So it’s crucial to follow the OE dimentions. If it will be too short, spark will occur outside the combustion chamber too long – it’ll collide with the piston.

Reach is a distance between spark plug seat and the end of a thread. Note: E3 and Autolite cannot be referenced by heat range. Since all manufacturers have their own heat ranges, we’ve unified all of them to NGK’s chart: heat range “14 (4)” means 14 is the brand’s heat range and 4 is NGK’s equivalent. race engines), some less, but all spark plugs should operate in same temperatures: from 500☌ and below 950☌. This parameter indicates how well spark plug transfer heat from the engine. You physically aren’t able to fit spark plug with another thread, so check it in a first place. Thread diameter and pitch are fundamental dimensions. That’s why it’s important to stick to OE gap sizes. On the other hand, bigger spark is harder to occur and has more chances to misfire. Bigger gap creates bigger spark, which ignite more fuel. The two things that can differ are materials and electrode design, since they are interchangeable.Gap is a distance between center and ground electrodes. For more information, check our spark plugs guide. Secondly, we ensure that spark plug is designed for the same engine condition: has the same heat range, gap, projection, resistor. If any of those parameters differ, the spark plug cannot be installed. Similar spark plugs are those which characteristics are fully or closely corresponding to each other.įirst of all, we make sure that spark plug will fit the engine by the thread diameter, thread pitch, hex size and reach. While cross-reference table is formed from manufacturer’s charts, this table we make based on our data.Įach spark plug has its own set of characteristics. That way we reference all plugs from several manufacturers’ charts to make a most comprehensive cross-reference table for spark plugs. Then we form tier 2 relations: if A is a replacement for B, and B equals to C, then A and C are also can be referenced (A = B = C). Using it we get a match-list and form tier 1 relations (A = B, B = C). This means you can choose any material as long as spark plugs fits by other parameters, yet it’s recommended to use more durable materials since they decrease chances of misfires.įor this relationship we use official documentation from manufacturers, like this one: They differ by the durability in following order (first the strongest): If you have an older car with little of electronics, you can use both resistor and non-resistor spark plugs.Īll materials works the same. If your car from factory has spark plugs with resistor, use only resisted spark plugs. Resistor surpress RFI and saves your electronics. RFI creates a static electricity, that can accumulate and discharge on car’s electronics and destroy it. Occurring of a spark plug is followed with another event – radio frequency interference (RFI). Gap is a distance between center and ground electrodes.

Ngk heat range chart