Category Archives: Intercooler

Cadillac STS-V inline flow-through intercooler tank

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The Cadillac STS-V intercooler cooling system holds a total of 2.6 quarts of coolant.  That’s 0.65 gallons.  The benefit of having little coolant is that it heats up quickly, and it cools down quickly.  However, I wonder if there is more disadvantage to such a low coolant capacity.  The LS9 engine in the ZR1 has a small rectangular intercooler coolant tank inline to hold more coolant.  D3 offers a small cylindrical reservoir for the STS-V to hold more coolant and reports good results.

I have ordered one of these AVS tanks hoping I can find a good spot to fit it:

AVS 1 gallon aluminum tank

The tank is 15.5″ long x 3.5″ diameter with fittings at each end. The 1/2″ fittings will be a bit of a flow restriction for the 3/4″ inner diameter intercooler hoses.

For my next experiment I a hoping to use the OEM heat exchanger with a front mounted heat exchanger in series.  That in itself will add 1.9 Liters (2 quarts) of additional coolant inline.  But I’ll get the tank in hand and see if I can figure out a place to mount it for an experiment another day.  Then we can get some real data to answer this question.

Repeating Cadillac STS-V Intercooler HX Tests

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I went back to rerun the test on the new Intercooler Heat Exchanger (Flexalite 45321) for confirmation of the original test, Initial IAT2 times with New HX – woops

Here was the test data from that test, suggesting the new HX is not as effective as the original:

My method plan was to rerun the test this weekend after the car has had a week to work the air out of the intercooler loop.

Current configuration:  Flexalite 45321 heat exchanger in the place of the OEM radiator type heat exchanger, no other heat exchanger in the circuit, no inline tank added.

What I found today was that the intercooler IAT2 temp never got below 131F, which is worse than the baseline above.  Unfortunately, test1 today I fumbled the mouse at the end of the test and lost all the test data by accidentally closing VCM Scanner (doh).  The STS-V was heat soaked before the test, starting at 156F for the IAT2, and was able to cool down to 131F and was still dropping slightly on highway runs.  But it was not getting to a steady state of under 120F as the OEM did.

I also got the impression there is some interplay between A/C on or off and intercooler IAT2 temps although I am not clear why.  My intuition is that A/C on would run the radiator fans and improve air flow and so lower IAT2, but on the ‘back’ of the loop where I normally do acceleration runs, I noted that when I turned off the A/C the IAT2s fell 5F quickly.

Now I’m not worried about performance runs for the STS-V when heat-soaked, but this does give us a way to test the efficiency of the intercooler cooling system, since it is presented with the greatest heat load.

After a break I’ll get back on to test2 and try to bring back a data stream this time!  Stay tuned.

UPDATE

Okay, refueled and reran the test loop.  I have added the retest new HX data to the previous data table.  I have also added in some data lines from Jaimie’s STS-V.  Jaime has an 07 STS-V with the 45321 HX in place of the OEM, a Frozen Boost front-mounted heat exchanger, and he has an aftermarket intercooler pump instead of the OEM pump.

Retest of New HX appears to confirm previous test

My conclusion is that my config is still running hotter than I want.  My plan is to return to the OEM intercooler heat exchanger, and add a new ZZP S3 front mounted heat exchanger under the bumper in series with the OEM hx.  So, another install weekend then hopefully more data.

Also, I found on the retest that the area I was in led to a decrease in the IAT2, not turning the A/C off.  The issue is that there is a zone of cooler air at the top of my test loop due to getting off the highway and I saw a drop in IAT2s in that area with the A/C left on during the retest.

 

Cadillac STS-V RX Performance Products Intercooler Tank Project

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I have been exchanging fitment photos and details with RX Performance Products in Florida regarding a variant of their new Cadillac CTS-V intercooler expansion tank for the Cadillac STS-V.

Cadillac CTS-V supercharger expansion tank from RX Performance Products Image by RX Performance Products

On the Cadillac CTS-V and the Cadillac STS-V there is an air escape (bleed) from the intercooler coolant system at a Tee-fitting, and this is where coolant may be added to the system when needed.  The idea RX Performance Products has had is to replace the T-fitting with a small tank and fittings.  This part of the intercooler coolant flow is on a ‘side-track’ to the main coolant loop.  If the intercooler coolant pump can’t pull fluid from its normal intake, for example when there is air in the system, it can pull coolant down this side-track and the air can escape up the side-track.

STS-V T-fitting fill tube

When one does need to add coolant to the system, the T-fitting tube will only accept a tube full, or under a pint of fluid.  Once the intercooler pump pulls that into the system you can add a bit more, rinse, repeat.  Each time even with a funnel there is some spillage during the add process.

With the small tank — the CTS-V tank is 1 quart– it will be easier to add fluid, and “overfill” the system a bit so that as the system does bleed air there is plenty of coolant to replace it.

The CTS-V T fitting is slightly different from the STS-V T-fitting; the CTS-V one has the same size in and out flow fittings, while the STS-V has a larger in than out.

I have emailed images along to RX Performance Products of my STS-V engine bay with various measures in order to help them to fab a tank for the STS-V.   In this photo I cut a granola box to 4″ x 4″ x 10.5″ to try to model what size tank might fit under the strut brace on the STS-V where the T-fitting is.

RX Performance Products
2200 US Hwy 301N
Ste 6
Palmetto, FL 34221

Based on the pictures and measurements we are hoping to size a tank for the STS-V similar to the CTS-V tank.  Stay Tuned.