Turbocharged Performance

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Turbocharged Performance

Vehicle manufacturers offer turbochargers and use smaller displacement and/or fewer cylinder engines to optimize power vs. fuel economy trade-offs. For example, instead of 6-cylinder engine, a manufacturer can offer a 4-cylinder with a turbocharger. When the turbo is operating, customers get the performance and power benefits of a 6-cylinder engine and when the turbo is off, they get the fuel economy of a 4-cylinder.

Since, an engine’s power is proportional to the amount of air and fuel delivered to the cylinders, the turbocharger increases the inlet manifold pressure and density so the cylinders get a greater mass of air during each intake stroke. The pressure ratio (πC) versus air flow determines the performance of the turbocharger.

πC = P2C/ P1C


P2c = Compressor discharge absolute pressure

P1c = Compressor inlet absolute pressure

The typical increase in intake manifold pressure (boost pressure) is around 12 psi gauge. Calculations for P1c must account for intercooler pressure drop and P2c must account for air filter pressure drop. With a sea level atmospheric pressure of 14.7 psi, intercooler pressure drop of 2 psi and air filter pressure drop of 0.5 psi:

πC = (12 + 2 + 14.7) / (14.7 -.5) = 2.02

The absolute pressure sensors used in an engine control system are typically rated at 200 kPa (2 atmospheres or 29.4 psia).


Pressure ratio vs. corrected airflow plot for a Garrett GT3582R compressor.

Source: EPI Inc.

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