17.3 AFR at anything out of overrun condition will cause serious damage - it has been proven time and again. Only in mitsu GDI engines do the AFR go to 40:1 on overrun and 16:1 on cruise. This is achieved by 2 steps. When accelerating at any pace the AFR immediately is tuned back to 13.5 or 13:9 (to keep itself in safe range) - the CR of this engine is really high too.
one injections stage happens when the air is swirling into the cylinders, a little fuel spray causes the "aerosol" type effect to absorb heat. When the compression happens and the airball is about spinning at insane speed on top of the piston crescent the fuel is injected about about 2 degrees leading ignition timing.
This cannot be applied to wet manifold engines in any sense unless you have frigid dry air ramming into the cylinders and somehow you are extracting more than 30% heat efficiency (transfer to mechanical energy) from the combustion process. In any case you cannot have an internal combustion engine give any sort of mechanical efficiency at that ratio as the heat would be at crazy level and the cat converter will also start to go bad - if the engine is VVT or has any mechanical cam advantage timing I can see a nice sort of disaster waiting to happen. More if the engine has any sort of EGR
Explain this in carburettor terms - because even with EFI the basic otto cycle engine is the same. If you lean out the mix to about 17.3:1 on a carby engine like a datsun A12 - what will happen?
I would like to see a freeze frame graph plot of the car with EC1 connected under load accelerating at a normal pace. I would like to see the ignition map, the MAP and MAF signal, the O2 or AFR signal and the LTFT and STFT too.