Dyno Correction Factors

JSH · 06-30-2021, 11:38 AM

CF works fairly well if less that 1000ft between dynos. It's primarily for use with weather changes within your shop.

The Society of Automotive Engineers (SAE) that publishes the correction factor (J1349), claims that it will be accurate when conditions are within +/- 7% (14% range). Beyond that, there will be some inaccuracy based on large changes in conditions.

At sea level, we will likely see a correction factor around 1.00 and at 6000' in Denver, it will be close to 1.35, which is a 35% difference. When adding a large percentage to a measured power value, this can make a large swing in corrected power. Since the correction factor also assumes 85% mechanical efficiency, if the engine is more or less mechanically efficient, then the correction factor may make more or less of a difference.

Bottom line for me:

I can't compare a dyno of my car in Denver to one in Houston. Dyno's are not designed for that condition.

I didn't know that.

HCI2000SS · 06-30-2021, 12:04 PM

Yep and then factor in that not all dynos are calibrated the same (even within the same type of dyno) and certain types of dynos are known for being higher and/or lower than others. Unless it's the same dyno on the same day it's practically impossible to compare

Gunkk · 06-30-2021, 12:44 PM

You can't trust the results from different dynos, at all, no matter where they're located. +/- 10% is common = +/- 40-50+hp on our cars.

Same dyno, different day, same setup, similar conditions using SAE CFs is about the best that most folks can practically ever get when doing mods if you want to trust what you're seeing on the charts.

06-30-2021, 11:38 AM	#1
JSH Drives: '20 ZLE Join Date: Jun 2020 Location: Mile High Posts: 3,562	Dyno Correction Factors CF works fairly well if less that 1000ft between dynos. It's primarily for use with weather changes within your shop. The Society of Automotive Engineers (SAE) that publishes the correction factor (J1349), claims that it will be accurate when conditions are within +/- 7% (14% range). Beyond that, there will be some inaccuracy based on large changes in conditions. At sea level, we will likely see a correction factor around 1.00 and at 6000' in Denver, it will be close to 1.35, which is a 35% difference. When adding a large percentage to a measured power value, this can make a large swing in corrected power. Since the correction factor also assumes 85% mechanical efficiency, if the engine is more or less mechanically efficient, then the correction factor may make more or less of a difference. Bottom line for me: I can't compare a dyno of my car in Denver to one in Houston. Dyno's are not designed for that condition. I didn't know that. __________________ '20 ZL1 1LE A10, OEM short block, LME heads/valve train, E2650. 100+ octanes, no eth, no meth, no N2O. 2/23 - 1031/1004 wheel. 4/23 - 1.41/9.61/145 at DA 7000 ft. (only made five passes). 2/24 - LME 390, E2650, FBO, 100 oct.; 1116hp/ 1063tq; 109 oct. dyno next.

06-30-2021, 12:04 PM	#2
HCI2000SS Drives: 2018 Camaro V6/RS Join Date: Nov 2018 Location: MI Posts: 1,596	Yep and then factor in that not all dynos are calibrated the same (even within the same type of dyno) and certain types of dynos are known for being higher and/or lower than others. Unless it's the same dyno on the same day it's practically impossible to compare

06-30-2021, 12:44 PM	#3
Gunkk Thank you Al Oppenheiser! Drives: Red Hot A10 ZL1 Convertible Join Date: Jun 2017 Location: Sarasota, FL Posts: 4,978 View My Garage	You can't trust the results from different dynos, at all, no matter where they're located. +/- 10% is common = +/- 40-50+hp on our cars. Same dyno, different day, same setup, similar conditions using SAE CFs is about the best that most folks can practically ever get when doing mods if you want to trust what you're seeing on the charts.

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