Started out on what seemed like a simple endeavor few weeks ago. Needed to re-scale the MAP sensor slope values using EFIlive on some LMM ECM's so CANbus will report up to 50lbs of boost. Similar to the LLY 5bar MAP mod demonstrated on here many moons ago.
Looks highly unlikely anyone has successfully remapped the LBZ/LMM MAP voltage tables before. LLY for certain, LML maybe, but not on a LMM that I can find. Several claims it can be done, and if money talks & BS walks, why is there cash still burning a hole in my pocket?
Even have several offers offers to help me dig thru the raw bin file for it, but I don't happen to have a unmolested 52628594.bin. If you do, please share one for science.
So what I stumbled onto trying to figure out the feasibility of a mod, there is 2 MAP pids used in this ECM. Most of you likely know that from using EFIlive. What you might not know, there is actually really two different pids for reading the same MAP sensors values. And they don't match up...
First you have your SAE.MAP pid that is used by many OBDII tools and Apps like Torque.
OBD ID: 0x0B - Intake manifold absolute pressure 0 -255 kPa (Absolute)
The Absolute here means our Dec value returned is absolute or the true kPa # without any scaling math. Same as:
BARO - 0x33 - Absolute Barometric Pressure 0-255 kPa (Absolute)
To get a true boost pressure figure you take the MAP value and subtract the BARO value and it equals your true boost. Sound correct??
Second PID we have is what's listed in EFIlive as GM.BOOST2_DMA or MAP2.
MAP2 reports as kPa while GM.BOOST2_DMA is in PSI. But it's the same PID being requested, converted by EFI.
GM ID: 0x84ae Turbo Boost Pressure 0-366 kPa or 0-53.1psi
So I hooked up my packet sniffer and found this one returns its raw values in Hectopascal or hPa. You divide by 10 to get kPa.
This second pid is typically used by calc pids to display true boost values up to like 39psi after subtracting the baro. Everyone still with me?
So I decided to scale both these out at the same time using a bench ECM, potemimoter, and EFIlive. Full sweep between 0-5v. Guess what, they don't match anywhere. At bottom end they are off by 1lb, mid-scale 3lbs, and over 6lbs at point where the OBD pid stops reporting, 37psi or 255kpa.
I even checked the raw data packets to rule out a typo in EFIlive pid files. Nope it all on GM. Check the pics below tell me what I missed..
-K
Looks highly unlikely anyone has successfully remapped the LBZ/LMM MAP voltage tables before. LLY for certain, LML maybe, but not on a LMM that I can find. Several claims it can be done, and if money talks & BS walks, why is there cash still burning a hole in my pocket?
Even have several offers offers to help me dig thru the raw bin file for it, but I don't happen to have a unmolested 52628594.bin. If you do, please share one for science.
So what I stumbled onto trying to figure out the feasibility of a mod, there is 2 MAP pids used in this ECM. Most of you likely know that from using EFIlive. What you might not know, there is actually really two different pids for reading the same MAP sensors values. And they don't match up...
First you have your SAE.MAP pid that is used by many OBDII tools and Apps like Torque.
OBD ID: 0x0B - Intake manifold absolute pressure 0 -255 kPa (Absolute)
The Absolute here means our Dec value returned is absolute or the true kPa # without any scaling math. Same as:
BARO - 0x33 - Absolute Barometric Pressure 0-255 kPa (Absolute)
To get a true boost pressure figure you take the MAP value and subtract the BARO value and it equals your true boost. Sound correct??
Second PID we have is what's listed in EFIlive as GM.BOOST2_DMA or MAP2.
MAP2 reports as kPa while GM.BOOST2_DMA is in PSI. But it's the same PID being requested, converted by EFI.
GM ID: 0x84ae Turbo Boost Pressure 0-366 kPa or 0-53.1psi
So I hooked up my packet sniffer and found this one returns its raw values in Hectopascal or hPa. You divide by 10 to get kPa.
This second pid is typically used by calc pids to display true boost values up to like 39psi after subtracting the baro. Everyone still with me?
So I decided to scale both these out at the same time using a bench ECM, potemimoter, and EFIlive. Full sweep between 0-5v. Guess what, they don't match anywhere. At bottom end they are off by 1lb, mid-scale 3lbs, and over 6lbs at point where the OBD pid stops reporting, 37psi or 255kpa.
I even checked the raw data packets to rule out a typo in EFIlive pid files. Nope it all on GM. Check the pics below tell me what I missed..
-K
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