Lean Cruise

[brandongarnold02]

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 it’s 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 don’t have a wideband to monitor this at the moment. I can only monitor what it’s commanding. My question is what is a safe afr to run lean cruise at? I have seen so many different answers online.

[LeMarky Dissod]

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?).

[B52Bombardier1]

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

[brandongarnold02]

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.

[brandongarnold02]

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

[LeMarky Dissod]

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.

[ralmo94]

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

[Pulse_GTO]

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.

[ralmo94]

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.

[brandongarnold02]

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

[brandongarnold02]

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

[LeMarky Dissod]

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 timeBut 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.

[brandongarnold02]

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

[LeMarky Dissod]

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 quicklyThen 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.

[ralmo94]

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.

[Pulse_GTO]

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.

I would download the bin with PCMHammer, apply the patch with TunerPro, then do a write full flash with PCMHammer. Afterwards read the file in HP Tuners and the parameters you need to fine tune Lean Cruise are there in HPT. Just make sure that your dad's truck uses OS 12587603.

[ralmo94]

I would download the bin with PCMHammer, apply the patch with TunerPro, then do a write full flash with PCMHammer. Afterwards read the file in HP Tuners and the parameters you need to fine tune Lean Cruise are there in HPT. Just make sure that your dad's truck uses OS 12587603.

Thought about that but unfortunately I don't have any pcm hammer combat able equipment.

[Pulse_GTO]

Thought about that but unfortunately I don't have any pcm hammer combat able equipment.

I use an OBDX Pro VT. It shows in stock on the website and along with a micro usb cable I'm able to read an write at 4X with PCMHammer.

[brandongarnold02]

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

I checked my data logs and on a steady 68 mph and my MAP sensor reading is sitting at around 55kpa at 16.9:1commanded afr. MAP kpa is around 30-35 at idle.

[brandongarnold02]

I use an OBDX Pro VT. It shows in stock on the website and along with a micro usb cable I'm able to read an write at 4X with PCMHammer.

I just ordered one of those yesterday. I’ve been using the obdlink sx. Kinda slow but gets the job done. I log with the PCM Hammer logger and create histograms with Megalogviewerhd. I also use the Universal Patcher because you can take the histograms and copy and past special into the tables on it. It’s just a little more difficult to maneuver through.

[joukoy]

I just ordered one of those yesterday. I’ve been using the obdlink sx. Kinda slow but gets the job done. I log with the PCM Hammer logger and create histograms with Megalogviewerhd. I also use the Universal Patcher because you can take the histograms and copy and past special into the tables on it. It’s just a little more difficult to maneuver through.

Good to know someone is actually using paste special :)
There is also histograms in UniversalPatcher:
Tuner -> right click table -> Show histogram
And logging is possible, too.

I hope you can test both features and give feedback.

[ralmo94]

Sounds like low enough load to possibly benefit from LC. What map does go back to stoich?
I don't think I would go any leaner, at least without a wideband to verify it's mixing fuel as desired.
I wouldn't make any changes until you verify the improvement for a whole fill up.
What was your baseline mpg?

[brandongarnold02]

Good to know someone is actually using paste special :)
There is also histograms in UniversalPatcher:
Tuner -> right click table -> Show histogram
And logging is possible, too.

I hope you can test both features and give feedback.

I have actually used Universal Patcher logger quite a bit the 3 weeks I was getting some irregular jumps in rpm readings sometimes. Let’s say I’m running a constant 1500rpm I would get quick spikes up to 8000rpm in the log. I am thinking it’s because I’m using the obdlink sx and it can’t keep up because when I'm using the PCM Hammer logger the data all freezes under acceration. When the obdx pro vt I ordered come in hopefully it will prevent these logging issues. I knew there was some kind of histogram stuff on there but wasn’t sure how to use it plus I got the Megalogviewerhd before I started looking at universal patcher so it’s been my go to plus I have the math set up for all my tables already. I will definitely be checking out the historgram creator on there. Actually Universal Patcher has quite a bit more capabilities than TunerPro.

[joukoy]

I have actually used Universal Patcher logger quite a bit the 3 weeks I was getting some irregular jumps in rpm readings sometimes. Let’s say I’m running a constant 1500rpm I would get quick spikes up to 8000rpm in the log. I am thinking it’s because I’m using the obdlink sx and it can’t keep up because when I'm using the PCM Hammer logger the data all freezes under acceration. When the obdx pro vt I ordered come in hopefully it will prevent these logging issues. I knew there was some kind of histogram stuff on there but wasn’t sure how to use it plus I got the Megalogviewerhd before I started looking at universal patcher so it’s been my go to plus I have the math set up for all my tables already. I will definitely be checking out the historgram creator on there. Actually Universal Patcher has quite a bit more capabilities than TunerPro.
Sounds like a bug: There should be no spikes even if there is communication problems.
If you want to help fixing this, enable debug log on patcher window, run log until you get this spike and send both: debug log & data log by email.
joukoy at gmail.com

[brandongarnold02]

Sounds like a bug: There should be no spikes even if there is communication problems.
If you want to help fixing this, enable debug log on patcher window, run log until you get this spike and send both: debug log & data log by email.
joukoy at gmail.com

I just sent you a debug log and a data log.

[joukoy]

I just sent you a debug log and a data log.

Thank you!

[joukoy]

I just sent you a debug log and a data log.

I can see from logfiles, you are using old version. Please download latest zip from github and try again, bug should be fixed already.

[ralmo94]

Brandongarnold02,
Where you ever able to verify fuel economy improvement with lean cruise?

[brandongarnold02]

Brandongarnold02,
Where you ever able to verify fuel economy improvement with lean cruise?

It actually seemed to decrease my in town fuel economy by about 3/4 of a gallon per mile. Went from 10.5 to 9.75. That’s with is leaning out to 16.5 to 1. Leaning out to a bit over 17 got me only 9.25 mpg. I turned off lean cruise and going to retest then may advance timing some after that and see if that increases fuel economy.

[ralmo94]

It actually seemed to decrease my in town fuel economy by about 3/4 of a gallon per mile. Went from 10.5 to 9.75. That’s with is leaning out to 16.5 to 1. Leaning out to a bit over 17 got me only 9.25 mpg. I turned off lean cruise and going to retest then may advance timing some after that and see if that increases fuel economy.

Is your tune spot on? Lt &St fuel trim within -5 to 0?
If so, I would try going a little richer about 15.8 and see what it does.
Spark definitely, there should be a segment to add or subtract acourding to fuel mixture.
Leaner mix needs more time to combust. If that's not already on I would definitely do that.

[brandongarnold02]

Is your tune spot on? Lt &St fuel trim within -5 to 0?
If so, I would try going a little richer about 15.8 and see what it does.
Spark definitely, there should be a segment to add or subtract acourding to fuel mixture.
Leaner mix needs more time to combust. If that's not already on I would definitely do that.

Yeah I fine tuned my maf and ve table a while back and got it within that window. There is a table that adds spark based off afr and I had it copied from the Holden file. No luck as of yet.

[ralmo94]

That table should add 0 for the 1 cell, then go up a couple degrees either side of it. I don't know how the xdf is defined, but in HP its the oposite of lambda.