Anginlumpur,
I'm not so sure as I rarely use B but the times I did, it went into DFCO almost instantly. Will need to test more to confirm.
I'm not so sure, need to do some research but i think because rich ratios do not bur completely or efficiently. There is only so much oxygen in every intake stroke so putting more fuel in will not result in more power. That's Y turbo and superchargers exist. To put more air in (compressed).
When the mixture is rich, you'll also notice the carbon deposits increase or it may foul up your plugs. So it's pretty sure that it does not fully burn up all fuel if the mix is too rich.
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View my fuel log 2013 Mirage (Malaysia) GS 1.2 automatic: 44.6 mpg (US) ... 19.0 km/L ... 5.3 L/100 km ... 53.6 mpg (Imp)