This listing is for TWO (2) E3 powersport spark plugs E3.39 with DiamondFire Technology. 

ONLY £14.98 for two

 These are fitment for the following Yamaha models:

E3 Advanced DiamondFire Technology

DiamondFire technology is the result of an intensive series of laboratory experiments that measured the power created by a spark plug. For the most accurate measurement of power…

Advanced Technology Overview

Engineering scientists studied the actual pressure rise from a single combustion event with different style spark plugs.The measurement is called the Indicated Mean Effective Pressure (IMEP). This value is arrived at by running series of combustion cycles and comparing the values from one spark plug to another, keeping all other parameters (load, rpm, temperature, humidity, etc.) equal. We focused on maximizing the peak pressure created by our proposed electrode designs.

Double blind tests were run comparing the area under the pressure curve itself (the "work" created) for 500 combustion cycles per spark plug design. We also refined our electrode designs to reduce the Coefficient of Variance (COV) of a series of combustion cycles. We performed this work at our test labs in Atlanta, and then continued the development at Georgia Tech and Michigan State University's Engine Research Laboratory.

The spark plug electrode design we achieved combines the benefits of three types of known performance plugs, and applies some new science as well. Our DiamondFire configuration outperformed all other spark plug designs available, including premium offerings from the major manufacturers.

There are three main components that determine how the E3 DiamondFire configuration works: 
 1] There is a component that mimics surface gap spark plugs (the type used in rotary engines and others) which directs the flame kernel to the piston (or rotor) more directly, reducing the travel time from the spark zone to the end gases. This avoids the "doughnut" shaped flame kernel produced by standard plugs, and is achieved by opening the section at the top of the electrode. Given the short time available to get combustion started, the faster you can get the flame to the piston, the better.
2] With retracted plug designs, the generated spark lies against the combustion chamber wall. So we designed the electrode to project farther forward into the combustion chamber. This brings the spark zone closer to areas of probable "good" air/fuel mixture. The E3 outward projection also creates beneficial "micro-aerodynamics" within the spark zone. The initial combustion wave leaves the spark area at supersonic speeds above Mach 1, and the elevated edge provides a kind of chimney effect so the next round of air/fuel mixture gets into the spark zone.
3] The strongest part of the E3 electrode design is the forced edge-to-edge spark discharge, which is the best way to get a spark to leave a surface. Our design improves upon the phenomena that drove race car drivers to "cut back" ordinary electrode spark plugs in order to improve the spark discharge. The spark itself occurs only when an avalanche of electrons migrates from the two electrodes (anode to cathode). Sharp edges are better at initiating electron migrations, and these accelerated electrons collide with matter inside the spark zone to release additional electrons. With the DiamondFire design, the whole population of electrons works to create a plasma channel through which the spark current flows more easily.