Trojan Boat Forum

I don't belive so Paul. I will look it up but that is what confuses people about plug heat ranges. Heat rating is about the dissipation of heat; the higher the rating, the more heat is dissipated thus a cooler tip. The lower the rating, the less heat dissipated....

Big D wrote:I don't believe so Paul. I will look it up but that is what confuses people about plug heat ranges. Heat rating is about the dissipation of heat; the higher the rating, the more heat is dissipated thus a cooler tip. The lower the rating, the less heat dissipated....

Heat ranges confuses people ? you got that right . The info you find is confusing for sure . And to make it worse on some brands the higher the number the hotter the plug and other brands the lower number .

Let me know what you find , I found info that confirms what I posted( see the qoute in the post But it can be miss-read .

The confusion is in the wording we've used for the last 70 years! When we describe a hotter plug, 9 out of ten people will think we're talking about a plug "producing" a hotter spark....that is incorrect. No matter how the different OEMs ratings are stated, they are describing the plug's ability to remove heat from the plug tip and dissipate to the engine's head in an attempt to keep the tip at the propper temp.

Here's something from NGK that may help but any OEM should describe just about the same:

"It is important to remember that spark plugs do not create heat, they can only remove heat. The spark plug works as a heat exchanger by pulling unwanted thermal energy away from the combustion chamber, and transferring the heat to the engine's cooling system. The heat range is defined as a plug's ability to dissipate heat.
The rate of heat transfer is determined by:
• The insulator nose length
• Gas volume around the insulator nose
• The materials/construction of the centre electrode and porcelain insulator
A spark plug's heat range has no relationship to the actual voltage transferred though the spark plug. Rather, the heat range is a measure of the spark plug's ability to remove heat from the combustion chamber. The heat range measurement is determined by several factors; the length of the ceramic centre insulator nose and its' ability to absorb and transfer combustion heat, the material composition of the insulator and centre electrode material.

………. The insulator nose length is the distance from the firing tip of the insulator to the point where insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling.

Whether the spark plugs are fitted in a lawnmower, boat, or a race car, the spark plug tip temperature must remain between 500C-850°C. If the tip temperature is lower than 500°C, the insulator area surrounding the centre electrode will not be hot enough to burn off carbon and combustion chamber deposits.

These accumulated deposits can result in spark plug fouling leading to misfire. If the tip temperature is higher than 850°C the spark plug will overheat which may cause the ceramic around the centre electrode to blister and the electrodes to melt. This may lead to pre-ignition/detonation and expensive engine damage. In identical spark plug types, the difference from one heat range to the next is the ability to remove approximately 70°C to 100°C from the combustion chamber. A projected style spark plug firing tip temperature is increased by 10°C to 20°C….."

Lot of info out there but it all boils down to heat dissipation not production.

Good info , but it leaves out what is hot and what is a cold plug .

I say a colder heat range plug dissipates more heat leaving a colder tip . A hotter heat range plug dissipates less heat leaving a "hotter tip"

What say you Big D ?

prowlersfish wrote:Good info , but it leaves out what is hot and what is a cold plug .

I say a colder heat range plug dissipates more heat leaving a colder tip . A hotter heat range plug dissipates less heat leaving a "hotter tip"

What say you Big D ?

So hotter plug raise combustion chamber temp. engine runs hotter and colder the opposite

ready123 wrote:

prowlersfish wrote:Good info , but it leaves out what is hot and what is a cold plug .

I say a colder heat range plug dissipates more heat leaving a colder tip . A hotter heat range plug dissipates less heat leaving a "hotter tip"

What say you Big D ?

So hotter plug raise combustion chamber temp. engine runs hotter and colder the opposite

You won't see a difference in engine temp , but to hot of a plug can cause pre-ignition and piston damage .

Remember we are talking tip temp.

Big D wrote:...the higher the rating, the more heat is dissipated thus a cooler tip. The lower the rating, the less heat dissipated....

See I got caught up in the confussion as well. It seems it's a symantics thing. The above statement depends on the OEM. In some cases as you mentioned Paul, it's the other way around as described in the link below. One needs to confirm the OEMs method of labeling its heat range spec. In any case, the main message that I am trying to get across is that it's not about a hotter spark, it's about keeping the plug at it's propper opperating temp for a particular app. The temp of a given plug will change from one engine to another based on several variables. It's how much heat we dissipate away from differing combustion chambers that determines whether the plug will opperate in its designed range.

Here is an example of how 3 OEM heat range numbering specs work.
http://www.championsparkplugs.com/gloss ... ?imgID=180

Spark plugs are always a fun debate .

Found this in some of my notes from NGK. Note the "Too high heat rating" at bottom left and "Too low heat rating" symptoms mid right of page. The moral is; check what method the OEM uses to determine heat range ie increasing numbers hotter or colder!

Sorry if I confused the issue, trying to explain the "science behind it" for pwllsch. Now we can say it is clear as mud

[img][img]http://i945.photobucket.com/albums/ad29 ... hot019.jpg[/img][/img]

And you wonder why I like diesels .

I am raw water.

Thanks everyone!

I will run this season on the base spec.. Got afresh $1,000 in fuel Friday.
Made sure my wife paid to share my love for maintenance.

Hard to believe I started this thread over 3 years ago!

Hard to believe I started this thread over 3 years ago!

Jim, I hadn't even noticed that!!

Got your answer now? No help from your techs??

Big D, It was so long ago I would have to check what I used. Sadly, as a Marina operator I rarely get out on the water (on my own boat). Probably not more than 25 hours since I replaced them with the NGK equavalent, I think.