Category Archives: STS-V

Cool Air, new Cadillac STS-V times

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I have some dyno time scheduled for Saturday, so I wanted to get a current baseline on my 08 Cadillac STS-V.

Racelogic PerformanceBox GPS times:

Speed(mph) Time(s) W/Rollout Dist(f)
10 0.95 0.56 6.34
20 1.64 1.25 21.45
30 2.31 1.92 45.86
40 3.05 2.66 84.29
50 3.94 3.55 143.25
60 4.94 4.55 223.83

New low time today — a 4.55 sec 0-60 mph with rollout, or 4.94 sec w/o rollout.  This was my goal for the V — to get to a solid <5 sec without rollout.  Car had 3/4 tank of fuel and the run not heat soaked.   The STS-V has the Spectre cold air intake and a Corsa axle-back exhaust system.  I weigh 35 lbs more than the standard 160 lbs for the buff magazine journalists who get the great times for car mag tests.    Local fuel is 93 octane E10.  The backup 0-60 run was 4.74/5.13 sec.

The 60′ time was 2.2 sec, which is an improvement from my usual 2.4 sec.  PkAccelG was 0.77G. The 1-2 shift was recorded at 0.4 seconds.

Peak Hp was calculated at 6,371 RPM: [click on the image to zoom, hit back to return]

Peak calculated HP at 6,371 RPM

Calculated HP has steadily run less than expected on this V, but I am not clear why.  It uses the Delivered Torque calculated by the engine at RPM to calculate theoretical HP.  The value is a notional figure and not considered accurate for tuning, but I use it as a relative indicator.  I am also not able to run flat out in 4th gear as on the dyno though.

Same run, peak HP at 65 mph at top of 2nd gear:

Top of 2nd gear at 65 mph

Interesting that boost in 2nd gear was running 10.6 psi vs 8.8 psi at the top of 1st gear.  I do not think this is a tuning issue but may have just been a transient thing.  The boost was trending in the 9s then dips and then peaks at 10.2 psi at the 1-2 shift in the scan.

Due to the low temps, the IAT Advance was actually ADDING timing instead of retarding!

Here is the cold air IAT / IAT2 histogram for the whole test cycle:

No KR anywhere on the run.   PE is commanding AFRs down to 10.5, so that is something to consider.  Safe AFR for a supercharged engine probably up at 11.5 to 11.8 where the engine should make more power.

Atmospheric Conditions:

Atmospheric conditions and effect on HP

 

Quest for Intercooler heat exchanger air flow

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I’ve been thinking about how to make my intercooler heat exchanger more effective before I add more parts.

The intercooler heat exchanger on the 2008 Cadillac STS-V is a small radiator in front of a line of other coolers and the main radiator – item 29 below.

STS-V LC3 Intercooler Flow path & Parts

Air flow paths are key to the performance of any radiator type cooling system. In this case the heat exchanger is facing cool air.

I intended to study the ducting to see what minor improvements could be made — such as sealing air flow to the bottom of the heat exchanger.  However, I was surprised to find that although Cadillac engineered exactly for this item, the plan for my STS-V is not working at the moment.

The way it is supposed to work is that there is a plastic belly pan below the nose of the car, running below the intercooler heat exchanger.  On top of the plastic belly pan is a long rectangular piece of foam that will nicely seal the air flow under the heat exchanger but still allow the water hoses to and from it to pass through.  However, on my STS-V the belly pan is sagging in the middle, and the foam is no longer sealing the lower part of the heat exchanger but rather allowing 2-3 inches of gap for air to flow through.  Since air will always take the path of least resistance, every bit that can is sliding under the car and away instead of cooling my intercooler.

Cadillac STS-V radiator air deflector

My belly pan (item 9) is missing any fasteners #8, which appear to be 14093088 although not shown in this diagram  — so that item 7, the foam bar, fills the gap there.

25802477 DEFLECTOR. Radiator Air
DEFLECTOR,FRT AIR. Required: 01For: DX (2006-2009) (2008 – 2009).

15248340 SEAL. Radiator Support Mounting
SEAL,RAD AIR LWR. Required: 01For: D29 (2005-2011) (2008 – 2009).

14093088 RETAINER; RETAINER FRONT. RETAINER. Front Fender Inner Wheel House. Air Cleaner Intake. Bumper/Fascia. Bumper/Fascia Energy Absorber. Capsule/Headlamp Washer/Wiper. Chassis/Engine Wiring Harness. Cowl Top Vent Louver. Engine Coolant Recovery. Folding Top Compartment. Front and Rear Bumper/Fascia Face. Front Compartment Pan. RETAINER FRT. Grooved. License Plate. Main Wiring Junction and Fuse Block. Mobile Telephone Radio. Radiator Air. Radiator Baffle and Shroud. Radiator Fan Shroud. Radiator Grille and Front End Panel. Rocker Panel Molding. Roof Headlining.

So tomorrow I will check with Pep Boys and Crest and see if I can get 2 retainers and put my intercooler heat exchanger back in the air flow.

Minor adjustments and temperature trends Cadillac STS-V

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Making more room for fast revving at gear changes:

  • Raised Cutoff by 200 rpm: Engine Fuel Cutoff DFCO Cutoff vs RPM
  • Raised cam disable by 300 rpm: Engine Airflow Variable Camshaft Hi RPM Disable
  • Lowered Transmission torque management by 50% at WOT — Transmission Torque Management — Adder Modifier -0.50 at RPM 4500

1-2 Shift max rpm 6529 (target 30 mph / 6500 rpm)

Resulting shift 1-2 took 0.3sec then 0.4s on 2nd test. Need to retest cold due to the engine making more power cold.

Temperature trends hot / heatsoaked versus cold:

Corsa Cold Baseline Mar 25 2012 2nd Run



Down Delta MPH (Temps in Deg Fahrenheit)
Item 0 30 45 60 Across Run Heat Add
Ambient 55 55 55 55 0
6 IAT1 61 63 63 63 2 8
32 IAT2 93 93 100 106 13 43
0 MAT 93 93 107 129 36 23
Corsa Hot Run 1 3/26



Down Delta MPH (Temps in Deg Fahrenheit)
Item 0 30 45 60 Across Run Heat Add
Ambient 82 82 82 82 0
8 IAT1 90 95 95 93 3 11
30 IAT2 120 120 127 135 15 42
1 MAT 121 120 126 159 38 24
Corsa Hot Run 2 3/26



Down Delta MPH (Temps in Deg Fahrenheit)
Item 0 30 45 60 Across Run Heat Add
Ambient 82 82 82 82 0
9 IAT1 91 93 91 90 -1 8
27 IAT2 118 118 126 131 13 41
1 MAT 119 118 125 152 33 21

Interesting consistency that IAT2 uniformly starts ~30F and ends ~40F hotter than IAT1 regardless of ambient.  This suggests a way to check effectiveness of changes to the intercooler cooling system.  Other runs show a end range of 40-47F.