The Shocking Truth About Dyno Differences... why the numbers don't always add up.

When it comes to measuring the performance of a vehicle, dyno testing is the gold standard. Dyno, short for dynamometer, is a device that allows experts to measure the power, torque, and other important parameters of an engine which can be useful in dialing in the tune and often time is used to showcase a engines performance in comparison to others. However, what many people don't realize is that not all dynos are created equal. In fact, there can be significant differences between different dyno types and brands, which can lead to misleading results and inaccurate comparisons.

Why do dynos differ?

There are several factors that contribute to the differences between dynos. One of the main factors is the type of dyno used. There are two common types of dynos: engine dynos and chassis dynos. Engine dynos measure the power output directly at the engine, while chassis dynos measure the power at the wheels. Each type has its own advantages and disadvantages, and within those 2 core types, there are even more differences between brands, logic used to measure and how the resistance or load is applied to engine or wheels or even hubs, so the results can vary depending on which type is used.

What are the limitations of dyno testing?

While dyno testing is a valuable tool for evaluating the performance of a vehicle, it is more useful as a tool to measure before and after when installing modifications and tuning, but it is important to understand its limitations. 1st limitation is that dyno testing is conducted in a controlled environment, while this is ideal for back to back tests especially in tuning as it allows controlled measurement of changes without outside factors being weighed, it may not accurately reflect real-world driving conditions. Factors such as air temperature, humidity, and altitude can all affect the performance of a vehicle, but these variables are often not taken into account during dyno testing. Understanding Dynos are best used as a tuning tool, vs an all out measurement of performance is key. 

How can dyno results be misleading?

Due to the differences between dynos and the limitations of dyno testing, it is possible for dyno results to be misleading. For example, a vehicle tested on one dyno may produce higher power figures compared to the same vehicle tested on a different dyno. There are also different standards in which Dyno operators use which can be misleading. These are called Correction Factors and the 2 most common correction factors are SAE and STD, there is also "Uncorrected" which is least commonly used.

SAE:
"SAE (Society of Automotive Engineers), USA. Power is corrected to reference conditions of 29.23 InHg (99 kPa) of dry air and 77 F (25°C). This SAE standard requires a correction for friction torque.

STD:
STD is Another power correction standard determined by the SAE. Power is corrected to reference conditions of 29.92 InHg (103.3 kPa) of dry air and 60 F (15.5°C). Because the reference conditions include higher pressure and cooler air than the SAE standard, these corrected power numbers will always be about 4 % higher than the SAE power numbers. Friction torque is handled in the same way as in the SAE standard."

Uncorrected as the name implies, applies zero correction and is considered the most raw measure of the vehicles or engines output. 

     This can create confusion and make it difficult to make accurate comparisons between different vehicles or modifications.

What should you consider when interpreting dyno results?

When interpreting dyno results, it is important to consider the type of dyno used, the conditions in which the testing was conducted, Correction factor used, even the level of something called "smoothing" which allows the dyno operator to visually smoothing out the line graph of a dyno run to remove small spikes and dips that tend to occur while testing and any other relevant factors. It is also helpful to look at the dyno's reputation and track record, as well as the expertise of the individuals conducting the testing. By taking these factors into account, you can get a more accurate understanding of a vehicle's performance.

Conclusion

Dyno testing is a valuable tool for tuning and evaluating the performance of a vehicle, but it is important to understand the differences between dynos and the limitations of dyno testing. By considering these factors and interpreting dyno results with caution, you can avoid being misled by inaccurate comparisons and make more informed decisions about your vehicle.