Quote:
Originally Posted by Old Mechanic
Olympiadis, I agree with your conclusion about throttle restriction. I would assume the reason why most here do not go the route of custom tuning and or running at higher than 14.7 to 1 ratios is the huge spike in NOX emissions you see when you go to more lean ratios.
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I would think more people don't use custom tuning because it's either too difficult (steep learning curve), and/or cost prohibitive.
Putting the NOx issue in perspective here,
a passing amount is in the range of 0.15% or a little over a tenth of one percent. Double that and you're up to three tenths of that same one percent.
Another important fact is that NOx goes back down as you approach the reasonable effective lean-limit of the engine at low loads. Low load means a necessarily lower combustion temp than when at high load. Even when you improve efficiency and combustion temp at low loads, you're still at a lower combustion temp than you are at higher loads. That means less total NOx is produced than the amount you are legally allowed to produce, because yes it is legal to drive at higher loads by climbing hills, carrying passengers, etc...
With a dynamic AFR tune, such as E4ODnut and myself are talking, the commanded AFR swings quickly from the lean-limit at low load to richer than stoich at higher loads. Not only is this more efficient, but NOx is also reduced lower than what would have been realized at 14.6:1 AFR.
At any rate, I do realize that there are emissions Nazis in every group ready to criticize individuals by spreading their misinformation and ignorance where it concerns their need to support a government controlled regulating body, and its associated very ill conceived legislation. That is unfortunate for us all.
http://www.legacygt.com/forums/attac...p;d=1268329060
Quote:
Originally Posted by Old Mechanic
Open loop basically goes outside the paramters of factory design and most likely creates emission issues that are unresolveable today.
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Yep, and many people are quite unaware of the other times and modes of operation where a 100% stock vehicle goes outside of the intended factory designed parameters, and also creates emission issues.
That's why the EPA peforms their emission test on a warmed up vehicle and measures average outputs over a range of relatively "mild" driving conditions during their driving simulation.
In order to meet ever stricter fuel mileage standards you will see auto manufacturers continue to increase the number of algorithms in the PCM, and also increase the amount of time that the engine runs outside of the 14.6:1 AFR window. Running at stoich is so inefficient that they will have no other choice but to do so.
The EPA has become an extremely corrupt arm of the government that has been used as justification to create economically destructive legislation.
For more than 20 years the EPA has required extra and expensive emissions equipment on our vehicles that was primarily designed to turn other combustion waste byproducts into CO2. Recently they have declared CO2 as a pollutant. They have legislatively backed themselves into a corner. Their way out of this conundrum is that they can legally place the responsibility of solving this problem squarely on the automotive manufacturers without enduring any of the responsibility themselves.
As far as being a mechanism to progress the improvement in fuel efficiency the EPA has been a complete and utter failure. If you look back over some of their published papers concerning engine analyzation and fuel economy tests they become downright embarrassing. As an example they were unable to find any fuel economy improvement on one vehicle when testing a set of under-drive pulleys that were submitted for their approval. The specifics of the test are all in print and it's absolutely atrocious, - the level of their incompetence.
I think what it boils down to, at least in part, is that government workers (the EPA) have no real desire to go out of their way to educate themselves, by at least reaching out to the automotive engineers to gain improved understanding of the engine management systems that they are tasked to test.
In a sense it is silly to expect more from such a government entity, but then again they wield a crippling power over us all.