You can correct to several different standards. It depends on what you are trying to accomplish.
Off the top of my head, the “standard” most engine dyno’s and flowbench‘s use is 60 degrees, zero humidity and a 29.92 barometer. That is pretty much the standard.
There are other correction “standards” in use, but all they do is change the “corrected” number coming off the software. This is done so you can test year round and you will know if you made an improvement with a 28.32 barometer, 90% humidity and 100 degrees when the tests you made earlier in the year had a 29.00 barometer, 30% humidity and 50 degrees.
If you don’t correct to some “standard” you won’t have a clue if you made or lost power just due to weather changes.
So you should also know all the above data PLUS what standard was used PLUS you should have the uncorrected numbers off the dyno. Because that is exactly what the engine makes for power on that day with that weather. It’s pure science. Is it perfect? No. But it’s closer than going to the track and guessing.
I asked the other guy who thinks a dyno is a waste of time but he didn’t want to answer so I’ll ask you.
How do you test headers at the track? Most headers are a bear to change. On the dyno it’s simple.
How do you do lash loops at the track? You are looking for 5 HP gains or losses. Lash loops give you a clue as to how close you are on cam. It’s near impossible to see 5 hp at the track.
How do you do timing loops at the track? Unless you have a data logger (that has to be well instrumented) you won’t know how much timing you need at peak torque and what you need for timing at peak hp and rpm. Also near impossible to test at the track.
Intake manifolds are about the same. Easier than the typical header, it’s still cumbersome to yank and seal an intake in the car. And to do it correctly you need to do an A-B-A test just to verify your results.
I know that people think the time slip says it all, but it doesn’t. Clearly you can’t test with the engine in the car at the track like you can on a dyno and get even reasonably accurate results.
And I’m not even taking into account the car and all its issues, the driver and his issues, weather and all the rest.
Any decent engine shop has a dyno. It’s not because they are stupid. It’s because the recognize the value of the tool.
Its interesting to see people who live and die by cylinder head flow numbers (which most likely uses the same correction scheme as the dyno does) absolutely claim the dyno numbers don’t mean a thing.
It couldn’t be the car is in need to a serious tune up that the dyno numbers don’t match. Or it could be that the corrected numbers are so far away from the weather at the track that it skews the numbers. That’s not the fault of the dyno. That is an end user issue.
Ive seen correction numbers 200-250 hp higher than the measured numbers a few times. It happens.
There are companies out there that have weather stations and software that allows you to enter the correction factor from the dyno numbers and it measures the current weather and then it gives you the actual hp at that weather.
The dyno is an invaluable tool. You can learn much more, much faster than going to the track. Last time I rented the track for one day it was almost the same money as a day on the dyno.
