Spark plug Temeperature Range

[kudzufarmer]

The stock spark plug for our Nomads is a 9 I believe.....has anyone tried an 8 temp range?......what would be the problems in doing this.....i put a set in "The Reverend" today and the bike seems to run better and sounds better.

[bobzinger]

The std is a DPR6EA-9. I use a NGK DPR8EIX-9 which is 2 steps colder.

[kudzufarmer]

Originally Posted by bobzinger

The std is a DPR6EA-9. I use a NGK DPR8EIX-9 which is 2 steps colder.

I thought it was the other way around the higher the number the hotter the plug....this may be for the iridium plugs and just oppopsite for the standard plugs....the ones I put in were the NGK DPR8EIX-9

[blowndodge]

Higher number in NGK is colder....

Manual calls for 6's and in extreme cold weather 5's...

[ringadingh]

I use an Iridium NGK plug and it is only available a heat range colder #7. And its worked fine the last two seasons.

[macmac]

You guys inderstand that hotter and colder are just a method to clean the inner ceramic on the plugs right? It is not related to hotter or colder spark....

[dkdixie]

"True" defination of heat range?


Heat range

The operating temperature of a spark plug is the actual physical temperature at the tip of the spark plug within the running engine. This is determined by a number of factors, but primarily the actual temperature within the combustion chamber. There is no direct relationship between the actual operating temperature of the spark plug and spark voltage. However, the level of torque currently being produced by the engine will strongly influence spark plug operating temperature because the maximum temperature and pressure occurs when the engine is operating near peak torque output (torque and RPM directly determine the power output). The temperature of the insulator responds to the thermal conditions it is exposed to in the combustion chamber but not vice versa. If the tip of the spark plug is too hot it can cause pre-ignition leading to detonation/knocking and damage may occur. If it is too cold, electrically conductive deposits may form on the insulator causing a loss of spark energy or the actual shorting-out of the spark current.

A spark plug is said to be "hot" if it is a better heat insulator, keeping more heat in the tip of the spark plug. A spark plug is said to be "cold" if it can conduct more heat out of the spark plug tip and lower the tip's temperature. Whether a spark plug is "hot" or "cold" is known as the heat range of the spark plug. The heat range of a spark plug is typically specified as a number, with some manufacturers using ascending numbers for hotter plugs and others doing the opposite, using ascending numbers for colder plugs.

The heat range of a spark plug (i.e. in scientific terms its thermal conductivity characteristics) is affected by the construction of the spark plug: the types of materials used, the length of insulator and the surface area of the plug exposed within the combustion chamber. For normal use, the selection of a spark plug heat range is a balance between keeping the tip hot enough at idle to prevent fouling and cold enough at maximum power to prevent pre-ignition leading to engine knocking. By examining "hotter" and "cooler" spark plugs of the same manufacturer side by side, the principle involved can be very clearly seen; the cooler plugs have more substantial ceramic insulators filling the gap between the center electrode and the shell, effectively carrying off the heat, while the hotter plugs have less ceramic material, so that the tip is more isolated from the body of the plug and retains heat better.

Heat from the combustion chamber escapes through the exhaust gases, the side walls of the cylinder and the spark plug itself. The heat range of a spark plug has only a minute effect on combustion chamber and overall engine temperature. A cold plug will not materially cool down an engine's running temperature. (Too hot of a plug may, however, indirectly lead to a runaway pre-ignition condition that can increase engine temperature.) Rather, the main effect of a "hot" or "cold" plug is to affect the temperature of the tip of the spark plug.

It was common before the modern era of computerized fuel injection to specify at least a couple of different heat ranges for plugs for an automobile engine; a hotter plug for cars which were mostly driven mildly around the city, and a colder plug for sustained high speed highway use. This practice has, however, largely become obsolete now that cars' fuel/air mixtures and cylinder temperatures are maintained within a narrow range, for purposes of limiting emissions. Racing engines, however, still benefit from picking a proper plug heat range. Very old racing engines will sometimes have two sets of plugs, one just for starting and another to be installed once the engine is warmed up, for actually driving the car.

[blowndodge]

Yes mac... I do..... this was discussed before where Nomad owners were running 8's thinking this would solve the "pinging" issue. Of course it won't. As you said it's the temp of the tip so as to make sure it spark keeps the center ceramic clean.

[trosco]

Excellent info Dkdixe! Great when our forums have that kind of documentation rather than all us old timer's just volunteering our opinions or memories!
Way-way-way back in time when most of the Jap bikes were little 2-strokes and NKG was the only plug supplier for them, the numbers on plugs related to how far into the combustion chamber the plug would extend. 2 strokes are very low compression (6/1 was common) and pre ignition because of the oil/fuel mixture was non existent. Back then you could change the performance characteristics of the engine changing plugs.
Not so anymore. My thought is that you can run your OEM plugs 50,000 or more miles and unless a person has problems with fouling or burning their plugs because of engine wear or modifications there will never be a reason to change heat ranges.