So i had my evo 8 tuned in california at sea level, im running basic mods, intake, full exhaust, evo 9 turbo, evo x bov and a bigger intercooler. I just moved to oregon and I live at about 3500-3900 feet elevation and the car has been running pretty iffy lately, i did a 3rd gear pull and this started happening, is this because of the elevation? My target boost is 24 psi and my car is really struggling to hit that now. I did a boost leak test and there was a very small leak coming from the screw hole to adjust the idle


please chime in if you can, thanks

 

Was that a full throttle pull?

Partial throttle flutter is normal if your DV is modified.

You will want it re-tuned however. Less air up there.

 

that was about 70% throttle, there was a couple times i did WOT and it got up to 15 psi and bounced around it and would not pass it

 

If the car is on a electronic boost solenoid on the factory ecu id say the elevation might be the issue.

 

yep, its on that setup, My tuner reccomended I get an MBC and turn the boost down. Shouldnt the tune self compensate for the elevation?

 

No, the ecu can only compensate so much. It's already been modified, so that window gets smaller.

It's been given a set of values based on how much air it should see, to calculate how much fuel. It's not getting enough air now, so it throws the equation off.

 

Most likely the ecu is causing the boost solenoid to open the waste-gate erratically.

 

When you go up in altitude , several things happen.
The air is thinner and a turbo works on "pressure ratios".
It's going to max out earlier because to make the same boost level, it's got to work at a greater pressure ratio.
Your boost gauge might read wrong. how far wrong depends on whether it's a mechanical gauge, MAP sensor based gauge (absolute pressure) electronic gauge referenced to atmosphere.


A factory BOV will start to open at a preset pressure, the actual pressure depends on the BOV. At 24 PSI boost , it'll be open a bit anyway, add to that the turbo nearly maxed out, that's what limits the boost.


If it's tuned properly, the altitude doesn't matter.
A stock ECU measured volume air, temp and barometer to give mass air flow.
SD measures the manifold density and estimates VE.

But if it's tuned wrong, it's wrong.

 

i think i need an mbc and/or retune, im going to take the car to lower elevation this week and see how it runs. i noticed when im 1000 feet lower it runs noticeably better.