Can someone explain something to me [correction factor]

cummins724

cummins724

BREAKING $HIT
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Apr 16, 2007
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I was talking to a guy who came to buy some parts from me. We started chatting about my truck/his "buddy's" truck. I told him my truck did 534hp & he asked what that would be uncorrected [not sure why that matters]. :doh: I have been looking at dyno charts & I just want to be sure on how the correction factor works. If you look at my dyno chart, there is a x= 4.240 in the bottom right corner. How would I go about figuring "uncorrected" numbers?

dyno graph.jpg
 
if you notice up top it says CF: SAE that means they are using the SAE correction factor.

then at the bottom it lists the conditions for temp, barometric pressure, and humidity. those 3 things are used to calculate the SAE correction factor. when you put it through the formula you will get an SAE correction factor of 0.95.
 
Thanks guys. I can't remember who it was that told me that my uncorrected number was 552hp? It was in one of my other threads, but can't recall.

TJ, I noticed on your graph, it also said "Smoothing 5" [top right corner] same as mine. Your numbers are uncorrected.....What does smoothing 5 mean?
 
its the smoothing...if you set it to zero the graph is really jumpy like a richter scale LOL when the smoothing is on 5 it makes the graph look much smoother


also...i think you are right...you dynoed in some nice cold air, ideal for making power. it corrected your numbers down to where they would have been if it was 77*, and 0% humidity. so your true number should be higher than what is on the graph.

534/.95=562 corrected

PS-i made 562 last year...but mine didnt carry for **** like yours does
 
Graphs are often smoothed by taking the running average of the last 3 or 5 (or more) numbers in the data stack.

The graphs can look jaggy because of the electronics. On a load cell dyno, you're taking on-the-fly data from a load cell and then digitizing with an A/D converter. Add in all the other variables and you wind up with less than glass-smooth curves. People don't like those, so they generally smooth 'em up before printing.

We might not all agree on what correction factors to use, but uncorrected numbers are kinda misleading in their own way as well.

If a guy in Cali dynos at 80F and a guy back east dynos at 40F or lower, there should be a difference that needs some kind of reference correction, or you've got apples and oranges.
 
getblown5.9 said:
its the smoothing...if you set it to zero the graph is really jumpy like a richter scale LOL when the smoothing is on 5 it makes the graph look much smoother


also...i think you are right...you dynoed in some nice cold air, ideal for making power. it corrected your numbers down to where they would have been if it was 77*, and 0% humidity. so your true number should be higher than what is on the graph.

534/.95=562 corrected

PS-i made 562 last year...but mine didnt carry for **** like yours does
Click to expand...


To be really precise, way more precise than the dyno instrument that created the numbers....

534.71/0.95 = 562.853 that rounds to 563!!!! good job you bested GetBlown by 0.853 HP, that's like 0.25" in a sled pull event!

Of course GetBlown now has P-Pump that will rev to the moon :kick:
 
horsepower is only a fraction of the equation on a sled pull track...

for instance i have beaten a few trucks with mid-high 700hp dyno sheets
 
getblown5.9 said:
its the smoothing...if you set it to zero the graph is really jumpy like a richter scale LOL when the smoothing is on 5 it makes the graph look much smoother


also...i think you are right...you dynoed in some nice cold air, ideal for making power. it corrected your numbers down to where they would have been if it was 77*, and 0% humidity. so your true number should be higher than what is on the graph.

534/.95=562 corrected

PS-i made 562 last year...but mine didnt carry for **** like yours does
Click to expand...

Ohhh. I've always wondered how that worked. Thanks man.
 
getblown5.9 said:
its the smoothing...if you set it to zero the graph is really jumpy like a richter scale LOL when the smoothing is on 5 it makes the graph look much smoother


also...i think you are right...you dynoed in some nice cold air, ideal for making power. it corrected your numbers down to where they would have been if it was 77*, and 0% humidity. so your true number should be higher than what is on the graph.

534/.95=562 corrected

PS-i made 562 last year...but mine didnt carry for **** like yours does
Click to expand...

nwpadmax said:
Graphs are often smoothed by taking the running average of the last 3 or 5 (or more) numbers in the data stack.

The graphs can look jaggy because of the electronics. On a load cell dyno, you're taking on-the-fly data from a load cell and then digitizing with an A/D converter. Add in all the other variables and you wind up with less than glass-smooth curves. People don't like those, so they generally smooth 'em up before printing.

We might not all agree on what correction factors to use, but uncorrected numbers are kinda misleading in their own way as well.

If a guy in Cali dynos at 80F and a guy back east dynos at 40F or lower, there should be a difference that needs some kind of reference correction, or you've got apples and oranges.
Click to expand...

Gotta make it a fair playing field I guess. Thanks for taking time to explain this. So the correction factor is always multiplied or subtracted by .95?
 
Big Blue24 said:
To be really precise, way more precise than the dyno instrument that created the numbers....

534.71/0.95 = 562.853 that rounds to 563!!!! good job you bested GetBlown by 0.853 HP, that's like 0.25" in a sled pull event!

Of course GetBlown now has P-Pump that will rev to the moon :kick:
Click to expand...

I was looking at TJ's graph, that thing is super smooth. He should get a few points for that.:hehe:
 
cummins724 said:
Gotta make it a fair playing field I guess. Thanks for taking time to explain this. So the correction factor is always multiplied or subtracted by .95?
Click to expand...

No, the numbers change with the weather/elevation.

Typically, the higher up you go in elevation, or the hotter it get's, the correction factor get's bigger. Lower elevation, cooler weather, it get's lower.

I think...I never pay attention to corrected numbers, I have always gotten uncorrected numbers when I dyno.

Chris
 
getblown5.9 said:
horsepower is only a fraction of the equation on a sled pull track...

for instance i have beaten a few trucks with mid-high 700hp dyno sheets
Click to expand...

I understand that, same here. It is mostly because they will either select the wrong gear or can't get the revs though. Your truck was a beast withe Redline TJ. I'm hoping my rig will run like yours did with this Redline box.
 
Signature600 said:
No, the numbers change with the weather/elevation.

Typically, the higher up you go in elevation, or the hotter it get's, the correction factor get's bigger. Lower elevation, cooler weather, it get's lower.

I think...I never pay attention to corrected numbers, I have always gotten uncorrected numbers when I dyno.

Chris
Click to expand...

Yeah, I just realized that my other run says .96 correction factor. I'm a dummy.:bang Thanks.
 
This is why Dynos shouldn't be used for anything other than tuning... using them for bragging rights is surely fun, but moot IMO.
 
Just trying to learn new things. LOL maybe a little bs on the side all in good fun.
 
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