Performing a volumetric efficiency test can reveal the accuracy of a vehicle's Mass Airflow Sensor (MAF) as well as potential issues with the engine and can be the key to successfully diagnosing and fixing a vehicle.
To perform a volumetric efficiency test, the engine must be at operating temperature. During a road test, perform a Wide Open Throttle (WOT) and record, with your scan tool's datastream, the highest readings during WOT of RPM, IAT and MAF. Your datastream reading during WOT needs to be recorded at the same timeframe as the highest RPM was reached. Enter the highest recorded Parameter Identifications (PIDs) in the calculator to the right.
IMPORTANT - the readings must be in the format below
- Degrees Fahrenheit
- RPM
- MAF in gs
- Engine size in liters
An acceptable VE range is between 75% to 90%.
When IAT reads in °C, the PID will have to be converted to °F.
Converting °C to °F: (°C x 1.8) + 32 = °F
It is important to learn how this test will perform in your area. Road testing a few vehicles to get a base line of what and how the test performs will help you with your diagnosis. Every test you perform will vary as the result of ambient conditions. Knowing how the test performs in your area will help you understand the results to expect from those variables.
The calculations does not apply a correction factor for Altitude, Temperature and Humidity. The calculations assumes the necessary modifications for ambient condition through the use of IAT and MAF. Diesel and Turbo charged engines could result with higher than 90% efficiency if in good shape.
There are many ways to perform VE test with numerous calculators available on the web. This simple calculator is one method to calculate VE.
