niterydr
10-16-2008, 07:48 AM
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.
"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.