Retest2 Cold for Comparison and more RPM reversion oddity

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Ran another cold test with the Amsoil eaau6065 filter.  More odd results from Virtual Dyno — although I see the issue in the data file, I just don’t know what is causing it.

Backstory:  I continue to test & tune my 2008 Cadillac STS-V with the 4.4L Supercharged VVT, DOHC V8.  Rated from the factory at 469 hp (350 kW; 476 PS) at 6400 rpm, 439 lb·ft (595 N·m) at 3900 rpm.  Goal: 440 whp or 550 hp.

Summary torque hp boost vacuum

and here is a comparison with the previous test results:

Comparison test to retest

Different days, so equivalent given the test method.

amsoil retest2 another odd run

Another odd result reflected in Virtual Dyno on the 1st (red) run.  I see the issue in the data file but I am uncertain if this reflects a data capture glitch, or an actual phenomena.  You can see the same issue in the Hp/Torque graphs above around 5500 rpm.  These are x-y graphs, so that divot near 5500 rpm means that the RPM built to 5600, then went back down to 5500, then up through to the shift point — all during wide open throttle.  I am unclear what is causing this.  The 2nd run at the same day same site is shown in blue; although it also shows a lower RPM hp peak it is much closer to the expected values.

amsoil retest hptuners 2013-06-16

I added a boost solenoid check to see if the boost solenoid was involved in the variance for the boost psi, but the solenoid remains at 100% duty throughout the scan.

Even on this ‘cold’ run, we are running into IAT2 retard of 1.3 degrees at redline, reducing total timing to 22 degrees.

Conclusion:

  • Continue to see occasional odd data around 5500.
  • Analysis of the delivered torque / hp appears to give a consistent method of determining progress in tuning.
  • Run to run variances appear to tie to the boost variances, which suggests that these may be actual changes and not sensor variances.
  • Max observed boost 9.7-10 PSI above 6300 RPM
  • Max MAF lb/min 60.5-61.5 lb/min
  • Injector Duty cycle 90-92%

Amsoil eaau6065 filter Cold Retest log

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I ran a cold/empty test for my 2008 Cadillac STS-V with Spectre CAI and an Amsoil eaau6065 filter this morning to have for reference.  Today’s run was with the normal 2-3 shift at peak.  [Click on images for larger versions; hit back in browser to return]

Torque vs Boost and SC Inlet Vacuum

Torque vs Boost and SC Inlet Vacuum

The comparison data is from “Rethink advance full cold 0531”.

Today’s run looks as expected.  MAF peak at 60+ Lb/min and Delivered Torque look on target with previous cold runs in warmer weather.  The SC inlet vacuum appears to run ~1.45 psi vs the ~1.3 psi we saw with the K&N filter.

Here was the HPtuner data at peak in 2nd gear:

HPtuners screen capture

HPtuners screen capture

The V was cool and almost out of fuel.

The Virtual Dyno run reads high Torque, Low HP:

Virtual Dyno suggests good Torque but low high RPM HP

Virtual Dyno suggests good Torque but low high RPM HP

I am uncertain how to interpret this relative to the other readings.

Conclusion:

I include these dataruns to study repeatability and build info on my current setup.  The key to tuning is to have a solid reference set to compare to.

 

K&N RU-3100 comparison to Amsoil eaau6065

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Amsoil 6065 filter installed on the Cadillac STS-V Spectre intake

Amsoil 6065 filter installed on the Cadillac STS-V Spectre intake

I recently replaced the Spectre filter in my 2008 Cadillac STS-V (supercharged 4.4L V8) with Spectre CAI with a K&N RU-3100 due to delayed availability of the Spectre replacement.  I also picked up an Amsoil eaau6065 filter.  These are both the same form factor — 6″ mouth, 6″ long, 7.5″ to 5″ cone shaped.  The K&N is oiled gauze, and the Amsoil is a microfiber dry filter.

The K&N was $39.86 ($43 delivered via Amazon) and the Amsoil $60.05 (just over $72 delivered).

The test runs were done using a similar method but on different days; 88F for the K&N, 91F for the Amsoil test.  To test the two filters I used HPTuners to capture both lb/min output from the MAF during a wide open throttle acceleration run in 2nd gear, and vacuum pressure at the supercharger inlet in PSI.

This was a heat-soaked test comparison, meaning that the engine of the STS-V, intercooler, and air inlet were hot, and the day was hot.  This results in lower performance, but was similar across the two tests.

MAF and SC Inlet Vacuum

MAF and SC Inlet Vacuum

A higher MAF reading is better, and a lower SC inlet pressure reading is better.

What the test showed is that the 2 filters recorded equivalent MAF readings, but the SC inlet vacuum for the K&N was lower than the Amsoil air filter by 0.0-0.15 psi, or 0-4 inches of water.

Comparison of hot runs K&N and Amsoil

Comparison of hot runs K&N and Amsoil

I also ran a virtual dyno which appeared to show equivalent performance with test to test variances.  The Amsoil result had equivalent peak hp (366 hp vs 367 hp) and appeared to make more torque at lower RPM, but my impression is this is virtual dyno variance because we don’t see a variance in the MAF readings at similar points.

Hp Tuners Delivered Torque Comparison

Hp Tuners Delivered Torque Comparison

The PCM’s evaluation of delivered torque from each run appears to be very equivalent.  Not surprising as this depends on MAF input, but persuasive that output performance between the two is similar.

Conclusion

The K&N appears to flow slightly better — less vacuum is pulled — but the resulting air flow through the MAF in lb/min and Delivered Torque calculations look very equivalent between the two.