High altitude boost question

Texaco

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MazdaSpeed3
My understanding is that a big advantage of the turbo charger / engine control is that boost is maintained even at higher elevations. This means my MS3 can hit 18psi at sea level and also at 9000 feet (I live at 8600 feet).

It seems though that in order to maintain boost at higher elevations the turbo must spin faster. Could this mean increased wear?

I believe a normally aspirated car up here loses about 10%-15% power. Does this mean my turbo is spinning 10-15% faster to maintain boost at 9000 feet? Do I really have the same power at 9000 feet versus sea level?
 
Do I really have the same power at 9000 feet versus sea level?

not unless ur running higher boost up there. you will be getting the same boost numbers but its not as dense of a charge so theres less oxygen in the charge you are getting so you cant add as much fuel resulting in a loss of power at that altitude. I.e. Kinda like 2 guys with the same motor and same turbo running the same boost but one of them has a way better intercooler, and that guy with the better intercooler will have a more powerful car even thought they are both running the same boost numbers on identical engines. Rule of thumb here is you gain 1% of your engines power for every 6 deg. F you reduce intake air charge because of air density. Which is also affected by altitude ( your situation)

I think the calculations come out to approx 1 psi per thousand feet
so if ur running 18 psi at sea level to actually see similar numbers on a dyno at 9000 ft you will need to increase boost to approx 27psi


As far as the turbo spinning faster to create the same boost level. i really dont think it does but im gonna need to read up on that.
 
i dont know the formula for power loss to elevation though

just know that at about 7200 feet where i used to live @ about 7-10 psi boost people would get the same readings on dynos to n/a cars at sea level
 
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My understanding is that a big advantage of the turbo charger / engine control is that boost is maintained even at higher elevations. This means my MS3 can hit 18psi at sea level and also at 9000 feet (I live at 8600 feet).

It seems though that in order to maintain boost at higher elevations the turbo must spin faster. Could this mean increased wear?

I believe a normally aspirated car up here loses about 10%-15% power. Does this mean my turbo is spinning 10-15% faster to maintain boost at 9000 feet? Do I really have the same power at 9000 feet versus sea level?

Your car will not hit 18psi up here (I am also in CO). Boost is not maintained unless you get a tune. Our ECU doesn't adjust for the lack of atmospheric pressure that is seen at sea level like some cars are able to. I am closer to 5300 being out of the mountains, and the average boost levels for any MS3/MS6 is around 13 at MAX. Most stock cars hold at around 10-11 is all up here sadly, which means that you have no more boost in 3rd-6th than you do in 1st and 2nd usually. Take a road trip to Sea Level with your car and datalog with a scanguage if you have doubts.... I drove to Oklahoma and watched my Max psi go from 12 here to 17-18 there. Big difference, especially 3rd-6th.
 
Great info all. I thought our ECU did try and adjust for lack of atmospheric pressure!

Crap...but I won't doubt the boost numbers eg6motion is seeing here in Colorado.

On the bright side maybe less boost means better long term reliability.

On the not so bright side I have never had this thing below 5000 feet to see how it really runs!
 
Great info all. I thought our ECU did try and adjust for lack of atmospheric pressure!

Crap...but I won't doubt the boost numbers eg6motion is seeing here in Colorado.

On the bright side maybe less boost means better long term reliability.

On the not so bright side I have never had this thing below 5000 feet to see how it really runs!

it's a major downside too...once you experience it. 3rd gear is far more fun at 17-18psi.
 
Sorry to wake an old thread but I recently moved from VA where the altitude was maybe 100 feet above sea level to the Denver area where I am at 6000 feet. I noticed that at altitude my boost spikes to 15.5 and holds at 14. I was seeing 3 psi more in VA. Even though the numbers are different, I still feel like I have the same power. 3rd to 6th doesn't pull as much down low though so I bet the shape of my torque curve changed.

On another note, My idle pressure at altitude is -17 to -15 inHg. In VA I was seeing -22 to 19 inHg.

It took a long time to get used to these differences. At first I thought something was wrong. (It didn't help that I didn't have my boost guage adjusted to the correct altitude when I first got here.)
 
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All you Colorado people should consider checking out coloradomazdaclub.com, where you'll find local peoples and discussions of some of the unique challenges (winters, high elevation) CO poses for fellow Mazda owners.
 
The big advantage turbos have over N/A at altitude is not adjusting for elevation, all EFI cars do that to some degree. The advantage is it doesn't rely on outside air density for it's air charge density. There are fewer oxygens up there, the turbo crams them closer together (more density), unlike N/A which just takes what it can suck in.
 
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