Correction Factors the same as bench racing?
Here is the info on how STD (standard) correction differs from the others:
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."
Skyline- 105 with some really good driving and a fairly light car. I have seen bonestock Evos (255-260whp on a dynojet) run 103-104 personally so I think it might be able to do it if everything came together.
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."
Skyline- 105 with some really good driving and a fairly light car. I have seen bonestock Evos (255-260whp on a dynojet) run 103-104 personally so I think it might be able to do it if everything came together.
Well if you view it as tool it doesnt matter. If you want to be able to compare A to B and never wonder about a dyno that has been played with you have to have a dyno that cant be manipulated.
This thread was more about correction factors than anything, since it seems that people get hung up on whether something is uncorrected what does it read corrected and vice versa. Its why I have taken to posting both numbers for those that want to compare to a local dynojet and also see what the car made that day.
We have people that will race all year long and be on the dyno 3 or 4 seperate times a year to see what the car is doing. I have one customer named Jesse that likes to know where his car is at all times. I have dyno'd it in the fairly average temps of spring, the 100+ heat of summer and most recently in the 19-20* weather of dry winter. Corrected his car is always right on where I'd expect it. Uncorrected it is within 40whp depending on ambient temps. He knows when most of the guys he races have dyno'd so he can do the math and figure out where they are on a given race vs where he is.
I think uncorrected numbers are legit and what should be posted (even if it means dynoing twice a year) because I cant race "corrected", I am what I am to quote Descartes.
This thread was more about correction factors than anything, since it seems that people get hung up on whether something is uncorrected what does it read corrected and vice versa. Its why I have taken to posting both numbers for those that want to compare to a local dynojet and also see what the car made that day.
We have people that will race all year long and be on the dyno 3 or 4 seperate times a year to see what the car is doing. I have one customer named Jesse that likes to know where his car is at all times. I have dyno'd it in the fairly average temps of spring, the 100+ heat of summer and most recently in the 19-20* weather of dry winter. Corrected his car is always right on where I'd expect it. Uncorrected it is within 40whp depending on ambient temps. He knows when most of the guys he races have dyno'd so he can do the math and figure out where they are on a given race vs where he is.
I think uncorrected numbers are legit and what should be posted (even if it means dynoing twice a year) because I cant race "corrected", I am what I am to quote Descartes.
It's always nice to be able to compare output with other cars in the country, but ultimately trap speeds are the most defined system of "checks and balances" that dyno operators can refer to.
I always prefer to use uncorrected figures. I don't particularly prefer a machine trying to calculate power up or down based on weather conditions. Living in NY we have weather swings from 25deg - 100deg. I know for a fact the car will make more power in colder climates, and I know for a fact the car will have higher trap speeds in colder climates. It's a given that the same car with the same tune and the same set of parts will make more power on a 30deg day vs a 90 deg day-- This is real power due to better quality air-- I don't want it taken away from the output.
In these recent times correction factoring has been mis-used by those who use dyno output as a sales ploy instead of a tuning tool-- And this is just wrong. When I first started tuning on dyno's I wanted a means to dial in a car on a 4th gear roll with vehicle speeds in excess of 140mph. Something that I considered too dangerous to do on the road. Minor fueling and timing changes let me know what created the best TQ---- I didn't even care about horsepower, because tq and traction are what move vehicle weight quickly through the 1/4mile.
Now that the "Dyno Queen" term has been born, peak hp on a piece of paper determines who is the best Tuner and who has the fastest car---- Not for me. I'll just keep sticking to maximizing the avg power/tq under the useable curve.
I am really enjoying this topic.
I was always very interested in the "dyno brand name debate". I understand now very clearly that the dyno operator plays more of a role than the brand of the dyno being used.
It's always nice to be able to compare output with other cars in the country, but ultimately trap speeds are the most defined system of "checks and balances" that dyno operators can refer to.
...
I am really enjoying this topic.
It's always nice to be able to compare output with other cars in the country, but ultimately trap speeds are the most defined system of "checks and balances" that dyno operators can refer to.
...
I am really enjoying this topic.
I think all vendors should only use uncorrected numbers as WCF is a worthless and sometimes seemingly a grossly overcorrected number--again, TTP's Mustang dyno read 495WHP (WCF) on my GT30 on pump gas whereas EPIC Motorsport's Mustang dyno in North Carolina read 435WHP (WCF). Nothing was changed on my car's tune at all yet these WCF numbers were significantly off.
BLUF: Weather corrected numbers seem to overcorrect, and are about as useful as any other ESTIMATION of a car's power output. I agree with Lucas. Trap speeds and uncorrected numbers are the best way to measure a car's performance.
This is an interesting topic but it seems to end in controversy every time. What irritates me about WCF numbers is that some vendors show ONLY those numbers. TTP does this a lot, in my impression. Yes, they're in Florida and it's always hot and humid so uncorrected numbers won't be the most impressive to customers, but AWD Motorsports is right there too breaking drag records. I'm sure there's other vendors that do this but I'm just speaking from experience.
I think all vendors should only use uncorrected numbers as WCF is a worthless and sometimes seemingly a grossly overcorrected number--again, TTP's Mustang dyno read 495WHP (WCF) on my GT30 on pump gas whereas EPIC Motorsport's Mustang dyno in North Carolina read 435WHP (WCF). Nothing was changed on my car's tune at all yet these WCF numbers were significantly off.
BLUF: Weather corrected numbers seem to overcorrect, and are about as useful as any other ESTIMATION of a car's power output. I agree with Lucas. Trap speeds and uncorrected numbers are the best way to measure a car's performance.
I think all vendors should only use uncorrected numbers as WCF is a worthless and sometimes seemingly a grossly overcorrected number--again, TTP's Mustang dyno read 495WHP (WCF) on my GT30 on pump gas whereas EPIC Motorsport's Mustang dyno in North Carolina read 435WHP (WCF). Nothing was changed on my car's tune at all yet these WCF numbers were significantly off.
BLUF: Weather corrected numbers seem to overcorrect, and are about as useful as any other ESTIMATION of a car's power output. I agree with Lucas. Trap speeds and uncorrected numbers are the best way to measure a car's performance.
I'm off to the snow, cheers all
- Bryan
Registered User
Joined: Nov 2007
Posts: 1,507
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From: Trinidad
Rav,
Weather correction is all relative to the form of correction being used:
http://www.land-and-sea.com/dyno-tec...horsepower.htm
So SAE is designed to correct to a day that is 77*F and 0% humidity. Basically for you since this temp is probably a little more average than here in the NW the correction is really relative to the ambient humidity the day that you dyno.
I believe all the major "schools" of correction are listed in that link, including the ones we'd never ever use.
Aaron
Weather correction is all relative to the form of correction being used:
http://www.land-and-sea.com/dyno-tec...horsepower.htm
So SAE is designed to correct to a day that is 77*F and 0% humidity. Basically for you since this temp is probably a little more average than here in the NW the correction is really relative to the ambient humidity the day that you dyno.
I believe all the major "schools" of correction are listed in that link, including the ones we'd never ever use.
Aaron
SAE: 498whp
Uncorrectted: 505whp
STD: 515whp
Thanks though, seems like a simple thing, stick with uncorrected settings for actual road conditions. in addition we have no real seasons or temperature swings.
Yes, they're in Florida and it's always hot and humid so uncorrected numbers won't be the most impressive to customers. I'm sure there's other vendors that do this but I'm just speaking from experience.
I think all vendors should only use uncorrected numbers as WCF is a worthless and sometimes seemingly a grossly overcorrected number--again, TTP's Mustang dyno read 495WHP (WCF) on my GT30 on pump gas whereas EPIC Motorsport's Mustang dyno in North Carolina read 435WHP (WCF).
I think all vendors should only use uncorrected numbers as WCF is a worthless and sometimes seemingly a grossly overcorrected number--again, TTP's Mustang dyno read 495WHP (WCF) on my GT30 on pump gas whereas EPIC Motorsport's Mustang dyno in North Carolina read 435WHP (WCF).
If you take a car with WCF in 98*F heat of sea level FL with 98% humidity using WCF which will increase whp due to extreme humidity and will raise figures and if you then take it to Fayetteville, NC at 59*F, at 0% humidity, the WCF will LOWER
whp figures so you will get a moronic dyno comparison.
YES YOU HEARD CORRECTLY. IF YOU DYNO YOUR CAR WITH WCF ON A MUSTANG DYNO BELOW 77*F, YOU WILL END UP WITH READING LOWER WITH WCF THAN 1.00% UNCORRECTED!
Dynoing a car with positive WCF on one dyno and comparing it to a car with NEGATIVE weather correction factor in another geographic location is about the dumbest thing you can do.
A positive corrected WCF dyno should be compared to an uncorrected dyno when a temperature above SAE J1349 77*F is used, the altitude is equal or lower and when the humidity is lower.
This is a sample WCF vs. UNCORRECTED reading from RIGHT NOW:
As you can see, we LOSE about 4% of our whp numbers at the current weather as of this minute. If we are to use UNCORRECTED FIGURES, they are about 4% HIGHER than WCF!
WCF should only be used when over the SAE threshold where a more northern location with colder temperatures, lower altitude and or lower humidity would increase power output on a car with the same exact tune. The power gains solely from changes in intake air temps, lower humidity=denser, more powerful air charge and lower altitude=denser, more powerful air charge.
It is easy to day "OUR SHOP NEVER USES WCF" when you are located on Long Island, NY currently 24*F, Low of 18*F, snow on the ground, 18% humidity and at sea level. Or how about Vancouver, WA in the Northwest corner of the continental USA, the closest land state to Canada and Alaska? Currently 37*F, low of 32*F tonight.
"I live in a median to colder climate which will never benefit from WCF, only from uncorrected figures, so you should use uncorrected figures too!" The funny part is that uncorrected numbers for median to colder climate locations have a WIN-WIN situation. Their dyno numbers are always in their favor "higher" during the warmer months, and then when the colder seasons arrive, the dyno numbers go even HIGHER!
You think it is a brilliant representative idea to compare 68*F with 50% humidity uncorrected to uncorrected to represent an apples to apples comparison of performance?
How much do you think 44*F drop in intake air temperature is worth? Sounds like the same effect a N20 or C02 sprayer has on a FMIC. Huge drops in charge air density and temperature, resistance to detonation and knock.
How about a 32% drop in humidity? Cool, dryer air makes more power, correct?
So it would make sense to compare the same car uncorrected in 24*F, 18% humidity to a car at 68*F with 50% humidity? Perfectly Logical?
WCF should be used for southern hemisphere and tropical climate dyno facilities and only during the months in which the temperature, humidity and altitude are higher than the SAE J1349 formula numbers of 77*F, 0% humidity and sea level altitute.
The exception being high altitude dyno facilities such as Colorado.
Originally Posted by Land-N_Sea
What is Corrected Horsepower?
We have all seen and made claims of an engine’s horsepower. However, this stated horsepower is almost never what the engine actually made for power. How can that be? Most of the stated horsepower numbers are “Corrected” values. The correction standards were developed to discount the observed horsepower readings taken at different locations and weather conditions. It is obvious that an engine builder in Colorado could not produce as much horsepower as a shop at sea level. There is just less oxygen for the engine to burn at the higher altitude. What are less obvious are the other weather condition effects on the engine. So in order to compensate for this all advertised horsepower is “corrected” to several different industry standards.
Most of you know about Atmospheric Correction Factors that are used to compare an engines power output for one day or location to another. However, these factors can be rather confusing and even deceptive. Everybody seems to declare there engine’s horsepower as “etched in stone” number, however we also know that the engine will make very different power on different days. Excluding other factors like engine temperature and quality of fuel used, the engine output is very dependant on the amount of oxygen in the air. So the only way to compare an engine’s horsepower is to correct the output on a given day to some standard.
The most common are the SAE standards. The older J607 standard considers that the engine was run on a 60°F day with 0% humidity and a barometric pressure of 29.92 in-Hg or the newer SAE J1349 standard of 77°F (25°C) day with 0% humidity and a barometric pressure of 29.234 in-Hg (99 KPa). Also the ECE standard is the same as the SAE J1349, but does not use mechanical efficiency in the calculations. The DIN standard which corrects to 68°F (20° C) day with 0% humidity and a barometric pressure of 29.92 in-Hg (101.3 KPa) and the JIS standard corrects 77°F (25° C) day with 0% humidity and a barometric pressure of 29.234 in-Hg (99 KPa), but uses different correction curves than the others (as a substitution for using mechanical efficiency factors). Further, we have the J1995 corrects 77°F (25° C) day with 0% humidity and a barometric pressure of 29.53 in-Hg (100 KPa).
Since very few engines are actually run in these conditions we apply these correction factors so that it is possible to compare the results taken on different days. First lets just look at the weather correction, we will see the second section dealing with mechanical efficiency later. Consider if you take a baseline run of a normally aspirated four stroke V-8 engine on a sultry day in late August, say 85°F and 85% humidity and 28.85 in-Hg and the engine produced 400 Hp. Then after you finished making all your modifications you retest the engine in late September when it is 55°F and 35% humidity and 30.10 in-Hg, the engine now makes 442 Hp. That’s almost an 11 percent increase in Hp, however the engine is actually producing the exact same amount of horsepower according to the J607 correction values of 400 Hp * 1.1005 ≈ 440 Hp and 442 * 0.994 ≈ 440 Hp. If you had retested the engine in the same weather conditions it would have made 400 Hp again.
We have all seen and made claims of an engine’s horsepower. However, this stated horsepower is almost never what the engine actually made for power. How can that be? Most of the stated horsepower numbers are “Corrected” values. The correction standards were developed to discount the observed horsepower readings taken at different locations and weather conditions. It is obvious that an engine builder in Colorado could not produce as much horsepower as a shop at sea level. There is just less oxygen for the engine to burn at the higher altitude. What are less obvious are the other weather condition effects on the engine. So in order to compensate for this all advertised horsepower is “corrected” to several different industry standards.
Most of you know about Atmospheric Correction Factors that are used to compare an engines power output for one day or location to another. However, these factors can be rather confusing and even deceptive. Everybody seems to declare there engine’s horsepower as “etched in stone” number, however we also know that the engine will make very different power on different days. Excluding other factors like engine temperature and quality of fuel used, the engine output is very dependant on the amount of oxygen in the air. So the only way to compare an engine’s horsepower is to correct the output on a given day to some standard.
The most common are the SAE standards. The older J607 standard considers that the engine was run on a 60°F day with 0% humidity and a barometric pressure of 29.92 in-Hg or the newer SAE J1349 standard of 77°F (25°C) day with 0% humidity and a barometric pressure of 29.234 in-Hg (99 KPa). Also the ECE standard is the same as the SAE J1349, but does not use mechanical efficiency in the calculations. The DIN standard which corrects to 68°F (20° C) day with 0% humidity and a barometric pressure of 29.92 in-Hg (101.3 KPa) and the JIS standard corrects 77°F (25° C) day with 0% humidity and a barometric pressure of 29.234 in-Hg (99 KPa), but uses different correction curves than the others (as a substitution for using mechanical efficiency factors). Further, we have the J1995 corrects 77°F (25° C) day with 0% humidity and a barometric pressure of 29.53 in-Hg (100 KPa).
Since very few engines are actually run in these conditions we apply these correction factors so that it is possible to compare the results taken on different days. First lets just look at the weather correction, we will see the second section dealing with mechanical efficiency later. Consider if you take a baseline run of a normally aspirated four stroke V-8 engine on a sultry day in late August, say 85°F and 85% humidity and 28.85 in-Hg and the engine produced 400 Hp. Then after you finished making all your modifications you retest the engine in late September when it is 55°F and 35% humidity and 30.10 in-Hg, the engine now makes 442 Hp. That’s almost an 11 percent increase in Hp, however the engine is actually producing the exact same amount of horsepower according to the J607 correction values of 400 Hp * 1.1005 ≈ 440 Hp and 442 * 0.994 ≈ 440 Hp. If you had retested the engine in the same weather conditions it would have made 400 Hp again.
Last edited by TTP Engineering; Dec 29, 2009 at 02:11 PM.
Actually Scott you missed the point and the post.
The point is the car needs to have a graph of both posted up since it doesnt stay 37* here all year long. If your weather doesnt change much then there is not a need to post anything but uncorrected numbers. If it has WIDE swings then yes it does need to have it posted up. I post both so people have a very definite feel of what the car is doing in a variety of climates.
On our dyno and the aforementioned customer, the 44* drop was worth 23whp on a car that made 625.xx corrected and 647.xx uncorrected. We are not half a$$ed as to only ever use the one standard, we show both to show what the car made and what you can compare it to.
People that cling to correction just to make their numbers better because its 118* and 100% humidity do their customers a disservice, just as the ones that live in 18* weather and 0% humidity do. Showing what the car did and what you can compare it to is the only fair way to post numbers. Or as was pointed out, just go by trap speeds.
The point is the car needs to have a graph of both posted up since it doesnt stay 37* here all year long. If your weather doesnt change much then there is not a need to post anything but uncorrected numbers. If it has WIDE swings then yes it does need to have it posted up. I post both so people have a very definite feel of what the car is doing in a variety of climates.
On our dyno and the aforementioned customer, the 44* drop was worth 23whp on a car that made 625.xx corrected and 647.xx uncorrected. We are not half a$$ed as to only ever use the one standard, we show both to show what the car made and what you can compare it to.
People that cling to correction just to make their numbers better because its 118* and 100% humidity do their customers a disservice, just as the ones that live in 18* weather and 0% humidity do. Showing what the car did and what you can compare it to is the only fair way to post numbers. Or as was pointed out, just go by trap speeds.
Last edited by JohnBradley; Dec 29, 2009 at 02:24 PM.
I am uncertain what the point is. First of all, the site rules clearly state that this section requires a dynosheet in the first post as this forum is used for dyno RESULTS. Technical data belongs in general or engine/drivetrain.
We appreciate your DATA documenting a 23whp difference in a 44* drop in temperature. To the geniuses stating "all dyno's should be run uncorrected", you will notice that those types of post seem to always come from geographic locations where snow is guaranteed to fall and are certainly not in shorts and a t-shirt with the air conditioning on as we are here typing this now.
It is no one's right or responsibility to dictate the rules regarding dyno results, however it should be explained to anyone whom asks, how numbers are obtained, what correction factor is being utilized, the dyno room temperature and humidity info recalled and whether the sheet is corrected or not.
Educating members on how dyno numbers are acheived, how geographic climate
variances can benefit or detract from your numbers depending on location and temps alone and demonstrating like you have above that the same car can change 24whp as stated above from climate differences alone does not mean that you have better or worse tune in your vehicle.
When I first read your post above I thought that you may have ACTUALLY tested a car under different climates. I would be more interested in an ACTUAL test where a 424x DJ test was run on car A in 32*F, then at 68*F uncorrected to uncorrected and see what the actual test results would should.
We appreciate your DATA documenting a 23whp difference in a 44* drop in temperature. To the geniuses stating "all dyno's should be run uncorrected", you will notice that those types of post seem to always come from geographic locations where snow is guaranteed to fall and are certainly not in shorts and a t-shirt with the air conditioning on as we are here typing this now.
It is no one's right or responsibility to dictate the rules regarding dyno results, however it should be explained to anyone whom asks, how numbers are obtained, what correction factor is being utilized, the dyno room temperature and humidity info recalled and whether the sheet is corrected or not.
Educating members on how dyno numbers are acheived, how geographic climate
variances can benefit or detract from your numbers depending on location and temps alone and demonstrating like you have above that the same car can change 24whp as stated above from climate differences alone does not mean that you have better or worse tune in your vehicle.
When I first read your post above I thought that you may have ACTUALLY tested a car under different climates. I would be more interested in an ACTUAL test where a 424x DJ test was run on car A in 32*F, then at 68*F uncorrected to uncorrected and see what the actual test results would should.
Actually Scott you missed the point and the post.
The pdoint is the car needs to have a graph of both posted up since it doesnt stay 37* here all year long. If your weather doesnt change much then there is not a need to post anything but uncorrected numbers. If it has WIDE swings then yes it does need to have it posted up. I post both so people have a very definite feel of what the car is doing in a variety of climates.
On our dyno and the aforementioned customer, the 44* drop was worth 23whp on a car that made 625.xx corrected and 647.xx uncorrected. We are not half a$$ed as to only ever use the one standard, we show both to show what the car made and what you can compare it to.
People that cling to correction just to make their numbers better because its 118* and 100% humidity do their customers a disservice, just as the ones that live in 18* weather and 0% humidity do. Showing what the car did and what you can compare it to is the only fair way to post numbers. Or as was pointed out, just go by trap speeds.
The pdoint is the car needs to have a graph of both posted up since it doesnt stay 37* here all year long. If your weather doesnt change much then there is not a need to post anything but uncorrected numbers. If it has WIDE swings then yes it does need to have it posted up. I post both so people have a very definite feel of what the car is doing in a variety of climates.
On our dyno and the aforementioned customer, the 44* drop was worth 23whp on a car that made 625.xx corrected and 647.xx uncorrected. We are not half a$$ed as to only ever use the one standard, we show both to show what the car made and what you can compare it to.
People that cling to correction just to make their numbers better because its 118* and 100% humidity do their customers a disservice, just as the ones that live in 18* weather and 0% humidity do. Showing what the car did and what you can compare it to is the only fair way to post numbers. Or as was pointed out, just go by trap speeds.
Last edited by TTP Engineering; Dec 29, 2009 at 02:51 PM.