At what temperature and barometric pressure is the STD conversion to SAE equal to each other? In other words, if you dyno on 100 degree day your STD will be low but correct up for SAE while if you dyno on a 40 degree day your STD will correct down for SAE. Where do they fall on par with each other? I'm assuming it's somewhere around 76 degrees and around 30.2 pressure [in].

 

SAE horsepower is based on 77deg F and barometric pressure at sea level which is 29.92 inhg or 14.696psi. There are deration factors for increase in temperature and elevation.

 

I started to say inches of mercury (hg). Thanks for the info. I think my next dyno will be as close to that mark as possible. For no real reason other than to have a 1 to 1 output.

 

There are 2 SAE correction factors.

I found the information below on a different forum:


Dyno correction factors allow a person to compare various results acquired under different test conditions.

As an example, let's say you dyno your car on a hot summer day and make 315hp. Unhappy with these results, you then install long tube headers in the fall and dyno again to see your gains. This time you make 360hp, now the question arises how much of this 45hp gain was from the headers and how much was from the now cooler(denser) fall air.

To answer these question correction factors were developed, one of the early standards was SAE J607. Another correction factor known as STD is a modified version of J607. J607 itself was replaced by J1349 which is known today as SAE. The test conditions for J607, SAE and STD are as follows.

Correction Factor.........Temperature.......Station Pressure....... Humidity
J607......................... 60° F...............29.92 inHg...............0%
J1349 (SAE)...............77.................. .29.234 inHg.............0%
STD......................... 77...................29.92 inHg...............0%

Here you can see that STD is assuming denser air and this will reflect in higher numbers when compared with SAE.

With this information you can apply a correction factor that will allow you to compare results taken under different conditions. The best calculator I have found is located here, you should be able to use it to convert between Uncorrected, STD, and SAE at will assuming you have the test conditions. I also intend to create my own calculator that will allow you to input your hp along with the conditions and return the results for all common correction factors but this project is still a work in progress.