Elevation and tuning
 

Curious, do I just have to recalibrate to make sure I'm hitting the psi I was tuned to?

My understanding... Less air higher you go. But if your FI 10lbs is 10lbs. My Turbo might have to work harder to make it, but as long as I re Cal the solenoid to my tuned psi it's good or no?

i think I'm around 6700' but I lost about 3.5 psi??
Any opinions??

For the same boost, the turbo will absolutely spin faster to attain the same boost pressure. This will cause the charge air to be hotter and you'll still be flowing less air for the given volume, as well as the turbo will fall off sooner. This is where you have to map out your turbo to see how far you can push it as you go higher in altitude. Ideally, you should be using barometric compensations to get the turbo to behave how you want it to do, for any given altitude. Ultimately, you should also be logging actual boost vs target boost to ensure the ECU is hitting the boost that is programmed via boost and comp tables.

Here is a recent tune I did on a Subaru... This is a comparison at 9xx ft ASL and 6,xxx ft ASL without any correction factor. The boost we are running at low altitude is not pushing the turbo all that hard, so we run the same boost at this altitude. The slightly lower boost seen on the graph seem to be inherent to that specific run. I was also driving the car on that run and let off at redline... Per the OEM tach.

https://cimg3.ibsrv.net/gimg/www.s2k...51f1fff869.jpg

Is that why on the Dyno at Oahu my boost plot was hitting 15psi but the bbg was only 14.5 and then on the baro and "absolute" it was like +.5psi so that equaled 15 total?

But does this not change every day? Like Altimeter?

Thank you for the response! I have a feel for what your saying, I wish I understood it more.

I checked my elevation last night, I'm in an around 1100' and where I lived on the hill of Oahu we were like 800-900 So is elevation the only thing that would effect a tune from location to location.
This original question was because I was in Colorado Springs at like 6700' and after a replaced Mac solenoid that burnt out or w.e. my DC was even off. So now that I'm closer in altitude would Absolute pressure match ...or correlate to elevation?

I don't know how they are applying it in that dyno, but barometric pressure is the atmospheric pressure around you. It'll change with altitude, heat, storm fronts, etc... Somewhere like here in Denver/Golden, I'll see 10.5-11.5 PSI (5,400 - 9,000 ft) of atmospheric pressure, but then I'll have customers in Omaha that will register low 14's for an atmospheric pressure. You'll use this pressure to calculate into tuning (absolute - atmospheric). On a MAF car, you can easily see how much less air you're flowing, given the same boost for an idea how much air you're really lacking. On many of the maps I've worked out with Subaru's, I have boost decrease as you go up in altitude, however, not the same for every setup. Someone with a larger turbo can push more up here or may be perfectly within the efficiency range of said turbo, so I won't have to bring it down so much at higher altitudes. On my personal Subaru, I run 23 PSI here, 25 PSI around 900 ft ASL, however, the turbo does have enough breath to run 25 up here, I prefer not to work it so hard.

I ended up making a spreadsheet for the way some of the older Subaru's calculate boost compensations based on baro. It just made things easier for me to plan out, input numbers into the map, and have a visual... I'm a visual person. This only covers targets, not what WGDC comps, which I adjust accordingly as well..

https://cimg1.ibsrv.net/gimg/www.s2k...b7c0b9c2ef.jpg

Also this graph is kinda interesting. Because vice versa between each (you said only elevation @ same psi) one provides a ton of mid range but only falls off at the end. I figured the higher elevation or opposite would completely lose in the entire graph in comparison. I'm trying to read an understand it all bc I read the higher you go will spool faster because it's less dense but actually making more power I don't know because it just doesn't make sense to me. Is the solid line the 9xx ASL? I usually call this MSL (mean sea level) are we talking the same thing?

The higher you go, the slower the spool and less air is moved. The graph shows just that. The higher altitude is behind in every way. Compare red vs blue.

Oh duh! Lol. I see the hp n trq cross now.

Lol that's exactly what I figured. I was talking with some drift team from their and they said opposite. Didn't make sense to me honestly.

:Suspicious:

I don't think I have ever seen compensations like that on ktuner or even flash pro for that matter.

but I did see my map (total psi) per Hawaii DC decrease in boost in Co. Springs by almost 2.5-3.0 psi

Thanks for all the info. Great stuff man!