Fan of the Cadillac STS-V intercooler heat exchanger

I have been thinking more about the STS-V intercooler heat exchanger design and replacement ideas.

Cadillac uses a separate cooling system for the Laminova style intercooler tubes, featuring a bosch intercooler pump and a 23.5″x14″x2″ outer measures intercooler radiator heat exchanger in front of the main radiator in the nose of the V.  So let’s call that a 20″ by 12″ working area.

The D3 solution is two-fold:  replace the heat exchanger with a tube and fin heat exchanger with 10″ pusher fan, and add a tank to hold additional intercooler coolant.

Other aftermarket solutions have included adding a new chin mounted heat exchanger instead of the current heat exchanger, or along with the current heat exchanger, or in series with a a tube and fin replacement.

After reading various experiments with adding fans on other vehicles, I am convinced that adding an intercooler heat exchanger fan is advantageous.  Although it is intuitive to think that a pusher fan could provide a block to the incoming airflow, testing has shown that is not the case on other models.

My plan is to keep the stock OEM heat exchanger, but add a 12″ pusher fan. I am thinking of a SPAL 12″/12v pusher fan or similar; space is a concern.  Use a fan controller to interface although it would be best if only on when the car is up to temperature etc.  The intercooler heat exchanger is in front of the main radiator, so pushing air through one will impact the other.

VA10-AP70/LL-61S * 12"C / 12V 12" Curved Blade High Performance Fan / 12V Pusher


Separately, I like the idea of using the LS9 coolant reservoir as additional coolant capacity especially in this system that is very capacity limited.

Next Cadillac update? Intercooler FMHE or Exhaust

I am split on my next Cadillac update.  The choices are to replace the mufflers with performance, high flow mufflers, or to begin to experiment with intercooler cooling system improvements.

For the exhaust I am settled on replacing the stock, low-noise mufflers with Magnaflow 14326 mufflers.  The exhaust system itself is stainless steel, and appears to already be bent properly.  The cost should be around $100 ea x2 for the hardware, plus installation.  I suspect it will free up 10-15 whp.

The intercooler system uses Laminova tubes with a small heat exchanger in front of the car.  I plan to add a 2nd front mounted heat exchanger in serial with the stock heat exchanger.    The original LC3 testing was done assuming harsh heat conditions with high intercooler coolant temps.  Later when required to SAE certify, the engineers also needed to reduce the temperature  for the intercooler coolant; the engine famously went from 440hp with the original assumptions to 469 hp with the cooler assumptions.  So I suspect that anything we can do to reduce the temperature of the intercooler coolant is worthwhile in terms of more hp.

Technically, reducing the intercooler air temp does not add more oxygen to the air, since at that point the mass of air coming into the system out of the supercharger is fixed.  However, what cooler air across the intercooler does do is allow the LC3 engine to run more timing, which it will do automatically, and achieve more power.  Reducing the temperature of the intercooler coolant is one way to achieve cooler intercooler exhaust (IAT2).

Another thumbrule I have read is that Laminova heat exchangers operate best if the area of the heat exchanger is equal to the area of the coolers.    I had to think about that a bit to understand what was meant.    For the Cadillac the area of the Laminova coolers would be 96 square inches.  The area of the stock heat exhanger would be 21×14=294 square inches, which would appear to meet the thumbrule.

It is inviting to do something really revolutionary like put an intercooler reservoir in the spare tire compartment and run hoses the length of the Cadillac, but probably better to stay conservative for a daily driver.

I am happy with my Ambient / IAT / IAT2 measurement capability.  I would like to have a direct measure of intercooler coolant temp before the next changes, but I am unsure how best to achieve and log that.

Monitoring IAT, IAT2 Cadillac STS-V

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?