NGK vs Other Brands (eg. Autolite).:
After you have identified the numbering system for your plug, merely raise or lower that number to change the heat range.
REMEMBER, NGK PLUGS GET COLDER THE HIGHER THE NUMBER, HOTTER THE LOWER THE NUMBER.
Heat ranges are not the same between brands.
Say you are starting with a BKR6E-11
if you want a colder plug, you would use BKR7E-11
if you want a hotter plug, you would use BKR5E-11
(again, on non-racing plugs, the number after the "-" refers to the gap)
The term spark plug heat range refers to the speed with which the plug can transfer heat from the combustion chamber to the engine head. Whether the plug is to be installed in a boat, lawnmower or racecar, it has been found the optimum combustion chamber temperature for gasoline engines is between 500°C–850°C. When it is within that range it is cool enough to avoid pre-ignition and plug tip overheating (which can cause engine damage), while still hot enough to burn off combustion deposits which cause fouling.
The spark plug can help maintain the optimum combustion chamber temperature. The primary method used to do this is by altering the internal length of the core nose, in addition, the alloy compositions in the electrodes can be changed. This means you may not be able to visually tell a difference between heat ranges. When a spark plug is referred to as a “cold plug”, it is one that transfers heat rapidly from the firing tip into the engine head, which keeps the firing tip cooler. A “hot plug” has a much slower rate of heat transfer, which keeps the firing tip hotter.
An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as a turbo, supercharger, increase compression, timing changes, use of alternate racing fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature and may necessitate a colder plug. A rule of thumb is, one heat range colder per modification or one heat range colder for every 75–100hp you increase. In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70°C to 100°C from the combustion chamber.
The heat range numbers used by spark plug manufacturers are not universal, by that we mean, a 10 heat range in Champion is not the same as a 10 heat range in NGK nor the same in Autolite. Some manufacturers numbering systems are opposite the other, for domestic manufacturers (Champion, Autolite, Splitfire), the higher the number, the hotter the plug. For Japanese manufacturers (NGK, Denso), the higher the number, the colder the plug.
Do not make spark plug changes at the same time as another engine modification such as injection, carburetion or timing changes as in the event of poor results, it can lead to misleading and inaccurate conclusions (an exception would be when the alternate plugs came as part of a single precalibrated upgrade kit). When making spark plug heat range changes, it is better to err on the side of too cold a plug. The worst thing that can happen from too cold a plug is a fouled spark plug, too hot a spark plug can cause severe engine damage.
How do I cross reference a spark plug from another brand into NGK?
Type the part number you wish to cross-reference into the PART NUMBER/CROSS-REFERENCE.
DO NOT include the manufacturers name in the part #
In other words if you are crossing over an AC MR43T, you would put in MR43T, NOT ACMR43T.
You will be supplied with the equivalent part number, or if the part number you selected is common with more than one manufacturer, you will be asked what brand you are crossing from.
Can I use platinum plugs with nitrous injection?
No, it is not suggested to use platinum plugs with nitrous oxide injection.
There have been instances where the platinum tip has lost its bond to either the center or ground electrode when they were used in a motor with nitrous.
Thus far the tech's say they have had no problems using Iridium plugs with nitrous.
Can I use Iridium plugs with nitrous injection or a blown alcohol motor?
Yes, and Yes.
We double checked with the tech’s on this one, they say, while they have been watching for problems, thus far, there has been no reports of any problems in using iridium plugs with a nitrous system.
There should not be any problems using Iridium with a blown alcohol motor .