Lean AFR for MPG
Thread Starter
Launching!
Joined: Apr 2004
Posts: 237
Likes: 0
From: Odessa, Texas
Lean AFR for MPG Ok for some of us without lean cruise (us car, non-us have lean cruise) Would it hurt the motor to maybe set air-fuel ratio at 15.0 or so on a long trip. I just dont know if running a engine like that would have any benefit on mpg versus lean cruise on non us-cars. I understand lean cruise runs around 15.5 or but changine afr in parameter B3601would that help any or just hurt the engine more? I was even thinking of setting PE a little lower and raising PE afr a little higher. Im not going to be doing WOT runs or anything just strickly for highway trip. Let me know your opinions guys 
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
stock O2 sensors aren't very accurate past stoich so results may not be very accurate... if you forced the car into open loop, you could then use a wideband to lean accurately lean the car out tot he desired AFR
Thread Starter
Launching!
Joined: Apr 2004
Posts: 237
Likes: 0
From: Odessa, Texas
Just curious to save a few bucks but didnt want to hurt the engine. I know some other countries lean cruise is an option but didnt how it quite worked because like you said o2's are not accruate outside of sotich.
Some of us are able to use the "lean cruise" functions of HPtuners..... IIRC 01+ vehicles. I am averaging 27-28mph on a H/C GTO with lean cruise enabled running about 16.5:1 Pretty neat feature. Those table were filled in from holden's lean cruise settings but I backed them off a bit since they run in the low 17:1 range!! Others are getting 30mpg....
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Thread Starter
Launching!
Joined: Apr 2004
Posts: 237
Likes: 0
From: Odessa, Texas
Originally Posted by mr2guru
Some of us are able to use the "lean cruise" functions of HPtuners..... IIRC 01+ vehicles. I am averaging 27-28mph on a H/C GTO with lean cruise enabled running about 16.5:1 Pretty neat feature. Those table were filled in from holden's lean cruise settings but I backed them off a bit since they run in the low 17:1 range!! Others are getting 30mpg....
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Launching!
Joined: Jan 2005
Posts: 227
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There is a way to actually load your .bin file into a hex editor and change some values to enable the lean cruise. I have not been able to obtain these values from anyone yet because it seems they are scared they would be breaking the law. Posting the information is not illegal, preforming it is 
Thread Starter
Launching!
Joined: Apr 2004
Posts: 237
Likes: 0
From: Odessa, Texas
Originally Posted by MrXerox
There is a way to actually load your .bin file into a hex editor and change some values to enable the lean cruise. I have not been able to obtain these values from anyone yet because it seems they are scared they would be breaking the law. Posting the information is not illegal, preforming it is
This is an interesting thought. I have an older truck that I think could benefit from a lean cruise mode, however I don't think the early pcm's had that feature (88 vintage TBI model).
So, I would have to lock it into open loop mode for lean cruise. Do any of you guys who have the lean cruise mode (aussies) know under what conditions the system goes into that mode ?
So, I would have to lock it into open loop mode for lean cruise. Do any of you guys who have the lean cruise mode (aussies) know under what conditions the system goes into that mode ?
Staging Lane
Joined: Mar 2005
Posts: 78
Likes: 2
From: So Cal.
The LM-1 has "Narrowband Emmulation" for just this purpose. You can replace your NB sensor with the LM-1 & its wideband sensor. Then, you can program the LM-1 to emmulate the narrowband signal at any AFR you want. 15.0, for example. This way, you can keep stock closed loop operation. It wll not affect open-loop/WOT operation.
With this setup, you can "lean out" for economy, just like we do with aircraft engines.
With this setup, you can "lean out" for economy, just like we do with aircraft engines.
