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Originally Posted by RealityRacer
Thanks mpgmike!
So engine efficiency can be increased and actually lower emissions?
What will engine efficiency do to power output?
I see on on your previously posted link a few good tricks to get better engine efficiency but what is there to help overcome ECU limitations on MPG?
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Back in the 1920's through 1940's a brilliant genius named George Arlington Moore pioneered more radical technologies for the internal combustion engine than anyone else. In fact, he holds (or at least held for several decades) the record for the most ICE related US Patents of any single individual. Reading through his writings (and many other inventors over the past century), references to emissions dictated exactly what was coming out of the engine. These folks weren't working with our modern catalyst system. Reading through practically anything pertaining to engine efficiency over the past 50 years, there is a mandatory section that describes how the technology interplays with the catalytic converters.
In a perfect world (Faraday, among others, say it does not exist), ALL of the HC fuel would oxidize inside the combustion chamber and emit only water vapor and carbon dioxide. In our real world, there is always some amount of the fuel that either doesn't burn at all (HC emissions), or only partially burns (CO emissions). To complicate things further, in the heat of combustion, the danged air tries to burn forming NO and NO2 emissions!
With that said, a good rule of thumb regarding the cats; less emissions
in = less emissions
out. It can only be a "rule of thumb" because in reality, the cats work only when hot. Where does the heat come from? Exhaust gasses still burning out the exhaust manifold, and HC & CO burning inside. If the cats cool, you better hope you have 0 PPM HC and 0.000% CO coming out the engine if you want ultra clean exhaust! Then there is the NOX reduction catalyst. It works not only by heat (as the primary cat does), but also by the absorption and release of oxygen. It needs some oxygen sometimes, and a pretty-much oxygen-free exhaust feed at others. It oscillates back and forth, absorbing, then releasing oxygen. It tries to pull the oxygen from the NOx and release it as O2.
My experience is that you can run the engine at extreme levels of combustion efficiency where the cats aren't doing much. Allow the ECU to occasionally dump a little extra fuel to stoke up the fires, and the emissions are squeaky clean, you're getting ~50% better fuel economy (that number chosen random), the cats are working awesome -- and no CEL comes on!
One trick I learned is to
wrap the exhaust between the engine and cat with a fiberglass header wrap. It holds the heat in. This does 2 things; your under-hood temps are lower, allowing longer life on belts, hoses, and even gaskets. It also keeps the cat hotter when improved combustion efficiency isn't feeding it as much HC/CO fuel.
Specifically pertaining to emissions, gains in the <40% to 50% range --
where combustion efficiency was improved -- almost never negate emissions. Above that, there arises a conflict between the catalyst functionality and an engine that's "too efficient". (If you research the Honda CVCC, you can learn much!) As for fuel economy gains, my experience is that the ECU rarely gives up more than 10% to 15% fuel economy increases, even if you improved combustion efficiency by 50% or more! There are parameters the ECU will not trespass. At this point, you need a bit of help (one of the things
we have conquered).
Regarding power output, that's the EASY part! By definition, improving
Combustion Efficiency means you are converting more of the chemical energy in the fuel to power at the crankshaft. POWER GOES UP! My approach of improving fuel economy is based on improving combustion efficiency so it requires less throttle to maintain speed (or get up to speed). Less throttle = less air AND less fuel (at any AFR).