Until the last several months I had never seen anything such as corrected and uncorrected hp and tq numbers. What is the difference, and how do you determine what is correct and what is not?

 

Corrected numbers use a correction factor to compensate for temperature, humidity, and barometric pressure.

On a turbodiesel, the raw numbers are usually more instructive. The turbodiesel tends to be less effected by changes in the weather than a naturally aspirated gasser (which is what the correction factors were developed on). Corrected numbers from a turbodiesel tend to the high side of reality on a hot sweaty summer day, and on the low side of reality on a nice crisp Fall day.

 

So what your saying if someone dynos on a warm day the numbers will read higher than they actually are and if it's on a cool day they'll read lower than they actually are?

 

Yes, on a hot humid day the correction factor will inflate the HP number and on a cool dry day the correction factor will lower the HP number.

 

makes sence, but how do you calculate?

 

Corrected / Uncorrected try to make things equal sort of like a golf handicap.

The idea is so that you can compare a dyno test result that is performed under all kinds of conditions with the truck about anywhere on the planet earth as if the truck was dyno'ing at place with standard conditions.

Examples of different conditions would be like varying elevations and atmospheric conditions, as stated above.

A standard condition would be something like the conditions at sea level with xxx atmospheric pressure, yyy ambient temperature and zzz relative humidity (etc...). These standard condtions remain the same and never change. So if a truck dyno'd exactly at these standard conditions the corrected and uncorrected numbers would be exactly equal.

Like a golf handicap, with a corrected number you never really know for sure who really played the best due to a fudge factor so it is a bit subjective at times.

Jim

 

And there are different correction factors to correct to different "standard day" conditions. For instance, ISO (International Standards Organization) standard day conditions are sea level and 15 degC (59 degF). For decades, however, industrial engines in the U.S. were rated at 1500 ft elevation and 80 degF. So, if a dyno operator gives you "corrected" data, the question you should ask is "corrected to what?"

Rust

 

Scroll to the bottom of this page for mathematical equation. Plus there is a bunch of other interesting information about dynos.

http://www.dynamometer.fsnet.co.uk/a...on-factors.htm