Im trying to understand why its so important to go by sae whp instead of uncorrected. from what my tuner explained to me the sae correction is just multiplying it by a certain percent, where im at its times the uncorrected number by .97

I like my uncorrected number better lol

 

SAE (Society of Automotive Engineers) correction factor, otherwise known as "corrected numbers" is an established baseline, to help increase the accuracy of the numbers a person sees, no matter what dyno they are on. It is the same thing as "EPA rated fuel economy" which means that all automotive manufacturers must perform their fuel rating testing according to the same standard/guidelines established by the EPA. This ensures that testing is the same for all manufacturers and prevents a company from over inflating their fuel economy numbers over another which could have the potential to sway sales.

From what I remember, SAE numbers were all based on an altitude of sea level (or close), a temperature of around 70 degrees and humidity factor of like 68% for example. Because dynos are in all parts of the country and are in various climates and elevations, the only way to create any level of accuracy in the testing numbers they produce is to use the SAE corrected numbers function.

If someone dyno'd at say 5000ft above seal level vs someone at sea level, with the exact same car using SAE numbers, the outcome should be roughly the same numbers from the dyno. If they were using the STD uncorrected numbers, the same car at high altitude will show much lower power output numbers than the car at sea level. The same thing happens when there is a difference in air temperatures during testing and humidity levels.

Some shops like using uncorrected numbers because they are usually higher than SAE numbers and that makes everyone look good and keeps the customer happy. My own personal feeling is there is no good reason for anyone to not use SAE numbers. My car makes more power on STD numbers than SAE but I NEVER refer to them or post them because to me, it's an inaccurate representation of what my car is doing compared to another.

The main thing to remember is that dynos are mainly for testing and tuning only and not for dictating how much a motor actually makes.

 

The correction factor should be variable pending the current conditions.

Whatever numbers/graph you decide to use should be based on the way you are using them.

An example, I'm in Denver, dyno is at ~5600 ft, it's fall/winter, temps are in the 40's-60's and humidity was high(raining). This is the SAE dyno:



Then this is the same engine Uncorrected this time



Naturally, I'm going to setup a 200whp car differently from a 250whp. And it's more exaggerated(of course) with higher power. So if you're using the dyno to find out the trap your shooting for and best gearing, use the uncorrected values. It's going to be the actual output of your car in the conditions you are racing under.

If you're using the graph to compare else-ware while looking for more power, SAE will be the best and most used standard.

It's all best guess anyway. The variance between different dyno's isn't a new idea. So round away and study curve behavior.

 

^^^^This is the best answer/example anyone can give that is easy to understand and visualize.

 

STD is a correction factor.

 

that makes the most sense to me what themidastouch said, Im within 300 feet of sea level and it was a 90 degree day when I tuned my car, which is why i didn't understand why my uncorrected wheel horsepower was less then my sae.

regardless, numbers are just that.... numbers.

 

Because most people like to cry about who has the biggest stick

 

what does it correct for?

 

standard

 

SAE is a correction factor, STD (standard) is NO correction, hence the term "uncorrected".

 

No sir, You would be incorrect. STD is also a correction factor . . The STD correction uses a lower temperature, which will often increase the HP numbers a bit if you are above the temperature. I think it is something like 60 degrees F.

STD is not the same as Un corrected . .. It will read higher than SAE, but not as high as Uncorrected

 

Here is some info:

UNCORRECTED:
It is just that . Uncorrected. No Corrections factors and no set parameters.

SAE:
"SAE (Society of Automotive Engineers), USA. Power is corrected to reference conditions of 29.23 InHg (99 kPa) of dry air and 77 F (25°C). This SAE standard requires a correction for friction torque.

STD:
STD is Another power correction standard determined by the SAE. Power is corrected to reference conditions of 29.92 InHg (103.3 kPa) of dry air and 60 F (15.5°C). Because the reference conditions include higher pressure and cooler air than the SAE standard, these corrected power numbers will always be about 4 % higher than the SAE power numbers. Friction torque is handled in the same way as in the SAE standard."


Here is some quick math (using assumptions and round numbers):

STD:
Air Temperature: 60F
Absolute Pressure: 29.92 inches Hg
Relative Humidity: 0%

Relative Horsepower : 104.8%
Air Density: 1.223kg/m3
Relative Air Density: 99.8%
Density Altitude: 67feet
Virtual Temperature: 60F
Vapor Pressure: 0 inches Hg
Dyno Correction Factor: .955

SAE:
Air Temperature: 77F
Absolute Pressure: 29.23 inches Hg
Relative Humidity: 0%

Relative Horsepower : 100%
Air Density: 1.157kg/m3
Relative Air Density: 94.4%
Density Altitude: 1952feet
Virtual Temperature: 77F
Vapor Pressure: 0 inches Hg
Dyno Correction Factor: 1

 

Winpep is a free download, get it and play around with it. If it says uncorrected it's uncorrected. Otherwise it is corrected (SAE, STD, DIN...)

Uncorrected can be higher or lower than SAE depending on the circumstances...

 

A dyno is just a tuning tool, the actual number is irrelevant. If you got your car dyno'd and then did a modification to it and wanted to see if you gained power you need to correct it. If the day you had it initially dyno's it was 90 degrees out and the day the dyno'd it after modification was only 60 degrees out your numbers are going to be falsely high (if uncorrected). If you are just shooting for the highest numbers so you can impress your buddies, you are just bench racing.

 

+1 for bench racing.

Im gonna have the worlds fastest bench this year.

 

I was trained by Dynojet in Las Vegas on a 248c back in 2000 so it's been a while and is hard to remember everything as I don't spend anywhere near the time on the dyno as I use to. I must say that I do not remember any other setting for the dyno other than SAE or STD which we always referred to as "uncorrected". Obviously the STD setting has factors set into it which are used to calculate power but by my basic definition of the term, I never considered it a "correction factor", just another setting.

 

I do beleive std is one of the like 8 correction factors that they have.

 

it really doesn't matter what correction factor you use as long as the car is properly tuned out.

many e-racers like to claim big dyno numbers without having track times to back them up, so they enjoy nice correction factors. For instance, some guy claims 270 WHP with his car that weighs in at 1950 with driver, yet he can only run 11.8@115.... well then we know something is wrong. Most all motor guys know that 270 WHP in a 1950 lb car should at worst run bottom 11's.

Honestly I'd rather run nice ET's with less claimed power, showing that I have better skills at making a fat power curve and setting my car up to efficiently run down the track.

 

If that were indeed true , then by your definition, SAE would just be another setting as well . .


haha yes sir . . . Thats why i love our mustang dyno . . . aka the heartbreaker haha. . .

284hp , 2100lbs , 10sec ETs . . lol

 

There is also a large misunderstanding of the actual figures coming from various brands of dyno. How can a certain brand that gives both wheel and estimated flywheel power show both as being lower than the high reading brand which has only one output that everyone assumes to be wheel power?
I hate dyno's because of the utter misuse and abuse they take and all the misinformation that arises from this.

Back to OP. SAE will give you the best chance of comparing changes made. Uncorrected ... well you might as well write down 50 different bhp numbers onto small bits of paper and pull one out of a hat at random!! If any of you want to sound "BIG" down the blue oyster bar, stick to uncorrected.

 

correct, however it was considered a "corrected" setting since it was an equalized standard all dynos would be measured and compared by.

 

Since lots of dynojet plots get posted with the STD correction factor that would seem to fit the same criteria.

 

well for the record, the definition of uncorrected is absolutely what the car actually put down for power at that very moment..

 

My question would then be, are all dyno STD settings (parameters) exactly the same? if they are and cannot be manipulated, then I would agree.

 

A DynoJet rep once told me that STD was DynoJet's 'in-house' correction factor, that should be used to compare between other DynoJet's.

This is just what I remember and the rep may have been full of it, but it makes sense, since no other dynamometer seems to have an 'STD' correction factor.

Absolutely. When I am done with a tune, I always print the graph in both Uncorrected and SAE, one representing what power the car is actually making given the current environment, and the other what they can use to compare to other people's builds and power numbers.