Tag Archives: HpTuners

ATS-V LF4 HPTuners Tune 3c2

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Current Scan snapshot:

Prior scan snap shot at same rpm/speed showing throttle closing then:

First test for my ATS-V LF4 with tune 3c2. My intent is to change the least number of parameters in order to allow the engine to make as much power as it can. My goal is a stable 18 psi tune with no KR and no throttle closing.

Current conditions were 68F, 12 mph wind, 92% humidity, 29.81 in Hg pressure. SAE correction factor 0.9923039631981221, so 467 hp equates to 463 SAE 1349 HP.

There was some Knock Retard (KR) at cylinder pressures 1.16-1.32 during full throttle operation. I used a table to analyze where I was getting KR by RPM and pressure, then reduced the spark commanded in this region by 1 point in the effected areas. A rule of thumb is reduce the spark 1/2 of the KR observed. In my case this appears to have reduced the KR but not totally, so I will need more attention here.

Torque Management – General – max engine torque limit – I multiplied the 0% and 20% alcohol rows by 1.2, for a 20% increase.

Torque Management – General – TCS max torque set from 445 lb ft to 550 lb ft.

Torque Management – Driver demand – tables A and C I multiplied the bottom row by 1.1, then the bottom 2 rows by 1.1, then the bottom 3 rows by 1.1. This applied a stacking increase the the bottom 3 rows.

Torque Management – S/C Boost control – max limit I added 2 psi across from the left up through manifold temp 158, leaving higher temps unchanged. This added 2 psi to ceiling when the manifold temperatures are in check.

Good news: Holding throttle. the first image shows throttle is matching the pedal input. Also, boost (math) around 18.x psi total; here, 17.8 psi versus 14.9 psi prior, so 2.9 psi increase.

To do list: Still some KR to clean up with reduced spark. I also still see hints of desired falling in ranges I am unsure why it is not holding stable, so more study needed.

I am making progress toward my goals; I see 18.4 psi of boost, and no throttle closing. More tuning needed for KR.

Cadillac ATS-V HPTuners Stock Scan & Throttle closing

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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.

Cadillac XLR LH2 Tuning — Tune 6F Mixed MAF recal

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Today’s Tune 6F uses the High Baro MAF calibration from 6B except from 4200-5200 rpm, where it pulls the air fuel ratio slightly (2%) richer.  What I hoped to see is a very flat air fuel ratio in the NBO2s, because that’s what we are commanding in the PE (12.5 AFR or 1.176).

The test setup had another freeze ahead of the test.  This time at least the XLR didn’t tilt, and after a few stop, turn the engine off, reassemble all connectors, restart the software, it started scanning again.

My prediction was that we would see the same result as Tune 6B, with better support from 4200-5200 RPM due to no fueling dip there.  Overall the result was not what I expected, but then, I’ve come to expect that.

XLR Tune 6F Mixed Maf

The red line is Tune 6B.  The ONLY difference between Tune 6B and Tune 6F is 4200-5200 rpm.  So the fact that Tune 6F comes to 4000 RPM 13 whp behind is a mystery (different days, different conditions, etc).  From 4200-5200 Tune 6E does well enough, but missing the tuned-in VVT hump at 5500 rpm.  Tune 6B does better from 6000+ rpm (but they are exactly the same out there!)

XLR Tune 6F AFR vs MAF Freq

This graph shows the narrow band trend for AFR for Tune 6F in blue, 6B in red.  I think the blue is much flatter, which was the goal for the test.  I included the MAF frequencies in yellow so I could easily relate the various regions to the way the MAF calibration works in the tuning tables.  Something odd happens to the air flow at 5200 rpm or so on both.

Again, the AFR is commanded flat from 4000-6800 RPM so I am calibrating the MAF to drive the blue line flat across the graph (ignoring the noise in the line).

XLR Tune 6F hptuners

Hptuners result showing max calculated HP for conditions for 6F.

XLR Tune 6B max HP b

Similar data for Tune 6B at max hp for that run.

In summary, good that the MAF calibration changes drove a more consistent AFR.  Again, not sure why I am seeing large day to day changes, except of course different days, different conditions, etc.  Perhaps every test needs to be Run Tune A, stop, recalibrate, Run Tune B, then compare.  That way they are on the same day, more or less similar conditions, etc.   Virtual Dyno does try to correct for baro and temp, but still seeing some variances creep into the tests.

UPDATE

After consideration, I believe part of the variability I am seeing is that Virtual Dyno corrects for baro and temp but not for humidity/dewpoint.   46% humidity (like today here) can double the dyno correction factor vs dry air.

xlr tune 6F comparison humidity corrected

I plan to return to a process of using a calculator to correct for altitude, dewpoint, and humidity to arrive at absolute pressure and temperature for dry air, then put those values into Virtual Dyno for each run.  That will eliminate another source of variation.

UPDATE 2:

After some comparisons I see that if I put in adjusted pressure in dry air and test temp (as opposed to dry air temp) then I get almost the same multiplier as suggested by the dyno adjustment, within 0.1%

XLR Tune 6F comparison corrected

So this is my new plan on how to input baro and temp for Virtual Dyno.  This still leaves Tune 6F below the prior runs, but I will get more samples and see if this one was an outlier or we learn more.