I just took a trip up to Montana from California. started at roughly sea level, passed about 7200 feet elevation at donner pass and through Nevada and Idaho it was mostly about 4500 feet. final elevation at lake Hebgen Montana was 6600 feet.
I drove my 08 LMM CCLB DRW, not towing but a few hundred pounds in the bed.
didn't have any problems getting there that i know of but when i was there and restarted the truck (now running on the high altitude tables) it was very laggy. so much so that while stopped i could press the pedal all the way to the floor and the truck wouldn't move until 30 seconds or so later. the RPMs would slowly climb and the truck would creep forward and then start to move. once moving it didn't have nearly as much lag and was tolerable but pulling into traffic was dangerous.
so i pulled out my laptop, Efi Live and V2 (always make sure to have it on long road trips) and looked over the tune. i also did some google searching to see if anyone else has done any similar tuning changes.
i did notice that i had set up the boost pressure for the medium and high altitude tables incorrectly. forgot to compensate for the PSI differences between altitudes correctly. made the changes in the tune and uploaded it. i also changed the air fuel ratio table to allow it give more fuel for spooling as it wasn't even giving a haze.
anyways, this helped but it was still pretty laggy and vary low on power.
i did a few logs to see if i could figure it out. what i noticed was the vanes would close down to 100% most of the time when driving. the few times it didn't the truck drove much better had more responsiveness. i believe the the PID controls are overriding the max vane table and forcing them closed because it didn't see enough boost, thus choking off the flow and preventing boost
being that i don't go up to higher elevations too much, logging and tweaking could take many years for me.
for those that have done their own tuning with Efi Live and have successively tuned for medium and high elevations, how much more timing did you add and how was boost setup relative to your low elevation tables? did you adjust the fuel pressure too?
sorry if this is a bit long
thanks Jason
I drove my 08 LMM CCLB DRW, not towing but a few hundred pounds in the bed.
didn't have any problems getting there that i know of but when i was there and restarted the truck (now running on the high altitude tables) it was very laggy. so much so that while stopped i could press the pedal all the way to the floor and the truck wouldn't move until 30 seconds or so later. the RPMs would slowly climb and the truck would creep forward and then start to move. once moving it didn't have nearly as much lag and was tolerable but pulling into traffic was dangerous.
so i pulled out my laptop, Efi Live and V2 (always make sure to have it on long road trips) and looked over the tune. i also did some google searching to see if anyone else has done any similar tuning changes.
i did notice that i had set up the boost pressure for the medium and high altitude tables incorrectly. forgot to compensate for the PSI differences between altitudes correctly. made the changes in the tune and uploaded it. i also changed the air fuel ratio table to allow it give more fuel for spooling as it wasn't even giving a haze.
anyways, this helped but it was still pretty laggy and vary low on power.
i did a few logs to see if i could figure it out. what i noticed was the vanes would close down to 100% most of the time when driving. the few times it didn't the truck drove much better had more responsiveness. i believe the the PID controls are overriding the max vane table and forcing them closed because it didn't see enough boost, thus choking off the flow and preventing boost
being that i don't go up to higher elevations too much, logging and tweaking could take many years for me.
for those that have done their own tuning with Efi Live and have successively tuned for medium and high elevations, how much more timing did you add and how was boost setup relative to your low elevation tables? did you adjust the fuel pressure too?
sorry if this is a bit long
thanks Jason