Tommy Cookers wrote: ↑
Wed Aug 31, 2022 1:49 pm
johnny comelately wrote: ↑
Wed Aug 31, 2022 12:14 am
... benefits of the ethanol content which is huge IMO for knock resistance.
the engine is anyway designed to behave in ways hitherto impossible
btw does Joe Citizen still use injector cleaning fuel additive ? (now we all use eg E10 fuel)
I'm surprised at your questioning tommy because you would know the answer with your experience. hoping youre not angling at another octane talk...
Nonetheless it is an interesting question that I will attempt in my capacity as a broken assed ex race mechanic, racer, autodidactic CAD and CAM journeyman, toolmaker, tuner, designer-in-the-dark, non-engineer.
there are two answer methods, one from practical experience and one scientific (pseudo in my case)
Firstly in this case the assumption is the blending produces an homogenous molecular compound, that is predictable, which it has to be.
From experience with methanol and with some ethanol comparison runs on a dyno, as the blend percentage increases the knock reduces, wonderful news indeed.
Generally the advance reduces and from that the power comes with a commensurate increase of compression...all other things being equal.
But being from the olden days the mixture always ends up being rich to finish a race.
This typifies the culture of tuning moving from the suck it and see in the 80's to the scientific approach. Being non tribal at this transition is important. It is exemplified by the Red Bull teams success by using data and experience on the chassis side, Honda maintains the data method which eventually succeeded.
During the war the decions were largely pragmatic/practical with great scientific contributions feeding that in power and armanent development.
But I digress.
The second reason may be the nature of the molecular bonds (and this is where the maxim "a little knowledge is dangerous" may be proven correct)
Not knowing the molecular structure of the blend but assuming it is a branched type, that this produces a more stable combustion. Stability reduces knock. Apparently it is a result of the intramolecular bond types. The intermolecualr bonds of the blend on the other hand produce the volatility and other associated characteristics.
This is slightly more challenging to light the wick but TJI ensures the mix sucumbs.
But the heat/enthalpy of combustion is higher and safer re knock.
The oxygen molecule in ethanol usually means more free power which is the case in a normal rich mixture engine but in this , as you say "impossible" scenario with excess air/oxygen I dont know how that plays out...anyone??
With the mandated flow rates and the 10% ethanol is where they lost power because normally they would richen the flow rate, so how they recovered that loss I dont know. Methinks it has been by refining the peripheral matters like heat containment via coatings etc.
The other matter is the latent heat characteristics of alcohols which do indeed produce a cooler situation as alluded to by Godlamereso (spelling) member here