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Discussion Starter #1
I was just wondering... and wanting to pick the brains of some of the other people who know allot more than me....

I know the Lean Burn Mode is achieved when a combination of things happen like Engine Temperature ( cold Air Mod helps there ) .... Engine Load... etc.....

I was wondering if the MAP sensor is what is telling the Insight Control System what load the Engine is under .... then once the Engine is up to Temperature and such... Could that Signal be intercepted.... the real signal given to MIMA so it can do its PIMA thing... and then when a switch is thrown a fake signal saying that the engine is under a small load be given to the Insight stock control system???

I am probably missing something.....

but I know that there are times... when I am close to the engine load where the Insight wants to kick out of lean burn and I want to stay in.... MIMA has helped allot.... and maybe somethign like this is to dangerous or not really worth doing.... but I thought I would ask... and see what others think.... I don't recall and didn't see a subject topic header that has talked about this... If I missed it ... anyone know under what thread it was???
 

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Its been asked and answered but its most often been imbedded in a thread on a similar topic.

See:

Suddenly warmer weather = Holy LB, Batman!
http://www.insightcentral.net/forum/vie ... php?t=4537

for one of the most recent. :)

The short answer if your a "Trekker" ;) would be one like Scotty's reply of, "Captian I canna change the laws of physics :!: " A classic line in response to the need to quickly restart the ship's engines and mix the matter & anti matter "cold".

Search the forums there are several _old_ threads on the topic too. But the answer is always the same. ;)

HTH! :)
 

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Discussion Starter #3
thanks..... I didn't read / research / search deep enough.... my bad.

Nut shell... there are too many related / involved factors....

There are egineering and chemical reasons the Insight only Lean Burns when it does....

The best we can do is try to make favorable conditions.... drive with less load on engine... cold air mod in winter for warmer air.... MIMA to take load from ICE and put it on the IMA.... that kind of thing....

for those who didn't follow the link more detail is included bellow pasted from the other topic...

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First off remember more power doesn't necessarily mean better MPG. You'd think that if the same engine can be coaxed to yield more power and you simply don't use it then it would consume less fuel since it doesn't have to "work" as hard. Which is true in part. This is where lean-burn comes in and turns that thinking upside down. Wink

Warmer weather vaporizes fuel better allowing for more complete combustion. Its a basic principal of all (AFAIK) liquid fuels commonly used today. Which effectively rules out anything not petroleum based. Even the fuel stingy Insight _requires_ a richer (greater fuel to air ratio) on a cold (ambient temperature) start to compensate for the inefficiencies. Thats one factor, getting the car warmed-up. And the lower temp you begin from the longer (and more fuel) its gonna take to get it up to operating temp. About 195F (90C) coolant temperature is fully warm.

In _cold_ weather this effect is still evident and more pronounced in an Insight _because_ of its fuel stinginess. Many members have demonstrated that the Insight won't reach operating temperature at idle in _cold_ weather. There's simply not enough fuel being consumed by the car with enough waste heat to compensate for the losses. Part of the reason that auto stop is disabled in temps 40F and below.

Pre-warming the intake air is a system that has been used in cars for _many_ years now. The problem used to be carburetor ice. Ice will form under some conditions due to atmospheric moisture and the evaporative cooling effect of the fuel mist. As you can imagine a car with a plug of ice in the intake will have serious power and performance problems. MPI (Multiport Fuel Injection, 1 injector per cyl usually mounted in the intake manifold and pointed at the intake valve) is not affected by the "old" carb ice condition so adding heat is not commonly used. There is a certain amount of heating the intake air that occurs because of engine and its radiant heat losses and the resulting under hood temperature. In colder weather the under hood temps will be correspondingly lower further reducing intake air and fuel temps (heating of the fuel rail).

The dynamics of lean burn require a good understanding of the chemistry and physics of combustion. To oversimplify; a lean charge tends to burn more slowly. Given x RPM's the exhaust valve is _going_ to open up in a predetermined amount of time regardless of whether combustion is complete. So simply "forcing" a lean mixture past a certain and _highly_ variable point (load, RPM, temperature and several other factors) will fail to produce power.

With a hot air mod in optimum temperature conditions you can partially simulate summer to the engine. Warm the intake air to 110-120F in cool conditions and you'll see a "widening" of the lean burn window. The theory is that when things get cool there's simply not enough time for the fuel to be sufficiently warmed by the intake air to vaporize as effectively and lean-burn doesn't like it. What's happening in reality is still open to some speculation. Honda doesn't publish all the parameters of engine operation that the lean-burn system is designed to work within. There is one, a lean burn speed limit for the Insight, 72 MPH ish ( Question ) The stratified charge concept is the basics of what allows lean burn and has been used by many Honda engines for almost 25 years. The concept is published in various sales brochures and technical manuals.

Now I know what your thinking. Wink Warm the fuel Exclamation Its done with diesel because in low temps it begins to congeal (turns to jello) and its not as _HIGHLY_ flammable as gasoline so its relatively safer to do. Ok then, let's warm the intake air even more. Well Rick Reece tried a 150F (HOT) intake air mod and during the coldest part of winter with no apparent MPG improvement. Probably related to your original thinking of colder air = more power. Heat the air too much and it thins too much, correspondingly reducing the available amount of O2 for combustion and resulting in a loss of power.

And then there are the additional factors of more aerodynamic load at speed with colder (more dense) air and less flex in the tires. And the different winter fuel blend and the... and... and...

Anyways there it is in a nutshell.

P.S. Willie

IIRC the coolant flow to the TB is there to normalize its temperature relative to the rest of the engine. Else fuel vapors traveling back up the intake will "freeze" there and more rapidly gunk up the TB. And the ice problem is still an issue. There is a temperature drop from the resulting pressure drop across the throttle plate. Although without the added evaporative cooling effect of fuel, like in a carburetor, I'd suspect ice is a rare occurence.


HTH! Smile
_________________
John K. Bullock

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Well Ian,

A link is all that's needed for any reader to find the full text. So such a large quote is a bit overdone (IMO). And a lot of the quote is not _precisely_ on point to lean-burn. And the emoticons got texed. But I am flattered you thought the information was helpful. :) Although it does consolidate the information under a better topic header.

Remember you _can_ "force" lean-burn right now. You just have to drive in the style that maximizes its window. Just watch the MPG meter bar graph for the race to the top :!: ;) :)

Happy Hypermileing :!: :)
 

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Well Ian, I read the whole thing and found it very interesting. There are reports from the turbonauts, that the lean burn entry window is widened allowing lean burn at higher speeds. This is quite surprising as required power goes up rapidly with speed.

It should mean that a turbo Insight will get better mileage when cruising at a constant speed. I have been puzzling as to what this means. Is this because it heats the intake air? Is it because the throttle plate does not have to be opened as wide to let in the same volume of air, and the EMC sensing the position of the throttle through a variable resistor assumes that there is less strain on the engine and kicks in the lean burn mode in spite of the higher power being produced? Or is it because the engine doesn't need to engage the second set of valves (VTEC) and therefore runs more efficiently due to the absence of the drag created by them?

Until we get a hyper miler to don a turbonaut suit and blast off at a snails pace, this remains a mystery wrapped in an enigma.
 

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IMO the "turbo" effect is two fold.

Since dynamic compression goes up with boost so does volumetric effiiciency. IIRC from reading the posts the lean burn window is shifted up the MPG scale by less than 10 MPH. Significant and helpful to those who feel they must drive in the 65-75 MPH zone. But there still is the ultimate _peak_ MPH probably still very close to the factory published 72 MPH. There's simply not enough time before the exhaust valve opens at that resulting engine RPM to burn a super lean mixture completely.

A significant percentage of its power comes from the hot exhaust gas (still expanding and otherwise "wasted" energy) so _overall_ pumping losses are probably improved.

It would be interesting to read a turbo Insighter's hypermileing thread.

Willie, Jack, Figgy :?:

HTH! :)
 

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Lean Burn/Purge Mode

Well, I'll try...
The turbo does warm the air a bit, but that has little effect with the turbo. But as it does help the hybrid turbo doesn't use an intercooler. What the turbo does is reduce engine load. The energy required to power the turbo is over compensated for with back pressure reduction from the exhaust mod.

Engine load, without positive boost, well within vacuum, the turbo noticably reduces ICE load for better efficiency, mpg. Once the car is warmed up and all the criteria are met for LB/P the reduced load causes LB/P to be induced easily and with little or no effort.

Aproximate results, NO drafting, surfing, etc. Stock Insight will LB, 43mph, 120mpg, with no traffic controls. Turbo will take that same senario to 48mph. Stock will LB to 68mph, turbo 72. Hybrid turbo spools early, well within prime LB torque range. It will do 64.5mpg at 80-82mph, what it was designed for. Excellent fuel economy at true highway speeds. Regular turbo will do aprox. 62mpg. Stock, 55mpg.

Any Insight, monitor OBD II, Oxygen Sensor 1, Bank 1. Normally reads .5XX thru .7XX aprox. At LB speed, ease back on throttle for a second then ease throttle back up. When you eased throttle back fuel mixture was leaned momentarily to aprox. .2XX, purging first cat. ECM was watching for just this.

If all other LB criteria have been met, LB/P mode has just been induced. With a little practice you can LB at will, walking car up while in LB to the max speed vehicle is capable of in LB. While in LB observe OBD, sensor 1. While in LB sensor 1 will read aprox. .2XX for about 16 seconds. Then ECM will purge NOx with richer fuel mixture, .7XX for aprox. 14 seconds. Then cycles back to LB, then purge and so on.

Probably the most fun is driving around neighborhood streets, ECM constantly jumping the car into LB right after turns. But the best is getting good mpg without driving slow :D .
EDIT thanks Willie
 

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lean burn

Jack;
Check your readings, you have the decimal point in the wrong place.

LB .180------.195

Higher the number........richer the mixture.

Willie :?
 
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