Cisco-Kid

Why do turbo cars perform better at high alt then NA cars? Is it because you can raise the boost to compensate for the loss of Oxygen? Thanks

Bubba-SanŽ

more air = more combustion = more power

all cars are affected by atmospheric pressure. boosted cars can compensate.

non-boosted cars air supply is limited by the ambient atmospheric pressure. at high altitudes that is less than 1 bar. (pressure at sea level = 1 bar)

boosted cars air supply is limited by their waste gate (ECU controlled in S4). the turbo will work harder to pump that thin air but you will get significantly more than ambient pressure.<p>'00 Silver S4
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el rojo

ECU allows intake pressure to be a certain maximum value. At altitude the turbo can therefore be allowed to spin faster to achieve that value, regardless (almost) of ambient pressure.

JayP

You can thank the Pike's Peak Hillclimb cars for that bit of technology.

Bubba-SanŽ

Anyone know how to edit these posts?<p>'00 Silver S4
UUC Shortshifter - 40%
MTM Pads, ATE Blue Fluid
APR SS Brake Lines
Neuspeed 19mm Rear Bar
StonGard Clear Bra
Tenzo AutoRing Pedals
Red Calipers

mrsteve

Everything you then post is editable.

winder

the temp and pressure of the exhaust is about the same at alt as sea level.
with less dense intake air the turbos spool faster. though it does take more volume to create the same boost pressure/compressed intake density.

i drove my Eclipse from Denver to LA and it had more punch off a lite at sea level than "up here". was only marginally stronger further up the revs/boost.

John

it does at sea level?"

It sounds as though the turbo can compensate for loss of air at higher altitudes, thereby making high altitude performance roughly equal to sea level performance. So there is no improvement, but there is no lack of performance that normally aspirated cars suffer at higher altitudes.