In an effort to get this part of the forum I figured i'd start a thread about correction factors and smoothing, and how they affect the end results on our dyno sheets.

There are many different correction factors, i'll go over the 3 main ones that we see. A modern dyno basically has a weather station built into it, it gives is real time temperature, humidity, barometric pressure and so on. Correction factors were developed to be used as a tool to compare results on different regions of the world. i.e. the results of an engine dyno'd in California could be compared to an engine dyno'd in Detroit, or anywhere else.

I took a bike I tuned recently and decided to use it as an example. I'll post the sheets in the differn't correction factors.

SAE correction: SAE corrects the actual run conditions to a standard of 77°F (25°C) with 0% humidity and a barometric pressure of 29.234 in-Hg (99 KPa).





STD correction: STD corrects to 60F (15.5C)with 0% humidity and a barometric pressure of 29.92 InHg (103.3 kPa)





UNCORRECTED: Uncorrected is exactly what it says, it is what your engine produced at the time it was ran on the dyno. that temp, humidity and barometric pressure.






These are all the same exact run, just with the correction factor changed. If you want to have an accurate comparison you need to make sure that the correction factor is the same. You can see in the example above that this particular bike made 3.71 more HP and 3.83 more torque simply by changing correction factors!! You can see that it made even more power and torque UNCORRECTED, it was an exceptional day when I tuned it. Hopefully this clears up a little on the correction factors and more importantly, how shops can use them to show better results.

 

Let's take this one step further and talk about SMOOTHING. Smoothing is basically exactly as it seams, when you run a bike on a dyno the lines are naturally "choppy", smoothing averages out the peaks and valleys. A smoothing of 0 (zero) has higher "peaks" and lower "valley's" than higher smoothing.

Let's now look at the same charts from above and change the smoothing factor to 0 (zero) and see what happens.

Keep in mind, these are the same exact runs as above, just with smoothing set to 0 (zero).

SAE CF Smoothing 0




STC CF smoothing 0





UNCORRECTED smoothing 0




So by doing nothing but clicking a couple buttons I can take this sheet and go from the lowest (SAE CF smoothing 5) and convert it to the highest (UNCORRECTED smoothing 0) and gain 5.69 HP and 5.82 TRQ

So in conclusion, when comparing dyno sheets make sure you are comparing apples to apples. I'm Leary of shops (in the US) that give printouts in anything other than SAE smoothing 5.

 

Great information, thanks for posting this up.

 

great info,

when a dyno sheet is printed to SAE should it only have the SAE standard run conditions listed on it or are they the run conditions of the day?

 

If you have the time. Post up sheets showing conditions and corrections factors for SAE and STD.

 

Those are the run conditions for the day it was run.

 

I thought of that right as I was posting them, but I saved it to a thumb drive and posted it from home. I'll try to remember der to do it tomorrow when I get to the shop. Thanks Jason

 

Here's the same runs with the Conditions

 

If you take the run file home instead of the Dynojet printouts and download winpep7 on your home PC, you can create whatever view you want at home instead of having to do it at the shop.