SAE vs. uncorrected numbers, question...
Thread Starter
Safety Car
Joined: Mar 2006
Posts: 3,538
Likes: 9
From: Pasadena, CA
SAE vs. uncorrected numbers, question...
Probably less likely than more, why would SAE numbers be higher than uncorrected? If the uncorrected numbers is the actual power the car is putting out at the time, I'm baffled how SAE numbers would be higher? FWIW, this would be pretty close to sea level.
Race Director
Joined: Dec 2000
Posts: 19,304
Likes: 85
From: San Diego CA
The dyno place that tested my C5 gave me a disc containing the raw data. I then downloaded a small program that allowed me to see what SAE, STD, and I believe, uncorrected numbers.
More info...
More info...
One common use of the dyno correction factor is to standardize the horsepower and torque readings, so that the effects of the ambient temperature and pressure are removed from the readings. By using the dyno correction factor, power and torque readings can be directly compared to the readings taken on some other day, or even taken at some other altitude.
That is, the corrected readings are the same as the result that you would get by taking the car (or engine) to a certain temperature controlled, humidity controlled, pressure controlled dyno shop where they measure "standard" power, based on the carefully controlled temperature, humidity and pressure.
If you take your car to the dyno on a cold day at low altitude, it will make a lot of power. And if you take exactly the same car back to the same dyno on a hot day, it will make less power. But if you take the exact same car to the "standard" dyno (where the temperature, humidity and pressure are all carefully controlled) on those different days, it will always make exactly the same power.
Sometimes you may want to know how much power you are really making on that specific day due to the temperature, humidity and pressure on that day; in that case, you should look at the uncorrected power readings.
But when you want to see how much more power you have solely due to the new headers, or the new cam, then you will find that the corrected power is more useful, since it removes the effects of the temperature, humidity and atmospheric pressure and just shows you how much more (or less) power you have than in your previous tests.
There is no "right" answer... it's simply a matter of how you want to use the information.
If you want to know whether you are going to burn up the tranny with too much power on a cool, humid day, then go to the dyno and look at uncorrected power to see how exactly much power you have under these conditions.
But if you want to compare the effects due to modifications, or you want to compare several different cars at different times, then the corrected readings of the "standard" dyno will be more useful.
That is, the corrected readings are the same as the result that you would get by taking the car (or engine) to a certain temperature controlled, humidity controlled, pressure controlled dyno shop where they measure "standard" power, based on the carefully controlled temperature, humidity and pressure.
If you take your car to the dyno on a cold day at low altitude, it will make a lot of power. And if you take exactly the same car back to the same dyno on a hot day, it will make less power. But if you take the exact same car to the "standard" dyno (where the temperature, humidity and pressure are all carefully controlled) on those different days, it will always make exactly the same power.
Sometimes you may want to know how much power you are really making on that specific day due to the temperature, humidity and pressure on that day; in that case, you should look at the uncorrected power readings.
But when you want to see how much more power you have solely due to the new headers, or the new cam, then you will find that the corrected power is more useful, since it removes the effects of the temperature, humidity and atmospheric pressure and just shows you how much more (or less) power you have than in your previous tests.
There is no "right" answer... it's simply a matter of how you want to use the information.
If you want to know whether you are going to burn up the tranny with too much power on a cool, humid day, then go to the dyno and look at uncorrected power to see how exactly much power you have under these conditions.
But if you want to compare the effects due to modifications, or you want to compare several different cars at different times, then the corrected readings of the "standard" dyno will be more useful.
Thread Starter
Safety Car
Joined: Mar 2006
Posts: 3,538
Likes: 9
From: Pasadena, CA
Interesting, thanks! 
So lets say your SAE numbers are higher than your uncorrected(actual) numbers, could you still rightfully say that the SAE numbers is accurate power of the car?
So lets say your SAE numbers are higher than your uncorrected(actual) numbers, could you still rightfully say that the SAE numbers is accurate power of the car?
Race Director
Joined: Dec 2000
Posts: 19,304
Likes: 85
From: San Diego CA
Yes - under the same conditions during which your car was tested. For example, let's say you had your car tested during the coldest day of the year, and the shop had its doors wide open. Uncorrected, your car would be cranking out some extra-impressive numbers (due to the greated density of the ambient air). So yes, you could always say that your RWHP is that much, but you couldn't compare it to that of another C5's RWHP unless it was tested back-to back with yours. (assuming both are uncorrected HP)
I saw some guys packing ice on their intake manifolds so that they could brag about having higher horsepower than similar cars. Since the dyno doesn't know about the ice, it may produce HP numbers that look extra good, even with correction factors.
I saw some guys packing ice on their intake manifolds so that they could brag about having higher horsepower than similar cars. Since the dyno doesn't know about the ice, it may produce HP numbers that look extra good, even with correction factors.
Safety Car
Joined: Jun 2006
Posts: 3,787
Likes: 2
From: Wildomar CA
uncorrected numbers are worthless. My car put down 427 rwhp before my tune and corrected was 380, then 401 after the tune. It was propably putting down 450ish uncorrected when we were dynoing after the tune. Sometimes the car is being dynoed in ideal situations, but that is rare.
Safety Car
Joined: Mar 2006
Posts: 4,448
Likes: 4
From: Sarasota Florida
St. Jude Donor '06
SAE numbers and STD numbers are simply corrected for different air density. They each use a different definition for "standard air", hence the difference between them.
On a non-computer-controlled car, the correction factors are quite accurate. However, on a computer-controlled car, they are not so accurate, as the computer itself will vary the car's tuning for the climate conditions.
For example, let's say the dyno session is at 100F, which is hotter than SAE standard conditions. The car will very likely be running less timing at WOT than it would if you were at 68F. If you were to compare the SAE numbers for that car at 100F to the SAE numbers for a run at 68F, it's very likely that the 68F run will be higher, even though both are corrected to the same air density, due to the computer dialing in more timing.
With intercooled forced induction cars there's even more of a variance, because the correction factors don't take into account the altered efficiency of the intercooler in different outside air conditions.
We all use SAE to compare cars because that's the best we've got. but your car will still dyno higher SAE on a cold day. If you want to know "the best she'll do" you need to get a dyno session in the winter.
On a non-computer-controlled car, the correction factors are quite accurate. However, on a computer-controlled car, they are not so accurate, as the computer itself will vary the car's tuning for the climate conditions.
For example, let's say the dyno session is at 100F, which is hotter than SAE standard conditions. The car will very likely be running less timing at WOT than it would if you were at 68F. If you were to compare the SAE numbers for that car at 100F to the SAE numbers for a run at 68F, it's very likely that the 68F run will be higher, even though both are corrected to the same air density, due to the computer dialing in more timing.
With intercooled forced induction cars there's even more of a variance, because the correction factors don't take into account the altered efficiency of the intercooler in different outside air conditions.
We all use SAE to compare cars because that's the best we've got. but your car will still dyno higher SAE on a cold day. If you want to know "the best she'll do" you need to get a dyno session in the winter.
Thread Starter
Safety Car
Joined: Mar 2006
Posts: 3,538
Likes: 9
From: Pasadena, CA
SAE numbers and STD numbers are simply corrected for different air density. They each use a different definition for "standard air", hence the difference between them.
On a non-computer-controlled car, the correction factors are quite accurate. However, on a computer-controlled car, they are not so accurate, as the computer itself will vary the car's tuning for the climate conditions.
For example, let's say the dyno session is at 100F, which is hotter than SAE standard conditions. The car will very likely be running less timing at WOT than it would if you were at 68F. If you were to compare the SAE numbers for that car at 100F to the SAE numbers for a run at 68F, it's very likely that the 68F run will be higher, even though both are corrected to the same air density, due to the computer dialing in more timing.
With intercooled forced induction cars there's even more of a variance, because the correction factors don't take into account the altered efficiency of the intercooler in different outside air conditions.
We all use SAE to compare cars because that's the best we've got. but your car will still dyno higher SAE on a cold day. If you want to know "the best she'll do" you need to get a dyno session in the winter.
On a non-computer-controlled car, the correction factors are quite accurate. However, on a computer-controlled car, they are not so accurate, as the computer itself will vary the car's tuning for the climate conditions.
For example, let's say the dyno session is at 100F, which is hotter than SAE standard conditions. The car will very likely be running less timing at WOT than it would if you were at 68F. If you were to compare the SAE numbers for that car at 100F to the SAE numbers for a run at 68F, it's very likely that the 68F run will be higher, even though both are corrected to the same air density, due to the computer dialing in more timing.
With intercooled forced induction cars there's even more of a variance, because the correction factors don't take into account the altered efficiency of the intercooler in different outside air conditions.
We all use SAE to compare cars because that's the best we've got. but your car will still dyno higher SAE on a cold day. If you want to know "the best she'll do" you need to get a dyno session in the winter.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Safety Car
Joined: Mar 2006
Posts: 4,448
Likes: 4
From: Sarasota Florida
St. Jude Donor '06
The current SAE standard is SAE J1349, which is 77F (25C) with 0% humidity and a barometric pressure of 29.23 in-Hg (99 KPa). I'm not sure about STD, but I think they use 68F (20C) with 0% humidity and a barometric pressure of 29.92 in-Hg (101.3 KPa).
If someone thinks I have any of the above wrong, please post a correction.
If someone thinks I have any of the above wrong, please post a correction.
