Originally Posted By: Alfred_B
Originally Posted By: djb
This is hugely bogus.
The projected environmental benefit is a fraud. The model they use for pollution was developed and set in stone in the 1970s. It can't (won't) be updated, because comparisons with historical values couldn't be easily made.
The problem is that in 1970s, most vehicles used carburetors. If you take a carburetor engine tuned for maximum performance at sea level then dilute the fuel with 10% alcohol, you'll see far lower emissions. If you dilute the fuel with 15% alcohol you'll see even lower emissions, especially with a full-choke cold start.
The flaw is that in the real world essentially all vehicles (excepting motorcycles) are fuel injected. When they are closed-loop, they don't run rich. They produce pretty much the same pollution, regardless of running E0, E10 or E15.
That would not be true. Ethanol is a hydrocarbon at C2H6O molecular composition. So it will produce water and carbon dioxide in a proper combustion. Carbon dioxide is a pollutant but won't cause acid rain or smog.
The main criticism of ethanol should be about using food as fuel, and lower energy density than gasoline (21 megajoules per liter versus 35 megajoules per liter of gasoline).
Just because you don't understand something doesn't make it untrue.
The carb thing is exactly why oxygentes got their gig.
The carb has liquid fuel running down the floor of the manifold, and significant mixture distribution differences from cylinder to cylinder...it has to be rich enough that the leanest cylinder gets to burn...it's typically set rich.
Under the choke start, the fuel is further enriched as there's limited heat for vaporisation to take place.
Under either of those modes, normal and on choke, the excess fuel produced HC and CO, in addition to CO2 and H2O...(these, and NOX, are formed normally under "proper combustion", as high temperature stoichiometry favours some of these fast forward reactions).
Anyway, adding oxygenates was a means of reducing the emissions of HC and CO that were part of carbed engine operation.
That's where they got the gig, and that's where they should have stayed.
There's no engineering reason for them these days with injection systems, and closed loop operation, it's all political, and feelgood greenhouse issues.