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Discussion Starter #1
I've read quite a number of posts etc.. in regards to lean burn, but as to date because I've heard so many differing stories I'm still not sure when lean burn kicks in?

Some say 2500rpm others 3500rpm anyone have some solid figures on this? Of the who what why where when's of this?

thanks!
 

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This has been discussed to many times since the Insight first came out in 2000. Try using the forum search feature.
 

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Discussion Starter #3
As stated above Resist reading the forums has only added to the confusion and I am still without a straight answer... seems to me no one agrees the the rpm figures...
 

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RPM is not the only variable. You can have a very high rpm and be coasting down a hill with little to no engine load and be in either lean burn or fuel cutout mode. In general however the lower the rpm the easier it is to maintain lean burn. Have fun, Rick
 

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From what I understand, to visually see Lean Burn use your metric mode display to see the fuel use. When it jumps to show you are using very little fuel, at freeway speeds.....then you are at lean burn.
 

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Re: Lean burn

BTOURES said:
Does a CVT have lean burn capability :?:
Capability.... maybe, but it's deffinitely not turned on for the United States version of the car.
 

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lean burn

Ricky,
Why does Honda's website show,( under the motor specs for a 5 spd) "lean burn" and for the CVT, they show "standard". Other specs that are comprable to both models, Honda also lists as standard? Also when i'm driving my car,and i am up to speed and i just feather the accelerator pedal, ( I call this the sweet spot) I can watch my mileage go way up and my speed is not decreasing. Is that the same feeling you achive when lean burn is active?
Thanks
 

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Discussion Starter #11
Well thanks for all the imput here folks, however I'm still scratching my head....

can anyone tell me when lean burn kicks in? I've read so much on this subject but am not seeing any real facts figures just assumptions.....

under highway conditions when does it kick in? I was reading a post that said it kicks in at 2500 rpm and the vtec portion kicks in at 3500 rpm ...

I'm sure there's a sweetspot and that is what I'm after.
 

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"normally" lean burn will activate around 2K and go away around 2.5K (in 5th gear) Considering all other perimeters are met for lean burn.
 

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meow77 said:
Well thanks for all the imput here folks, however I'm still scratching my head....
<snip>

I'm sure there's a sweetspot and that is what I'm after.

Scratching the wrong end me thinks :?: :p

Its a seat of the pants connection to the right foot "itch". ;)

Find the lightest pedal pressure that maximizes MPG without sacrificing MPH beyond what your choice is. If you've got a scan tool monitor the O2 sensor's output. It will dance .185 - .220 v. while in lean burn. Yes, you can also get hyper MPG with O2 sensor readings outside this range, but your not in lean burn.

The whole aura surrounding lean burn is a good example of too narrow a focus in regard to MPG. Its not something magic. If you really want to learn what it is, it requires a good general understanding of the chemistry of combustion and flow dynamics of intake air charge as it relates to an internal combustion engine. Understanding the physical properties of matter and energy (losses of efficiency in conversion of energy forms, heat, chemical, mechanical) will be necessary to complete the puzzle so that the nagging questions of, "But if you could just do _X_ then you could *simply* get 100 MPG" will already be answered.

Your MPG readout will be the only guide that factors in all the variables and effectively shows you the big picture in its most elementary form, the final result, MPG. Temperature, fuel grade (knock sensor), load, speed, altitude, road surface friction, etc. are all factors in being able to sustain lean burn. Honda only gives a general expectation and probably ultimate high limit as to how high an engine RPM (which can be translated to speed) that beyond lean burn will no longer be available. It's in the I.C. encyclopedia. But at these higher limits you will see this "window" narrow and easily close. Heck, it's tricky enough at optimal speeds of 45-55 MPH and closes frequently due to "normal" driving factors even at these speeds.
 

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Insightful Trekker said:
MPH beyond what your choice is. If you've got a scan tool monitor the O2 sensor's output. It will dance .185 - .220 v. while in lean burn. Yes, you can also get hyper MPG with O2 sensor readings outside this range, but your not in lean burn.
Well son of a.... :) This is EXACTLY the information I needed to sort out my issues. My LAF is a full volt higher.
 

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If it really is reading 1.2 V when it is warmed up and running, then you have a problem. When I first start it reads over 1 V for a few seconds. Otherwise it is essentially either at the low (0.2 area) for lean burn or fuel cut or around 0.5 give or take during normal running. This is O2 Bank1 Sensor 1.
 

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Then your running slightly rich or not in lean burn as it works in an 02 model anyway. There is a LAF sensor difference in the 00's and possibly breaking somewhere in the 01 model year. So exactly how Honda implements "lean-burn" with this different arrangement remains to be seen. :(

Not trying to be difficult, but I don't want to send you in the wrong direction when there are possible differences. And IAT will probably impact this value. Haven't checked it in ambient below the mid 60F's. And my hot air mod was typically pumping IAT to 90+F

Colder IAT's are known to narrow the lean burn window. How this will impact sensor data has not been confirmed AFAIK.

Anyway HTH! :) (with the qualifications as included above :? )
 

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figgy said:
If it really is reading 1.2 V when it is warmed up and running, then you have a problem.
Sorry, meant to say a full 100 mV higher. I almost always do that, to the confusion of everyone....The real concern is to whether this is a cause or symptom, because it can swing either way. :)
 

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Discussion Starter #18
Hi Insight thanks for the detailed info... however like most on this site I simply don't have the time to understand the full physics and chemistry of lean burn nor do I want to....

I think Willy answered my question best when can I expect lean burn to kick in? 2k rpm ending at 2.5k rpm is the answer I got from him... and I suspect its pretty accurate?

thanks
 

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Discussion Starter #19
oops I must add though... I've heard different figures from different posts.. and I guess that's where a more detailed understanding would be necessary however I'm only really after rough figures...
 

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Lean burn is not entirely RPM dependant. It's mainly pedal position and load dependant. Based on my measurements, the lean burn "window" extends from about 1500 RPM to a little over 2500 RPM. But the main "window" of lean burn is set by throttle position.

To put the car into lean burn:

1. Make sure the mileage gauge/FCD iset to MPG/Miles.
2. Accellerate to slightly past the target speed. For example, accel to 65 MPH.
3. Slowly release the throttle under the instantanious MPG bar is around 100MPG, and hold it there for a second or two.
4. You should see the instant MPG bar shoot past 100MPG, past 120MPG and on to 150MPG. "Catch it" with your foot and slowly depress the throttle until the bar is reading 75 MPG. You are now at the minimum MPG in which lean burn can be held.
5. Based on you speed, slowly get off the throttle, letting the MPG bar move closer to 100MPG. Find a spot between 75 MPG and wherever that allows you to maintain your speed. Likely, this speed will be between 60 and 70 MPH on level ground.
6. Every few minutes, the car will "kick" you out of lean burn to purge NOX from the cat. The result will be a speed increase and a MPG drop. You will learn to compensate for this by automatically letting off the throttle during the purge, then getting back on it when you are back in lean burn.
 
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