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Old 02-14-2013, 10:59 PM   #1 (permalink)
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Join Date: Aug 2012
Location: Bay Area, California
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Mo' Mon-nay! - '00 Honda Civic HX
90 day: 52.26 mpg (US)

Carbon Silver - '06 Honda Insight
90 day: 82.2 mpg (US)
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Honda Civic HX lean burn Notes/How To

OK well I've owned a 2000 civic HX for about 6 months now. I have an Ultra Gauge, and MPGuino installed, and I watch them both pretty closely.

I figured Ecomodder needs a thread where everyone can collectively pool their knowledge about how to get the pesky HX into lean burn - and stay there.

So far, this is what I know:
First my specs:
2000 Honda Civic HX, 5speed manual, 125k miles, currently running a 49state ECU. all maintnance up to spec.

* engine must be fully up to operating tempature (about 183 degrees F) for lean burn to work. have the defroster on HOT to ensure that your whole coolant system is up to tempature.
* Lean burn much easier to achieve above 2600 RPM, which works out to about 65mph in 5th gear
* Lean burn can be achieved at as low as ~1800rpm (about 50mph), but most cars require the fuel additive "Marvel Mystery Oil" to make that happen. It takes about 3 tanks or 1500~ miles before it really starts to kick in and do its job. 2oz per 10gallons seems to be enough. MUUUCH easier to get it into lean burn with MMO added to the fuel
* it seems to get into lean burn a bit easier if you are kinda heavy on the throttle for a few seconds, then pull throttle back to about 20% until you feel it click into lean burn
* TPS must be below 20% for it to go into lean burn (at any RPM). if lean burn is working correctly - it should pop right in like flipping a switch once you drop to below 20% TPS
* once in lean burn, TPS can go as high as 30%, and load as high as 90% before it will want to slip back to normal non-lean-burn mode.
* once it enters lean burn, power will drop signifigantly (maybe 15%?) - requiring you to increase throttle SLOWLY to maintain the same speed. If it drops out of lean burn, power will increase - so you must let off throttle a bit to avoid accelerating. all this is totally normal.
* Once you enter lean burn, you must be steady with the gas especially the first few seconds, or it will pop right back out of lean burn. let it stabilize for a few seconds, then you can start applying throttle up to 30% TPS and/or 90% engine load.
* with a CA state ECU, its much harder to get into, and stay in lean burn, especially at low RPM. more testing on this to come....
* I *think* I am finding that it has a much harder time going into lean burn if the gas tank has 1/3 or less in it. maybe i'm just crazy, and more testing is needed, but that seeeeems to be the case (anyone else wanna deny/confirm this?)

thats all i got for now, i'm sure i'll add more later....

so please add to this list of knowledge, or if you have found different results, let me know !!!

2000 Honda Civic HX with mild aero mods

2006 Honda Insight
MIMA, FAS, no passenger sideview mirror, race style drivers mirror, front and rear underbody aero, temporary front air dam

Last edited by SpeedyCorky; 02-08-2015 at 04:34 PM..
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