Andrewr
How does lambda at peak EGT compare to the lambda for maximum power? Maximum efficiency?
I don't know why you're pissing around with the fuel air equivalence ratio. You're dealing with the fuel pumped into your aircraft so fuel air ratio is good enough. ie the mixture
1 Maximum efficiency occurs when all the fuel is burned and some excess oxygen is in the exhaust gas. ie a lop mixture. 50* - 80* is good to ensure absolutely all the fuel is burnt.
2 Peak EGT all the fuel and all the oxygen is used up ( theoretically )
3 Maximum power occurs about 40* rich of peak.To ensure all the oxygen is burnt a small excess of fuel is used (slightly rich mixture ) The unburnt fuel goes down the exhaust. Efficiency is fairly good but not as good as at peak and less again than lop. 40* rop is very hard on the engine.
40* rop gives the fastest mixture burn (due to a shorter ignition latency period after the spark event ) This means all the mixture is burnt sooner than than is good for the engine. Sometimes the burn is complete at or just after top dead centre and sometimes even worse before TDC. This means maximum pressure occurs when the swept volume of the cylinder is smallest and the mechanical advantage (ability to impart rotational energy) is zero or actually negative.
This is very hard on the mechanical parts of the engine and it creates a lot of heat which you read on the CHT gauge. Imagine riding a bicycle and applying maximum pressure to the pedal at the top or just before the start of the down stroke. You may push as much as you like but nothing much happens till you obtain quite a few degrees of mechanical advantage.
The ignition timing on an engine is set so that maximum pressure in the cylinder occurs 5* to 15* after top dead centre. As it is a fixed ignition system a compromise has to be made and so it is set for normal mixtures.ie 40* LOP or more or 100* + ROP