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Re: FI questions
In a message dated 97-04-22 19:44:40 EDT, you write:
<< I will grant you that altitude (atmosperic pressure) is important with
respect to setup values, especially with non-O2 sensor (Lambda) equipped
as are the older euro models. The Lambda control circuitry in US cars takes
care of tuning after initial warm-up, all altitude (atmosperic pressure)
affects is initial cold start conditions. I guess our US spec cares are
better than the euros in motor control respects.
The altitude compensation circuit in the 3B is there only to prevent turbo
over-spin. That's what the Audi service training manual says anyway...
Good post, steve. And correct. Altitude compensation, esp on the 3B is only
to prevent that hot spinning k24 from shrapnel. Engine temp and Charge air
temps are easier and cheaper methods of alt compensation when the Lambda
circuit is in place. For all intents and purposes on a turbo (altitude
compensating method, of which audis are) boost is a measure in terms of a
Pressure Ratio (atmospheric + boost/atmospheric or PR = Po + P1/Po), that is
all the computer is looking for, the rest can be addressed by the other
sensors. The computer is programmed to know that beyond a give PR, the turbo
will fail, and therefore the protection, but only for overreving the turbine.