| volumetric efficiency but yet do not understand the concept or how it would be measured. This really is an interesting topic and it has been apparent that many have enjoyed a "learning curve" in the process. I'm not sure how many get it just yet, but VE in a turbocharged setup is not as simple as VE in a naturally aspirated setup. Boost pressure must be accounted for in the VE calculation to standardize the result. By incorporating pressure into the equation, you are adding another dimension which results in a unit containing density and volume, which directly relates to the mass of the charged air. (The end value is unitless, but the variables are taking pressure into account, which gives a mass-airflow value) Standard:
VE = (Actual Airflow * 100) / Theoretical Airflow The standard theoretical airflow calculation is:
TA = (EngineRPM * Displacement)/3456 What this equation doesn't have in it is the value of "1" for the pressure ratio, as it is presumed that your manifold is at 1 atmosphere. But in a boosted application, this isn't the case. The pressure-corrected equation for theoretical airflow will be:
TA(pc) = ((EngineRPM * Displacement)/3456) * AbsoluteManifoldPressure Multiplying the airflow volume by the pressure reveals density, which can be converted into mass. When taking the actual measurement of airflow into our systems, one could use the mass airflow sensor to determine the actual massflow into the engine. So calculating the VE in our engines will be: VE(pc) MassAirflowValue * 100 / TheoreticalAirflow(pressure corrected) I'm not sure I would call this "VE" per-se, it is more MAE, mass-airflow efficiency, which is basically one in the same (standard VE uses a value of "1" for the pressure, so it can simply be neglected out of the standard naturally aspirated equation of "VE".) Because of this, one must refer to the efficiency of the turbocharged application in terms of massflow per RPM, which I have been trying to ease people into the understanding of and posting the dynocharts of the torque curves, which are directly correlated to the massflow. The differences in massflow are what is making the biggest impact on performance, and the massflow is primarily dependent on how the turbine spools the compressor. The answer to my question should be pretty simple for you now. Manifold pressure must be accounted for when calculating the efficiency of the engine, and by doing so, your units will reflect massflow efficiency. This is exactly why I say that VE has no effect on maximum boost, and why I say it is an illogical statement: the massflow of the system is primarily dependent on the boost level: you will not see any huge differences in power/torque output between vehicles with relatively similar setups at the same boost and RPM. The original statement (VE affects boost) is a simple case of confused cause-effect relationships, at least, within the definitions of the words.
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