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Discussion Starter #1 (Edited)
I have been trying to get a feel for lean burn. Mostly in my car that means I get in it on level or slight down slope. Then as my speed drops on the slightest up grade and I have to give it a little gas, I lose it. There seems to be an advantage to dropping a gear to a higher rpm. I have tried google custom search on the site and ran into what a moderator called “haystack” : too many long winded technical threads, without a seeming conclusion. And I do read them. Granted I am trying this when it is 35 to 45 degrees out on the occasional long stretch without a stop in Portland. But I actually noticed it on my last 800 mile freeway trip at 70 degrees. Is my car just weak or is it a tight wire walk at best? What, in a sentence or two of plain English is the latest strategy?
 

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After 2+ years, I’ve abandoned trying to quantify the best set of circumstances that produce lean burn. Even on the same route every day is different. Temps, wind, traffic, precip.

The best advice I can give is to fly more by the seat of your pants and less by instrumentation. I divide the speed by ten and round up or down to pick my gear. Hold it steady a bit, speed up a bit, and then lighten your foot and you’ll hit it.

The engine will drop and pick up power as it enters and leaves the lean state. Your foot probably wants to adjust when that happens. Hold steady and see what happens. You have to be gentle with the throttle.

One mistake I made early on was following the damned “up shift” signal. Stupid-a$$ thing makes the car a joke to drive. Oftentimes you can hit lean burn in 3rd instead of shaking along in 5th.

Warmer weather helps. Have patience. Pay attention to the way the car feels. You’ll grow the skills.

Once you get good at highway speeds you can start chasing “super lean burn.” On my car, it’s in 5th, around 48 mph on perfectly flat roads. It’ll jump into the 100 mpg range and stay there for miles at a time. I can get it sometimes, but only when I’ve been living right!
 

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Discussion Starter #3
Thanks Arbus. That’s what my best guesses were leading me to. Like most small
Engines I’ve driven, the Insight three banger seems happy around three grand,and even happier at more. It can definitely purr at lower speeds under light load tho. I’ll give it some time.
 

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Step one
Get and obd2 bluetooth reader (or if u can afford it peters gizmo) reader is less than 10 dollars

Step 2
Download torque

Step 3
Set up air to fuel ratio gauge (you have to program it i posted on a thread how to do that)

Step4

On your torque ap have a gauge for throttle position and air fuel ratio

Step 5

Accelerate to a maximum cruising speed you can get where you can maintain 25% throttle without lean burn.

Step 6

Once you are at a steady speed reduce throttle position to 16 to 18 %

When airfuel ratio goes from 14.7 to around 22 u are in lean burn

Step7

Slowly increase your throttle up to 30% sometimes u can go to 32

Best to keep it at 28

Step 8

Keep throttled steady not speed throttle position

Let car go whatever speed it wans to go

Step 9

When air fuel ratio goes down to 14.7 ( momentarily even 13.2)

Reduce throttle as in step 6

Repeat step 6 through 9 over and over

The lower your throttle position in step 7 the longer the lean burn between purges

In 5th gear

During lean burn

18% throttle instant mpg above 120

23% throttle 90 to 110

25% throttle 75 to 90 mpg

29% throttle 65 to 75

31% throttle 60

Im going by memory so my numbers will be off

Thus is at 4000 ft altitude

Of course if u have a head wind your speed will be slower ect

This is a good starting place

When you go down hill you may not be lean burning but just have injector shutoff or near injector shut off somewhere below 14% throttle this happens

You can force your purge to happen as you go uphill so as not to waste a purge in down hill or flats. If you commute the same route with practice u will develop an instinct on when to initiate a lean burn and a purge
 

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Discussion Starter #5
I’m willing to get the reader and program it. I wonder tho, after reading thru your list if the throttle adjust regimen can be learned and finessed by just watching the mpg gauge. It seems to tell me pretty accurately when I’m in lean burn mode. Plus I think I can feel slight hesitation and surge already from my limited experience, as it cycles in and out. Thanks I will copy this and study it so I can learn the sequence.
 

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Yeah but with the gauge its so much easier

You can also use engine load instead of throttle. Also with the gauge its easier to get to the maximum throttle with lean burn point
 

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I would love to read the Insight ECU's code, find all the places where it switches to lean burn, and learn what criteria are preventing it from doing so at any moment. It would be great to see just what needs to be changed to enter lean burn at any moment.
 

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My lean burn experience has been that it is load and temerature dependant. This time of year it really does not work much below an engine temp of ~160F, And the hotter then engine the wider the lean burn window. Dropping from fifth gear to fourth gear will sometimes trigger lean burn when it is reluctant in fifth. This is at speeds of around 50MPH or less with a low, 160 - 175F, engine temp.
 

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I dont understand why your temperature stays so low. Does you thermostat not fully close?

Or at certain temperatures the engine runs cold even without water circulation?

If the first is true get a new thermostat

If the second is true block the air going into your engine compartment
 

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Sometimes it seems as if you do a couple of high rpm heavy throttle shifts after a long time lean burning it goes into lean burn easier but that may just be my mind playing tricks.
 

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Discussion Starter #13
I dont understand why your temperature stays so low. Does you thermostat not fully close?

Or at certain temperatures the engine runs cold even without water circulation?

If the first is true get a new thermostat

If the second is true block the air going into your engine compartment
Like a kid who’s a picky eater the engine must like it just right. Right temp. Right
Load etc for lean burn. What does it not like that would be programmed to shut down lean burn.
 

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It may vary from model year to model year, but in my 2000, lean burn is pretty straightforward, at least to me:

IF the coolant temperature is above a certain amount (~150F), lean burn can engage. Lean burn engages when the engine load is below a certain percentage and within a certain RPM range. I'm uncertain if it's actually load, or just throttle position.

Example: If I'm cruising along at 55mph on the highway and I let the pedal out until the FCD displays ~95mpg, after a moment the FCD will jump up to around 140mpg without my having moved the pedal any further - the car is now in lean burn. The car will stay in lean burn until I push the pedal beyond the point at which the FCD is displaying ~70mpg. Pushing it past this point, it will seem to hang for a moment, and then the gauge will rapidly drop to ~50mpg. At this point the car has exited lean burn.

~

Typically on level ground, I can cruise at ~60-65mph max before I can no longer maintain speed in lean burn. Aero mods, warmer weather, higher tire pressure and the right tires all reduce the amount of energy needed to maintain speed and can thus make this number higher or lower. None of these factors seems to affect whether the car actually enters lean burn, just whether or not the needed amount of throttle to maintain speed will let you stay in it.

My car will enter and maintain lean burn down to around idle speed. I can cruise at ~30mph in 5th gear in lean burn, but drop any lower (where the engine gets rough and it's below idle speed) and the car will drop out of lean burn.

Above ~72mph the car will not enter lean burn. However, if you're already in lean burn and start going down hill, the car will stay in lean burn above this speed. I'm uncertain if it's RPM or absolute speed based.

It seems I can get lean burn in any gear. Since 4th gear is ~80% as tall as 5th, rather than ~95mpg and ~70mpg being the thresholds it's more like ~75mpg and ~55mpg. Ditto with 3rd and 2nd gear.

When cruising in lean burn, the car will periodically do what's called a purge. This is when it will briefly drop out of lean burn (~5-10 seconds) and run rich, to purge the catalytic converters of trapped NOx. Otherwise they would get gunked up and quit working. So long as you don't change throttle position, the car will resume lean burn on its own.

~

Lean burn seems to improve economy by a bit. I'm sure it reduces losses related to vacuum since the throttle is open wider. I'm uncertain if you actually get more energy out of a fixed amount of gasoline or if it's just parasitic losses which are reduced. The difference from my experience can be ~5-10mpg in the best conditions, but is typically much smaller if I have a lot of mixed driving.

There is some debate as to whether it's better to run in a lower gear in lean burn or if it's always better to stay in a higher gear - for example climbing a shallow grade, 5th gear w/o lean burn vs 4th gear with. I've seen evidence for both sides which is pretty convincing.

Two things we DO know are that this engine is most efficient around 2000rpm and ~80% load, and that higher RPM means more parasitic losses due to friction and such. I imagine there are cases where slightly higher RPM (e.g. a lower gear) will return better economy, and cases where keeping RPM down to reduce frictional losses will return better economy.
 

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As someone who has only driven the insight a month, I find that lean burn seems inconsistent. Sometimes it's ridiculously easy to get into and sometimes, I'm looking at the gauge and wondering why it isn't in lean burn.

For me, it seems that around 60mph is good with my car on flat land. I don't have LRR tires though so that may be a problem.

I have noticed that drafting behind a semi (not too close) makes a huge difference. It does in all cars, but seems greater with this car due to aero.
 

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Ecky gave you some nice suggestions. I'll mention a couple of things which were passed along to me early in my hypermiling days. First, If I'm in no real hurry, there is a pretty good sweet spot in the 2000-2200 RPM range. That translates to about 50-54 mph in fifth, if I remember correctly. Any lower engine speed, you don't have enough torque.

Second, if you are having hill trouble, try dropping from 5th to 4th just before you reach the bottom of the downhill. That will give you time to reestablish lean burn in 4th, then you can nurse that as far as possible.

Lots and lots of adjustments can help. Airing tires to 60-80lbs for the real aggressive efforts.

I found that using the same 10-20 mile circuit, hopefully with little traffic, lights or stop signs helped me sort out what really worked for me. Traffic and stops just adds too much noise to figure out what is really working. Do your training in round trips of your circuit. Forget tanks for training work.
 

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There is some debate as to whether it's better to run in a lower gear in lean burn or if it's always better to stay in a higher gear - for example climbing a shallow grade, 5th gear w/o lean burn vs 4th gear with. I've seen evidence for both sides which is pretty convincing.
I have noticed this too. Sometimes I will keep it in 4th longer due to this. I try to do what I can to stay in lean burn and sometimes on small grade, the higher rpms are better for MPGs and overall drivability.
 

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I recorded every parameter my tester would allow during a long drive last evening. This plot of RPM vs Air/Fuel Ratio shows that the "sweet spot" for lean burn was 1700-2200 RPM and that I was never in lean burn outside of 1500-2500 RPM.

IMPORTANT: I am chasing down a problem which is affecting my MPG, so this should NOT be considered indicative of the performance of other Insights!
lean-burn-vs-RPM.jpg

Bottom line - for my 2004 MT, if you are not within 1500-2500 RPM you aren't going to be in Lean Burn.

The chart is imperfect; it took 3 seconds to record all parameters once so the match between RPM and Air/Fuel Ratio is not exact. But I tried to filter out any data points where the RPM had changed more than 100 RPM between samples.
 
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