A/F/R gauge for tuning

Dale Davies said
Rich in, rich out. A missfire pushes out the air molecules as well as the complex of HC molecules. The air is only composed of 21.9% O2 molecules which is displaced by the HCs, still reading rich.
Remember that liquids change phase when going to the gaseous state and increase in volumn tremendously during that phase change, displacing the air/nitrogen. This is how the mixture reads rich when air/fuel passes out the exhaust valve during the critical scavenge cycle if EVC is a bit late for the head flows available. To compensate the exhaust valves could be recessed or sunk into the head a bit, allowing the fresh charge to pass over the almost closed exhaust valve.
Water when changing phase from liquid to steam expands 1,600 times. This phase change requires huge amounts of heat taken from the air when using water injection in an ICE, which elps control detonation. The huge expansion also aids cylinder pressure.

Im starting to change my thinking about EVO and EVC. Not so much as it relates to overlap but more in general terms how EVC and EVO are affected by rod to stroke ratio and the time that the piston spends around TDC and BDC.

To that end, a higher R/S ratio may want an earlier EVO so that when the piston reaches BDC you are at or near atmospheric pressure to reduce pumping losses. Since the piston is moving around BDC quicker (and I’m assuming faster) if you delay EVO you increase the pumping loss.

Which makes me assume (at least at this point) that when the cam is advanced and the power goes up that it is more likely due to the earlier EVO and reduced pumping losses (even though you may and probably do give up some of the expansion) and not so much to the earlier IVC.

And if that’s the case then a high(re) R/S ratio and a late EVO may be hurting power.

Ive always been of the opinion to delay EVO so that you get as much out of the expansion stroke as you can. But now I’m questioning that philosophy.

I also think that header sizing is impacted by this, as the sound/pressure waves would have to be different with different EVO’s.

The more I learn the more I learn I don’t know much.