Dyno Correction Factor Calculator (online)

[regular guy]

Dyno correction formulas come up all the time in discussions on car forums. Few people know how they work, and even fewer people know what each dyno vendor uses and how they use it. And even fewer have a calculator that can calculate more than one type of dyno correction.

So to help demystify it a little, I came up with dyno correction calculator page. For now, I'm not going to explain the math behind it. For that, I'd simply ask to read and absorb everything you can from this site:
http://wahiduddin.net/calc/calc_cf.htm

If you want to see how dyno correction works and compares from one dyno vendor to another, then go kick the tires of my Mega Dyno Correction Calculator.
http://www.bigdynodatabase.com/DynoCF.php

These are the supported dyno correction formulas, and a demystified version of what some vendors are doing. The accuracy was calculated by comparing the formula against actual results on that dyno. The sample set was taken over the entire range of temperature, pressure, and humidity in addition to lowest and highest correction factors observed in Dyno Database (http://www.s65dynos.com). The sample data set allowed me to tweak the reference values to discover that Dynapack uses hard coded constants in their formulas instead of calculating the reference temperature from it's known base (see "Notes"). Given the accuracy of each and the wide range of sample data used for testing, I have pretty decent confidence that I figured out what each of these vendors were doing.

Summary:

Correction Type	Base Formula	Accuracy	Ref. Temp	Ref. Pressure	Ref. Efficiency	Notes
J607	J607	1.000000	60 deg-F	29.92 inHg	100.00%	Normal J607 does not remove effects of humidity.
J1394 (1990)	J1394	1.000000	77 deg-F	990 mBar	84.75%	All J1394 variants remove effects of humidity.
J1394 (2004)	J1394	1.000000	77 deg-F	990 mBar	85.00%	Current SAE standard reference formula.
Dynojet STD	J607	1.000131	77 deg-F	29.92 inHg	100.00%	Uses slightly modified J607 formula by removing effects of humidity.
Dynojet SAE	J1394	1.000040	77 deg-F	990 mBar	85.00%	Dynojet uses current SAE standard reference formula.
Dynapack STP	J607	0.999995	288.7 deg-K	29.92 inHg	100.00%	Temperature reference rounded to 59.99 deg-F (288.8 deg-K).
Dynapack SAE (2004)	J1394	0.999162	298.0 deg-K	990 mBar	85.00%	Temperature reference rounded to 76.73 deg-F (298.0 deg-K).
Dynapack SAE Adapted	J1394	1.000615	288.7 deg-K	29.725 inHg	84.75%	Standard J1394, but using Dynapack's own reference values.

[saxonb]

Sticky this. Very useful.

Thanks RG.

[M3ANMACHINE]

So which correction factor is preferred? STD or SAE?

[regular guy]

Originally Posted by M3ANMACHINE

So which correction factor is preferred? STD or SAE?

SAE is the industry standard. Some use STD because it gives higher numbers.

[FogCityM3]

Very helpful, thx!

[regular guy]

I added Density Altitude calculations to the page. Now along with your dyno correction factors, it will calculate density altitude as well.

If you don't know the earth altitude of the dyno shop, you can look it up on Google Earth (hover mouse over location and look at bottom of the page).

[IMG]

This is awesome ,Thx RG !

[pbonsalb]

Does the conversion include load, which the operator can vary, or just weather?

[regular guy]

Originally Posted by pbonsalb

Does the conversion include load, which the operator can vary, or just weather?

It's a weather correction calculator to give dyno correction factors for all of the major correction types in current use.

No load calculations or anything.