Environment & Energy
In reply to the discussion: Mileage (mpg) Using Ethanol Seen 20% Higher Than EPA Says - Bloomberg [View all]PamW
(1,825 posts)Last edited Sun Sep 22, 2013, 08:14 PM - Edit history (1)
Bill_USA states:
singing off now.
Whatever you are singing; I hope it's a better tune to the nonsense you're attempting to peddle above.
Contrary to your condescending statement above; when you said "latent heat"; I knew EXACTLY that you meant "latent heat of vaporization". It' just doesn't make your case.
I have ZERO need for the remedial writings you link to above; I know this material and can computationally simulate it in more detail than is available in a web posting meant for the general public.
I completely understand that the higher octane rating allows higher pressures without predetonation.
However, one thing that the article in question fails to address is the changes in exhaust gas pollutants, as I see no measurements of those. Students of automobile history are familiar with the reduction of compression ratios, as well as the simultaneous introduction of Exhaust Gas Recirculation (EGR) in the late '60s and early '70s. These were both done for the same reason; to reduce combustion chamber temperatures as a way of combating the emission of oxides of nitrogen (NOx). Although the reduced combustion chamber temperatures reduced NOx, they also increased the amount of unburned hydro-carbons (HC) produced. However, the industry had a solution for the latter; catalytic converters.
So the proposed scheme of effectively increasing compression ratios will also increase combustion chamber temperatures and the emission of NOx. The authors do not address whether their modified engine meets NOx emission standards which is doubtful.
As long as one is willing to allow violation of the rules concerning NOx emission, then Detroit and Japan can accomplish what the MIT scientists did in any number of ways. However, they can't put those vehicles on the street; so such a "solution" is pretty meaningless.
However, the place where you made your ERROR is in linking that to efficiency. The other posters were talking about efficiency and "fuel economy" which is NOT 1:1 correlated with octane rating.
In fact, there's less energy in high octane gas than there is in low octane gas. Provided you can burn it effectively; you will get better economy i.e. better mpg with the low octane vis-a-vis the high octane. The high octane gas has components with lower heat value.
You have to learn to disentangle your confused logic. You are equating things such as "latent heat" and "fuel economy"; when there isn't a 1:1 correlation.
Again, that higher octane lets you run your engine at higher pressures with higher boost, hence more air. However, you only get more energy out if you put in more fuel. So the higher octane gives you more energy per piston stroke; but at the cost of using more fuel.
The fact that you use more fuel to get more power doesn't necessarily mean you get better economy or "mpg" which is what the discussion was about.
You are in ERROR, 100% WRONG, and MISTAKEN. Accept that your ego is writing checks your abilities and knowledge can't cash.
PamW