High Altitude Performance
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11-14-2016, 10:12 AM
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11-14-2016, 02:34 PM
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11-19-2016, 08:36 PM
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11-19-2016, 09:16 PM
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It isn't just the thinner air. It's the lower atmospheric pressure. Atmospheric pressure is what pushes the air into the cylinders when the pistons travel down. Less pressure means less air getting into the cylinder. Then the computer reduces the amount of fuel injected based on inputs from the oxygen sensors.
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11-23-2016, 01:15 PM
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11-25-2016, 10:54 PM
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Here is the formula for a naturally aspirated vehicle.
HP Loss = (elevation x 0.03 x horsepower @ sea level)/1000
It is less for force induction, but how much will depend on a few things.
Mcstiff on another forum says it well:
HP Loss = (elevation x 0.03 x horsepower @ sea level)/1000
It is less for force induction, but how much will depend on a few things.
Mcstiff on another forum says it well:
One thing to remember is that a turbo is not rated for a specific psi.
Turbo efficiency is measured against flow at a specific pressure ratio. Altitude requires a higher pressure ratio to maintain the same flow and this commonly pushes the turbocharger to a lower efficiency island. Lower efficiency raises heat.
Another thing to consider is that the efficiency of the intercooler is reduced because of lower air density; again increasing heat.
Lastly, a cubic foot of air in Denver contains fewer molecules of oxygen. This means that to burn the same amount of fuel, basically making x hp, as at sea level the turbo has to flow more air. Heat again.
Turbo efficiency is measured against flow at a specific pressure ratio. Altitude requires a higher pressure ratio to maintain the same flow and this commonly pushes the turbocharger to a lower efficiency island. Lower efficiency raises heat.
Another thing to consider is that the efficiency of the intercooler is reduced because of lower air density; again increasing heat.
Lastly, a cubic foot of air in Denver contains fewer molecules of oxygen. This means that to burn the same amount of fuel, basically making x hp, as at sea level the turbo has to flow more air. Heat again.