Open vs Closed Intake Turbo Outlet Air Temperature

Looking over a recent data log of some pulls I noticed that the compressor outlet temperatures were in the 400-450 degF range and I thought that was a bit warmer than what I’m accustomed to seeing. Usually, the temperature just approaches 400 degF.

IS38 Turbo Compressor Outlet Temperature
IS38 Turbo Compressor Outlet Temperature

The only recent change I’ve made on the car that logically would affect the turbo outlet temperature was swapping to an open intake from the closed Eventuri that I usually use.

Going back to a pair of recent logs with the closed intake installed I pulled the peak compressor outlet temperatures and plotted them versus the open intake.

IS38 Turbo Compressor Outlet Temperature Trends
IS38 Turbo Compressor Outlet Temperature Trends

Clearly, there is a difference between the open and closed intakes.

A couple of things are interesting about this, first is that when I logged the air temperature going into the turbocharger using an open intake (with a shroud as this one has) I had not measured substantially higher inlet air temperatures with the open intake.

It was higher than a closed intake, but not 50 degF greater, which is what the average difference in the compressor outlet temperatures is.

One thought is that I don’t have the shroud for this open intake properly positioned.

Another thought is that higher intake air temperatures are “amplified” when going through the compressor and they produce increases to the outlet air temperature that are not in proportion to the changes in the temperature going into the compressor.

On a different note, you may have heard people use a phrase to describe a turbo like: “At some point it’s just a hair dryer“, implying that it’s just putting out hot air and not operating efficiently.

The typical hair dryer outputs air around 140-150 degF maximum.

Hair Dryer
Hair Dryer

The IS38 crushes a hair dryer.

A hair dryer outputs cool air compared to the turbocharger compressor.

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