High Altitude

Optimistic Paranoid

Optimistic Paranoid

Adventurist
So, the highest drivable paved roads in the world, by continent:

South America - Chivay-Arequipa in Peru, 16,110 feet
Asia - Khunjerab Pass in Pakistan, 15,529 feet
North America - Mount Evans in Colorado, 14,131 feet
Oceana - Mauna Loa in Hawaii, 11,169 feet
Europe - Pico del Veleta in Spain, 11,136 feet
Africa - Tlaeeng Pass in Lethsoto, 10,666 feet

The Indian Army maintains several so-called drivable roads in the Himalaya's that claim altitudes of 17 and 18 thousand feet and even one, at Umlinga La that is slightly over 19,000 feet, but these are gravel and not paved.

I've been pondering this a bit. I'm old enough to remember when we used to use a vacuum gauge to diagnose engines. Normal vacuum was considered 17 to 22 inches of mercury - AT SEA LEVEL - and the rule of thumb was to deduct one inch for each 1,000 feet of elevation. So at 5,000 feet, a normal engine reading would be 12 to 17 inches of mercury.

At 16,000 feet and up, you'd have almost no vacuum at all.

Of course, that's a normally aspirated gasoline engine. I'm not sure that it would apply to diesel engines. And of course, turbo-chargers would also be a game changer.

Some of the things I've been wondering:

Do only diesel engines drive that high?

If you turned a turbo-charged engine off at those kinds of altitudes, could you restart it?

I'm guessing the power brakes that use vacuum stop being power brakes at those altitudes?

I'm wondering if the modern computer controls are programmed to deal with those altitudes? I know they read barometric pressure. I wonder if they would go "and the barometric pressure is - wait a minute, THAT can't be right!"?

Thoughts and guesses, everyone?

BTW, anyone here driven Mount Evans in CO? What was it like?
 
I've had my '05 Rubicon over Imogene Pass in CO that is over 13,000', the Jeep is anemic as all get out but it still runs and stops. 13,114' (https://en.wikipedia.org/wiki/Imogene_Pass)

(Faith and mysticism factoid) I've heard the rule of thumb for a normally aspirated engine is a 10% loss of horsepower per 1000ft. That rule seems too perfect to be true, but what the hell, I'll pass it along.
 
Optimistic Paranoid said:
So, the highest drivable paved roads in the world, by continent:

South America - Chivay-Arequipa in Peru, 16,110 feet
Asia - Khunjerab Pass in Pakistan, 15,529 feet
North America - Mount Evans in Colorado, 14,131 feet
Oceana - Mauna Loa in Hawaii, 11,169 feet
Europe - Pico del Veleta in Spain, 11,136 feet
Africa - Tlaeeng Pass in Lethsoto, 10,666 feet

The Indian Army maintains several so-called drivable roads in the Himalaya's that claim altitudes of 17 and 18 thousand feet and even one, at Umlinga La that is slightly over 19,000 feet, but these are gravel and not paved.

I've been pondering this a bit. I'm old enough to remember when we used to use a vacuum gauge to diagnose engines. Normal vacuum was considered 17 to 22 inches of mercury - AT SEA LEVEL - and the rule of thumb was to deduct one inch for each 1,000 feet of elevation. So at 5,000 feet, a normal engine reading would be 12 to 17 inches of mercury.

At 16,000 feet and up, you'd have almost no vacuum at all.

Of course, that's a normally aspirated gasoline engine. I'm not sure that it would apply to diesel engines. And of course, turbo-chargers would also be a game changer.

Some of the things I've been wondering:

Do only diesel engines drive that high?

If you turned a turbo-charged engine off at those kinds of altitudes, could you restart it?

I'm guessing the power brakes that use vacuum stop being power brakes at those altitudes?

I'm wondering if the modern computer controls are programmed to deal with those altitudes? I know they read barometric pressure. I wonder if they would go "and the barometric pressure is - wait a minute, THAT can't be right!"?

Thoughts and guesses, everyone?

BTW, anyone here driven Mount Evans in CO? What was it like?
Click to expand...

Thoughts? Yes, but in the form of a question...

What other gasoline engines operate at that altitude and even higher?

Literally, hundreds of thousands for decades... :D
 
Obviously, piston aircraft engines. By World War 2, all military engines were supercharged. I've been trying to find a record for the highest altitude achieved by non-supercharged aircraft, just out of curiosity, but have had no luck.
 
I go to 14k+ several times/year here in Colorado. I/we always take the truck because it is turbocharged. Modern fuel injected engines can handle the altitude , but continually detune (less fuel) due to altitude. Even supercharged engines will start to lose power at altitude (depends on fuel maps and boost). I know I start to lose boost around 13,000 feet, not much, but some. Carburated engines generally operate in a much narrower altitude range.

Power loss is a bout 3% or .03/1000ft. 10,000ft: 10 x .03 = .3 or 30%. for turboed engines it is about 1%. Less O2 is still less 02. Overboosting will give the blow off valve a workout.

My truck makes ~365 hp. At 14,000ft the loss would be 14 x .01 x 365 = 51 hp
5.0 coyote makes ~ 360. At 14,000ft the loss would be 14 x .03 x 366 = 151 hp


Mt Evans is very cool.
 
BTW, one of those roads maintained by the Indian Army, built in 1976, was opened to the public in 1988 and has since turned into something of a tourist trap. Many automotive, motorcycle, and even mountain bike expeditions go there, and Wikipedia reports that:

"The elevation of Khardung La is 5,359 m (17,582 ft). Local summit signs and dozens of stores selling shirts in Leh incorrectly claim that its elevation is in the vicinity of 5,602 m (18,379 ft) and that it is the world's highest motorable pass."

That just seems . . . wrong . . .
 
Optimistic Paranoid said:
At 16,000 feet and up, you'd have almost no vacuum at all.
Click to expand...
The vacuum is relative air pressure. A 350 cu” engine will still be taking in 350 cu” of air per revolution. The air, being much less dense at that altitude just contains that much less O2. The “vacuum” in the intake manifold will still measure minus relative to the outside atmosphere as long as the engine is turning, and there is actually some atmosphere.
 
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