Comparing IAT1, IAT2, RPM & different cooling strategies

Just getting the hang of histograms in HPtuners.  These are powerful analysis tools that allow comparison of occurences of a variable, say IAT2 temperature in the manifold after the supercharger, in a table defined by IAT1, intake temperature, and engine RPM.  The higher the RPM, the faster the supercharger spins, and the more likely the IAT2 will heat up.

Here is an example heatsoaked from my STS-V with the OEM cooling system:

Bruce Heat-soaked Run

Reading the histogram:  down the left axis are a range of values for the IAT1, intake air.  Across the top are various engine speeds in RPM/1000, so 2 means 2000 rpm.  The values in the body of the table show what the average IAT2 or manifold air temperature after the supercharger heats up the air and the intercooler cools it back down was at the given IAT1 and RPM.  The cells are colored green for cooler temps up to red for hotter temps to make it easy to read.

We can see in this diagram that anytime the engine was at  6500 RPM and the intake temp at 95F the average IAT2 temp was 142F, or +47F hotter.

The STS-V has plenty of opportunity for heat soak.  Heat soak is when the engine has been run and retained the heat so that the intake tubing, manifold, and IAT2 sensor are all hot.  For contrast, here is a run with my STS-V not heat soaked:

Bruce not heat soaked run

We see here that when the IAT1 was 65F and the engine hit 6500 the average IAT2 was 108F, or +43F.

Jaimie has a custom intercooler cooling system on his STS-V consisting of a replacement for the OEM heat exchanger, a 2nd front-mounted heat exchanger, and a high-flow intercooler coolant pump. He was nice enough to send me some scans from his STS-V and I have run them on the same histogram below:

Run 3-23-12

Jaimie 3-23-12

In Jaimie’s run, when IAT1 was 70F, when the engine passed 6500 RPM the IAT2 averaged 126F or +56F.

Run 3-23-22

Jaimie Run 3-23-22

Run 3-27-12

Jaimie run 3-27-12

Obviously the sets of runs are on different days, different regions, different cars.  Also while I tend to mix in a variety of stop and go and 0-60 runs, Jaime tends to have stop and go and a single long run from 30-40 up through the gears to higher speeds.

I am however struck that none of Jaimie’s runs look like my heat-soaked all red first snapshot.   This may be because while the OEM intercooler heat exchanger is sufficient to maintain steady state in a cool V, it can’t overcome the heat stored on a heat soaked run.  Jaimie’s additional intercooler cooling capacity allows his system to overcome the heat soak load and get back in the green.

What do you think?  How would you further analyze this info?

2 thoughts on “Comparing IAT1, IAT2, RPM & different cooling strategies

  1. I’ve found it more useful to log temp change over time to see how well my upgraded heat exchangers work on XLR-V… while the temp at rpm is interesting to look at, I don’t think there’s anything actionable there…. unlike, a AFR histogram where you can directly adjust based on the data you see.

    I’ve been reading your posts regularly, and one think you may want to try (I’m in Houston) is to change both your coolant and intercooler fluid mix to 80/20 (water/dexacool) and add water wetter… it will exchanger heat better and will still give you about 20deg F anti-freeze protection which I’m guessing should be ok in DFW.

    I’ve also been adjusting the flow rate on my upgraded johnson cm90 pump and found that flow rate drastically affects IAT2 temp recovery. Read this:

    Would love to chat more, feel free to email me…

  2. Hi Richard,

    Thanks for your comment — I love hearing from other V owners.

    How did you upgrade your heat exchanger system? Any scans you can share with IAT/IAT2 monitoring for comparison?

    Jaimie’s system has the Froozenboost 101 FMHE under the bumper, and a Flex-a-lite 45321 in place of the OEM heat exchanger, and I think a WP136S Pump. My study here was to see if Jaimie’s system was actually more effective in keeping cool and provided a way to compare the two.

    Interesting Silverado SS article. Their method for measuring the benefit of various voltages on the intercooler water pump was well done and would make a very interesting experiment on our Cadillacs. I don’t see before/after discussion on 50/50 dexcool vs 80/20 distilled water / coolant but I agree water has more heat transfer capability than coolant.

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