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Yeah I have been trying (and did some today actually) to use lower gears for LB, but holding it in LB in 3rd at 50mph sounds crazy, I will make sure to try that out tomorrow and see what happens. :)
I think one of the most common things people do that gives them the 'impression' an ICE has less available power .. than it really does .. is they stay at very low RPMs in high gear.

Once warmed up and such .. you can keep LB up to about ~2,900 RPMs 3rd , 4th, or 5th gears .. it just mean different MPH speeds to reach that ~2,900 RPMs in those different gears.

Also keep in mind the Gen1 Insight has some tall gears .. forgetting about LB for a moment .. you could go 100 MPH in 3rd gear and not yet reach the ICE RPM red line ~6,000 RPMs.

Higher gears to give lower RPMs and less power at a given speed .. those are for when you need/want less ICE output power .. and thus consume less .. thus get higher MPG at the same speed and power.

When you need/want more power .. acceleration .. hill climbing .. etc .. you need higher ICE RPMs at that same ICE Load to get higher ICE output power.

The Gen1's max non-LB ICE power ~50kw is not available at slower than 5,700 RPMs .. LB's max about ~20 kw is not available slower than about ~2,900 RPMs .. of course if you need/want less than that max .. stay in a higher gear at lower RPMs and enjoy the higher MPG.

If you ever have to choose between LB in lower gear .. or non-LB in higher gear .. it's more energy efficient to be in LB than to be in higher gear non-LB .. of course .. if your power needs are low enough and you can have both LB and higher gear that would be best .. but if you have to choose between them .. choose the gear that gives you the power you need/want in LB.

The one thing to keep in the back of your mind when it comes to lower gears and higher RPMs .. many people find more power to be addictive .. if you develop a 'lead foot' that psychological effect will reduce your MPG .. although a LB lead foot is still more efficient than a non-LB lead foot. ;)
 

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The "sweet spot" for "lean burn" is right at 2500 RPM.
(That's my take)

Bye, got work to do.
HTH
Willie
 

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Discussion Starter #43
Okay so without starting a new thread, I do want to ask about the temperature of air in the intake.

I know lots of people like to funnel hoses over to the cat and suck air off of there because it's warmer. But in other cars they always use colder air for greater horsepower.

In my situation, with the wrong tires, where I feel like the car does not have the power to keep rolling in LB and wants to decelerate, if I rigged a WAI setup of some sort, wouldn't that decrease horsepower and force me to exit lean burn more frequently, leading to lower MPG in the long run? Or am I completely misunderstanding the whole situation? Conversely, if I build an intake like this one and get slightly more horsepower (but colder air) will I improve FE or lose it?
 

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LB is actually regulated by the "Load" on the engine. (After some other things are taken into consideration.)
Lean burn is not a fixed position on the throttle either. Their is a min. and a max. on the TPS to maintain LB.
The Insight is pretty good with the air flow. I don't any benefit in trying to gain FE, other than a turbo (without boost).

Willie
 

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Okay so without starting a new thread, I do want to ask about the temperature of air in the intake.

I know lots of people like to funnel hoses over to the cat and suck air off of there because it's warmer. But in other cars they always use colder air for greater horsepower.

My butt dyno says that my Insight seems to like the ambient air temperature to be in the mid 80s F. The IAT intake air temperature runs about 115° then.

In my situation, with the wrong tires, where I feel like the car does not have the power to keep rolling in LB and wants to decelerate,

Maybe you are just going too fast? My mpg went up ~10% when I changed from the wrong worn down tires [175x14] that had the same rolling diameter (checked with GPS) to new RE-92s.

if I rigged a WAI setup of some sort, wouldn't that decrease horsepower and force me to exit lean burn more frequently, leading to lower MPG in the long run?

People that have a heated air intake mod do report better mpg -but- I think that is mostly in cooler (think real Winter) areas of the country. IIRC 115° F is considered a good intake temperature to shoot for. Luckily that's about what my IAT is without the intake mod.

Or am I completely misunderstanding the whole situation? Conversely, if I build an intake like this one and get slightly more horsepower (but colder air) will I improve FE or lose it?
He did feel that his mpg increased slightly.

My feeling is that if you have slightly more hp available with cooler intake air that you ought to be able to let up on the throttle slightly to not use that extra power to maintain lean burn. But and it's a big but, that increases pumping looses (higher intake vacuum) which could decrease the mpg. When you're looking for a few 0.1% change in mpg every little thing counts.

From what I've read on the forum I think if you disconnect the long plastic intake tube and turn the 180° turn rubber tube right at the inlet of the air cleaner so it points under the battery tray you could rig up a temporary hot air tube to the cat converter for an easy to remove test hot air intake setup. Don't forget to seal the smaller tube on the 180° shaped intake tube that used to go to the resonator.

That would allow you to see how your car responds to warmer intake air.

Lean burn:
On a flat surface I can LB around 60-65 Kmh (37 to 40 Mph) in 4th or 5th and the car won't slow down. Throw in a hill and the jig is up, the car just can't get up even a shallow hill in LB.

That sounds normal for a long shallow uphill climb. Time to down shift. 40 mph in my car is slightly better in 4th. 45 mph is fine in 5th. At 30 mph I use 3rd get 90 to 120 mpg depending on who knows what.

Also, low highway speeds in LB are a write-off

At what speed?

I just took an open, flat road, no A/C, no wind or traffic, drive at ~64 mph for 58 miles and averaged 78 mpg. On the way home it got hot so I ran the A/C, slowed down to ~60-62 mpg and averaged 76 mpg. Slowing down helped to balance the additional load of the A/C. Every little thing helps/hinders.


My hope is that when I get new RE92's I'll be able to stay in lean burn at higher speeds. Is this a reasonable expectation?

Depends upon what you call "higher speeds".

Generally lean burn won't kick in above ~70 mph. But traffic around you can greatly change that (I call it "inadvertent drafting".) I once had a friend with me (-~10% mpg) the A/C ON (-~10% mpg) driving at 68 mph (IIRC) in lean burn getting 85 mpg. A semi truck was slowly gaining and finally passed us. While alongside the trailer with a constant throttle, my speed went up to 72 mph and I was getting 120 mpg!! When the drafting affect went away we were back at 68 mph and 85 mpg.


I think what I've learned so far is that new plugs and a clean EGR might help you get into Lean Burn, but none of the stuff I've done will let you stay there without driving like a turtle.
Some times -Turtles Are Us- is us (if you want to get the mpg you read about.).

As Scotty said on Star Trek, "Captain, you cann'a change the laws of physics!".

SLOW DOWN. You only have so much hp vs losses to play with. When I got my car with 48K on it the lmpg was 47 mpg. I reset it and I'm getting 70 lmpg in town.
 

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What gear?
 

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Maybe put that in mpg and I can understand better. Sorry this old brain is tired of converting.
 

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Thank You.
Wait until you get the proper tires, and get them "seasoned" in. LB will be there but don't expect to get any LB when going up a slight incline.

HTH
Willie
 

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4 and 5. I tried 3rd at 50 mph as was mentioned above, but instant FCD was saying like 5 or 6 l/100km which either means it's no longer in LB or it just sucks because it's really high.
Instant FCD doesn't give you a good indication weather you are in LB or not.
You can be down under 50MPG but still be in LB .. or you can be up over 150 MPG not in LB.

It can take a very perceptive driver to just 'feel it' ... it is more obvious at the moment when it kicks in, or kicks out .. otherwise you need a device to give you a good indicator to know when you are or are not in LB.

For Example:
Peter's OBDIIC&C gives a nice easy green light turns on when in LB .. Green light off non-LB.
 

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What is your "in" and "out" reading of TP when in LB?
 

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LB is not the holy grail. My Ultragauge tells me when my car does LB, and ist does it quite often although it's not perfect (missing belly panel, steel rims, all season tyres).

So what I have learned: even without LB is is a fuel saving car. It can drive below 4 l/100 km without doing LB. But I know, that's only my driving profile.
 

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LB is not the holy grail.

even without LB is is a fuel saving car.
Agreed.
As far as I've read .. LB by-itself offers at most about a ~20% improvement to BSFC .. and even that , only under the conditions it applies to , like when you need less than 20kw of ICE power.
 

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Just for interest's sake (because none of you have my set-up and so can't do this), I run lean burn all the time now in 4th and 5th gears at all manifold pressures under 100 kPa (ie off-boost).

There are a few other inputs (eg engine coolant temp has to be over 80 degrees C, and full throttle not being used for a few seconds), but I'm basically in lean burn nearly all the time.

My lean burn varies from 18:1 AFR to about 22:1 AFR - higher load = less lean.

I must take issue with the suggestion that it takes a sensitive driver to tell when you're in lean burn - I always found it very noticeable on the standard car and I have spent many hours making my system of lean burn much less noticeable to the driver.

Making the transition to lean burn occur only on a gear change (ie going into 4th or 5th) was one huge step in making its presence less noticeable.
 

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I must take issue with the suggestion that it takes a sensitive driver to tell when you're in lean burn
To each their own... shrug.

I could feel the difference in mine long before I had any instrumentation confirmation .. but .. I also have also meet and talked to many other drivers over the years who could not feel it at all .. not ever .. Even going with them on drives to 'show it to them' .. some were never able to to feel it .. some could only tell at the moment it went in .. or the moment it dropped out .. and if they missed either of those events they would never feel it while it was in it or while it was out of it .. I've numerous times talked with people who incorrectly equated high instant MPG readings over 100 with being in LB ... or if under 75MPG being out of LB .. etc ... etc.

Some people can feel it .. some can't .. in my experience .. most fall somewhere in the middle .. able to feel the obvious transitions most of the time .. Because of this uncertainty .. instrumentation that can give an objective confirmation one way or the other .. that removes the uncertainty .. there is than no question of 'if' they are in LB or not .. that creates an objective indicator of weather they are or not.
 

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If I'm not watching for the LB light on the scangauge I can tell LB by the exhaust sound. A different freq./tone.
(I'm running a modified exhaust though)

HTH
Willie
 

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Here's how I did a lean burn monitor on the standard car back in 2008 - AutoSpeed - Monitoring Factory Oxygen Sensors, Part 2

I am not saying that a monitor isn't useful, but I am talking more about the driveability changes - the sudden drop in power on the transition into lean burn, the abrupt increase in power as you go out of lean burn (eg with throttle movement), and the lack of throttle response in lean burn. It doesn't have to be like this!

A bit like the factory ride height (simply too low), lean burn in the standard car has been configured with eyes on fuel economy and nothing else. I am talking about the actual AFR in lean burn, and the way it jumps into and out of lean burn - both giving far worse driveability than varying the AFR in lean burn to be commensurate with load, and moving into and out of lean burn in an unnoticeable way.

I guess it's a topic for another thread - if you could have lean burn configured any way you like, how would you do it?
 
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