Banks experiment - altitude and hp
Neat video...I skipped past some of the explanation portion as it drug on some. His 8.1L starts out at 347hp and then drops to 285hp at 5600'. Video
Forum Discussion
4x4ord wrote:ShinerBock wrote:
Haven't watched the video, but that is about right doing the math. An N/A engine drops about 3% power every 1,000 ft above sea level.
3 x 5.6 = 16.8
347 hp - 16.8% = 289 hp
Not too far off.
Not that it makes a huge difference but if the power drops off 3% every 1000 feet the power would have dropped to:
.97^5.6 x 347 = 292.6 HP
To determine what percent hp drop there is per 1000 feet of elevation gain when the engine went from 347 down to 285 hp over 5600 feet of elevation gain you would set up an equation like this:
x^5.6 * 347 = 285 so x^5.6 =.8213 and therefore x = .8213^(1/5.6) or .965 which means that the power drops off 3.5% per 1000 feet of elevation gain.
I guess I should have explained it better, but I figured the math I stated would have. It is a cumulative 3% every 1000 ft from hp at sea level, not 3% off from every value at each 1,000 ft in elevation. That is the way it was explained to me from an engineer at Cummins that will get you the closes to actual. It seems that they were correct based on the cumulative percentage being closer to the actual number stated. It just used as a general rule of thumb, and not exact science.
