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Originally posted by tinkerbell View Postwhy would it create more 'powerful' combustion?
the most heat is created at stoich, and leaner also means slower burning...
(unless you are detonating, but that is not what you should be setting out to achieve)
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Originally posted by stevan View PostBecause one would assume leaner mixtures will have fully combusted fuel hence a greater energy release, this is obviously reliant on the fuel volume being the same in both cases.
leaner = more air (oxygen) than can actually be used to combust with the fuel... richer = more fuel than can be completely burned...
I did not consider that highest power output would be by cramming as much fuel into the cylinder as possible in which case the AFR would be rich as Tom mentioned.
i have tried to find some sources for you , but hard to provide a distinct 'simple answer' as it is massively complicated...
here is a response to a similar question:
http://www.newton.dep.anl.gov/askasc...9/eng99611.htm
Hi Jesse,
You are correct that in order to produce maximum power, a very small enrichment is helpful, especially when accelerating. But it is completely incorrect that a lean mixture burns hotter. The hottest flame temperature occurs at the stoichiometric ratio of 14.7:1. The old wives tale that a leaner mixture burns hotter, came about because years ago as a result of relatively primitive fuel metering devices like carburetors, most engines had to run a little rich (around 13:1 or so was common) all the time to allow reasonable "driveability". So when the mixture was leaned out to a "perfect" 14.7:1, more heat was produced. But mixtures leaner than 14.7:1 burn progressively cooler, not hotter.
The reason for this is pretty obvious when one thinks about it, and you were right to be suspicious. The amount of air an engine inhales at full throttle is the same, no matter what the mixture is. To get a lean mixture, you must inject less fuel. It makes no sense that injecting less fuel, will result in more heat! With that logic, injecting no fuel at all, will result in an infinite amount of heat! Of course, that would be nonsense.
As a mixture is made more and more lean, more and more air that is not used for combustion, and this air only serves to dilute the charge, and cool the combustion process. As stated above, the combustion chamber temperature is at its highest, when a "perfect" 14.7:1 mixture is used, and the temperature falls when the mixture is either made more rich or made more lean.
http://www.autoshop101.com/forms/h55.pdf
page two, last para covers the rich/stoich/lean behaviours...... retired/
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look, it'd be even better if i could relate the info to E85... but i can't...
I only know my engine & how it responds on petrol, would love to try it on E85 (I am 12.5:1 CR) but if i did - it would be a caged track car only...
i assume the different fuel density positively effects power, but to what extent is the question? I just keep on 98 'for the convenience'....... retired/
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calling all E85 tuners???
I know Toda is one...
EDIT: the output i am gunning for (not reached) with my engine is the one set by Troy with his 2.0L B18C with ITB's @ 165kW on E85Last edited by tinkerbell; 17-01-12, 10:00 PM.... retired/
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