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Turbos at Altitude (more)


Vehicle Information: Year: 2003; Body Type: Coupe; Total Mileage: 4400;

Thanks for the information regarding boost pressure at altitude. It's still rather unclear as to whether or not the Turbo can compensate for the lesser air pressure at altitude. I've heard that the power loss for a normally aspirated car can be about 15% at our 'mile high' altitude. If the turbo can compensate for this, it's a great feature indeed.If the ECU is measuring boost pressure, the key is to know how it is measuring, and to what reference it's comparing. As I see it, pressure is relative, and if the ECU compares boost pressure to the outside air, then it is not compensating at all.Perhaps someone has done Dyno testing somewhere is Colorado? Looking forward to your reply...quote:The 996tt ECU regulates the boost pressure rather than the air mass flow as was done with the 993tt. There is a very involved description of the system function and design in the factory Service Information Technik publication, PNA.488.120 pages 2-5 and 2-6. I don't see anything about altitude compensation per se. I suspect the compensation is from the values seen by the sensors and by following the standard logic, not by referencing anything to sea level.

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