Sparkplug technical information.

[Momus]

My question, for the same given length of porcelain, is it a hotter plug if more is protruding into the combustion-chamber (exposed to more flame)' or a colder plug (exposed to cooling mixture before ignition).

Well my 2c opinion is  8's is 8's and 9's is 9's regardless of construction. Protruding or not if its been labeled an 8 by ngk then that's what it is. :-)

If you look at a plug heat range conversion chart it will for example, tell you an ngk 8 is a denso 24. No mention of any other factors.

You might choose a different construction tho because of considerations other than heat range.

We ran surface gap plugs in rotaries; around an 11 in NGK and had to use a 6 or 7 to warm up or they would foul.

[tony27]

  HI John.  Champion and NGK has released some very good Tech articles over the years . Make very good reading.

   One interesting article is on  Surface Gap Plugs, No Heat Range. Hard to foul.

   Made for 2 stoke outboards, Nitro engines . Used by Porsche,F1 and in other race cars using mechanical Fuel injection. Do not know if there still used. Except Drag cars.

   Also Oem Spark plugs on the early Kawasaki Mach 1.   Requires a very High energy ignition System to fire the plug.

    BuY the way . Supercheap NGK BR9EG $13.95. A good Price.

 

Yeh l run "surface discharge" plugs in my race GSXR1000 Superbike.

When the first Sherco 450s came out the importer at the time loaned me his personal bike as way of getting them seen & he was running a surface discharge plug out of the 600 supersport kit for GSXRs, I'm pretty sure it had come out of 1 of the WSS bikes he'd worked on in Italy. He told me the cost of each plug in the kit & it was scary

[Nebo]

    Yes Momus i forgot about Rotary Engines.   Very hard on Plugs.  Especially  if it has been Ported and Turbo charged  and a big Weber Carb.

     Another Engine hard on Plugs. The Honda CX650 Turbo. Even B9EGV NGK,s would not last more than 5000 to 7000KM,s.  A friend had one.

    It would just burn the end of the Electrodes.  I think this happened because there was no intercooling. Causing Very High Combustion Tempertures.

     Even tryed special Turbo Porsche/Bosch  racing plugs .  Both Silver and Platinium.   Cost a heap.  Lasted about 10K.

     May be Surface gap plugs would have lasted longer.  He still Loved the Bike .  100HP Claimed.  260kg Claimed.  Comstar Wheels. Did not handle great.

 

[John Orchard]

So, I have been measuring plugs .....

Between a B8ES and a B9ES, the porcelain on an 8 travels 3mm further (longer) down into the metal casing than a 9.

The difference between a B8ES and a BP8ES, the porcelain is the same length, on a BP the porcelain protrudes 2mm further into the combustion chamber but also travels 2mm less down into the outer metal casing.

Now my interest is; would one or the other (projected v non projected) run hotter or cooler for the same given porcelain length (quoted heat-range)?  Exposure to either cooling incoming fuel/air charge or more exposure to combustion flame-front?

My testing continues  :-)

[ralph311]

Now my interest is; would one or the other (projected v non projected) run hotter or cooler

The heat range of both is 8, regardless of design parameters. Not sure what you're chasing?

[Tomas]

I would say BP would run hotter than B in the same engine. Two are designed for different applications.

[John Orchard]

Now my interest is; would one or the other (projected v non projected) run hotter or cooler

The heat range of both is 8, regardless of design parameters. Not sure what you're chasing?

ls it porcelain length alone denoting heat-range then?

[pokey]

HEAT refers to the encapsulated zone. IE depth not length, The porcelain is an insulator not a heatsink and not a conductor. While the fresh cooling fuel charge washes over the exposed plug the VOID is mostly unaffected so it stays hotter. Longer the Void the Hotter it remains. Make sense?

[John Orchard]

HEAT refers to the encapsulated zone. IE depth not length, The porcelain is an insulator not a heatsink and not a conductor. While the fresh cooling fuel charge washes over the exposed plug the VOID is mostly unaffected so it stays hotter. Longer the Void the Hotter it remains. Make sense?

An angle l've not considered, thanks, this is why l ask the question here :-)

[sleepy]

Have you read this from NGK
https://www.ngk.com.au/technical_info/heat-range/
Doesn't answer your question on protruding plugs.
In my past life as a car Dyno operator plugs of different design were often tried and I can't say we ever noticed any differences between protruding and not of the same heat range. Did used to run BP5ES in my Bultaco trials bike to help stop fowling at low revs but never did a back to back with a B5ES probably because I had boxes of the BP5ES for my car. 

[80-85 husky]

i fouled an "R" plug in my 2000 kato 250 and replaced it with a plain jane B8ES but a month or two later i noticed it breaking down at high revs?? cleaned filter carb etc with no change then got told "you need a racing plug" and bang, sorted... i was suprised it made that much difference

[sleepy]

i fouled an "R" plug in my 2000 kato 250 and replaced it with a plain jane B8ES but a month or two later i noticed it breaking down at high revs?? cleaned filter carb etc with no change then got told "you need a racing plug" and bang, sorted... i was suprised it made that much difference

The R stands for resistor not racing.