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S4 and 91 200TQ 20V boost at high altitude


I checked my documentation and on the 92 S4  (2.15 bar max turbo pressure 
during 15 second overboost condition) the barometric pressure sensor is mounted
 on the top of the ECU and the info says:
 " At altitudes above 3200 feet (low air pressure), the charge pressure is reduced
 to avoid overrevving of the turbocharger. At altitudes above 10,000, the charge
 pressure control system is switched off." Unfortunately it does not say how much
 the boost is lowered under these conditions. It also indicates that the Baro sensor 
is used for cold starting at high altitudes to reduce the chance of flooding the engine.

For the 91 200TQ 20V motor it indicates that the maximum
boost for this motor is 1.82 bar. It has a separately mounted Altitude 
(barometric) sensor and the explanation  says basically the same thing
"At altitudes above 3,300 feet, the boost  pressure is reduced as the altitude
 is increased. The reason for this is to avoid  overreving of the turbocharger". 
It further says " If the sensor should fail, an altitude of 13,124 feet is assumed 
and the boost pressure is reduced to its minimum level".

What turbo pressure is indicated on your S4 when driving at full throttle at 
aprox 5,000 ft in Colorodo?

Scott M.