Where's my power?
#31
11-12-2010, 03:09 PM
Registered User
This is not true. 8psi is 8psi, and 5psi is 5psi. The internal pressure of a turbo charger is independent of the outside air pressure. If the boost gauge reads 8psi, then the turbo is just working a bit harder to make that 8psi at 5000 feet than it would be at sea level.
When we're talking about power production though, the engine at 5000 feet requires 8 p.s.i. above ambient to produce the same power the engine at sea level will produce with 5 p.s.i. above ambient.
If we boosted an engine at 5000 feet with ~3 p.s.i., we'd find we achieve the same power output of an equivalent normally aspirated engine located at sea level - again given the same air temperature and standard pressure.
This is the point I was attempting to make. It takes more boost at higher altitude to produce the same air density that can be produced with less (or no) boost at lower altitude. If we boost our engine at 5000 feet ~3 p.s.i. to do nothing more than counter the effect of altitude we're not stressing the engine internals any more than it would be if it were not boosted and operating at sea level - because it's producing the same power it was rated for from the factory.
I should have left out the p.s.i. reference and been more clear about our goal of attaining horsepower unaffected by altitude.
#32
11-12-2010, 03:21 PM
You're correct that the pressure output by the turbocharger is, for argument's sake, independent of ambient air pressure.
When we're talking about power production though, the engine at 5000 feet requires 8 p.s.i. above ambient to produce the same power the engine at sea level will produce with 5 p.s.i. above ambient.
If we boosted an engine at 5000 feet with ~3 p.s.i., we'd find we achieve the same power output of an equivalent normally aspirated engine located at sea level - again given the same air temperature and standard pressure.
This is the point I was attempting to make. It takes more boost at higher altitude to produce the same air density that can be produced with less (or no) boost at lower altitude. If we boost our engine at 5000 feet ~3 p.s.i. to do nothing more than counter the effect of altitude we're not stressing the engine internals any more than it would be if it were not boosted and operating at sea level - because it's producing the same power it was rated for from the factory.
I should have left out the p.s.i. reference and been more clear about our goal of attaining horsepower unaffected by altitude.
When we're talking about power production though, the engine at 5000 feet requires 8 p.s.i. above ambient to produce the same power the engine at sea level will produce with 5 p.s.i. above ambient.
If we boosted an engine at 5000 feet with ~3 p.s.i., we'd find we achieve the same power output of an equivalent normally aspirated engine located at sea level - again given the same air temperature and standard pressure.
This is the point I was attempting to make. It takes more boost at higher altitude to produce the same air density that can be produced with less (or no) boost at lower altitude. If we boost our engine at 5000 feet ~3 p.s.i. to do nothing more than counter the effect of altitude we're not stressing the engine internals any more than it would be if it were not boosted and operating at sea level - because it's producing the same power it was rated for from the factory.
I should have left out the p.s.i. reference and been more clear about our goal of attaining horsepower unaffected by altitude.
Sounds pretty relevant to me!!
#33
11-12-2010, 04:15 PM
Here's a link to a thread posted by another Colorado resident who wasn't pleased with his g's performance. Ultimately altitude sickness was the diagnosis.
thats my initial thread haha!
I live in colorado too, the altitude does kill our cars. Ive researched it and really not a whole lot you can do to fix it. My car only puts down like 190HP(no dyno, just some math i did lol) after the 5at loss and altitude loss. Keep in mind the elevation and the DA(density altitude) differ.
For instance the elevation can be say 5000FT, but with humidity and temp etc the DA is more like 7800FT(in the hot summer). With the cold tempature here our current DA is 5571 above sea level.
What i was told is for every 1000FT above sea level you lose approx 3% HP.
You can check your DA here: http://www.dragtimes.com/da-density-...calculator.php
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