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Thread: Lean Cruise

  1. #1
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    Lean Cruise

    Another fuel economy question here. Anyone familiar with Lean Cruise? I was able to get it to enabled on my 2005 2500hd 6.0 and itís working except I lost cruise control but I knew that was probably going to happen. I copied the settings from a Holden bin. I was seeing commanded afr at a hair above 17. I donít have a wideband to monitor this at the moment. I can only monitor what itís commanding. My question is what is a safe afr to run lean cruise at? I have seen so many different answers online.

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    Quote Originally Posted by brandongarnold02 View Post
    What is a safe afr to run lean cruise at? I have seen so many different answers online.
    Not an easy question to answer broadly or generally. What is it you're concerned with or for?
    So long as it kicks out of Lean Cruise when it's supposed to, 17.7 wouldn't scare me a bit.
    You copied the settings from a Holden .bin - can't imagine those settings are a danger for your 2500 (pickup truck or Suburban?).
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    When you know it is running in Lean Cruise mode, what do your Short Term and Long Term Fuel Trims indicate? Is the PCM maxing those values out at +25?

    Rick
    1970 Chevy El Camino, LM7 Engine, 4L60E - Two 896 and two 0411 PCM's

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    Quote Originally Posted by LeMarky Dissod View Post
    Not an easy question to answer broadly or generally. What is it you're concerned with or for?
    So long as it kicks out of Lean Cruise when it's supposed to, 17.7 wouldn't scare me a bit.
    You copied the settings from a Holden .bin - can't imagine those settings are a danger for your 2500 (pickup truck or Suburban?).
    My concern was any kind of issues with high egts. As for kicking out of lean cruise as soon as throttle beyond trying to maintain a certain speed it falls back to 14.7.

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    Quote Originally Posted by B52Bombardier1 View Post
    When you know it is running in Lean Cruise mode, what do your Short Term and Long Term Fuel Trims indicate? Is the PCM maxing those values out at +25?

    Rick
    My long terms do some sort of shifting but short term go to zero

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    Quote Originally Posted by brandongarnold02 View Post
    My concern was any kind of issues with high egts. As for kicking out of lean cruise as soon as throttle beyond trying to maintain a certain speed it falls back to 14.7.
    Engine speed & load have to be pretty low before Lean Cruise bit will enable, much less activate.
    While Lean Cruise is active, EGT would be no hotter, and nearly always colder than cruising at 14.7.
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    Fuel Injected! ralmo94's Avatar
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    My 2 cents on Lean Cruise,
    Take all this as not absolute fact, majority is not from my own personal experiance, but from hours and hours of reading things on the internet over the several years.

    Lambda 1 stoichiometric 14.7 : 1 100% gas is the mixture that produces the most heat. Less fuel, less heat, More fuel, the fuel has a cooling effect to some degree.

    Usually when people talk about running lean and doing damage, as far as I understand, it is mostly during a load that would require power enrichment and the cooling effect from the extra fuel, and possibly detonation. This is where the Cruise part of Lean Cruise comes in. During cruise conditions, there shouldn't be enough load to cause any damage to anything, assuming you have no knock.

    People who talk about setting up carburetors for lean cruise, usually say lean it out until you get a little lean stubble, then either add a degree or two of timing, or go just a bit richer to eliminate the stumble. Every combination of vehicle and engine will want something a little different. Most LS engines I have read about, people seem to say that to lean negates any MPG benefit, and actuality uses more than leaving it stock. They usually don't say at what KPA they go from rich to lean though.

    On flat ground, maintaining speed what KPA do you cruise at. What KPA does it idle at. If you are at 80 kpa most of the time, you probably wont see much improvement.
    But you should be able to go fairly lean until about 70 or 75 kpa. If you look at a stock $OD bin on the Open loop AFR table, you can see that they have low load areas lean until around there. Of course it would never use that stock in closed loop, but gives you an idea of what GM thought was safe in the 90's. I think they have it set to around 16, or 16.5, or so. On your LS, I would take advantage of the spark adder table that adds or subtracts timing for deviations from stoich.
    Be careful as I think most bins are set up for vacuum kpa, and not Manifold Absolute pressure. Big difference

    Stock on a truck tune, I think it would be debatable how much damage you could cause running lean at high load, with the theory of less fuel is less heat, being that a stock truck tune usually doesn't take full advantage of Power enrichment. It is usually on a delayed timer and ramped in at a slow rate. I had a 2006 Dodge 1500, after looking at the tune in it, I seen it was set up to never engage PE unless It was floored TPS 100%. I pulled trailers to heavy for a half ton lots and lots of miles. It has close to 300K miles on it and it never melted anything. If the most heat is at stoich, this should have killed that engine if running lean would.

    As far as how lean is safe, from what I know, leaner is safer, as long as there is no heat, or knock, detonation.

    I've look at the holden stock lean cruise bits before, and thought they were a little conservative, I'm surprised you were getting 17:1 commanded with it, but its been a while since I looked at it. Did you notice any MPG improvement? Leaner doesn't always mean better mpg, because you loose a little power, and that increases load.
    googling shows best Fuel economy at 15.8 - 17, depending on what chart you find.

    If anyone wants to correct me on any of that, please do. I remember how hard it was to find anything on lean cruise when I would look the last couple of years.
    I have gained so much from this forum I would like to be able to give some back. Hope that helps

  8. #8
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    I put together a Lean Cruise and Flex Fuel patch for the 12587603 OS for a P59 PCM. What OS are you using?

    I posted it over at pcmhacking and I'll post it here too. According to some testers, this patch keeps cruise control working. Please read below on how it works.

    !!! DISCLAIMER !!!
    I'M NOT RESPONSIBLE IF FLEX FUEL OR LEAN CRUISE BLOW UP OR MELT YOUR ENGINE. BE SMART, USE YOUR BRAIN AND ASK QUESTIONS IF YOU ARE NOT SURE ABOUT SOMETHING.


    FLEX FUEL PATCH - Applying this patch will turn FF on and populate all the necessary parameters with values taken from a P59 2004 Flex Fuel Silverado L59. There are 30+ parameters that need to change for FF to work as the factory intended and they are automatically populated when applying the patch. Will additional tuning be required? Of course. The patch gives you a good starting point.

    YOU WILL NEED TO INSTALL AND WIRE IN A GM FLEX FUEL SENSOR BEFORE APPLYING THIS PATCH!!! There are some notes in the patch parameter summary, but it is not by any means a complete write up.


    LEAN CRUISE PATCH - Applying this patch will turn on Lean Cruise like in the Holden vehicles and populate all the necessary parameters with values taken from a 2004 5.7L Holden Commodore M6. There are 9 parameters that need to change for Lean Cruise to work and they are automatically populated when applying the patch. Again be smart, use a wideband and verify that the PCM is applying Lean Cruise correctly.

    Make sure you do a full flash (Write Entire) of the bin file after applying the Lean Cruise patch.

    If you see multiple tables for the same address those are duplicates with either different units on the rows and columns, different units in the parameter or the rows and columns are transposed to make it easier to copy and paste from other sources. No need to change them all, a change in one will be reflected in the others. Regarding table B3639 - Lean Cruise Enleanment, only make changes to the EQ Ratio table, the two other tables, AFR and Lambda, are there only for reference/sanity check. If you make changes to these table you will wind up with garbage data.

    If you see any errors, please comment so that I can make any necessary changes.
    Last edited by Pulse_GTO; 04-10-2022 at 07:44 PM. Reason: Update XDF file

  9. #9
    Fuel Injected! ralmo94's Avatar
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    Quote Originally Posted by Pulse_GTO View Post
    I put together a Lean Cruise and Flex Fuel patch for the 12587603 OS for a P59 PCM. What OS are you using?

    I posted it over at pcmhacking and I'll post it here too. According to some testers, this patch keeps cruise control working. Please read below on how it works.

    !!! DISCLAIMER !!!
    I'M NOT RESPONSIBLE IF FLEX FUEL OR LEAN CRUISE BLOW UP OR MELT YOUR ENGINE. BE SMART, USE YOUR BRAIN AND ASK QUESTIONS IF YOU ARE NOT SURE ABOUT SOMETHING.


    FLEX FUEL PATCH - Applying this patch will turn FF on and populate all the necessary parameters with values taken from a P59 2004 Flex Fuel Silverado L59. There are 30+ parameters that need to change for FF to work as the factory intended and they are automatically populated when applying the patch. Will additional tuning be required? Of course. The patch gives you a good starting point.

    YOU WILL NEED TO INSTALL AND WIRE IN A GM FLEX FUEL SENSOR BEFORE APPLYING THIS PATCH!!! There are some notes in the patch parameter summary, but it is not by any means a complete write up.


    LEAN CRUISE PATCH - Applying this patch will turn on Lean Cruise like in the Holden vehicles and populate all the necessary parameters with values taken from a 2004 5.7L Holden Commodore M6. There are 9 parameters that need to change for Lean Cruise to work and they are automatically populated when applying the patch. Again be smart, use a wideband and verify that the PCM is applying Lean Cruise correctly.

    Make sure you do a full flash (Write Entire) of the bin file after applying the Lean Cruise patch.

    If you see multiple tables for the same address those are duplicates with either different units on the rows and columns, different units in the parameter or the rows and columns are transposed to make it easier to copy and paste from other sources. No need to change them all, a change in one will be reflected in the others. Regarding table B3639 - Lean Cruise Enleanment, only make changes to the EQ Ratio table, the two other tables, AFR and Lambda, are there only for reference/sanity check. If you make changes to these table you will wind up with garbage data.

    If you see any errors, please comment so that I can make any necessary changes.
    Wish there was a way to add it with hp tuners. My dad drives an 04 DBW 5.3. I turned LC on for it, but had to change it back. No cruise was not an option for him. Lol. Getting ready to do a 2000 mile trip in that truck, would be awesome to have LC and CC.

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    Quote Originally Posted by Pulse_GTO View Post
    I put together a Lean Cruise and Flex Fuel patch for the 12587603 OS for a P59 PCM. What OS are you using?

    I posted it over at pcmhacking and I'll post it here too. According to some testers, this patch keeps cruise control working. Please read below on how it works.

    !!! DISCLAIMER !!!
    I'M NOT RESPONSIBLE IF FLEX FUEL OR LEAN CRUISE BLOW UP OR MELT YOUR ENGINE. BE SMART, USE YOUR BRAIN AND ASK QUESTIONS IF YOU ARE NOT SURE ABOUT SOMETHING.


    FLEX FUEL PATCH - Applying this patch will turn FF on and populate all the necessary parameters with values taken from a P59 2004 Flex Fuel Silverado L59. There are 30+ parameters that need to change for FF to work as the factory intended and they are automatically populated when applying the patch. Will additional tuning be required? Of course. The patch gives you a good starting point.

    YOU WILL NEED TO INSTALL AND WIRE IN A GM FLEX FUEL SENSOR BEFORE APPLYING THIS PATCH!!! There are some notes in the patch parameter summary, but it is not by any means a complete write up.


    LEAN CRUISE PATCH - Applying this patch will turn on Lean Cruise like in the Holden vehicles and populate all the necessary parameters with values taken from a 2004 5.7L Holden Commodore M6. There are 9 parameters that need to change for Lean Cruise to work and they are automatically populated when applying the patch. Again be smart, use a wideband and verify that the PCM is applying Lean Cruise correctly.

    Make sure you do a full flash (Write Entire) of the bin file after applying the Lean Cruise patch.

    If you see multiple tables for the same address those are duplicates with either different units on the rows and columns, different units in the parameter or the rows and columns are transposed to make it easier to copy and paste from other sources. No need to change them all, a change in one will be reflected in the others. Regarding table B3639 - Lean Cruise Enleanment, only make changes to the EQ Ratio table, the two other tables, AFR and Lambda, are there only for reference/sanity check. If you make changes to these table you will wind up with garbage data.

    If you see any errors, please comment so that I can make any necessary changes.
    I added this patch for the lean cruise for the 7603 os Sunday night and tested it out Monday and it works and I have cruise again. Thanks

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    Thanks for the input. Being a truck I’m not planning to leave lean cruise activated if I plan on towing. I will have to check my kpa while cruising and have to report back and as far as fuel saving I am going to figure it up on this tank of gas but I only do mostly in town driving during the week so my mpg will be based off mostly city driving this time

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    Quote Originally Posted by brandongarnold02 View Post
    Thanks for the input. Being a truck I’m not planning to leave lean cruise activated if I plan on towing. I will have to check my kpa while cruising and have to report back and as far as fuel saving I am going to figure it up on this tank of gas but I only do mostly in town driving during the week so my mpg will be based off mostly city driving this time
    But it should either kick itself out of Lean Cruise, or avoid enabling Lean Cruise if the load is too heavy.
    In other words, if properly programmed, the only thing you have to worry about is driving. If you're towing it may never kick in in the 1st place.

    So far as city MpGs are concerned, it won't save any in 1st and / or 2nd gear, only 3rd & 4th. Again, in metro-urbania, it may never kick in.
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    Quote Originally Posted by LeMarky Dissod View Post
    But it should either kick itself out of Lean Cruise, or avoid enabling Lean Cruise if the load is too heavy.
    In other words, if properly programmed, the only thing you have to worry about is driving. If you're towing it may never kick in in the 1st place.

    So far as city MpGs are concerned, it won't save any in 1st and / or 2nd gear, only 3rd & 4th. Again, in metro-urbania, it may never kick in.
    I have it set to enable at 38 and and disable at 35 and have is set to enable after 30 seconds off idle so it does enable on my commute to work. There are a few good stretches of 40-45 mph between lights. It is commanding a leaner afr on those stretches for sure. Also as soon as I give it more throttle than required to just maintain a certain speed it drops back to 14.7 quickly

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    Quote Originally Posted by brandongarnold02 View Post
    I have it set to enable at 38 and and disable at 35 and have is set to enable after 30 seconds off idle so it does enable on my commute to work. There are a few good stretches of 40-45 mph between lights. It is commanding a leaner afr on those stretches for sure. Also as soon as I give it more throttle than required to just maintain a certain speed it drops back to 14.7 quickly
    Then it's working well.
    If, as you say, it drops out of Lean Cruise once the load gets heavy enough, then you should not need to worry about disabling it, since it has already proven to disable itself.
    THEY are NOT Lying to You. You are NOT Lying to Yourself. You ARE Being Lied to - BY Your Self
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  15. #15
    Fuel Injected! ralmo94's Avatar
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    sounds like everything should be in order. Only thing to do now is verify mpg improvement.
    I'm sure you have a good base line mpg to prove it works or doesn't.
    If it was mine I would probably experiment withh each tank different afrs and advance to see what it wants the most. I always use save file as and give a new file name when making changes so I can return to last calibration easy.

    Another thing about mpg and towing worth thinking about is how the tcc is programed.
    I never drove an 05, but I drove an 06 6ltr 4l80e classic. Pulling a grade stock with an RV on it would go to 2nd gear and tcc was never allowed to lock in 2nd. Converter slip caused heat, high atf temps. Resulted in going only about 30mph up long grades to keep temps low enough.
    I recalibrated the shift schedule ann tcc lockup tables, and it pulled like a completely different truck. You could pull almost any grade at almost any speed you wanted, and it never got hot, and had plenty of power. Also removed Tq management.
    You have to be careful not to program loops and such if you do, such as up shift down shift up down up down, lk unlk lk unlk.

    As far as mpgs some trucks I have drove feel extremely loose in the trans taking off, and tighter programming helps in town mpg. Not a lot but a little and it feels better. Some times it takes alot of testing to get where you like it though.
    Last edited by ralmo94; 03-16-2022 at 04:33 AM. Reason: typos

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