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Power at altitude! (Revised power loss os 1.41% for every 333 feet)
An explanation of why the T7 is so much superior
to the T5 and other Turbo or non Turbo engines.
First a few rules:
a) Air pressure and oxygen content drop with altitude which reduces engine power by 1.41% every 333 feet of altitude.
b) A high pressure front (good weather) can compensate for this up to 1500 feet of altitude.
Normally Aspirated engine: ie. New Audi 3.0 L 30V
225 Hp up to 1500 feet of altitude, above that it loses
1.41% of power for every 333 feet of altitude.
Normal Turbo car ie Audi TT / T5 SAAB (not tuned)
Through the use of data from the air mass meter
and through the use of a turbo with some reserves
the power can be maintained up to 5000 feet. Above that
altitude the loss in oxygen will lead the engine to lose
1.41% of power every 333 feet.
Tuned normal Turbo car: ie Audi S3 ABT 250Hp
The reserves from the turbo are used to generate more
boost al lower altitudes, as no reserves are left the
engine will behave like a normally aspirated engine,
loosing 1.41% of power every 333 feet above 1500 feet
of altitude.
Saab with T7 ie. 9-5 Aero
Like a normal Turbo car data is obtained from the
air mass meter but also from the Trionic Direct
Ignition which provides data in the oxygen content
during combustion. As the Viggen and Aero are fitted
with larger size turbos the ECU increases boost to
compensate for loss of air pressure like a regular
turbo car but also for the loss of oxygen content.
This allows it to maintain full power up to 10000 feet
of altitude or during severe temperature variations (heat).
So what...
A little chart to explain what that means...
Alt. feet: 1500 5000 8500 10000
S4 265 265 228 209hp
S3 ABT 250 210 174 162hp
Aero 230 230 230 230hp :)
TTs 225 225 193 177hp
A4 30v 225 185 157 146hp
330ci 231 190 161 150p
This chart is an approximation, but it will
give you a good idea on how much more high tech
the T7 system is.
The power loss of only 1% per 333 feet was optimistic...
feel sorry for non T7 drivers...
Regards,
Coolknight
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