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On another forum one of the moderators was fairly adamant about the importance of measuring temp and pressure at various points on the inlet track to measure intake effectiveness. In the end, he though pre-turbo was most important. He recommended this fairly low cost Bosch combination 1 bar MAP and IAT: https://www.bmotorsports.com/shop/pr...oducts_id/2270.
That makes no sense to measure pressure pre turbo. Temp, maybe but I wouldn't consider it very useful. Common sense would tell me intake temp/pressure would be most important as close to the throttle body as possible. The s2k IAT sensor tends to heat soak so putting it on a charge pipe would be the most accurate.
The discussion had been about cold air intakes on turbo engines. In this case, a rather detailed response indicated without the pressure and temp readings it was hard to evaluate how the system was operating. What the actual pressure drops were. How efficient the turbo and intercooler were.
He had posted an unlabeled graph measurements of different cold air intakes at different mass flow rates. They showed that the pressure drop increased significantly at higher flow rates.
A quick calc shows the difference between 90F air with a 0.25 psig pressure drop vs 120F underhood ar with a 1.25 psig could be a 50F hotter turbo discharge temp.
The discussion had been about cold air intakes on turbo engines. In this case, a rather detailed response indicated without the pressure and temp readings it was hard to evaluate how the system was operating. What the actual pressure drops were. How efficient the turbo and intercooler were.
He had posted an unlabeled graph measurements of different cold air intakes at different mass flow rates. They showed that the pressure drop increased significantly at higher flow rates.
A quick calc shows the difference between 90F air with a 0.25 psig pressure drop vs 120F underhood ar with a 1.25 psig could be a 50F hotter turbo discharge temp.
Colder air intake into a turbo reduces required compressor power > reduce turbine power > reduced back pressure > more power. Also quicker spool, faster transient.
Colder air intake into a turbo reduces required compressor power > reduce turbine power > reduced back pressure > more power. Also quicker spool, faster transient.
"reduces required compressor power > reduce turbine power > reduced back pressure > more power"
I'm wondering if this is true. The compressor usually seeks a specific intake manifold pressure controlled by the ECU and wastegate controller. As your articles state, required compressor power is a function of mass. Won't colder air require more power to compress the higher mass to the same pressure? The denser air will create more power though if higher cylinder pressures don't cause knock.
A reduction in inlet pressure drop from ambient or reduced pressure drop across the intercooler will require less pressure gain, a lower pressure ratio, across the compressor because less compression is required to achieve the specified manifold pressure. That will require less power to drive the turbo resulting in lower back pressure and reduce heating in the compressor because of the lower pressure ratio. It won't increase mass flow.
"reduces required compressor power > reduce turbine power > reduced back pressure > more power"
I'm wondering if this is true. The compressor usually seeks a specific intake manifold pressure controlled by the ECU and wastegate controller. As your articles state, required compressor power is a function of mass. Won't colder air require more power to compress the higher mass to the same pressure? The denser air will create more power though if higher cylinder pressures don't cause knock.
A reduction in inlet pressure drop from ambient or reduced pressure drop across the intercooler will require less pressure gain, a lower pressure ratio, across the compressor because less compression is required to achieve the specified manifold pressure. That will require less power to drive the turbo resulting in lower back pressure and reduce heating in the compressor because of the lower pressure ratio. It won't increase mass flow.
Compressor power is a function of mass flow, pressure ratio, AND compressor inlet temperature. The higher the compressor inlet temperature, the more compressor power is required for the same mass flow and pressure ratio. Engine power is a function of mass flow. Pressure ratio is a function of mass flow and engine volumetric efficiency. The F20/F22 have very high volumetric efficiency, so less pressure ratio is required to get the same mass flow (and therefore power) as an engine with lower volumetric efficiency, say like an old SR20 or 4G63. Those engines require more boost for the same power compared to the F20/F22.
You are also correct in that reducing pressure drop before the compressor inlet and through all the piping and IC will reduce the compressor pressure ratio requirement which in turn reduces compressor power requirement leading to more power.
06-27-2018, 09:09 PM
Sensor for Pre-Turbo IAT/MAP Measurement
