Cars at altitude - Economy

[Quint]

Was giving it a bit of thought and i figured that if you drove your car (specifically, turbo) at a high altitude, lets say the desert road, so ~800m above sea level, The air would be of a lower density when it is inducted into the turbo, so it'd have to spin that little bit more to get the air to the same amount of pressure as you would at sea level, thereby makeing your car less effeciant because of the extra spooling the turbo would need before it added any gain to the engine.

What do you reckon? true? false? make no differance?

/mindless brain fart.

[HELBND]

iirc, yes thats true

[CozmoNz]

Isnt it monsta Tajemas car or whatever (yeh so i cant spell)

that makes something like 1200 at the bottom of the hill, in race to the sky, and something like 800 at the top?

[Virtual Genocide]

Superchargers were orginally used so that planes would be able to fly alot higher.

[Scotty]

Isnt it monsta Tajemas car or whatever (yeh so i cant spell)

that makes something like 1200 at the bottom of the hill, in race to the sky, and something like 800 at the top?

i thinks his car or maybe one of the pikes peaks car that runs ~30psi at the bottom and ~70psi at the top. so yes you are right

[KinLoud]

Just make sure you know if you are talking about efficiency or power!
Engines can become more efficient at high altitudes.
We lived in Taupo (about 350m above sealevel) for about 3 years - for Sarah's (my partner) Camry we always keep a notebook of km and fuel. We always got an average of 8.1 L/100km in Taupo.
Having lived in Hamilton for the last 20 months we get 8.8L per 100km

If you want power...
Normally aspirated (n/a) engines will lose power as height increase.
Turbo engines, hmmm, well if you start with the turbo working as hard it can to produce boost at sea level then power will decrease as altitude increases. BUT if you set a maximum boost limit and have a turbo capable of more boost than the max... you start with the turbo doing not much work at sea level but work it harder as you climb to keep the boost at the maximum - this means you can keep the power constant up to a much higher altitude.
Also as altitude increases the turbo backpressure decreases. This decrease in backpressure is purely related to the lower atmospheric pressure. The engine has to do a bit less work to spin the turbo. So it can pick up efficiency.
Throttle losses - if you are using less than full power... at sea level the engine is using some of it's power to suck air past the partly closed throttle. This is less efficient.
If you want the same power but are at a higher alttitude the throttle will be wider open so the engine loses less power sucking the air in. This is more efficient.

Ken
Ham
021 408 863

[saft]

you can run lower octane fuel at altitude

[bluemaumau]

Superchargers were orginally used so that planes would be able to fly alot higher.

if thats true its a interesting fact, never would of guessed that

[jasestu]

We lived in Taupo (about 350m above sealevel) for about 3 years - for Sarah's (my partner) Camry we always keep a notebook of km and fuel. We always got an average of 8.1 L/100km in Taupo.
Having lived in Hamilton for the last 20 months we get 8.8L per 100km

Not disputing your other points about altitude (in fact I concur), but can you be certain that the difference in fuel economy is not due to the different type of driving in Taupo vs Hamilton? Also, what's the standard deviation on those averages?

[TrouserFxGt]

Superchargers were orginally used so that planes would be able to fly alot higher.

if thats true its a interesting fact, never would of guessed that

and the turbocharger was a well kept American military secret. The British were kept in the dark about that for ages.