Re: Max timing advance topic L6's
I adhere to the max timing advance for my '72 1150, but i don't understand some things: Why does it melt the pistons? My first thought is that it must be lean on fuel to burn a piston. I understand piston displacement and the ratio of the event cycle (intake or exhaust) does it run into an overlap on these cycles that it is firing when there is still burned fuel in the cumbustion chamber?
Temperature too high will melt a piston. That can be had in several ways.
1. Lean burn. In a 2 cycle engine, excess fuel is used to slow down and cool the combustion process. Modern DFI engines go at this the other way, by delivering sparse fuel directly into the combustion chamber and timing it down the stroke to provide a smooth, relatively cool burn.
2. Cooling failure.. Self explanatory
3. Pre-ignition. If the fuel charge is ignited while it is still being compressed, and the cylinder pressures get too high, temperatures also get too high. When you increase the pressure on a gas, it is heated. That's what makes a diesel ignite the fuel, and why you can burn your hand on an air compressor. Normally things are flying around pretty fast, so it's normal to light the fire considerably BTDC so it is going when the expanding gases are needed ATDC. If you get carried away, the pressures get too high.
hope it helps
John
