STS-V OEM air filter

[Bruce Nunnally]

I went back to consider the OEM air filter. I like my Spectre intake, and it proved out on the dyno to add 20+ WHP. But I know the factory guys worked hard on the intake, and I am specifically interested in the paper filter approach they used.

These shots show the opening the OEM paper filter breathed through, and a shot of the OEM paper filter outside of its housing.

[Bruce Nunnally]

Wow these bad boys are $75 on amazon from AC Delco p/n A3078C GM 15813300 and Delco suggests a list price of $160. For the filter element. Apparently this part was unique to the STS-V

http://www.amazon.com/ACDelco-A3078C-Air-Filter-Element/dp/B000IZ3MTI

[Texas Jim]

Man.... They are proud of them things.... LOL

[Cadillac Jim]

I just checked Rock Auto and they are $77 and, yes, they are unique to the STS-V.

The flow isn't clear to me from the photos. I can't imagine that the factory arrangement has the air going through *all* that paper. The high-performance requirement would make the design maximize the paper area, but I don't see a flow pattern that would see just one side of that roll of corrugated paper.

[Bruce Nunnally]

The air would appear to flow end-on as shown. Not clear to me what the filtering mechanism was, unless perhaps each honeycomb hole makes a turn at some point. If I hold it up to the light I can see some light through it. Some of the honeycomb passages appear to be sealed with a wax or similar substance.

The casing also has a catch-pad and trap mechanism for some air to travel through a separate small panel back to the filter; not sure if that is a water trap or provided some sound deadening.

[Bruce Nunnally]

air filter sizing / calculations: http://www.gnttype.org/techarea/turbo/airfilter.html

CFM required for a 4 stroke motor = CID x Maximum RPM / 3456 x (1+ Boost/14.7)

K&N:

• Universal Round Taper: (Base + Top) / 2 = A; Take A x Length x 6 x 3.14

For STS-V,: 266 x 6700 / 3456 x (1+ 12/14.7) = 515 x 1.81 = 933 CFM required

Current cone filter (Spectre) 7.5" base, 5" top = 6.25 A; 6.25" length.

6.25x6.25x6x3.14 = 735 CFM with no restriction (if the Spectre flowed as well as a K&N)

[Z15]

The looks like a Donaldson Powercore filter. They also use a Powercore on 2007+ Duramax diesel engine.

http://www.donaldson.com/en/engine/support/datalibrary/059806.pdf

[Bruce Nunnally]

Thanks! The description does appear to be the way this one worked.

[Bruce Nunnally]

Wish I could filter down hot air temps #Motorama

Posted on May 22, 2013by bwnunnally

After a recent test I noted that the Spectre filter in my 2008 STS-V with Spectre CAI was dirty. I placed a Spectre replacement filter Spectre Performance SPE-HPR9886K Air Filter on order, but it was delayed — now due May 29. In the mean time I ordered a cleaning kit, Spectre 884820 Accucharge Filter Kit and an equivalent K&N filter, K&N RU-3100 Universal Rubber Filter

Read more: http://caddyinfo.com/wordpress/install-a-new-clean-filter-go-slower/

[Z15]

You should check out these AMSOIL replacement filters. They don't need any oil and can be vaccumed clean.

http://www.amsoil.com/shop/by-product/filters-and-by-pass-systems/air/amsoil-ea-universal-air-induction-filters/?zo=34396'>AMSOIL Ea Universal Air Induction Filters

Here is a link to the sizes, http://www.amsoil.com/products/ea_filters/EaAU_Photos_and_Specs.pdf

EaAU6065 seems to be close to the Spectre filter?

[Bruce Nunnally]

Thanks; yes those look interesting too. I would like to get one of those; I agree that model nbr is the size. The placement is limited to that length in the STS-V Spectre CAI setup.

[Bruce Nunnally]

Re-test of K&N filter on Spectre CAI with Virtual Dyno

Posted on May 24, 2013by bwnunnally

This morning I ran some cold comparison tests for the K&N Filter in the Spectre CAI.

I changed my test method for these runs — same test route, but instead of starting from a stop, I started from a roll with the transmission manually selected to 2nd gear. My thinking was that this would be less stress on the tires/drivetrain, and give better low rpm torque readings.

Read More: http://caddyinfo.com/wordpress/re-test-of-kn-filter-on-spectre-cai-with-virtual-dyno/

[Texas Jim]

That is an odd result...

[Bruce Nunnally]

I found some seeming comparables here http://caddyinfo.com/wordpress/virtual-dyno-building-a-sample-set/

To think about where I was testing using a similar method, but again with diff results.

The new test certainly looks like the engine is not getting enough air at high rpm, or one tire is low (or similar hindrance at higher speed?)

[Texas Jim]

That was my thought... not enough air at high RPM...

[Cadillac Jim]

There are some strange variations that I don't understand. Is it possible that there are some resonances in the intake that are modified by the use of different air filters? If there are horns that dead-end coming off the intake horn, that may be something to think about.

[Bruce Nunnally]

I am thinking the same line but different direction -- the MAF raw reading show plenty of air coming in in lb/min. It is making a ton of torque compared to normal.

I am wondering if it is blowing off air charge, or limiting boost for some reason and am studying that angle.

[Bruce Nunnally]

Reset all three ways for the PCM to control / limit boost and re-ran hot. I added back 2 previous runs when I first put on the K&N hot also.

This doesn't tell me what the V will do cool, but have to wait for it to cool overnight and a good weather window to test.

Red run is tonight; blue and green are previous K&N hot runs.

HPTuners screen shot in case needed for later reference:

[Bruce Nunnally]

I am gathering more test information using HPTuners and Virtual Dyno on my 2008 Cadillac STS-V across different modifications. Today’s runs with a full tank of gas and nice weather after an overnight rain. HPTuners shows the baro that the engine perceives, so I am using that for baro adjustments.

Read More: http://caddyinfo.com/wordpress/more-air-filter-testing-kn-on-spectre-cai-coldfull/

[Cadillac Jim]

I believe that the MAF senses the air after the boost bypass gate, otherwise it would not be useful in controlling the mixture. Perhaps the spark advance? That would differ over temperature.

[Bruce Nunnally]

The MAF is just inside from the air filter -- the air filter attaches to a velocity stack that reduces from 6" filter to 3" intake tube and that flows into a calibration tube and the MAF. The boost bypass is all the way up on the supercharger.

Yes, the engine pulls advance and fuel in relation to temperature. The part that is subtle is that I feel the effect of temperature because it pulls power for this car is larger than the compensating formula in the SAE standard for temperature. Of course, the SAE formula can't and doesn't try to account for things the vehicle does due to changes in conditions.

[Bruce Nunnally]

Virtual Dyno, Wheel HP, Calculated Engine HP, and You #Motorama

Posted on May 25, 2013by bwnunnally

My Cadillac STS-V as most modern cars keeps up with how much torque the powertrain is delivering. It uses this info to make adjustments in power delivery if needed.

Knowing the Delivered Torque, we can derive the Calculated HP, since we know the standard definition HP = (Torque x RPM)/5252

Engine RPM (SAE) rpm Delivered Engine Torque ft.lb Calc Engine HP 3564 423 287.05

Virtual Dyno focuses on lovely HP/Torque graphs of power at the wheels, but of course is based on data tables which one can read from the graph node points.

Read More: http://caddyinfo.com/wordpress/wheel-hp-calcualted-hp-and-you/

[Cadillac Jim]

Sorry, I thought that the MAF you were referring to was the same one as is in my old 1997 ETC, in the throttle body which is right on the intake manifold plenum, just preceding the throttle plate.

I just looked in the 2011 CTS-V shop manual and found this boost control diagram:

The numbers are:

1. By-pass Valve Actuator
2. Boost Signal
3. Boost Control Solenoid
4. Boost Vacuum Source
5. Supercharger
6. Intake Plenum
7. By-pass Valve (normally closed)
8. Throttle Body
9. Air Cleaner
10. MAF Sensor
11. Inlet Vacuum Signal

If yours is similar as I expect that it is, the boost bypass is back into the intake and the MAF is indeed just in front of the throttle body, which is in front of the supercharger. Since there is no waste gate back out into the world, the MAF as placed does provide input to the PCM to maintain air/fuel ratio, although I suspect that it needs the oxygen sensors to keep track during quick changes in throttle position or load.

If the MAF is indicating the amount of air that the engine is getting and the air-to-fuel is within bounds, the variable is the engine efficiency. The biggest handle that the PCM has on efficiency is the spark advance, which is based on elementary principles on the knock sensor, and, in fact, probably based on the ECT, IAT, and IAT2 sensors too, and thus would show a decrease in power on boost when the engine was hot for the same MAF readings at a given RPM range.

This doesn't explain changes in shape. With the stock setup the torque is almost constant over the entire operating range of RPM for the CTS-V, something that I have marveled at since it came out. We're seeing rolling hills and swoops now, which is what led me to think that we were modifying resonances somewhere, the resonances that are put in the intake an exhaust during engine development to shape the torque curve.

[Bruce Nunnally]

Thanks for posting. Yes I was on the same trail regarding causes of the 5/24 early torque peak outputs. Since today's correction is back to a more normal, expected shape I am going to assign it to something engaging early in boost control.

I did take apart the filter and velocity stack and reassemble to make sure no obvious physical factors were the cause. I also adjusted the tune to ensure no boost controls could engage. The troubling thing between the two is still the huge mid-range torque hill (which I would prefer to have kept!)

I think part of the lesson I need to keep repeating to myself is: "When presented with contradictory results, use the primary sensor for each input and solve for X".

So when presented with an input that appeared to clearly suggest lack of air, go to the air sensor (MAF) and see what it said.

[Cadillac Jim]

The really low-end torque peaks are usually a result of resonances in the exhaust system. Maybe your mufflers had some moisture in them in one run but not the other, and that changed things. That's a stretch for such a big thing, but I would look at the exhaust and see if something had changed, like a loose clamp or a high-center making a dent or something.