Quote:
Originally Posted by Hersbird
On topic I have often wondered if the thinner air hurt engine efficiency more then it helped aerodynamics. In carborator days I think the mixture became to rich but with modern computers it adjusts. You may lose power but gain mpg. One big reason if towing in high elevations a turbo is nice.
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The thinner air improves engine efficiency if you only need the 10 to 20 horsepower needed to maintain cruising speed. As the air thins, you need to open the throttle wider to produce the same power output, reducing your pumping losses. You get up high enough and you'll be at the desired 80% throttle setting you normally use for accelerating in P&G driving while the engine is only pumping out the 16 horsepower needed for cruising. At this point you're running the equivalent of what would be a 20 horsepower engine if you operated it at full throttle. The turbo just allows you to produce sea level power outputs at higher altitudes, but it doesn't save you any fuel as long as you're using it.