Remove Beauty, Free the Beast: @Cadillac STS-V LC3 Thoughts

For my upcoming Spectre Intake install the beauty cover on the LC3 4.4L DOHC VVT V8 in my 2008 STS-V will need to go.  Technically, it can stay with less underpadding, but good excuse to remove it.

The top of the engine — the intercooler on top of the supercharger on top of the engine — is capped with this nice Cadillac beauty cover.

In my opinion, a beauty cover misses the point.  I get that it cleans up the engine compartment nicely and all.  But the beauty part should be the engine, not a molded cover hiding the engine.

Here’s what it looks like with the covers removed: (click on images for larger versions)

STS-V Engine with Covers Removed

With dirt, part of the underside of the foam from the beauty cover, et al.

This actually is MUCH more interesting to me, and you can see the air intake piping, the intercooler and cooling lines, and even down to the right the belt drive for the supercharger.

Cadillac STS-V intercooler coolant reservoir

This is a close-up shot of the intercooler coolant reservoir.  Yes, it looks like it is just a filler neck because that is what it is.  The fill cold line is near or at the top of the tube.  You can just see the actual coolant in the tube just at the bottom of the tube before the insulated covering.

The tube coming out of the top of the reservoir is a vent drain to an empty spot in front of the battery.

It strikes me that replacing this small tube with a larger but sized to fit in the space reservoir would add more fluid capacity to the system and if selected appropriately bolt in.

It is very hard to photograph the front heat exchangers, but here is a shot and bear with me because we’ll switch to diagrams after the photo:

STS-V heat exchangers engine shot

There are three different heat exchangers in view at the front of the STS-V.

STS-V LC3 Engine Coolers; Radiator, A/C Condenser, Intercooler

The are in order from back to front, 22 the radiator, 21 the transmission oil cooler, 19 the A/C condenser (CONDENSER,A/C ACDelco #15-63240), and 17 the intercooler front-mounted heat exchanger (FMHE), (RADIATOR,CHRG AIR CLR, 25770419).

STS-V LC3 Intercooler Heat Exchanger

So looking at that, this view looking forward in the engine compartment probably shows the item 19 (black); the intercooler heat exhanger is a smaller item ahead of that and not visible.

This diagram shows just the intercooler flow paths and parts:

STS-V LC3 Intercooler Flow path & Parts

This gives me pause — the assembly diagram shows a reservoir (1) and the line from the tube running to that reservoir.  My STS-V does not have this item (1) at all, so I’ll have to check with other owners to see what they have.

The intercooler pump part number and info is

018 22718756 PUMP. Turbocharger/Supercharger Cooling.
PUMP,CHRG AIR CLR COOL(LESS CLAMP). Required: 01For: DX 4.4D(LC3) (2006-2009) (2006 – 2008).

STS-V LC3 Engine Compartment with side covers and front cover on


The front center cover over the heat exchangers strikes me as perhaps functional, and used as a shroud to keep air flowing through the radiator.  I put that one and the side covers back on for every day use.

Questions to ponder:

Is there an easy way to expand the intercooler coolant reservoir at the overflow and so add more coolant to the system for heat buffering?

The standard front mounted heat exchanger for the intercooler appears to be large and very functional.  Is this really a weak spot and needing to be changed, or is the issue really the amount of fluid in the system?

Next Project: Get out there and clean up the engine compartment!

Project Cadillac Tuning Plan

I am enjoying my 2008 Cadillac STS-V; it is a terrific design right out of the box.   Cadillac pulled out some stops in developing this unique 4.4L Supercharged Northstar variant.  For example, the exhaust manifold was extrude honed to optimize flow.  Originally the V was rumored to get 440 hp, but with some final tuning the team was able to raise the STS-V to 469 hp.

An engine dyno as in the graph above measures horepower at the crank (hp).  A chassis dyno measures horsepower at the wheels (whp).  Horsepower at the wheels includes inefficiencies of the powertrain.

For an automatic RWD automobile, powertrain inefficiencies often run 20% of the power.  So for a 469 hp STS-V, one might expect to measure 469 x 0.8 = 375 hp at the wheels.  From my research, most STS-Vs measure 360-370 hp at the wheels, so perhaps a bit more than 20% loss at 22-24% due to luxury isolation in the powertrain. One outlier pulled 379-387 whp however.

HP is often used to indicate hp at the crank, and whp, or wheel horsepower, is used to indicate horsepower at the wheels.

To go from chassis dyno wheel hp to hp at the crank, divide by 1-inefficiency.  So if inefficiency = 20%, WHP/(1-20%) = WHP/80% = crank hp.

The classic hot rodding questions are,

  • How much money do you have?  and
  • How fast do you want to go?

The hidden gem in this discussion is, before you sink a ton of money into your car, you should have a plan.  If you want to achieve a specific goal, then you might start with a different car, for an extreme example.

Supercharged Northstar

My goals for developing my STS-V:

  • It is a Cadillac: maintain luxury features,  & avoid “noise for noise sake”
  • Test and Tune:  only add / change items which prove to add performance
  • Phase 1:  500 hp, so 400 whp
  • Phase 2: 550 hp, so 440 whp

What will that let me do?

  • Be happy that the Cadillac STS-V is tuned to optimum performance
  • Enjoy the journey of researching, selecting, testing, and writing about the Cadillac Project

My first Project looks set to be a Spectre intake from Jaime at StreetSideAuto.  In Spectre’s tests the intake added 40+ whp.  True Street Motorsports has agreed to help with testing the new intake once it arrives using their Dynojet dyno.  First we’ll establish a baseline for the STS-V stock.  Then hopefully we can get clear before/after apples to apples tests with and without each modification.

In my True Streets Motorsports correspondence they refer to the test as “Project Cadillac”, hence today’s title.

Other project ideas in sight:

  • Custom Tuning
  • Intercooler pump, reservoir or heat exchanger mods

More to come as things change, arrive, and evolve.

What would you like to see tested on a Cadillac STS-V?  If you have a performance product you would like to have independently tested on a Cadillac STS-V, please let me know.