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The smaller gap provides for longer service life in-gap between adjustments.
Dyno tests with higher output applications with the T5 and T7 have shown that the system develops larger HP with the larger gap. As the power is increased, things are running hotter and the DIC's knocking scheme starts to become a bit conservative as the hotter plug electrodes increase plasma conductance* in a way that is not associated with knocking conditions. The wider gap tends to counteract that tendency. But then you need to be watching the gap and regapping much more often. A larger gap is not a critical issue for lower power setups as that is what the system was designed to manage, so then the convenience of the smaller gap can be useful.
You can use the smaller gaps with a higher output ECU mod, but will not get all of the power that is possible. The 6ES plugs will run too hot and that will limit power or perhaps become a source of auto ignition. Nick is quite specific about using 7ES plugs for high output mods. He is also very spoecific about not using platinum plugs. Other tuners say the same thing.
* As electrode temperatures increase, everything else been equal, the breakdown voltage of the spark gap decreases. As the electrodes are made smaller, like the platinum's, the breakdown voltage of the gap decreases. So these effects, smaller electrodes, and higher temperatures also increase the plasma conductance of the spark gap, which is what the DIC measures as an analog to knocking conditions. As boost pressure is increased, the breakdown voltage of the gap increases and a conventional ignition system can have trouble firing the plugs at high boost. For those applications, the gap is often decreased to overcome this higher breakdown voltage. For turbo applications, more powerful ignition systems are used to be able to fire the plugs under high boost. The DIC was developed in part to be able to deal with these high breakdown voltage issues. The DIC also uses the plugs as knock sensors and that means that there is one sensor per cylinder. The DIC has a high degree of control over what is happening in each cylinder. At lower RPMs, if the DIC detects that the charge did not ignite with the spark, it will spark again to attempt to get ignition. This probably only becomes useful when the engine is cold, the plugs are worn/fowled or the injectors are fouled.
, Mon, 19 Jun 2006 10:45:16, Sun, 18 Jun 2006 18:10:32
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