Dyno Question

[ViperRon]

If you where to dyno your car at sea level in California and again at 5000 feet in Colorado would the results be the same? I'm think I know the answer but thought I would ask. I've got a friend in Denver with a 2000 Viper and he is very upset with the performance compared to his last Viper.Through the years I seem to think I've had a lot of guys tell me their cars seemed to really start running at around 10,000 miles, the other common denominator was how hard it was driven when it was new.In the 60's I've seen stock 62 Chevy 250 hp 327's beat 62 Chevy 300 hp 327's. Common sense would tell us that should not happen.Just a note back then I had a stock 59 Dodge Royal Lancer, 361 with a 2 barrell carb with a torqueflite trans and a good running 327 four speed would pull me about 1/2 a car length per gear. Done rambling

 

[Sonny 00 GTS ACR]

Hi, I'm sure you guessed correctly. At 5000 ft. you would have less air per volume than at sea-level. With a carbureted engine the jets would need to be changed to introduce less fuel or the mixture would end up being too rich. In an airplane, a normally asperated engine has a mixture adjustment to lean out the mixture as you climb, and richen it as you descend. The horsepower drops as you climb because the appropriate mixture would produce a smaller volume for the engine to use. The same would hold true for an automobile. In cars or airplanes that use turbochargers, the horsepower can be increased or at least maintained based on the extra volume of air available to be mixed with the proper amount of fuel.

I hope this answered you question.

 

[Bob Woodhouse]

Gentlemen: A normally aspirated engine loses 4% of the power it has at Sea Level for every 1000 ft above sea level.
You can also count on dyno's being accurate within some margin of error as all specifications are corrected back to sea level mathematically.
You can also not worry about your air to fuel ratio. These things are under the good management of your on board computer that constantly adjusts the A/F ratio based on many parameters including atmospheric pressure, ie: it knows how high above sea level it is at all times.