Hi all,

I was wondering if anyone has had experience tuning at high elevations? Specifically, 5000-6500 feet? How does that affect the tune?

Here are my thoughts: I would think that at high elevation, the thin air and pressure will make the car run even richer with the stock tune. It also probably has a harder time making as much boost.

My guess would be that given the same map, the car would run richer at 5000 feet than sea level. So if my car was tuned for the high elevation, I could probably run leaner fuel maps than another car at sea level. Is that true? Similarly, I might have to raise the wastegate duty cycles in order to achieve the desired peak boost? Thanks for any ideas!

The engine will be less responsive off-boost and take a longer time to build boost - that's just due to there being less air at that altitude.

As far as fueling and timing - the system will detect less air and dispense [less] fuel accordingly.

Trust me... it sucks

The engine will be less responsive off-boost and take a longer time to build boost - that's just due to there being less air at that altitude.

As far as fueling and timing - the system will detect less air and dispense [less] fuel accordingly.

Thanks, I was thinking and reading more about this. My guess is the car will be hitting lower load cells, so I'll be fine tuning lower load cells compared to others at sea level. Also, I read more about how hard the turbo has to work at high elevation. It seems that I may need to adjust the boost targets lower so the turbo is not out of its efficiency range. I may only be able to hit a 20-22 psi peak at this elevation. The good news seems to be that at this elevation, the car might be able to run more timing without knocking. Does this sound right?


Trust me... it sucks

Any tips to make it suck less? ;)

If you look at a compressor map, you will generally see pressure ratio on the left vertical scale with airflow across the horizontal scale. Then assorted efficiency ovals and speed curves in the chart itself.

At higher altitude the inlet pressure will be lower, say ambient pressure in the 12 PSIA range for 5-6K so for 22 PSIG boost pressure, the Pressure Ratio will be higher. Example:

1 bar of boost, 14 PSIG, at sea level makes ~28.6 PSIA while at 6K altitude it makes only ~26.6. So the pressure out/pressure in gets higher at higher altitude:

28.6/14.6 = 1.958 PR
26.6/12.6 = 2.111 PR

And the airflow would change a wee bit also, but not as much. So you can look at the comp map to see where the efficiency moves to but also watch for max shaft speeds and surging on the maps.

Any tips to make it suck less? Actually you want it, the engine, to suck more, and faster.

Do things that allow the boost to come on sooner/faster. Off-boost will be further away from the detonation limit, and generally the air is colder. The jury is still out on whether to advance or retard ignition timing to make better boost response (advancing allows the engine to increase in RPM quicker while retarding keeps more heat in the exhaust).

HTH!

Actually you want it, the engine, to suck more, and faster.

:godance:

Any tips to make it suck less? ;)

a bigger turbo is the best cure. honestly.

your going to get dismal gains compared to someone like me (I'm at about 100ft above sea level) a big turbo with a 50 dry shot, or 75-100 wet, to help her spool up will make that thing a beast, but that wont be too cheap.

Thanks guys for the feedback. I plan on keeping the car stock, so does anyone have the compressor map for the stock x turbo? I've tried searching and can't seem to find it anywhere :(

a bigger turbo is the best cure. honestly. That just increases the lag times compared to what the engine has now. On-boost will be better but getting there will be worse.

You also need to consider whether that car will ever come down off the hill and be careful to not do things that will require retuning just for a trip down the hill.

Yeah, definately not a bigger turbo...

The stock turbo is starving for air as it is. Looking at the problem from outside the box would suggest just more air... and how do you increase air flow? New filter or intake.