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An engine will run more efficiently at low altitudes because of a dense air. That's why you make more horsepower at sea level.
There is a 33% loss of horsepower at 12,000 feet altitude as compared to sea-level.
Less air -> less fuel for a given throttle position. Engine computer in closed loop reduces fuel to compensate for less air. Result is less power.
So, biological computer in the left seat compensates for less power by increasing throttle position to increase power to maintain speed. Result is same fuel burn. Overall, there is less total power
available at WOT
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fyi, turbo or non turbo diesel engines do not have a carb only gas engines do..
A dirty air filter could restrict air flow enough to cause a problem. I had a similar problem with my central and after installing a new filter the power came back to normal.
Please tell me you didn't revive a 10-month-old resolved thread to post this Captain Obvious statement.
So when a manufacturer claims a certain horsepower do they adjust that figure for altitude and assume sea level to get the highest number or do they actually test at sea level?
Let me try to tackle this question as my experience is mostly altitude & concrete. At sea level there is a pressure equivalent to 10 meters of water pressing down on all of us all the time. This is because of the weight of the air above us in the atmosphere. When you travel up a mountain, there is less air above you in the atmosphere,
The important effect of this decrease in pressure is this: in a given volume of air, there are fewer molecules present. This is really just another way of saying that the pressure is lower. (This is called Boyle's law.) The percentage of those molecules that are oxygen is exactly the same: 21%. The problem is that there are fewer molecules of everything present, including oxygen. Less Molecules=Less Energy
This is why rockets or most rockets get into space because they carry boat loads of stored molecules in Hydrogen & Oxygen is separate tanks.
There are exceptions as in solid rockets that use chemical reactions, but if you look at the chemistry Oxygen is produced.
We all love watching the funny cars run on Nitro, but Nitrous Oxide has tons of oxygen stored as a liquid. I am lousy explaining things but I tried.
Back in the early 80's when there were still a lot of carburetors on vehicles, I would remove the top of the air intake and it would seem to help out some at high altitude. Would at least keep it running better. On newer vehicles, I thought the computer maximized the running power. I understand the loss of power at higher altitude, but the computer compensates to some degree.
I am wondering how hyrbid 4 cylinder engines perform at high altitude and if there is a benefit in performance. Has anyone rue a Ford Fusion or some other hybrid at high altitude? If so, how do they do when climbing and accelerating?
<>I am wondering how hyrbid 4 cylinder engines perform at high altitude and if there is a benefit in performance. Has anyone rue a Ford Fusion or some other hybrid at high altitude? If so, how do they do when climbing and accelerating?
Air pressure has little to no effect on electrons.
BTW, did you notice the date of the original post?
"Bump"
Back when carbureted engines were the norm, I saw a formula that said rule of thumb is 3% loss of power for every thousand feet of elevation gain. Supposedly, FI engines automatically adjust so that the loss isn't as big, but they still lose some power.
So, for the carbureted engine at 7000 to 8000 ft, that would be 21 to 24% loss, which is huge, and definitely noticeable in a low-hp engine.
I had a similar experience when I moved to CO 30 yrs ago. My truck at that time had a carbureted 2.0L 4cyl engine. I was mortified by how anemic it was climbing mountain grades on I-70 and US285. (Short hills on lower-speed roads were not a problem.) A dealer checked it and made some adjustments, but it didn't make much difference. Downshifting and revving higher than I normally would helped.
The solution that I found satisfactory was something else: My next truck had a 6cyl engine. And the one after that, and the one after that...
Get yourself some forced induction and you'll be fine. A turbo does just fine at elevation but you do lose power in NA motors. Not exactly the same but my car runs better in the fall than other seasons, cooler less dense air vs. hot muggy, humid air makes a difference.
When this thread was started ... cars still had carburetors !! :-0
A FI car / engine still looses approximately 3.5% of its HP for every 1,000 feet of elevation gain.
The computer will adjust the fuel / air ratio (the the engine will run better / cleaner) but FI engine still loose HP unless turbocharged or supercharged.
Most (all?) published HP figures are adjusted for / report the HP at sea level.
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