altitude performance

[2004LB7]

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

 

[tsd_billy]

How Are your high altitude vane tables set up ?


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[IOWA LLY]

I personally think your issue lies in the max fuel vs airflow tables.
Your vane position sounds far from optimum but when you press the throttle from a stop down it should jump forward. Even without boost.

Keep adding fuel until you get a light haze out the tailpipe and your issue will be much less I'll bet.

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[2004LB7]

currently my vane tables are set up with medium being 10% more than low and high being 20% more than low.

my low table seems to be close to actual with the PID control not changing much. when cruising down the highway at about 65~70 at low altitude it seems that the vanes hang out around 35%. when i was cruising at 4500 ft elevation i managed a few times to get it to settle down around 65% but i had to get on the accelerator and let it build a little boost (not easy with the vanes at 100% and choking off flow) and then let off some. i think this make enough boost that when i let off it was now in a different area of the map that called for less boost so it would open up the vanes. then if i manipulated the pedal just right i could get it to settle down at less than 100%.

after i did this it would cruise with less fuel used, better MPG and better power. but it would happily shoot up to 100% the moment there was a mismatch between desired and actual.

I know that my airflow vs fuel table is not dialed in as i have adjusted the PW table quite a bit from stock. i lowered the whole map down by 0.2 so as to allow it to add more fuel at low boost just to see how it responds. it was better but the vanes still didn't want to budge from 100% vary much. after this i could get it to smoke pretty good if i was a little too fast on the accelerator and just a light haze if i eased into it.

compounding this, i couldn't get the actual boost pid to work (likely selected the wrong one) so i was only able to rely on desired boost, desired vane and actual vane, + all of the usual pids such as mm3, duration, timing, etc. and to top it off my AC adaptor crapped out on the trip so i couldn't charge my laptop and had to use what little battery i had left to make whatever changes i needed to the tune and shut down as soon as possible to save battery power.

almost made me want to shut off the PID control/allowing the ECM to control boost just to see how it would drive

 

[IOWA LLY]

Why don't you just set your maximum vane position table down to a reasonable level????

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[2004LB7]

The PID control seems to override that as it is going passed the max vane table. Well i assume that it is the PID control as i have no other explaination for it going past.

 

[tsd_billy]

I'll send you a message with how my vanes are set up for my colorado trips


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[2004LB7]

Thanks. Got it.

 

[2004LB7]

Billy, Do you do anything different for timing? Or fuel pressure?

 

[2004LB7]

Bumping this up instead of making a new thread.

I was messing around with my truck over the weekend, thought maybe I should take it out for a drive as it has been sitting a while and the batteries needed a charge. Anyways I noticed the filter minder sitting in the red and thought to myself "how would it do without any filter?"

Its been raining a bunch here lately and the streets and air is quite clean so I gave it a try.

My god the turbo lag is much worse. But when it lights a second later it hits hard. With the filter it seems to spool normally with little lag but hazes more up top. Without the air filter, it lags a little then hits hard with no smoke

Anyone have any good thoughts on why this is? Is it because the turbo blades now have access to much more air and thus more resistance to turning but when it gets up to speed then it can build higher boost?

I assume if I get a new or better flowing filter then I can probably tune the vanes better in efi live to eliminate or reduce that lag and still get some of the stronger boost mid throttle, am I wrong here?

 

[2004LB7]

Ran a log in a parking lot to see if anything stood out. not sure what to make of it. maybe too much vane position???