Rausche Posted August 1, 2007 Report Share Posted August 1, 2007 Okay, so normally you can't enable lean cruise because it's disabled in code hidden in the PCM, right? What if you install the Custom OS (like EFILive offers), and crossed over the Lean Cruise Mode data? Wouldn't you then not have that hidden line of code that says "if vehicle type not equal to holden then set lean cruise to 0" or whatever? Doesn't the custom OS rewrite everything on the PCM? Also, would it be possible to reflash the cluster into telling you on the DIC when lean cruise is on? or maybe by illuminating the shift up light or blinking the gas light or something? I feel like i'm on a roll with this one, I'm just waiting for someone to shut me down, because this is so obvious someone must have tried it already... Quote Link to comment Share on other sites More sharing options...
misterp Posted August 1, 2007 Report Share Posted August 1, 2007 The PCM will do exactly what you instruct it to Yes custom O/S means that the entire flash area is rewritten with all new contents (code and data both). Nobody has completely disassembled the GM OS's used in the Gen-III controllers, the custom OS's are simply factory code with some new features hacked-in. More to your issue, the contemporary thought on lean cruise is to identify the dozen or so cells that are hit during cruise conditions and lean them down in the master AFR table; testing in a base 5.3L Silverado EC shows best economy to be somewhere in the mid-15:1 range. Mr. P. Quote Link to comment Share on other sites More sharing options...
PladdPezzPunk Posted August 1, 2007 Report Share Posted August 1, 2007 well put mr. p. using one of EFI Lives Custom OS's you can enable Lean Cruise. I had it done on my SSS and really was luckey to see more than a .5 MPG boost. It isn't really worth it on a tub like a truck. With a supercharger (I know there will be 20 people telling me i'm nuts but its simple thermodynamics) It would be much more effictive to lean out (15.6 is the most i could get out of this big engine) the mixture under cruise conditions. Actually the Turbo 2.2L run a lean cruis program and it pulls fuel back to about a 22:1 AF ratio(Super Lean, but super cold) I would expect the results to be doubled to 1-1.2 MPG increase. After I put my blower on, i never enable lean cruise but I was able to make much more reliable power running in Open loop SD. In effect, i gained alot of gas milage for the simple fact that everytime i accelerated normally (from a light or stop not jucing it) The MAF never got the chance to throw the mixture rich before evening out. Quote Link to comment Share on other sites More sharing options...
Rausche Posted August 1, 2007 Author Report Share Posted August 1, 2007 The PCM will do exactly what you instruct it to Yes custom O/S means that the entire flash area is rewritten with all new contents (code and data both). Nobody has completely disassembled the GM OS's used in the Gen-III controllers, the custom OS's are simply factory code with some new features hacked-in. More to your issue, the contemporary thought on lean cruise is to identify the dozen or so cells that are hit during cruise conditions and lean them down in the master AFR table; testing in a base 5.3L Silverado EC shows best economy to be somewhere in the mid-15:1 range. Mr. P. Right, but from my understanding there is already a set of parameters and table ready to go for lean cruise ( to work and for the PCM to control it as a function without any issues... From what I've heard you can enable it in the tuning software, but it won't actually happen because the PCM has a fail-safe built into its code that won't allow the mode to enable... My question is if that fail-safe isn't in the Custom OS, then you'd be able to fill in the values in the table for lean cruise, turn it on, and watch it go... right? Also, I know there are tuners out there that will enable it for you... Do they actually go though the PCM and kill the failsafe, or do they just modify the AFR table to try and meet that 15:1 at 60mph or whatever... When the tuners enable it, is it only when cruise control is on or all the time? Quote Link to comment Share on other sites More sharing options...
.justin. Posted August 1, 2007 Report Share Posted August 1, 2007 Right, but from my understanding there is already a set of parameters and table ready to go for lean cruise ( to work and for the PCM to control it as a function without any issues... From what I've heard you can enable it in the tuning software, but it won't actually happen because the PCM has a fail-safe built into its code that won't allow the mode to enable... My question is if that fail-safe isn't in the Custom OS, then you'd be able to fill in the values in the table for lean cruise, turn it on, and watch it go... right? Also, I know there are tuners out there that will enable it for you... Do they actually go though the PCM and kill the failsafe, or do they just modify the AFR table to try and meet that 15:1 at 60mph or whatever... When the tuners enable it, is it only when cruise control is on or all the time? The tuners that enable it are either hacking the PCM's calibration directly, or are making other adjustments that have a similar effect, but do not utilize GM's "lean cruise" functions. The Custom OS's still have the vehicle check in the code. The benefit with the COS is that you are able to use the revamped commanded AFR by RPM/Map table to achieve the same effect. Quote Link to comment Share on other sites More sharing options...
misterp Posted August 1, 2007 Report Share Posted August 1, 2007 well put mr. p. using one of EFI Lives Custom OS's you can enable Lean Cruise. I had it done on my SSS and really was luckey to see more than a .5 MPG boost. ... The owner/tuner of the 5.3L Silverado EC I mentioned told me he was able to *average* almost 17-mpg DIC. I do agree that there is so much aero improvement to be made on a truck that economy efforts should not come soley from PCM tuning alone. Mr. P. Quote Link to comment Share on other sites More sharing options...
Rausche Posted August 11, 2007 Author Report Share Posted August 11, 2007 Okay, so, final note on this is that the Custom OS does not allow you to enable the actual Lean Cruise function, correct? To make this work it's just basically a matter of programming the AFR table to be 15:1 around highway speeds? Would it be a bad thing to have that on all the time? I'm just really liking the idea of have the AFR change away from prime only under certain conditions (speed is +45, cruise control on, etc...) And so far there's no way to do this without digging through ALL off the GM code, erasing it, and doing a new checksum, right? Quote Link to comment Share on other sites More sharing options...
chpspecial Posted August 11, 2007 Report Share Posted August 11, 2007 you can do it manually but I wouldn't recomend it for long freeway drives. When I took the EFI101 class one of the examples given was about a german tuned WRX STI that was making some crazy power and it survided trough all of the hells that it was put trough while tuning. However when the owner was on the autobanh, after a few hours of driving the motor graneded. He was not doing anything crazy or abusing it. He was simply just cruising along. Apparently he drove in a lean condition for such a long time that the pistons and cylinders got so hot, to the point that the motor blew. I don't think that that guy saved enough money on gas to buy himself a new motor. Quote Link to comment Share on other sites More sharing options...
PladdPezzPunk Posted August 11, 2007 Report Share Posted August 11, 2007 yes somewhat true. however if you are able to lean the mixture out enough, it will run just as cold and eq1. there is a point where oxygen will cool charge instead of making it hotter. this is very tough to acheive with our v8 as the timing tabels are soo limited. Quote Link to comment Share on other sites More sharing options...
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