Quote:
Originally Posted by frank316
Ok guys I have a 1999 honda civic that has a programable engine managment system(crome). I have been messing around with lean burn and seeing what I can fiddle with to up the mpg. the main thing i am wondering about it is how lean is too lean.. I'm sure there is some point where leaning requires more manifold pressure and thus more fuel to keep accelerating I just wonder if its in the realm of afrs we can acheive?
I have a non-vtec y7 engine and with the manifold pressure around 10-12 inches is around 18-1. Any higher manifold pressures (14"-18") where i normally cruise are leaner than that, guessing 22ish to 1 with no indication of breaking up.. anyone know any gauge type widebands that will read higher than 18 or 20 to one? Also the factory timing in those areas of the tune are around 38-42*. In my tune i'm running anywhere from 48-50 degrees of timing.
I'm considering trying out a set of vx spark plugs(one stage hotter than whats in it now, stock) and leaning farther, but I currently don't have an instaneous mpg gauge so it makes fine tuning difficult to have to drive a few hundered miles to see what changes i've made.. I just started keeping a log on here, but over the past few months of testing i've been getting anywhere from 35mpg driving to work and home(5.5 miles 35-45 mph 5 stop signs) to a few tanks in the mid 60's doing highway trips.
anyone have any ideas or thoughts or concerns about lean burn lets hear what you think!
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what I would be worried/concerned about is burning the valves with such lean mixtures and high advance. running even hotter plugs only makes it worse. Not sure there are wide bands that lean on market (other than emission type sensors ).
I would check what your exhaust gas temps are , seeing if its getting much higher than stock and seeing what plugs look like before leaning further or running hotter plugs .