Cadillac ATS-V engine run time delays

Did you know there are limits in your Cadillac ATS-V that are programmed based on engine run time (ERT)? ERT as in the amount of time the engine has been running that session.

The intercooler pump won’t start running for the first 10 seconds. Hard to make a lot of boost with no intercooler flow, but 10 seconds is a pretty short delay.

The intake cam and exhaust cam won’t vary their positions for the first 2 seconds (not much of a restriction there!) but again, don’t start the ATS-V then gun it and expect full performance.

If the engine coolant is VERY cold, under -4F, there is a fuel cut out after 5,200 RPM.

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.