When measuring horsepower and torque on a dyno, the results can vary depending on factors like temperature, humidity, barometric pressure, and altitude. To ensure consistent and comparable data, correction factors are applied to standardize the dyno results. These correction factors adjust the measured horsepower and torque values to reflect standard conditions as defined by various organizations around the world.

Here’s an explanation of the most commonly used correction standards:

1. SAE (Society of Automotive Engineers) Correction Factor

The SAE correction factor is one of the most commonly used standards in North America, developed by the Society of Automotive Engineers (SAE). It accounts for variations in atmospheric conditions such as air temperature, barometric pressure, and humidity to create consistent and comparable results. The latest version is the SAE J1349, uses the following standard conditions:

• Temperature: 77°F (25°C)
• Barometric Pressure: 29.23 inHg (993 mbar)
• Humidity: 0% (dry air)

The SAE correction factor is more conservative compared to others like STD, meaning it typically results in slightly lower power numbers because it aims to reflect real-world driving conditions more accurately.

2. STD (Standard Temperature and Pressure) Correction Factor

The STD correction factor, used primarily in older North American dyno results, uses different atmospheric conditions compared to the SAE standard. The standard atmospheric conditions for STD are:

• Temperature: 60°F (15.6°C)
• Barometric Pressure: 29.92 inHg (1013 mbar)
• Humidity: 0%

Since the temperature in the STD standard is cooler, vehicles generally produce higher power numbers when corrected using this factor. STD correction tends to result in higher readings than SAE, so be sure to ask your tuner for both sets of numbers.

3. DIN (Deutsches Institut für Normung) Correction Factor

The DIN correction factor is used primarily in Europe and is defined by the German standards body. Like SAE, it adjusts for atmospheric conditions, but the standard conditions differ:

• Temperature: 68°F (20°C)
• Barometric Pressure: 29.53 inHg (1000 mbar)
• Humidity: 0%

DIN correction factors tend to produce slightly higher results than SAE but are generally considered more conservative than the STD standard. It reflects a balanced European standard for vehicle power output and is widely used by European tuners.

4. EEC (European Economic Community) Correction Factor

The EEC correction factor is based on European regulations and was developed to ensure uniform testing standards across member countries of the European Union. The standard conditions are close to those used by the DIN standard:

• Temperature: 68°F (20°C)
• Barometric Pressure: 29.61 inHg (1003 mbar)

While not as commonly referenced as DIN, it is used for specific regulatory and testing purposes within the European automotive industry.

5. JIS (Japanese Industrial Standards) Correction Factor

The JIS correction factor is used in Japan and adjusts dyno readings to specific atmospheric conditions defined by Japanese standards. These standards are:

• Temperature: 77°F (25°C)
• Barometric Pressure: 29.15 inHg (987 mbar)
• Humidity: 0%

This standard is typically used for vehicles and engines manufactured in Japan and is tailored for the climate and conditions typically found in that region.

6. Uncorrected Dyno Results

In some cases, dyno results maycan be displayed as uncorrected, meaning no atmospheric adjustment is made. These results reflect the exact conditions at the time of the test. Uncorrected numbers are typically more variable and can fluctuate based on factors such as the weather, altitude, and atmospheric pressure on the day of testing. While uncorrected data shows raw vehicle output, it’s not useful for comparison against other tests conducted under different environmental conditions.

Why Use Correction Factors?

Correction factors ensure that dyno results from different locations, times of the year, or weather conditions can be compared fairly. They level the playing field by standardizing the atmospheric conditions under which a vehicle is tested.

Typically, we will use STD for customers that are just simply looking for their horsepower numbers. If we are tuning the vehicle, we usually use SAE. Some customers have also asked us for the uncorrected data, which we will happily provide as well.