24, 2018 by daverclasper

[Pete Lewis]

They screw in where they are , been like that for years and years, as for triple , its unlikely to get 3 sparks , think you get  one of the three 

which ever electrode  is easiest    made as a a must have  

If you think about the  spark on a std plug it jumps linear from the tip of the centre electrode to the earth bar. So it doenst matter which way that faces

Pete

 

[JohnD]

   "Indexing" the plugs is something you do to get an extra 0.0001 - no, 0.000000000001%.  As the position of the earth elctrod e is random in relation to the thread, you can only do it by A/  using shim washers that are thousands of an inch different for each one, and B/ on an engine dyno.

 

AND, multi-electrode plugs were invented to make fleet managers happy as all they do is provide another, correctly gapped earth when the first wears out.   They last three times, or four times, as long, reducing service needs.    They DON'T improve performance.e

John

[Nick Jones]

Indexed plugs is for people with severe ocd and too much time on their hands.

3 or 4 electrode plugs are for longer life, not specifically for performance. However, they are also side electrode so the spark is exposed to the open chamber rather than hidden behind the earth electrode. Some engines like this, Triumph engines amongst them. I discovered this by chance about 20 years ago and have used them ever since.

No sneering until you’ve tried them please.

Nick

 

[daverclasper]

Thanks folks.  Out of interest Nick, what plugs are you using and aside from longevity, what running improvements did you have please.

Cheers, Dave

[thescrapman]

I use a Bosch one, undoubtably a model recommended by Nick.

They seem much harder to foul, a bonus for a PI user. 

[Nick Jones]

I like Bosch and currently use WR7DTC.  These are resistive to go with the engine management the non-resistive equivalent being W7DTC.  In practice you'll find either of those (especially the non-resistive) very hard to find now as Bosch seem to be standardising on the 4 electrode versions (WR78 IIRC).  NGK BUR6ET are also triple electrode though I'm no longer an NGK believer.

The effect of the triples (and highly likely the same for the quads) is an improvement in the smoothness and crispness of the engine.  Noticeably sweeter and more eager.

Nick

[JohnD]

If your Pi plugs foul, its because you aren't using it hard enough!    Pi runs lean at the top end, so is set to be rich and prevent detonation at high revs.

A hotter plug may suit better.    This chart may help (https://www.ngk.com/learning-center/article/251/heat-range-conversion-chart)

John

[Nick Jones]

If you PI is fouling plugs, more likely its just set too rich as so many of them are. It doesn’t help that as a vacuum referenced system anything that reduces the volumetric efficiency (ie reduces vacuum reading for any given running condition) will cause it to run richer.

The issue with NGKs is that many of them can’t withstand fuel wetting and stop working for ever if their internal insulator gets wet. New plugs are worse affected than ones that have run long enough to have combustion deposits on the insulator.

Nick