V-V-V Shopping Spree

Darin Partin of Crest Cadillac emailed me to let me know they got in some new V-Series models on the used car side.

  • 2009 CTS-V 15,000 miles Red/Ebony
  • 2009 CTS-V 22,000 miles Black/Ebony
  • 2011 CTS-V Gray/Ebony 3,700 miles w/Recaro seat package

Of course I’m not in the market since my 2008 STS-V is still new-to-me, but I am always glad to see more choice V-Series examples pop up on the local sales scene.

The 2009-current CTS-V has the Supercharged 6.2L LSA V8 for 556 hp, magnetic suspension, Brembo brakes, and is quite literally a supercar in a tuxedo, with running shoes on, if that doesn’t ruin the metaphor for you.  And perhaps a tasteful tattoo of the rock band the V plays in.

My Wife sees exponentially more colors than I do, but feels cars should be pretty Red, so I was shopping for a red 2009 CTS-V when I found my 2008 STS- in Houston.  The STS-V has some luxury features the CTS-V line does not, but oh that LSA Supercharged 6.2L engine what a nice powerplant; the resulting power in the CTS-V is game changing.

These are terrific, world-class sports luxury cars and I hope they go to nice new homes where people can appreciate them.

So, if you have been waiting on the side lines for the ‘right’ time to grab up a nice pre-owned CTS-V you might give Darin at Crest a call; he has 3.



Cadillac STS-V LC3 Boost vs Engine RPM, Gear

Taking an export from my HP Tuners datalog, I have been doing a bit more data analysis of various parameters.

Perhaps I am doing something wrong, but there appears to be a ‘hiccup’ in the csv export of the HP Tuners, in that the RPM is exported to the comma delimited file with a comma-formatted value.  For example, 2450 rpm is exported as 2,450 rpm so when imported as a comma delimited value it gets split into 2 and 450.  So, once I manually fixed that in my target file then I could import the data and begin to make some charts.

These charts show RPM across speed 0-60 mph, along with Boost at the same speeds.

RPM vs Speed vs Boost PSI

RPM is shown on the left Y axis, and Boost PSI on the right Y axis.  Speed in MPH is along the X axis.

Boost is certainly spikey measured this way.  There may also be other factors involved.

The Boost PSI is calculated by comparing the Manifold Absolute Pressure (MAP) with the V’s Barometric calculation (Baro).  One can see that the V does not shift at exactly the same RPM at 1-2 and at 2-3 although I believe they are both specified to shift at 6500 RPM.

This is the same graph with some smoothing done by averaging of values, 2 prior to and 2 after each point.

RPM vs Speed vs Boost PSI Smoothed

Finally, here is a graph showing boost in the target range of 4500 RPM to 6500 RPM with boost in 1st gear shown in blue and boost in 2nd gear shown in red:

Boost by RPM by Gear


My conclusion is that boost is in fact higher in 2nd gear than 1st gear.  This is perhaps due to more air flow into the intake at speed?  I am not certain.

On the graph Boost appears to settle around 9 PSI at high RPMs.  Boost in this dataset peaks at 9.86 PSI which in the smoothed set is 9.43 PSI.  The STS-V was designed for 12 PSI of boost.  If we assume the supercharger makes 12 PSI of boost then this reading after the Laminova tube intercooler suggests that the pressure drop of air across the intercooler is 2.57-2.14 PSI.

@Cadillac STS-V Supercharger & Intercooler Ideas #Motorama

The Cadillac STS-V (2006-2009) featured the 4.4L DOHC VVT LC3 V8 with a custom Eaton M122 Supercharger and integrated intercooler.

This photo shows the Cadillac LC3 engine without the ‘beauty cover’, looking from the rear of the engine — so the front of the Cadillac would be right and away.

Air flows in the black tubes at the top of the engine to the ‘back’ of the engine, and into the supercharger.  Note the noise baffles in the intake tubing intended to isolate the whine of the supercharger.

This view is of the supercharger+intercooler from the back:


and the next view is the reverse angle or ‘front facing’ shot of the coolant in/out tubes flowing to the intercooler (black part).  The ‘snout’ is the drive for the supercharger.  A belt runs from a pulley below to turn the Supercharger, pressurizing the incoming air.

Once you open and separate the supercharger and intercooler they look like this — note the intercooler is flipped upside down here, as if you simply removed it by ‘opening it up’:

STS-V Intercooler removed from Supercharger

The intercooler is an air to water system, and features Laminova laminar flow heat exchange tubes.

The air flows into the back of the supercharger through the long intake.  Then it is pumped up from the center of the supercharger through the intercooler past the Laminova tubes, and then it flows down the sides of the intercooler casing and the supercharger casing and into the engine.

Each of the four Laminova tubes look like this up close:

Laminova STS-V Intercooler Tubes

The science of the Laminova design is to create huge surface area with minimal air flow restriction.  The very thin fins, 0.2 mm each, along each Laminova tube collect the heat from the air passing through the 0.3 mm gaps between the fins.  The surface area presented to the air flow is approximately 5 times greater than a conventional plate-style intercooler according to Laminova, as well as reducing noise and pulsation.

The heat is conducted to channels surrounding the solid core of each Laminova tube, where liquid coolant is passing through to remove it.

It appears that the coolant flows into the intercooler, circulates through all 4 Laminova intercooler tubes, and then flows back to the intercooler heat exchanger.  The heat exchanger is like a small radiator.  The intercooler coolant system is completely separate from the engine cooling system/radiator.

The advantage of the Laminova design is that they have a very good efficiency with low pressure disruption and light weight.   A disadvantage is cost.

The CTS-V LSA engine uses a finned box air to water intercooler:

This shot shows the CTS-V LSA intercooler upside down.

How can the STS-V intercooler be improved?

An interesting ‘science project’ for the STS-V intercooler would be to replace the intercooler endcaps that direct coolant flow through one Laminova core after another with a custom endcap that directed coolant flow in parallel with all 4 Laminova cores and out after one pass.

One expert mentions that it is helpful to ‘index’ the 4 Laminova cores, so that the large fins are facing the air flow.  I am not clear looking at the images what is intended, as the Laminova cores appear to be uniform and symmetrical, unless the intent is to rotate the ‘sleeves’ the cores are contained in?

Owners are also experimenting with larger heat exchangers at the other end of the system, larger fluid reservoirs to allow more fluid to circulate and absorb heat, and higher capacity intercooler coolant pumps to circulate fluid.

On the slots that allow flow across the Laminova tubes, are the cross-pieces structurally needed?  If removed, so that the slots were just continuous single slots — flow would be increased.

Do you see other avenues to explore?