Plugs: I'll use a motoX experiance that may help. My buddie is a mad man on a dirt bike and uses plug heat range X. I get on his bike and won't rev it out and drive the piss out of it cause I'm too scared. Shortly, I foul his plugs and he is all pissed off at me and calls me bad names cause I won't hit a 60ft double on bike; I just put around and foul his plugs. while he was riding, he ran the motor full tilt and it was very hot. His range of plug was 'cool', the plug is designed to cool off faster and stay cooler through the whole 2 stroke process. For him ( and us in a similar 'drive the piss out of the car' situation) his engine ran better and he had less chance of a really hot plug igniting the fuel before the timing spark. When I rode the bike, I didn't run the living piss out of it and everything was much cooler, including the plug so it didn't burn off any gas or oil (2 stroke) that was collecting on it, I would have been much better off with a warmer plug for my putting around. Different setups (motor, gas, power) AND driving will each have an optimal plug heat range. For daily driving you want good idle and low power use. For track use you want to keep the plug cool so it doesn't ignite fuel. Many tuners will say things like for these type turbos I find it best to run a stock heat range. Which is kind of meaningless with out mentioning if the motor is going to be run for 20-30 minutes flat out on a track or run and tuned for the street. but I am no expert. Doug picks my plugs
Good analogy with the dirt bike. I know I've heated many a plug up with a torch trying to get a ragged out dirt bike to start. I see two reasons for cooler plugs now though. The one where you basically use a cooler plug because of the more extreme condition that occurs while staying on the gas all day, and the other two burn the fuel a little bit slower. My next question is what is the biggest difference between a slower fuel burn and a little bit less timing in terms of performance gains?
The colder plug doesnt have anything to do with the fuel burning slower. The fuel burning slower is what actually allows you to run more timing.
So here's some more basic questions: When you say more timing, do you mean closer to TDC or further away? And, what does more timing do exactly to create a more dangerous evironment in the cumbustion chamber. I know how ping or knocks damage the cylinder wall, I just don't know where it starts in the cumbustion process.
Man, this is some great info....I need to get mine done after I get a bigger turbo....eventually...always a great learning experience on the forums... Mark
I dont know the answer to the top one. Ping occurs when the air fuel mixture ignites before the spark plug fires.
If you imagine the piston coming up to TDC, if the plug didn't fire until TDC the flame front would essentially be "chasing" the piston back down on the power stroke. If you fire it BEFORE TDC then the flame front its already propagating at TDC and has WAY more pressure pushing down on the piston for the power stroke. If you fire it too early, it increases the cylinder pressure early and can cause "auto-ignition" (also pre-ignition in this case) at other points in the combustion chamber. When the flame front from the spark and the flame front from the auto-ignition meet; BAM JDM, you have ping. It's like a hammer blow on the piston... That ends today's Siegel Lesson SS