Lean Burn

[niterydr]

Best fuel economy isn't at 16:1, sorry...you are just creating excessive strain and heat. Try to stick to STOIC for gasoline vehicles.

[iceminion]

niterydr, thx for the advice, but please read up on leanburn

"The newer Honda stratified charge (lean burn engines) will operate on air-fuel ratios as high as 22:1. The amount of fuel drawn into the engine is much lower than a typical gasoline engine which operates at 14.7:1, the chemical stoichiometric ideal for complete combustion when averaging gasoline to be the petrochemical industries' accepted standard of C6H8."

everyone on the Megasquirt and DSMAP forums also has conflicting information to what you just said

yes, running lean while under boost creates lots of heat and melted parts, but while idling away on the freeway, running lean cannot damage the engine because there is not enough fuel.

As a matter of fact, you were telling me about how you could lean tune your DSM to 36MPG, I didnt believe you at the time, I have no idea why you have reversed your stance

[iceminion]

http://en.wikipedia.org/wiki/Lean_burn

[niterydr]

I try for 15.5ish max for "lean" anything else is just creating heat. I am sure people aren't mearly driving differently to help them achieve results....

90% of your fuel economy gains are with tuning decel fuel and throttle tip in fueling, not cruise fueling.

[Kracka]

I created this thread since its something I've been thinking about recently and it was being discussed in another thread. The above posts have been taken from the DD Civic thread in "Projects" section.

"Lean Burn" is a popular mod on the Evo's as it can be done very easily within the stock ECU. I figured it creates more heat therefore more wear on the engine (as backed up by Swanny), but am sure but how much. I used to run mine at ~15.6:1 (I've set many other local Evo's to the same) but am now back at 14.7:1 since installing my 850cc injectors; I know Scheides is at 16.0:1. I've been contemplating adding it back on my car to see if I can save a bit of gas. Swanny, could you please elaborate more on why you have chosen 15.5:1 and what made you come to that conclusion? Anyone else have any experience or insights?

[Speedfreak]

My understanding from the EFI 101 class is that when not under load, it's OK to lean out as far as your car will go. They said to find that point you lean it out until the car just doesn't behave correctly(bucking etc) and add fuel until it's all smooth. **This is NOT under load and is in the cruising area of the map.** This is a very simplistic post about how to do it, but you get the idea.

The basic thought is this.. When not under load, leaning it out does not create extra heat. The less fuel, the less burn, the less heat is the way EFI 101 put it. I can pull out my notes from the class to quote exactly if needed, as I was very interested in this exact topic, and we went over it extensively..

[Kracka]

When I setup lean-burn on the Evo's I do it in the 2000-4000rpm and load value 30-70 range. A load value of 30-70 is only seen during steady throttle cruising.

[turbotalon1g]

It seems to be a popular mod, i have been thinking about this and i cannot wait until V3 to implement it on my car, but I am skeptical about what AFR to do it too as well.
I know that some domestic tuners, more than one shop. Tunes cars past 16.0 cruising, my friends mustang is set to 16.8-17.0ish for cruise.
Thats a little too lean for me, but there is some more info, car is on E85. I don't think it is tuned for lean burn on gasoline.

[Goat Blower]

Don't do it on an E85 mix, it's definitely different. On the Duluth cruise I had to add some regular 92 octane piss to get me to an E85 station and was running at about 16.5:1. It bucked under any load at all and really got hot under the hood. I'll stick to stoich.

[turbotalon1g]

I would think the cooling effect of E85 would help to keep temps down even more so compared to reg. gasoline.

[niterydr]

Originally Posted by Kracka

I created this thread since its something I've been thinking about recently and it was being discussed in another thread. The above posts have been taken from the DD Civic thread in "Projects" section.

"Lean Burn" is a popular mod on the Evo's as it can be done very easily within the stock ECU. I figured it creates more heat therefore more wear on the engine (as backed up by Swanny), but am sure but how much. I used to run mine at ~15.6:1 (I've set many other local Evo's to the same) but am now back at 14.7:1 since installing my 850cc injectors; I know Scheides is at 16.0:1. I've been contemplating adding it back on my car to see if I can save a bit of gas. Swanny, could you please elaborate more on why you have chosen 15.5:1 and what made you come to that conclusion? Anyone else have any experience or insights?

I've just noticed that unless in a no-load atmosphere most cars do not transition smoothly off those load cells to something requiring power. Most cars I tune with a standalone idle around 14.7-15.0, and cruise in the same range. Under the very load cells I might get the car to behave with good throttle tip in and torque on demand as lean as 15.5, but I've noticed the slight increase in mpg is negligated by the fact that you need a higher initial squirt of fuel upon throttle tip in. Holding throttle steady (not to much accel fuel) and tuning decel fuel (aka shutting off the injectors asap), usually shows much larger gains in MPG, and allows for a great driving car without "dead spots".

Realistically you can pull fuel or add timing until the vehicle runs a leaner afr, but that really can create an excess of hydrocarbons. It isn't the problem of running leaner than the 16 range at that particular time, just when you have to transisition into other areas of the map is when problem occur. Face it people, we don't drive these sports cars to get peak MPG. Lean burn is a great concept in commuter cars, but there are reasons why honda and other manufactures put throttle limit and load limits on the cars that employ these designs. Spend time nailing your accel/decel fuel settings, get as much of your cruising/low load map around stoic, with possibly erroring to the lean side, and make your target WOT AFR appropiate for your engine and you will see good mpg. Then when you just want to crack the throttle to pass a car, you can.

Tuning really is an art-form with many different ways to achieve the same result. I've just noticed that cars usually behave better (street cars), when the extremely lean afr isn't targeted in low load. I shoot for driveability in street cars and will leave a little hp, little torque, little strain, and a 1 or 2 mpg on the table when I tune cars. Race cars I will push a bit more to that ragged edge as the cars are not intended to run great in all weather conditions, under any load circumstance possible.

*This is in regards to 92 octane straight.

[jhaan_dude]

unless he got stuck running mostly 92 on a E85 tune like he said...

[niterydr]

Originally Posted by Speedfreak

My understanding from the EFI 101 class is that when not under load, it's OK to lean out as far as your car will go. They said to find that point you lean it out until the car just doesn't behave correctly(bucking etc) and add fuel until it's all smooth. **This is NOT under load and is in the cruising area of the map.** This is a very simplistic post about how to do it, but you get the idea.

The basic thought is this.. When not under load, leaning it out does not create extra heat. The less fuel, the less burn, the less heat is the way EFI 101 put it. I can pull out my notes from the class to quote exactly if needed, as I was very interested in this exact topic, and we went over it extensively..

Exactly it. I've noticed that most modern hemi head style import engines usually don't behave properly after around 15.5 under low load environments. Some will be okay at extremly low load cells in the 16 range, but if you push it to far the car will get into a bucking pattern. Plus the amount of accel fuel you need to recover from that usually offsets the lean cells. How many of us can cruise for hours on end without throttle tip in, getting into boost, or racing another car?

[Kracka]

Good info so far; thanks Josh!

[niterydr]

Originally Posted by Kracka

Good info so far; thanks Josh!

Just sharing what I've found, I am sure everyones experience varies on this subject as well as findings.