Getting the most out of lean burn (Honda)
 

I've had this idea for a long time that our civic leanburn engines didn't have to be handicapped due to emissions, I believe they have a lot more potential than the EPA allows them to have.

The subject will be the 92-95 Civic VX, D15Z1 or D15 vtec-e equivalent, that is what I'll be doing here. The idea is to maintain a leanburn under all - or almost all - conditions except for mid and max power. Unfortunately, the US P07 ecu limits leanburn to 2600 rpm and the only way out of that is to find a UK version P07 which is extremely rare.

A full retune with another engine management system would be best, but aside from the cost I do foresee some possible implications - a monetary risk would be at stake.




Goal -

1. Allow leanburn to activate at approximately 140 degrees coolant temp and in all gears; 1st gear leanburn is blocked and 2,3, and 4 gears have coolant temp restrictions.

2. Leanburn at idle and when stationary.

3. Allow leanburn to remain engaged at nearly ambient manifold pressures.



To achieve #1 the ecu must see the car as being in neutral and coasting - neutral uses same tables as 5th gear.

To achieve #2 the ecu must see the car as being in neutral and coasting, the TPS sensor must also output a off-idle signal, but must be switchable back to idle values in order for the fuel cut to activate while in gear. Additionally, a greater volume of air must pass through the throttle body to maintain a 500+ rpm idle speed due to the higher manifold pressure required under a leanburn condition.

To achieve #3 a false map sensor signal must be sent to the ecu. The ecu must see a lower manifold pressure than is actually present. The ignition timing will be advanced because of this - every manifold pressure value has a corresponding ignition and fuel value. Distributor compensation may be required and closed loop fueling may need compensation due to potentially exceeding the ecu's limitations on the max percentage of O2 correction, this will be corrected by increasing the fuel pressure. Fueling under full throttle is a lesser concern since the air/fuel ratios are already 12.3-12.6. This engine will produce more power more efficiently at approx 13.5 AFR with its low compression, but with the onboard devices this will be trimmed to its optimal value further lowering the BSFC.


Just for the record - here's a quick and crude vid I shot on the route to establish a baseline for the STOCK leanburn limits. EDIT - I lost this video...



UPDATE EDIT - Here were the results -->



Achieved:

*Leanburn in neutral and stationary while throttle is depressed -

http://s12.photobucket.com/user/grea...606d9.mp4.html

*Leanburn in 1st gear

*Leanburn in all gears (rather than 5th only) at cool engine temps - engages about 1 mile sooner than before.

*Leanburn at/near ambient manifold pressure

*More usable torque in leanburn

http://s12.photobucket.com/user/grea...9efec.mp4.html

*VTEC does not engage until 3000 under any condition

*Max power air/fuel ratios can be held at 13.5 for optimal efficiency.


http://s12.photobucket.com/user/grea...d9905.mp4.html


*A solid 2mpg gain.



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Added parts - Apexi fuel controller, ebay square wave generator

Beginning with #1 - to make the ECU think the car is coasting we need to feed a false vehicle speed signal to the ecu. The signal is a pulse type wave or half of a square wave. Here is a variable frequency and variable duty cycle square wave generator with a diode in line to block half of the wave. Now a 12v+ pulse signal can be sent to the ecu.

http://i12.photobucket.com/albums/a2..._/DSC01183.jpg

http://i12.photobucket.com/albums/a2..._/DSC01241.jpg





EDIT - This particular wave generator isn't really a full wave it's a half wave already, I didn't realize this until I saw it on the oscilloscope. There is no need for a diode.

Wow greasemonkee truly great stuff .Thanks

Wow I have to follow this, it could have a dramatic effect on overall VX MPG
Question tho .. why no gas log for your car

I think you're probably going to run into issues doing any of those modifications. There are reasons lean burn isn't used all the time and its not just emissions related. You seem to know what you're doing, but I have a feeling you're going to run into misfiring problems.

There have been many Honda "tuners" that claim to have their cars tuned to run more lean and get 50+ mpg. Not sure how valid these claims are, how reliable the cars are afterward, or what long term effects or problems this might have on the engine. Eccentrically make any car a "lean burn."

One would think if safety and emissions allowed it, all the car manufacturers would be tuning their cars this way.

Spoofing the ecu with a false VSS signal is successful, but crude. For some reason the VSS acts as a current limiter of sorts so the signal had to be routed through that before going to the ecu. I'll be trying to eliminate having to carry around a spare VSS under the dash to make this thing work.

Now we have leanburn in 1st gear and at idle and as low as approx 600 rpm with the throttle slightly depressed.

http://s12.photobucket.com/user/grea...606d9.mp4.html

Cable throttle...you're going to be stuck in lean burn the whole time? Or do you plan to have a lean burn off switch? Acceleration with very lean mixtures will be less efficient.

I feel like the best way to do this would be a wideband O2 sensor and standalone, that way you won't need to remember to manually put it on the original tune to make sure the fuel trims stay accurately calibrated. Along with a button for map switching of course, since your power will be quite limited. Lambda at full throttle is usually 0.9 (typically lower though, to protect catalysts and stuff), so if you're going to run lean your lambda should probably be no less than 1.3ish to reduce exhaust temperatures.

The leanburn idle feature will need to have a manual on/off of some type in order for the fuel cut to work. The reason for leanburn at idle and 1st is for city driving at low speeds or briefly stopped. To accelerate most efficiently to 40-50 mph I don't use leanburn anyway and is easily overridden by depressing the throttle more.

The lambda at full load with this stock ecu/engine is 1.0 up to 2700 rpm then it goes rich to .85 lambda. Only rare WOT occasions does rpm exceed this. Leanburn is 1.55 on a stock VX, that's probably about where it needs to be.

Tuning this type of engine with a standalone system will require a minimum of 3 fuel maps and preferably two different closed loop lambda target values aside from having an egr valve to control. I wouldn't say this is insurmountable, but certainly a load of work if there is even a system out there capable of doing this - if so, I'm unaware of it.

Alright, for a brief update -

I hooked up the square wave generator to the oscilloscope and it turns out the device is fully capable of satisfying the needs of the ecu by itself without having to add any components to the board. With a cold engine under 42~ mph the ecu will allow leanburn to activate only in 5th gear in its stock form, now I can hit any gear, even idle, but the ecu is limited to 2000 rpm until full operating temp - nevertheless, enough rpm to get down the road and save fuel until it's warmed up.


I've installed the Apexi VAFC controller and removed 5% fuel for a quick test run. That 5% allowed a 2"Hg manifold pressure, what a great sound through the throat of the microbeast. I may have to adjust the timing later and play with the settings some more. I see no skipping or any adverse effects thus far. I have hope, will report back as the project progresses.

Honda CVCC ran lean 100% of then time, >18:1. it was easier back then just to rejet the carb and play with the timing advance.

Wow, I am surprised you were able to idle running that lean. Just goes to show Honda really can make a nice engine.

How much does the ignition timing advance when it switches to lean burn mode?

I believe it was approx 10 degrees more than stoich burn with very little advance - this was at no load.

I'll have more timing data tomorrow as I'll have to see how much the fuel controller threw the timing out. Here's the thread where I'm putting the data I've collected, which gets updated frequently. There's always something unusual that pops up about this engine. Today I confirmed this engine operates in closed loop under ALL operating conditions.

http://ecomodder.com/forum/showthrea...nfo-18050.html

I'm just thinking, maybe it would be easier to switch ECU with Megasquirt or any other EFI computer and not fool stock ECU with additional signals to get what you want?

So in the video how did you jump into lean burn so easily? (still trying to learn how to use my HX after having it for 6 years) do you just floor and let off and match up the vacuum meter at 4? Also you say lean burn stays on in 5th gear and neutral. Is that why mine idles high when I'm coasting in 5th and than when I stop the idle drops?

Absolutely, 5th gear tables are the same as neutral so it behaves the same, if the ecu senses the car is moving it switches to the moving idle and 5th gear tables.

In the p07-A00, US federal 92-95 ecu, leanburn is reactivated by letting off the manifold pressure until you reach 7in/Hg, then it kicks in again. This is the reset procedure - otherwise it would constantly toggle between leanburn and stoich burn at the slightest throttle movement, that would be an annoyance.



As I stated before, tuning this engine with the available software on the market (ie. neptune,crome,ectune,hondata, ect) there are many obstacle to overcome that would have to be worked around aside from the cost. Just as what happens in the above paragraph, I've studied Neptune (personal favorite) and see no way to mimic that behavior. Did I mention cost? Approx $800 by the time I get another laptop to go with it. What I'm doing in spoofing the ecu only costs about $150

i have a question. you said in the first post somthing about using a p07 ecu from england. what is the difference between them? do they run lean burn at different times or more frequently?

What is the guage you are using to read AFR? 4 inches of murcery? I have a 2010 honda insight and myself and a few other owners find light throttle 50 mph and about 4 on the MAP sensor on the sg2 we reach 100 mpg on the MID. Wonder how this would work with the Insight 2?

There was a thread recently about the UK P07, specifically the P07-G01 ecu, which is what basjoos has in the aerocivic. Supposedly this ecu does not cut leanburn off at 2600 and stays engaged in vtec. I pondered this a while and realized running the extra rpm my defeat the purpose of staying in leanburn in the first place, but nevertheless better than the US version. Good luck finding one.




Innovate XD16 gauge and LC1 wideband controller, I just put a new sensor in.

The vacuum gauge is an autometer Z series, but am uncertain of its accuracy.



If Honda used a pressure sensor on their insight engines you could probably fudge it a bit with the fuel controller and turn the map signal down some.



Thus far I'm running leanburn about 1" of vacuum on the gauge, the Apexi meter says 15 kpa so that might as well be throttleless, it only took 7% reduction to achieve this. There's definitely a lot more useable torque and in many places where only running in 4th and <63 mph was possible I can now run the same speed or greater in 5th.

In doing this the stoichiometric burn window in getting narrow, so now engine output seems to be more fuel ratio and rpm based rather than throttle position. Accelerating through 1st in leanburn goes pretty quick and staying up with traffic from a dead stop is possible most of the time. Also the engine is producing more HP and more efficiently at high load/rpm since the air/fuel is now about 13.3 rather than 12.3.

I'm searching for a suitable air solenoid right now, the resistor jumper on the TPS signal works too. Will post values and wire specs after I wrap this up, then we'll see if it was all worth it.

So you are doing a tps resister so the Ecu will think you are always in range? Ok to recap... Give it like 40% throttle for a split seccond and let off? And keep it below like 36 percent? And what does the shif light indicate? Is that telling you are in LB even if you shift before it? And lastly, do you think headers would help to keep your EGT's down? How do the vx and HX like those? Because I'm thinking my cat is seriously clogged.

I don't know how the HX engines operate, but for the VX getting back into leanburn after heavy load is a matter of letting off the throttle and getting back on it. I don't know what the shift light is indicating other than optimal shift points.

TPS bypass is for leanburn in idle.

Headers may help to some marginal degree for more efficient power production, probably not worth the cost unless your'e going all out.

EGT's are no concern with what were doing, I only mentioned it because its a direct indication of why leanburn is more efficient than shoichiometric burn.




Mileage on the first controlled tank was 58.3 on my WNC mountain route. This is up about 1.8 mpg from previous weeks, but it was also cooler tonight which must be taken into consideration. I believe the current mods yielded a solid 2mpg gain, but will have a more solid number in a few days. I'm still working on the final mod. 60mpg+ on the mountain run will be easy to hit once the fuel sucking tires are replaced.

...And for what it's worth, I'll probably be selling the fuel controller and using a $2 variable resistor to accomplish the same thing.

Update -

Goal #1 and #3 have been achieved, #2 was becoming more complex than it was worth - the fuel cut is disabled if the ecu sees an off-idle signal so the revs would drop too slow during shifts. Also, any additional load (headlights, turn signal) bogs the engine running leanburn that low and since there's no idle air control valve working the engine is purely at the mercy of an axillary air source for rpm control, that would take far too much time and funding trying to create a system to maintain a stable idle. What has been done thus far is about 90% of the gains to be had so this is where I'll conclude the project. The 60mpg barrier on my route average will have to be accomplished with aero mods, tires, wheels, and caps are next - 2mpg to go.

Achieved:

Leanburn in neutral and stationary while throttle is depressed

Leanburn in 1st gear

Leanburn in all gears (rather than 5th only) at cool engine temps - engages about 1 mile sooner than before.

Leanburn at/near ambient manifold pressure

More usable torque in leanburn

VTEC does not engage until 3000 under any condition

Max power air/fuel ratios can be held at 13.5 for optimal efficiency.

A solid 2mpg gain.

----------------------------------------

Added parts - Apexi fuel controller, ebay square wave generator


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Leanburn idle

http://s12.photobucket.com/user/grea...606d9.mp4.html




Ambient manifold pressure leanburn

http://s12.photobucket.com/user/grea...9efec.mp4.html




More efficient air/fuel ratio under high rpm/high load

http://s12.photobucket.com/user/grea...d9905.mp4.html

great job brother!

greasemonkee:
Sounds great .. But can you please explain how and what you did in layman's terms, maybe add a few pics and a parts list.
I would love to be able to replicate what you did but I don't understand how.
Thanks Dennis

This is the best I can break it down:


Here's the pulse generator - New NE555 Square wave signal generator 1hz-500khz | eBay

It's not perfect, but does the job. This makes the ecu think the car is rolling at 60 mph, to the speed lower the board would need to be modified, doubtful it would make a difference anyway. The jumper must go in the 50 Hz to 1Khz slot and the frequency turned down to the lower end of the adjustment - frequency and duty cycle should really should be matched up to the waveform of the stock VSS with a scope, but you might get lucky and hit the sweet spot.

*Signal line - Intercept the VSS signal to the ecu, that is pin B10 (yel/blu). Cut that line, cap the side going back into the harness and feed the output signal of the pulse generator into the ecu.

*12V+ can be found at A25 or B1 (yel/blk)

* Ground can be found at A23 or A24 (blk)

Solder the lines to the pulse generator, grab a small project box from radio shack, and stuff some foam around the board to secure it.

Now you've got leanburn in any gear, when stationary with the throttle slightly depressed, and at lower coolant temps.

NOTE: fast idle is always active and might kick up the idle a hair, add a toggle switch in the VSS line if necessary.


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Removing MAP signal may be as easy as using a resistor in the map signal line, but the better way would be to grab an Apexi SAFC, VAFC, VAFC2, or NEO. The older non-vtec version should work fine, they often go for $100-$150 on craigslist or ebay. This way you have more control over rpm and throttle position over how much fuel you're pulling.

Be aware that the more fuel you pull, the more timing you add, also the timing curves get more out of whack so use with caution and listen for detonation. My settings wound up at -8% fuel and 12* distributor timing. The oxygen sensor will add fuel as needed to compensate so increasing the fuel pressure is not necessary.

Thanks .. ordered the pulse generator

Do you have any mpg numbers before and after these mods?

How is the apexi unit installed?

thanks for the vid. i don't drive a civic but i have done a similar ecu tune for mpg on my impreza to run extra lean in closed loop. it pays off over time for it self.

http://imageshack.us/a/img641/56/josetrix1stdyno2.jpg

That vid ^ is the all stock setup.

The fuel controller intercepts the MAP signal, APEXI website has PDF manuals for all models.

On my work route the average had been approx 56.3 now 58.3 is the norm for non-rush days, this is with 195-50-15 ultra performance tires and eggbeater wheels. This is mostly interstate and over mountainous, fuel sucking terrain - 2000' drop in a 3 minute period.

^ :thumbup:

Has anyone ever listed out the lean burn differences between the VX, HX, and insight? From what I can tell with the HX, I can have lean burn all the way to 3,100 rpm.

On a personal side, I struggle to engage lean burn if I am not around 2400 - 2500 rpm, under 20% throttle, under 70 LOD, and on a warm engine. Are these 4 factors what limit lean burn?

I am really interested in this work. I know there are also alot of HX and insight owners that would could benifit from this!

I have both a VX and an HX and there is a big difference in Lean Burn between the two. I would really like it if I could get the HX to behave more like the VX for starters and then ideally apply these changes as well. I have tried to read up here on LB and have had some dialogue with Brucepick who yielded some good information and the Marvel Mystery Oil tip. I've only been driving the HX for a short time but the HX seems to limit LB engagement until it's above about 1900 rpms where the VX did not. It also will not engage sometimes after it is warm under the same conditions that it normally would and I find that I have to run the speed/rpm's up really high (~70mph) and then it will engage again but only stay in LB down to about 65 mph. I'm looking for any additional useful information or suggestions.

Lean burn can be finicky in my HCH. If I drive 60mph I can maintain it indefinitely as long as there is no significant grade. But at 65mph it almost never uses lean burn. If I were to gently accelerate from 60 to 65 it will stay in lean burn, but once it's pushed out it won't go back in. The Scangauge is very helpful in maintaining lean burn. I find that as long as I keep engine load under 90 it will stay in lean burn, and if it gets forced out I can usually resume lean burn by dropping the TPS under 20.

Seconded!

Interesting work on this project.

Nice! This is definitely some impressive work..

Alright, lets see how long the motor lasts. I had a supercharged tacoma with the v6 and trd charger. This was before they added the 7th injector. I was doing between 15-17 to 1 ratios and once at a dyno pull they stopped it claiming I had seriously fuel issues and needed to get it checked or a piggy back system.

There is a big difference between ruing boost at higher RPM and increasing lean burn on an NA car at idle...

I ran my high mileage (200k plus pontiac vibe) in lean burn all the time with my supercharger and it lasted about 25k miles..probably woulda of lasted alot longer if i hadnt went to a smaller pulley and kept my foot outta the pedal. Oh and i also was using water injection for anything over 6-7 psi...Long story short if your running low boost no more then .5 bar, then you should be able to run lean for short periods with out any negative effects.

The car manufactures are owned by the government and the government is owned by the oil companies. Any questions?