Originally posted by 87LtdT
Would like to hear from experts on the effects of wide vs small plug gaps. What are the benefits of either, and what are the dangers of either?
Do these benefits or dangers apply equally through the different plug heat ranges, or does a colder plug react differently than a hotter plug to a gap change??
Notta expert, but I can pass along a few bits of info..
The Dr's Guide to Optimising Your Ignition System is a fairly good read on ignitions and in part covers plugs. Just gotta bear in mind he sells ignition systems so there is some slant to what he writes.
To cover alot of material with just the basics:
The reason for running any timing advance it to allow for the flame to start the reaction in the chamber, and allow enough time for the reaction to about complete in a way that recovers the most energy.
The Spark / flame varies is small, but as the flame kernel gets to about .1" it then has enough surface area to almost explode thru out the chamber. So running as close as possible gap to .1" would be a good thing. Since you could run alot less timing and still have a good reaction in the chamber.
Going just from 035 to 060 allows you to run 3-4d of less timing, and the engine response is noticably better.
So when you close up the gap, you in effect retarding the timing, and generating a poorer flame front. BUT as opposed to a miss, it's the lesser of two evils.
On a 6 cylinder while you might tink the power lose from a miss would be bout 15% it's more like 22%. Not is there the lose of HP from the event, the engine had to carry the cylinder thru compression which costs HP. The above statements are in reference to 1 HP cycle, ie two engine revolutions.
While the stock DIS is miles ahead of a single coil ignition system, it pales compared to a Coil Near Plug set up. I have an eDIST on my GN, and while it might not make me any serious amounts of more HP, it mins the possibility of HP losses from poor ignition events. As a test, I took and broke off the side electrodes on a set of plugs so that the gap was .105. Things were fine until 22 PSI. It takes a hellva spark to fire that much of a gap at 22. But, since I run more then 22, I had to pass on that much gap. For the moment, I've returned to .035. Reguardless of the weather, it never takes more then 2 engine revs for the system to synch and fire the engine. The reason for 2 revs is that it takes that long at times for a cam synch signal.
While often min or ignored, the ignition is just as important as fuel.
Justa summary.....
