Cadillac ATS-V LF4 Tune E1

Purpose: Keep the throttle closed again after boost ramp up. Eliminate TCC slip. Study KR vs PE by going richer, so closer to tune c2.

Plan: Raise PE to 12.7 to try to address KR; no change to spark map for this run. Address TUTD shift RPM to try to enable automatic shift up in 1/2/3/4 not 5/6/7/8 so can hold those if needed for dyno. Adjust Turbo Knock Mass to raise desired boost level to try to close throttle. Study scanner with car to understand missing channels. Modify TCC pressure apply ramp to reduce TCC slip. Rescan.

Conditions: 76F, 29.83 baro, 87% humidity. SAE J1349 correction 1.0052575076413.

2nd gear 456.8 hp @ 5838 rpm / 458 torque @ 5126 RPM with 17.4 psi boost at peak hp
3rd gear 464.8 hp at 5320 rpm / 469.5 torque @ 4660 RPM; with 19.4 psi boost at peak hp
Corrected 3 gear: 467.2 hp / 471.9 lb-ft torque

Result: Still getting KR at WOT at 12.7:1 PE and current spark map.
Throttle opened at 5718 RPM in at 71 mph on one test, stayed closed in another. Desired boost just before 34.5, actual boost 34.4 psi. Then desired boost falls off and throttle opens. 2.3 degrees KR showing at that point. MAT 133F. Boost 19.1 psi. Cyl airmass 1.34. fine on boost max limit but pinched on knock airmass. So further knock airmass adjust?

Comparative results from last 3 scans on TCC slip error; still needs attention. For the gallery images, right-click then select view in new tab to see full page versions.

Missing parameters: Connected to vehicle, then repolled vehicle for parameters. Now everything is showing again. I think this happened after I changed from stable release to beta release, but beta release is seeing all the parameters after repolling.

Cadillac ATS-V HPTuners Stock Scan & Throttle closing

I am starting to run driving scans on my 2016 ATS-V to get a feel for how the engine operates. The LF4 twin turbo 3.6L engines use a torque management based strategy. The control sorts out what torque is desired, then manages the powertrain to make that torque, independent of throttle input. The throttle input (gas pedal) is treated as a request — so you might have the pedal on the floor, but if the engine is making over 100% of the torque planned at that moment, the actual throttle may close to maintain the torque to the planned levels.

In the image above, the Cadillac is accelerating through 61 mph, at 5313 RPM. The pedal is at 100%. The actual throttle however, is at 67.8%. The ATS-V was making “too much” power at that moment. If you examine the 2nd row in chart vs time, the green line is throttle %, so where we see dips in the green vs yellow line is where the ATS-V is reducing engine power to desired or planned output.

In this case, at this point, the total boost pressure of 31.5 psi (without adjusting for baro) was higher than the Desired Boost pressure of 30.7 psi. So the engine controller is pulling back the throttle because too much power is being made.

I also note that the stock file is running a few points of KR, or knock retard. There is a ramp up of the planned advance in that range. The engine controller goes from a spark advance of 8 degrees up to 10.5 then down to 10 degrees. That appears to be too much since the KR (knock retard) is going to 2-3 degrees there. Although it is possible that a richer air fuel ratio (AFR) would be fine.

The ‘stock’ commanded AFR is 12.8, lamda 0.909 equivalence ratio commanded. This is within the range of what most tuners are doing with the LF4 direct injected V6. This ATS-V may prefer to be slightly richer, but needs more research.

Correction Factor: Ambient air: 72F, Intake air 75F. Baro 29.5223 inHg, 83.13% humidity so SAE J1349 correction of 1.01555. 453.6 hp corrects to 460.7 hp.

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.