specific Energy ratio, Equivalency ratio, air fuel ratio, lambda ratio, oxidizer to carbon ratio, mole structure of charge, laminar flame speed of velocity, latent heat of efficiency, total jet area, pph of air, pph of fuel, BSFC to VE, DA, ect. all have something to do with it, and are all most factual points of reference to ICE's. If you are on the dyno, you are looking at ratio's, most times you are looking at, and tuning air to fuel. some like it, some think less of it, and some flat out ignore it. most cases very hard to tune for max efficiently with out it, or some other form exhaust gas analyzer. I can not tune EFI without a form of air to fuel reference. most efi systems do not run very well without a reference to lambda of 1.
i have run a lot of nitrous in the range 18:1 A/F ratios with c25. very cold fuel with alot of RVP. Most basic spark ignitions can not carry a flame close to or even past lamb of 1. as it begins to misfire. addition of nitrogen (in nitrous) helps extends the lean burn efficiency limit of petrol to 1.0-1.2 with methanol and ethanol increase 1.2-1.5 respectfully.
408 SBC 4150 "1050" annular meth/nitro blend SG is around .850 @ 68. with plans of tipping a little h2o2 in the mix.
will be splitting the frog hairs 4 ways on the dyno later this month, with 8 egt and 10 o2 sensors, and see what's good...or not.