SAE vs Uncorrected
Thread Starter
Safety Car
Joined: Mar 1999
Posts: 3,611
Likes: 182
From: Toronto, Canada
SAE vs Uncorrected
Is it better to compare forced induction cars uncorrected?
I've been comparing cars with different power levels and noticed when uncorrected in good weather they pick up a lot of power vs sae.
Two cars with similiar power make about the same sae, but if one of the cars was dynoed in better weather it makes much more uncorrected!
Your thoughts?
I've been comparing cars with different power levels and noticed when uncorrected in good weather they pick up a lot of power vs sae.
Two cars with similiar power make about the same sae, but if one of the cars was dynoed in better weather it makes much more uncorrected!
Your thoughts?
Melting Slicks
Joined: Aug 2008
Posts: 3,451
Likes: 27
From: Bay Area CA
My thoughts are....you never see people compare 1/4 mile ET's corrected for weather. They show what they did on that day, at that track. So for me.....same holds true for dyno numbers. What did it do on that day, on that dyno
Pro
Joined: Feb 2005
Posts: 652
Likes: 16
From: Upton MA
Uncorrected is the actual horsepower the car put down to the drum at the time of measurement. Corrected is the calculations made for what it would have put down under STP conditions, standard temp and pressure also water vapor.
If for example you lived in Denver your actual horsepower to the drum would ony be about 80% of your corrected because of lower atmospheric pressure.
If you are using the same dyno evrytime the biggest correction will be temparature. The colder it is the higher the horsepower to the drum. SAE is an attemp to give you the same number you would get at STP.
If for example you lived in Denver your actual horsepower to the drum would ony be about 80% of your corrected because of lower atmospheric pressure.
If you are using the same dyno evrytime the biggest correction will be temparature. The colder it is the higher the horsepower to the drum. SAE is an attemp to give you the same number you would get at STP.
Le Mans Master
Joined: Jul 2005
Posts: 7,121
Likes: 3
From: Shreveport/Bossier Louisiana
St. Jude Donor '08
Awsome numbers,
but... why are you SAE correcting a turbo setup? I was told a while back by Dynojet themselves and if you read on how J1349 is, that a system that controls the amount of boost via pressure (wastegate) eliminates correction needs... as you obtain same amount of pressure of air regardless of elevation.
you will hit x amount of boost, lets say its 16psi regardless if your 3000ft up or sea level.
and 16psi of air contains the same weight of oxygen regardless where you are. (because it is a positive pressure) The only thing that changes is the curve, you obtain your desired boost quicker because you gather more air per impeller rotation at sea level vs high up so your power curve shifts. Uncorrected should be used for truer numbers.
Is Dan Hourigan at dynojet wrong to say No correction for turbos? No. and here is why...
SAE correction for turbo charged cars is not correct because turbo's run off wastegates and a set boost pressure. This pressure will be reached regardless of elevation. Spring pressures don't change.
The content makeup of 'air' does not change the higher you go up either, the oxygen, nitrogen, argon, co2 etc is just spread further apart... but when compressed, its the same. 16psi of air collected from 10,000ft will contain the same o2 content as 16psi of air collected from sea level. (one just takes longer to collect)
There are light factors that come into play such as turbos will spin faster at higher elevation and create more heat and possibly exit their ideal efficiency range, but overall these variances are no where near how much SAE corrects for. The other is if the turbo is maxed out, as in, not reaching boost spring pressure.
but... why are you SAE correcting a turbo setup? I was told a while back by Dynojet themselves and if you read on how J1349 is, that a system that controls the amount of boost via pressure (wastegate) eliminates correction needs... as you obtain same amount of pressure of air regardless of elevation.
you will hit x amount of boost, lets say its 16psi regardless if your 3000ft up or sea level.
and 16psi of air contains the same weight of oxygen regardless where you are. (because it is a positive pressure) The only thing that changes is the curve, you obtain your desired boost quicker because you gather more air per impeller rotation at sea level vs high up so your power curve shifts. Uncorrected should be used for truer numbers.
Is Dan Hourigan at dynojet wrong to say No correction for turbos? No. and here is why...
SAE correction for turbo charged cars is not correct because turbo's run off wastegates and a set boost pressure. This pressure will be reached regardless of elevation. Spring pressures don't change.
The content makeup of 'air' does not change the higher you go up either, the oxygen, nitrogen, argon, co2 etc is just spread further apart... but when compressed, its the same. 16psi of air collected from 10,000ft will contain the same o2 content as 16psi of air collected from sea level. (one just takes longer to collect)
There are light factors that come into play such as turbos will spin faster at higher elevation and create more heat and possibly exit their ideal efficiency range, but overall these variances are no where near how much SAE corrects for. The other is if the turbo is maxed out, as in, not reaching boost spring pressure.
Melting Slicks
Joined: Mar 2007
Posts: 2,158
Likes: 1
From: Always In Front, Colorado
