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Old 02-08-2019, 10:27 PM   #1 (permalink)
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Default Best rpm / mph for lean burn

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?

Last edited by EricTheWood; 02-08-2019 at 10:30 PM.
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Old 02-08-2019, 10:54 PM   #2 (permalink)
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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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Old 02-08-2019, 11:51 PM   #3 (permalink)
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Thanks Arbus. Thatís what my best guesses were leading me to. Like most small
Engines Iíve 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. Iíll give it some time.
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Old 02-09-2019, 12:09 AM   #4 (permalink)
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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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Old 02-09-2019, 12:50 AM   #5 (permalink)
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Iím 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 Iím 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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Old 02-09-2019, 12:52 AM   #6 (permalink)
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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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Old 02-09-2019, 01:16 AM   #7 (permalink)
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I just looked on line. They all seem to be android compatible. I use apple. Is there one that’s apple compatible?

Found one.

Last edited by EricTheWood; 02-09-2019 at 02:27 AM.
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Old 02-09-2019, 03:27 AM   #8 (permalink)
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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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Old 02-09-2019, 04:17 AM   #9 (permalink)
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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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Old 02-09-2019, 07:37 AM   #10 (permalink)
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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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