Are auto emissions really directly related to fuel effeciency?

Isn't it possible to reduce automobile pollution (i.e., "emissions") without increasing fuel efficiency? And if so, shouldn't discussions (and political agendas) focused around fuel economy be considered misleading?

Put another way, are we confusing discussions over oil independence (an important discussion on its own) with discussions over global warming?

Answer:
No, it's not possible. Not when you include CO2.

When you look at gasoline strictly as a hydrocarbon (ie, without the trace atoms/molecules that make-up "traditional" pollution) then you have a given amount of energy that can be derived from that fuel. The most efficient combustion of a hydrocarbon yields CO2 and H2O. Period. It comes down to stoichiometry. That is exactly what all the sensors for temperature, pressure, O2, etc are trying to accomplish in a modern fuel injection system.

Anything less efficient results in other byproducts like carbon soot, carbon monoxide, and unburnt fuel - that is, an INCREASE in (traditional) pollutants. It is no coincidence that most ULEV and SULEV badges (Ultra Low Emission Vehicle and Super ULEV) are found on high-efficiency vehicles like the Prius or Civic Hybrid.

Do you think that it would be right if a poorly-maintained, poor running 1970 Cadillac DeVille puts out LESS CO2 per gallon of gas than a 2007 Prius?

So, you tell me. Do you think that CO2 should be lumped in with all the other traditional pollutants?
Good question.

It is possible to reduce SOME harmful emissions without increasing efficiency.. Automobile companies have reduced NOx emissions and CO emissions with catalytic converters that change the NOx & CO to N2 and O2 or CO2.

However, the CO2 is now the culprit.. because it is thought that the CO2 causes the greenhouse effect and global warming...

The amount of CO2 (neglecting CO emissions) is directly related to Fuel Efficiency.. the more fuel burned the more CO2 related...

So YES fuel efficiency, oil independence and global warming are related...
yes
yes
no
no, just you it seems
No, they are not. And I do not think so.

The relationship is complex, and different kinds of emissions peak out at different points..

Fuel efficiency is a function of engine geometry, mass being moved, accelerations expected, back pressures (often inversely related to noise pollution!!) shape of the cylinder, ignition efficiency, swept and unswept areas..the list goes on..

And what is the best efficiency of conversion of the hydrocarbons and oxygenated fuels into energy will not necessarily be the best one for getting going rapidly enough to be useful. Or for minimizing NOx pollution.

Cars are used to transport people and loads from one place to another, and usually designed to try to do so at speeds and distances that make it economically worthwhile.

Since assuming proper design, and proper adjustments, the best economy is where the fuel is burned and turned into energy in the best manner, emissions are likely to be least.

When you "step on it" you run engines in a fuel-rich mode that increases the raw horsepower output, but at the expense of lots of unburned and partially-burned hydrocarbons being released...but people do not want to start up at a long crawl.

You want the best current practical conversion of fuel to useable energy, push for the gas turbine...jet planes use it because it is so much more efficient, and NASCAR bans it because of the same reason...shows up the piston-engine cars too badly

You want the lowest pollution, leave the vehicle in the garage.
Then its emissions will be 0. Don't know about yours tho!
WHAT
That depends on the emission or pollution you are talking about.

If you are talking about CO, NOx, SOx, and unburned hydrocarbons--including evaporation from the fuel tank and during refueling. The answer to you question is that they are mostly unrelated. Newer cars have greatly reduced them over cars made even 10 years ago. Not to mention replacement of air sensors, catalytic converters, and tune-ups have a great effect on these actual pollutants.

If you are trying to refer to carbon dioxide (CO2) the answer is a resounding YES. Basically CO2 is the ideal result of burning the fuel. SOx, NOx, CO, and unburned hydrocarbons are all sources of inefficiency in your engine, but producing CO2 means the fuel was fully burned.

On another level, the actual chemical composition of the fuel, which varies greatly, will affect how much CO2 vs H20 is produced from burning the hydrocarbon. But this will be a relatively small effect on the overall amount of emissions unless you are talking about short-chain hydrocarbons (meth- and eth-) or hydrogen.

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