Tag Archives: 2008 Cadillac STS-V

Cadillac Video HPTuners Dashboard playback showing IAT2 trends

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Here is a short video capture of an HPTuners VCM Scanner output of a test run to monitor intake air temperatures through the MAF (IAT1) versus after the intercooler (IAT2) or ambient.

The source video was over 1080 pixels but Youtube offers it for viewing in up to 1080p so please select the highest resolution your playback can handle and hit the fullscreen gadget for the video then pop back and comment.

I am still synthesizing the data.  It appears to me that as the STS-V accelerates the IAT2 temp rises from 131F to 151F the slowly drops down again.

There is some Knock retard coming in at high RPM.  The V will also pull timing at higher IAT2 temps.

Let me know what you think about the run data and this method of reviewing it.

Monitoring IAT, IAT2 Cadillac STS-V

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This morning I did some data-logging with HPTuners up and down the highway.  I am still learning the software, so feel free to make suggestions.

I grabbed these screen shots of a couple of points: (click on the image for a zoom-in version, then hit back to come back):

HPTuners datalog screenshot 1

What the first screenshot shows is that at 69 mph and 6651 RPM the supercharger was making 10.7 psi.  During this portion of the run, ambient air temperature was 90F, IAT air coming into the MAF temperature sensor was 108F, and IAT2 air leaving the intercooler was at 151F.

Actually I would have expected the car to shift at 6500 rpm, but 6651 is close enough I suppose.

In the chart display at the bottom however, you can see that the IAT2 was already elevated before the higher-RPM event occurs.

The question for today though is how the IAT2 151F compares with ambient air 90F.  The Supercharger adds heat to the intake air in the process of compressing it.  At maximum RPM as here, the Supercharger is spinning at 2.1:1 and so 13,967 rpm.   This can add up to 200F to the air coming into the intercooler.   Today the air coming in to the supercharger was already 108F, so heating it by a couple hundred degrees puts some very hot air across the Laminova intercooler tubes. The goal for the Intercooler is to reduce the heated air back as close to ambient air as possible, pulling the air back from 200F+ down to 151F in this example.  The unachievable ideal is that the intercooler get the air down to the intercooler heat exchanger’s own cooling source, which is the ambient air coming into the front grill at 90F.

HP Tuners datalog screen shot 2

In the second screen shot, at 39 mph and 6502 rpm, ambient air was 88F, MAF intake air 108F, and IAT2 after the supercharger was 135F.

On a separate topic, long term fuel trims appear to be small, which I think is good.

Points to ponder:

How to reduce the IAT2 temperatures from 151F when accelerating at highway speeds

Why the max pressure seen was 10.7 psi instead of 12 psi?  Is this also temperature related?

How will these readings change in cool air?