Spark Plug heat range, a question.

[4js]

I pulled the plugs on my boat yesterday, and I find Champion RS12YC in it.

Manual calls for Champion RS9YC.

Can anyone tell me the difference in the two plugs?(what heat range for each) I actually replaced the RS12YC Champions with NGK BPR6EFS plugs, which is one of the option that the manual calls for.

The Champions were not old (only a couple of hours on them, the dealer changed before my test drive) but are black, indicating cold fouling. It "could" (?) be becuase these plugs have been fogged out twice in the first couple of hours of use since they were installed, and have not been run more than an hour between foggings. My thought process there is that maybe all the fogging oil has not had a chance to burn off.... OR, maybe they are black from being the wrong plug (wrong heat range).

Anyone have any answers/input?
Thanks,

 

[4js]

Re: Spark Plug heat range, a question.

Appears that the RS9YC (what manual calls for) is a "step colder" than the RS12YC's...but I am not sure what effect that has on the firing/performance of the engine..

 

[Bondo]

Re: Spark Plug heat range, a question.

Ayuh,... What Motor We talkin' 'bout here anyways,..??

 

[4js]

Re: Spark Plug heat range, a question.

In my profile (pretty sure it is) . 97 3.0 lx

 

[fat fanny]

Re: Spark Plug heat range, a question.

Biggest problem I see is thie not A/C R43ts I never had any luck with Champion always fouling. My 96 3.0LX runs perect with them and like sh-t without them.

 

[Oldskool]

Re: Spark Plug heat range, a question.

"Heat range" doesn't mean that the plug tip itself runs or burns hotter, it refers to the plugs ability to allow the combustion chamber to dissipate heat. A "hotter" plug will allow a greater amount of heat within the chamber which can result in premature engine failure. While a lower heat range may in fact result in a fouled plug, you do not want to run a hotter plug than the manufacturer calls for.

 

[infideltarget]

Re: Spark Plug heat range, a question.

I pulled the plugs on my boat yesterday, and I find Champion RS12YC in it.

Manual calls for Champion RS9YC.

Can anyone tell me the difference in the two plugs?(what heat range for each) I actually replaced the RS12YC Champions with NGK BPR6EFS plugs, which is one of the option that the manual calls for.

The Champions were not old (only a couple of hours on them, the dealer changed before my test drive) but are black, indicating cold fouling. It "could" (?) be becuase these plugs have been fogged out twice in the first couple of hours of use since they were installed, and have not been run more than an hour between foggings. My thought process there is that maybe all the fogging oil has not had a chance to burn off.... OR, maybe they are black from being the wrong plug (wrong heat range).

Anyone have any answers/input?
Thanks,

If the ceramic around the electrode is black and wet, and allowed to stay that way, the unglazed ceramic around that electrode can absorb the oil/gas/whatever and render the plug useless and uncleanable. I sold a bunch of plugs back in the days of the parts store, and I have to agree that the (cheap) Champion plugs had the highest return rate. AC Delco had a much lower return rate. Your local prts store can cross reference your required plug to whichever name brand you chose to use.

 

[4js]

Re: Spark Plug heat range, a question.

So in your opinion is NGK a good plug? The Champions I pulled out were black (like spray painted, not caked up), and just barely damp. All 4 looked exactly the same.
The engine (before changing) started verrrry easy hot or cold.
I have read that cold fouling, or wet fouling (I would say these were cold fouled) may be an indication of the fuel being too rich, or that the incorrect plug was used.
I'm going to run these new ones a few hours and pull them to see what they look like.

Thanks for the input.

 

[infideltarget]

Re: Spark Plug heat range, a question.

"Heat range" doesn't mean that the plug tip itself runs or burns hotter, it refers to the plugs ability to allow the combustion chamber to dissipate heat. A "hotter" plug will allow a greater amount of heat within the chamber which can result in premature engine failure. While a lower heat range may in fact result in a fouled plug, you do not want to run a hotter plug than the manufacturer calls for.

This is right, but it also indicates the plugs ability to "self clean" with a hotter plug typically being able to retain the heat you describe for proper combustion temps, but it is also doing so to clean deposits and gunk from its tip. A colder plug will tend to foul in an engine that has blow-by, or leaky valve seats due to its inability to retain enough heat to burn off the oily deposits on the unglazed ceramic around the electrode, causing it to become saturated, and causing arcing inside the plug, and misfires, which leads to unburned gas in the cylinder, and more wetness on the plug..........

Old hot rodders would use a hotter plug in a loose engine to help avoid oil fouling. Same with old lawn mowers, and oily 2-strokes. 1-2 steps hotter in a normal engine will not typically harm anything. Manufacturers state certain heat ranges to maintain combustion temps to stay within EPA pollution guidelines more than to protect the engine. In a high compression engine, or an engine with a power adder (turbo, SC, etc) a hotter plug can cause predetonation (pinging) which will cause major damage.

Edit: If your engine has a large amount of carbon build-up inside, this can raise the compression ratio to the point of predetonation, in which case a hotter plug can make it worse.

 

[infideltarget]

Re: Spark Plug heat range, a question.

So in your opinion is NGK a good plug? The Champions I pulled out were black (like spray painted, not caked up), and just barely damp. All 4 looked exactly the same.
The engine (before changing) started verrrry easy hot or cold.
I have read that cold fouling, or wet fouling (I would say these were cold fouled) may be an indication of the fuel being too rich, or that the incorrect plug was used.
I'm going to run these new ones a few hours and pull them to see what they look like.

Thanks for the input.

Depends on which NGK you are referring to. Just like every other company, NGK makes some el cheapo plugs. Bosch makes a great plug, but the Bosch Super is not one of them. As a general rule, I would recommend NGK over, say, Nippon Denso any time. If that is a GM engine, I would have to recommend AC Delco. Their standard plugs are top notch, and the double platinums are even better. Expensive, but very good. If your engine is running rich, or using a bit-o-oil, go a heat range or two hotter, until you can get it fixed. Then step back down to the recommended range. IMO.