ok im doin a plug change this sunday in my 01' t/a with some NGK tr55's im readin that i should and most people gap at .55,

what id like to know is what is changed by diffrent gaps, (burning characteristics,heat) what would be diffrent with say (ex.. .45 gap to a .55). what changes as the gap is increased or decreased

 

In VERY simple terms, the hotter/bigger the spark, the faster/more completely the fuel is ignited.

However, there comes a point that the ignition system can't shoot a spark across the electrodes because there's too much gap. There's also a point where increasing the gap won't matter much, such as in an MSD, where the plug fires multiple times during combustion.

Mike

 

that didnt tell me what gap does i know hotter burns more

 

Here's one link of many that I found on Google. Check the NGK site as well.
There are some tech tips and install information that will help you out.

http://www.akamoto.co.uk/resource-spark-plugs.htm

 

It takes more voltage to fire a bigger gap = more spark energy released = better light-off of the mixture.

 

Voltage doesn't create the heat, the amperage does.
Higher gaps increase the required voltage, but due to the conservation of energy, that means less amperage.
Wider gaps greatly increase misfires depending on the ignition type. Multiple strikes negate this for the most part, but not at higher RPM where the multiple goes back to single.
Tighter gaps mean less resistance to electrical flow, so the atoms inside the gap space heat up more during the spark.
You can only go so tight before you begin to lose power by electrode shrouding, but that's why race plugs come with very tight gaps and shorter ground straps that do not shroud the spark as much.

 

what would cause me to get detnation after a plug change when the motors runnin smoothly other wise, and thereall gapped correctly ?