Can altitude affect my boost levels?
06-26-05, 12:22 AM
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Can altitude affect my boost levels?
So I live in Atlanta which is pretty much at sea level but I go to school at Virginia Tech which is sorta-kinda in the Appilachian mountains. While at home I was hitting and holding steady at 7-8 psi. Now that I am at school, some times when Im in boost Im only making at most 6 psi, is this the altitude affecting it?
06-26-05, 12:35 AM
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Very much could be...at higher altitude the air is thinner....you can figure it out from there...less air, less compbustion....less air pressure in general...I don't have a turbo but on all cars I have driven lose power when I go to higher altitudes. If I were you, I would not adjust anything to try and correct that.
06-26-05, 12:48 AM
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06-26-05, 08:24 AM
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Yes, when I lived in Colorado Springs at 6K ft elevation, I would only see a max of 10PSI, now that I live in NJ, I reach 14PSI, and my car feels like a ape that was raped with a much larger piece at sea level vs Colorado..
06-26-05, 09:40 AM
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Originally Posted by Impreza2RX7
Yes, when I lived in Colorado Springs at 6K ft elevation, I would only see a max of 10PSI, now that I live in NJ, I reach 14PSI, and my car feels like a ape that was raped with a much larger piece at sea level vs Colorado..
06-26-05, 03:09 PM
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I can tell you first hand after doing a lot of research and flying around as high as 18000 (so far) that altitude makes a bid difference. Short and simple, at sea level 15psi of boost is a pressure ratio of about 2. At 17,000 feet, 15 PSI is a pressure ratio of 3. Look on most of the compressor maps you can find and you will see that is now at the very upper limit. You can extrapolate for the intermediate altitudes.
Also, since you waste-gate actuator compares the boost pressure to ambient, when you go higher the ambient pressure goes down and the waste gate will open up at a lower boost pressure.
Lastly, 5 psi of boost at SL is about 40" MAP. At 10,000 5psi of boost corresponds to a MAP of a little over 30". And it is MAP (Manifold Absolute Pressure) that makes the horses run.
Also, since you waste-gate actuator compares the boost pressure to ambient, when you go higher the ambient pressure goes down and the waste gate will open up at a lower boost pressure.
Lastly, 5 psi of boost at SL is about 40" MAP. At 10,000 5psi of boost corresponds to a MAP of a little over 30". And it is MAP (Manifold Absolute Pressure) that makes the horses run.
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06-26-05, 05:09 PM
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Originally Posted by homebrewer
I'm lucky in that my turbo car (not an RX7) doesn't have a BOV or wastegate. Its a VNT and is able to provide max boost up to 10,000 feet altitude.
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