2008 Cadillac STS-V Spectre CAI + Corsa 394.3 whp 380.4 lb ft

Today I headed back to True Street Motorsports in McKinney Texas to get some dyno time in and check my air fuel ratios after the addition of the Corsa axle back exhaust.  Click on the graph to zoom in, then hit back on your browser to get back.

STS-V WHP and Torque vs Engine RPM

Coincidentally, the Spectre Cold Air Intake (CAI) added 19 wheel horsepower (whp) over the baseline pre-Spectre CAI, and the Cora axle-back with the Spectre added another 19 whp for a total of 38 whp.  The Corsa addition opened up a nice 20 ft lb of torque.

A dyno measures horsepower at the wheels, or whp.  This is always less than the manufacturer’s advertised engine horsepower, or hp at the crank of the engine.  WHP is hp after losses through the transmission and drivetrain.  A reasonable figure for these losses on the STS-V’s 6L80e transmission is 20-24%.  On my STS-V, the stock car was rated for 469 crank hp and made 356 whp on the dyno, or  a 24% loss.  if we use 22% as an average then the V originally made 456 hp stock.  The addition of the Spectre got the car to 375 whp or +24 crank hp, and the addition of the Corsa with the Spectre CAI got the STS-V to 394 whp or +49 crank hp.  Overall a nice gain for two easy bolt-ons, and the STS-V is now making 394 whp which at 20-24% losses equates to 492-518 hp at the crank.

Air Fuel Ratios

Part of the point of the visit was to ensure the Air Fuel ratio was in the right range and stayed there throughout the Wide Open Throttle dyno run.    The resulting fuel levels are safe and consistent with commanded.

This graph shows the same info zoomed in a bit and with a detail point showing that the new exhaust at key points actually adds +27 lb ft of torque:

I am close to my power goal of over 400 whp on the dyno at 394 whp.   I want to run a new baseline on the dyno with the car cool and not heat-soaked for comparison.  In fact, our 3rd run was at the same whp as the initial run today, but with the intercooler Intake Air Temp 2s (IAT2) hitting 150F+ due to the stress of repeat dyno runs on the original,  stock intercooler cooling system.    That suggests that the V may put down 400 whp when not heat soaked.

Fun day, and as always the True Street Motorsports team is easy to work with and helpful.

Cadillac STS-V Spectre Intake dyno test

I had a great time with my Cadillac STS-V this morning at True Street Motorsports in McKinney.  We did a baseline dyno run on my 2008 Cadillac STS-V, then installed a Spectre custom intake for the STS-V, and ran a new dyno for before/after tests.   The Spectre intake was custom ordered through Streetsideauto.

Cadillac STS-V on the Dynojet dyno

As soon as I arrived the True Street Motorsports crew got the Cadillac on the dyno and off we went.

A first casualty of the day were the batteries in my flip camera, so I switched my kodak to video mode and captured videos of the dyno runs:

True Street  Motorsports uses an in-ground Dynojet dyno.  A dyno reads horsepower at the wheels, after losses through the transmission and rolling losses.

One might expect an STS-V to put 360-370 hp to the wheels based on other results I have seen; my STS-V today did 356.8 whp and 350.2 ft-lb of torque, so a bit below average.

Once we had a baseline, the team started removing the intake and replacing it with the Spectre custom STS-V intake.

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

This was the dirty picture from after I first removed the beauty cover to give an idea of the original intake tubing in place.

For the first run it was 92.9F 29.64 in Hg Baro, humidity 15%.  By the ‘after’ runs it was 99.4F.

Spectre intake parts ready to go in

Spectre intake parts ready to go in

The new intake parts replaced all the factory intake from the box to the intake pipes leading around the engine.

Spectre Intake installed STS-V

The OEM intake has baffles to reduce the supercharger characteristic whine; the new intake is lighter and has no sound baffles.

OEM intake piping with baffles

With the intake installed, coolant hosing routed appropriately, and fuel trims reset, we were ready for the AFTER dyno pulls

UPDATE: replaced the ‘after’ video with higher rez combination of the two video files.

This chart shows the before/after dyno runs on a single comparison chart:

2008 STS-V Before/After dyno runs

Lots of things to consider in these results.  First, I am happy with the Spectre Intake and the support from StreetSideAuto, and I had a blast at TrueStreet Motorsports, so thanks all around to everyone.  I’ll be doing more dyno runs at True Street Motorsports in the future.

The results were somewhat worse than hoped — I was hoping to see +40 whp before/after and we saw +19 whp.  If the 356.5 whp was 469 hp at the crank “before” (24% losses) under perfect conditions, then the after reading of 375.4 whp might equate to 493 hp at the crank “after” with only the Spectre Intake mod, or +24hp.

It was very hot here in Texas, and although the dynojet uses a correction factor to ‘standard’ conditions, that may or may not compensate adequately for the actual hp lost due to the hot air for a supercharged Cadillac.

HP vs Torque across all 4 runs exported Run Viewer

This chart is the same data done using the raw files and the dynojet viewer.   Click on the image for a larger copy, then hit back to return.

Next I want to wait a couple of weeks, then rerun a ‘check’ dyno, and swap the MAF to a different lot of the same p/n MAF and retest.


Good day, parts works, good times were had.

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!