Dyno Season

[plongson]

I wonder if the time of year has an outcome on dyno results. Is the heat of the summer a poor time to look for high numbers or is winter better when the air is cooler and more dense...

[Steve Handy]

My Dynojet 250 has a computer program and a weather station that compensates for altitude ,tempature, and humidity to put the results on a EQUAL playing field...
If you look at my print outs you will see conditions and SAE correction factor...
on my last run on my bike it was 105 deg bar 28.8inhg SAE factor was 1.05.....this means the read out was 5% more than actual reading at that time to compensate for the HEAT...
Hope this helped...
Steve The Dyno Man

[springer-]

Originally Posted by plongson

I wonder if the time of year has an outcome on dyno results. Is the heat of the summer a poor time to look for high numbers or is winter better when the air is cooler and more dense...

This is a part of what is wrong with the dyno industry as a whole. The short answer is yes, it makes a difference. The long answer is the dyno is a tuning tool and using it to look for numbers or for comparing dyno sheets, it just is not accurate. In the example above (no offense Steve, not picking on anyone), the conditions stated will not give an accurate SAE correction number. In the J1349 standard defining the SAE correction factor, Section 5.1 of the AUG2004 revision states that this correction factor is not intended to provide accurate corrections over a wide range of conditions, the range of air temperatures is 59F to 95F, and the range of dry absolute air pressures of 26.57 to 31.00 in-Hg.

Anything outside that range does not fall within the SAE correction standard.

The SAE correction standard also limits the acceptable range of correction to +- 7%. So even if the conditions are within the limits it still may not be considered an acceptable SAE correction. Example, 90F and 27.5 in-Hg with 0 humidity would yield a correction of 1.09 and that is 9%, outside of the acceptable range to put a SAE tag on it.

The SAE formula accepts any numbers plugged into it and outputs a number. All the dyno programs that I am aware of will just apply the formula and spit out a correction factor based on the numbers in and not necessarily based on the SAE standard.

When a Dyno is used as a tuning tool, none of the above matters. When it is used as a comparison standard, it is often misused.

[claytp1]

Originally Posted by springer-

This is a part of what is wrong with the dyno industry as a whole. The short answer is yes, it makes a difference. The long answer is the dyno is a tuning tool and using it to look for numbers or for comparing dyno sheets, it just is not accurate. In the example above (no offense Steve, not picking on anyone), the conditions stated will not give an accurate SAE correction number. In the J1349 standard defining the SAE correction factor, Section 5.1 of the AUG2004 revision states that this correction factor is not intended to provide accurate corrections over a wide range of conditions, the range of air temperatures is 59F to 95F, and the range of dry absolute air pressures of 26.57 to 31.00 in-Hg.

Anything outside that range does not fall within the SAE correction standard.

The SAE correction standard also limits the acceptable range of correction to +- 7%. So even if the conditions are within the limits it still may not be considered an acceptable SAE correction. Example, 90F and 27.5 in-Hg with 0 humidity would yield a correction of 1.09 and that is 9%, outside of the acceptable range to put a SAE tag on it.

The SAE formula accepts any numbers plugged into it and outputs a number. All the dyno programs that I am aware of will just apply the formula and spit out a correction factor based on the numbers in and not necessarily based on the SAE standard.

When a Dyno is used as a tuning tool, none of the above matters. When it is used as a comparison standard, it is often misused.

I would tend to read into your post that the correction factor is determined off of empirical data versus a scientific formula. I.e., they use look up tables for the conditions and take something of an educated guess as to the correction factor.

Correct?

[ejk_dyna]

<<The SAE correction standard also limits the acceptable range of correction to +- 7%. So even if the conditions are within the limits it still may not be considered an acceptable SAE correction. Example, 90F and 27.5 in-Hg with 0 humidity would yield a correction of 1.09 and that is 9%, outside of the acceptable range to put a SAE tag on it.>>

can you explain how CF 1.09 vs 1.07 is 9% outside of the acceptable range? i would think 1.09 is only 1.9% beyond the acceptable limit of 1.07.

[springer-]

Originally Posted by ejk_dyna

<<The SAE correction standard also limits the acceptable range of correction to +- 7%. So even if the conditions are within the limits it still may not be considered an acceptable SAE correction. Example, 90F and 27.5 in-Hg with 0 humidity would yield a correction of 1.09 and that is 9%, outside of the acceptable range to put a SAE tag on it.>>

can you explain how CF 1.09 vs 1.07 is 9% outside of the acceptable range? i would think 1.09 is only 1.9% beyond the acceptable limit of 1.07.

Please re-read the sentance that you refer to. It does not say "9% outside the acceptable range." There is a COMMA after the 9%. It states that it is 9% COMMA outside the acceptable range. This means that is is 9% and that 9% is outside the acceptable range, NOT that it is 9% outside of the acceptable range. There is big difference.

1.09 is 9% AND 9% is outside the acceptable range of +-7% and therefor does not fall in the SAE standards.

[BVBOB]

I will put this in much simpler terms, good air is good air, correction factor or not, I have one example on an 06 RK that made just under 100 torque and low 90's hp last fall, this spring just for the heck of it I put it back on the dyno on a nice cool low humidity day, gained over 5% with no tuning whatsoever, better fuel possibly, who knows, as far as I am concerned the correction factor is helpful in comparing builds from around the country but far from perfect. Too many variables to assume that these numbers from any dyno make or model should be taken as gospel. It's all about making these things run right, not the final numbers.
If there is anything to be gained from the dyno report on a dynojet brand it is the torque curve, this seems to be the only constant that actually carries over to how the bike performs when you actually ride it on the highway. But even that can be manipulated or "enhanced" as the case may be.

[ejk_dyna]

<<Please re-read the sentance that you refer to....There is a COMMA after the 9%.>>

got it. sorry about that.

[C-Cat]

Originally Posted by BVBOB

I will put this in much simpler terms, good air is good air, correction factor or not, I have one example on an 06 RK that made just under 100 torque and low 90's hp last fall, this spring just for the heck of it I put it back on the dyno on a nice cool low humidity day, gained over 5% with no tuning whatsoever, better fuel possibly, who knows, as far as I am concerned the correction factor is helpful in comparing builds from around the country but far from perfect. Too many variables to assume that these numbers from any dyno make or model should be taken as gospel. It's all about making these things run right, not the final numbers.
If there is anything to be gained from the dyno report on a dynojet brand it is the torque curve, this seems to be the only constant that actually carries over to how the bike performs when you actually ride it on the highway. But even that can be manipulated or "enhanced" as the case may be.

that's why some tuners prefer actual. i've seen .20 variaces in my cars et from mid summer to mid october. but drag racing doesn't incorporate a correction factor, even when they race at the high alttitude tracks, times still can't be duplicated no matter how much they change their tune ups. i just know i'm going to get better times in the cooler weather, and a tenth to a fifteenth slower in the hot, humid weather.

[Hillside]

That IS, why some tuners use actual.

[shrinkman2]

Within any statistical research, the goals is 100% fact when the final correlation coefficient is reported. You have to take into account the margin of error to get the overall picture which is a factor given to account for research error in the study. LIKE ALL THAT BULLSTUFF??? LOL Very simply, margin of error is a number that should always be presented in research that says..."this is what we found...er.....give or take thisss much". Research is like tuning...there are just toooo many uncontrolled factors to give an exact report. The correction on a dyno is like the margin or error...it tries to guestimate and correct for all the variable factors (eg. humidity, heat, etc). I HATE RESEARCH!!!!! LOL Isn't this what you're saying Springer???

[Hillside]

The correction factor is calculated, actual, is actually what the machine is doing that day.
The records that are set in competition at NHRA, AHDRA, IDBA, IHRA, etc, are NOT calculated, as that is what that exact vehicle did that day at that track.
Scott

[rodriguc]

Great thread. This has definitely helped me to understand both the industry SAE correction standard and why over the years there was so much controversy regarding dyno results. Results from a tuning/diagonostic tool have been used to support bragging rights. The real question that should have been asked is, can my engine be tuned properly during periods of high humidity or temperatures?

[springer-]

It does not matter what is used for tuning. Actual, SAE, STD, DIN or anything else, when it is tuned, it is tuned.

Margin of error is a little different. The correction factors don't add a margin of error, the brand or type of Dyno, the accuracy of the atmospheric condition and the calibration add a margin of error. Even then it is not a scientific margin of error as much as design limitations, IMO.

Actual should not be confused with Real bona fide TQ/HP by definition. "Actual" on many dynos is a derived number based on a formula and not actually measured. A drag strip is a form of actual measurement based on time, distance and speed in ACTUAL numbers. That time, distance and speed can easily be compared with other numbers from other tracks and be a very accurate comparison since the distance does not change. There are so many more variables in drag racing that the total amount of TQ/HP is usually NOT the deciding factor and therefor have less bearing on what was done on any particular day. The comparison to dyno tuning and numbers is not accurate, IMO.

Originally Posted by rodriguc

Great thread. This has definitely helped me to understand both the industry SAE correction standard and why over the years there was so much controversy regarding dyno results. Results from a tuning/diagonostic tool have been used to support bragging rights. The real question that should have been asked is, can my engine be tuned properly during periods of high humidity or temperatures?

In Blue, This is barely the tip of the iceberg.

In Red, BINGO

In Green, While the ECM is capable of adjustments for a wide range of conditions it is always better to tune an engine in similar conditions to which it is intended to be used. For example, you would not tune a snowmobile in the summer for use in the winter, likewise don't tune your Harley in the winter.

[FLTRI]

Actually I like the idea of doing away with using a correction factor.
I'm @ 165ft above sea level right near the East Bay where the temps are normally mild.

However I'm not sure guys like Steve (GMR) will like the idea as he's about 6k ft above sea level and the temps can go way over 90.

IMO correction factoring is to be used as a playing field leveling device so a bike can be dyno tuned in San Francisco and travel to Denver and get resonably close comparison.

Hope this is taken in the spirit in which it was intended,
Bob