Am I also correct thinking that as the piston is going up the glowing hot plug fires off the mixture before the spark happens? and that is the same as advancing the timing?
What you just described is pre-ignition not knock. Knock can lead to pre-ignition but they are different processes.
High plug temps, can be due to too hot of a heat range on the plug, poor torque on the plug screwing up heat transfer to the head, lean fuel air mixture, or too advanced timing.
There is no law that says you have to run the same heat range plug in both cylinders.
Try running that cylinder with one heat range cooler than the other.
As you say check for fuel mixture imbalance, that cylinder may be running leaner than the other.
Many sources recommend retracted gap or short nose plugs on nitrous.
An engines octane requirement drops as rpm goes up, your low rpm knock implies you are running too much spark advance to me. Are you using spark retard when you go on the spray?
Are you sure both cylinders are running the same effective spark timing, if the ignition system has lots of spark scatter or some how fires one cylinder a bit earlier (in crankshaft degrees) than the other you will have a chronic problem with the most advanced cylinder. You will never be able to get maximum performance out of the late cylinder without getting into detonation on the advanced cylinder. Likewise with mixture imbalance the lean cylinder will always limit your power.
Also check your actual valve timing on both cylinders one may have more effective cam timing than the other resulting in higher cylinder pressures in one cylinder than the other.
Another possible cause is actual deck height and rod lengths or piston crown specifications, you might have a tolerance problem where one cylinder has all the short parts and the other has all the long parts so their actual compression ratios are not what you think they are.
If you are using port injection of the nitrous, you could also try running richer jetting of the N2O in that hot cylinder.
Aircraft engines have some of the best research on internal combustion engines. You might find these two articles useful.
http://www.avweb.com/news/pelican/182132-1.htmlhttp://www.avweb.com/news/pelican/182084-1.htmlWhen all the shouting is over, knock (detonation) is a function of peak cylinder pressures and charge air temperatures, those two parameters determine what the octane requirement of a specific engine is, with proper ignition advance and fuel octane, being secondary. Research by NACA during WWII found that with known ideal ignition timing, and a known fuel octane, they could predict the onset of knock in a given engine design, knowing only the intake air charge temperature and peak cylinder pressure. There was a maximum value for both that could not be exceeded without causing knock.
Larry
