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SpeedyCorky 02-14-2013 10:59 PM

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 !!!

tony_2018 02-15-2013 11:02 PM

Wow, thats good info. I'm gonna go buy some mmo tomorrow. I still need to to hook up my mpguino. What settings did you input?

tony_2018 02-15-2013 11:02 PM

damn I almost didn't notice that dot in front of the 20%!!!

SpeedyCorky 02-16-2013 02:39 PM


Originally Posted by tony_2018 (Post 356665)
Wow, thats good info. I'm gonna go buy some mmo tomorrow. I still need to to hook up my mpguino. What settings did you input?

this link got me the info i needed for the install.

dot in front of the 20% (?)

tony_2018 02-17-2013 10:07 PM

whoops my bad, my laptop screen has a mark on the screen.

1carnut 02-18-2013 10:40 AM

The 1/3 tank thing could be related to MMO also. For me, it takes awhile for me to go through a whole tank so I find that for my car (97 HX) that it behaves best when I add some additional MMO about once a week if I haven't filled up.

SpeedyCorky 02-18-2013 06:17 PM

awe, maybe the oil sinking to the bottom of the tank and getting burned first, hence the last 1/3 of the tank doesnt have much MMO in it? perhaps.....

not a bad idea to top off w/ an OZ of MMO every week or so

tony_2018 02-18-2013 10:54 PM

I don't want to seem way off for saying this, but after adding the 4oz of mmo, topping gas off, marking my mileage for data, and filling my tires to 40psi ( didn't really go down but I checked anyways ) I notice right off my car was idling way better than before. I mean it was fine idling at 1k rpm but it was idling down to 800-900 rpm. Engine sound very quiet.

Today took it to work and home and I have to say that it drove very different. I won't comment on miles until the end of my tank.

surfstar 02-19-2013 05:03 PM

I've owned my HX since Aug '12 and have basically the same findings as you [OP]. Although I notice the exact same in/out of lean burn requirements with the CA ecu. If I drive the car more often, it seems to LB more easily. The other day during one drive cycle it took WAY longer than normal to achieve LB. Quite annoying as I hate having to go that slow for it to kick in. Leads to my additional bullet:
  • Once initially achieving LB in a drive cycle, it will go back in very easily and at higher and lower speed/rpm. Highest I've seen is ~75mph. At ~80mph LB kicks out (due to rpm I think).
I'll try MMO in the future, but really don't see how it could make a difference. Never noticed any difference in achieving LB with TCW3, or FP60 fuel additives so far.

Also, check your speedometer accuracy with GPS or scan gauge. My reads 4-5 mph too slow at speeds above 30mph! Verified with GPS and my ultraguage. Stock tire size.

SpeedyCorky 02-20-2013 07:06 PM

yea, mine will pop out of lean burn above 80mph as well, also suspected to be a funciton of RPM rather than speed. i dunno who is trying to get supurb mileage at 90mph hahaha

never tested my speedo VS a proper GPS, but that would be something to do for sure - thanx for the suggestion.

once i get my aero work done on the car, i'll do some testing of Federal ECU VS CA ECU and hopefully come up with some good solid data. but the long and short of it is that, the requirements and limitations are basically the same - but w/ the CA ECU it doesnt like to go into lean burn as easily, and is MUCH easier to slip out of lean burn

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