The science hasn't changed. Less air, less power. Feel free to Google if you need proof.

I did google it. If I had found anything I would not have wasted my time asking you for your proof. Obviously, you have none.

Andy do you work for Toyota, or do you just make things up?

What is your source?

http://www.greenhybrid.com/discuss/f...ountains-6361/

http://www.greenhybrid.com/discuss/f...ountains-4939/

http://www.greenhybrid.com/discuss/f...39/index2.html

You can't be serious? Their are tons of available calculations to determine horsepower loss at altitude. Pilots use them. Drag racers use them. Supercharged engines, carburated engines, mass-air lambda sond computer engines... No matter how new or old, if they have less air to breathe, make less horsepower. There is no magic, only physics...

http://www.csgnetwork.com/relhumhpcalc.html Here's a java script calculator. <<This Relative Horsepower Calculator determines the relative torque and horsepower available at any temperature, barometric pressure, humidity, and altitude. The calculations are derived from public domain information, SAE J1349 Revision, June of 1990. The calculator shows you how much the air conditions on any given day will alter the horsepower of a normally aspirated internal combustion engine. This calculator uses relative humidity which requires some caution because the relative humidity changes radically during the day as the air temperature changes. To use this calculator, just enter the temperature, barometric pressure, humidity and altitude and click on the calculate button. Air density is affected by the temperature and humidity of the air. On a hot day, or at high altitude, or on a moist day, the air is less dense. A reduction in air density reduces the amount of oxygen available for combustion and therefore reduces the engine horsepower and torque. This calculator shows you how much the air conditions on any given day will alter the horsepower of a normally aspirated internal combustion engine. For example, at 85 degrees F, 30.14 Inches Hg (mercury) barometer reading, 40% relative humidity and 5000 feet altitude, the engine only produces about 81.1% of the rated horsepower. The dynamometer correction factor shown above is the reciprocal of the relative horsepower number. The dynamometer correction factor, the actual air pressure and the vapor pressure are included for comparisons to DynoJet chassis dynamometer test data. The air temperature should ideally be the temperature of the air that is going into your engine. The barometric pressure is the corrected to sea level atmospheric pressure that is typically reported on the local news or may be available from a local airport (this is not the same as absolute pressure, actual air pressure or station pressure). The humidity and barometric pressure can generally be gathered from a local weather report or the national weather service. The humidity inside a closed building may be markedly different from the outdoor readings. The altitude can be found on topographical maps or by calling a local airport. For these calculations, the standard conditions are air temperature 77 degrees F, 29.235 Inches Hg Barometer, 0 feet altitude, 0% relative humidity. >>

OK, I was wrong.

From what I have been able to find, horsepower losses in carbureted engines would usually be significantly more because they do not automatically adjust the air intake to compensate for the lower air pressure.

From my own experience, I haven't really noticed a significant power loss driving at high altitudes. I guess you have to try to drive in a manner that would require the extra power before you would realize that it wasn't there.

AND absolutely right that modern engines with mass air sensors and high volumetric efficiency don't notice the difference near as much as dinosaur cars with carburators.

MM

OK, so I'm a little late to answer the question but we just bought a 2008 Highlander Hybrid Limited and returned from a trip to Steamboat from Oklahoma which required two trips throught the Eisenhower tunnel. We had no problem passing trucks, cars or anything else that was moving slower than 75. We had two adults, 2 kids and all the ski gear. As a sidebar, we averaged 25.6 mpg between Denver and Silverthorne and 34.3 mpg between Silverthorne and Steamboat. We're loving it!

What, pray tell, did you feed Google? I tried "engine power altitude" and got back 300k hits, with this calculator as the first -- http://wahiduddin.net/calc/calc_hp_dp.htm which also corrects for temperature and humidity. 3% reduction in power per 1000 feet of altitude is a pretty standard approximation.

I think carburetted engines of old lost power due to both the thinning air as well as the fuel/air mixture going wrong, whereas modern automotive FI does a better job of compensating the mixture with altitude. They still lose power due to altitude.

Benton 3may08

I admitted I was wrong four months ago. Try reading post #15.

Nice first post.

Didn't realize the topic was going stale, I started with the most recently active thread and worked my way back, hit this thread pretty early. I just started reading the forum a couple days ago and registered today. Thought I had a couple factoids to toss on the fire. Sure, air gets thinner with altitude; thought that was obvious if not taught in HS science. Heat cuts engine performance just like altitude. Humidity too, in so far as it displaces O2. Water vapor also cuts air density -- an H2O molecule is lighter than either N2 or O2. (Funny, that.) All those affect engine performance.

Your body reacts the same way. The FAA sez pilots of unpressurized aircraft must use supplemental oxygen when above 10k feet for more than a half hour and at all times above 12k feet. You body is an engine...

Ah, so many firsts in a life well lived. Hey, make it one to remember!

Yeah, I debated whether to post that, or at least change the tone. I guess I didn't debate long enough. So, seriously, what did you feed Google? Picking keywords to get a best result can be an art, but to fail completely? (I Googled 'hybrid car forum' to find my way here, worked a charm -- first result!) I've apparently become too comfortable on the other forums and mail-lists I follow where we yank each other's chains regularly. I'm the new kid (heh!) here, and could have taken a little more time to gauge the tone.

I've a million questions and maybe a few answers. The block-heater thread was particularly interesting -- the hybrid in the family is the wife's daily driver. We've been a little disappointed that it's not making anything like book numbers through the cold season (if you can call the Willamette valley cold in the winter,) and had already attributed it to her short commute and the engine running a larger fraction of the drive than average. When I drive it, carefully and on longer runs, I think I can do somewhat better than the window-sheet numbers.

Benton 4may08