Help me understand “Correction Factor”

On my Weather Station app., what is STD Correction Factor, and how does it differ from SAE Correction Factor?

While we’re at it: what seems to be the main prediction factor for you?.... Temp? Density Altitude? Humidity? Water Grains?

Thanks in advance.

Woah, man, that one's a seriously layered, complicated matter.... and one I've been fascinated with
my whole life. No easy answer to that one.
From being a kid in Atlanta in the 60's and having Guy Sharpe as a childhood hero (along with Hank Aaron,
of course) to now, I've maintained a fascination with just what makes weather "tick".

(For those who don't know, Guy Sharpe was a local fixture in TV weathermen in Atlanta for like 50 years and
was pretty much the prototype for today's "weatherman with personality" types we see everywhere now.
He visited our school every year and was just great with kids, especially mini-nerds like me).

Terrain, prevailing upper level airstream patterns, regional nuances, history - there's just so much more to it
than what one reads on our little mini-weather stations (yeah, always had one of those, fairly fancy one now).
Some of it is just plain knowing where you are and "gut instincts", too.
I have a friend who is a proper, acknowledged on-air meteorologist in DC now who swears I have a knack for
it and should have pursued it when I was younger. He's being very generous there, that's for sure.
He sees what I sometimes post on facebook to friends and neighbors when I think something of concern
is coming our way (especially friggin' tornados, which I have a more-than-average dread of, having seen a
couple up close as a kid) and of course, having all the resources he has at his disposal, will check up on
us down this way, then messages me on whether or not he concurs with my concerns - always in a positive,
encouraging way, even when he's basically saying "you're way off on this one, Ed").

Long-winded way of my answering your question is - it's complicated, man.

Simple. Standard correction takes current weather, temp, humidity, barometer and converts it to the given SAE standard. Grains,D/A, etc are all calculated from these 3. This way you can see how weather effects HP. Since a barometer reads air pressure changes in altitude, this change is factored in as well. Any dyno numbers will be corrected to this standard. That being said is it dead accurate? No, but it's close. Crew Chief pro allows you to tailor these factors to your specific combo. Different engine combos are affected by the 3 inputs in different ways. In perspective 2 weeks ago my car ran 9.244. Last weekend with better weather it ran 9.188 with 90lbs of ballast. Would've been 9.10 w/o ballast. Since I run index we do the correction every pass and add weight as needed to keep the ET the same. Over 3 days last weekend we ran 9.244- 9.275 on a 9.25 index. Ballast ranged from 35lbs to 110lbs along with partially closing the carbs down.
Doug

Just from my experience, no matter what you will have a + or - factor of 2 maybe 3%.
Other factors come in to place such as wind speed and direction.(In my case wind changes constantly)
I would say dvw may have the most experience on this subject.Just remember you are dealing with fickle Mother Nature,that's why they call it weather prediction .

I can’t say for sure, since I’m not familiar with what you’re working with, but fundamentally.......
“STD” correction would be 29.92” baro, 60* temp, zero humidity.
The “SAE” correction has changed a bit over the years.
You should be able to find it pretty easily with a search, but it’s something like 29.23” baro, 77* temp, zero humidity.

If you’re using a run predictor, it’s correcting a run in the observed weather conditions to those in the correction.
In other words, what it would theoretically run in that weather.

Correcting the runs back to a std allows you to gauge the performance of the car(to some degree) without the weather being a variable.

LemonWedge said:

On my Weather Station app., what is STD Correction Factor, and how does it differ from SAE Correction Factor?

While we’re at it: what seems to be the main prediction factor for you?.... Temp? Density Altitude? Humidity? Water Grains?

Thanks in advance.

Click to expand...

PRHeads answered your first question.

DA will be the prediction factor. It combines the three measurements to a value that can be meaningfully compared to the standard conditions (STD or SAE) or to itself throughout the day.

LemonWedge said:

On my Weather Station app., what is STD Correction Factor?

Thanks in advance.

Click to expand...

I thought it was a condom.

Its got to be a fair amount of wind to make a change. Most times I ignore it. Using the 3 basic factors in differing values you can still come up with the same D/A. Different humidity, temp, baro may affect your combo differently. So D/A can be suspect.
Doug

Thanks for all the reply’s! I think I understand correction factor better. I am currently typically using a combination of Temp., DA, and and humidity, comparing all to my log book and previous similar runs to influence my dial decisions. The more I understand, the better prepared I feel.

(For those who don't know, Guy Sharpe was a local fixture in TV weathermen in Atlanta for like 50 years and
was pretty much the prototype for today's "weatherman with personality" types we see everywhere now.
He visited our school every year and was just great with kids, especially mini-nerds like me).


I grew up in Atlanta, and I also met him when he came to my Elementary school ( E. Rivers). Still remember after all these years.
Neat guy!