2015 Subaru STI Development Update – COBB SF Intake Testing

So, you’ve probably seen some pretty cool early results from hardware swaps on the 2015 STI platform.  But, have you seen any actual data besides some basic dyno charts with really high smoothing?  Probably not. :) Lucky for you, we’re here to provide actual quantified data behind the madness.

Many people were initially disappointed that our first release only included Stage1 maps.  This was because we prefer to *thoroughly* test parts to find out what each modification will do so that we can be sure our Staged Package offerings have a definitive gain for your investment.  For example, here is a NASIOC thread showing some of the testing we did to compare power output when a downpipe is added to a 2015 STI: http://forums.nasioc.com/forums/showthread.php?t=2639122

For intakes, we decided that looking at only power wasn’t good enough.  An age-old claim in Subaru world is that the factory airbox is not restrictive with the stock turbo, and we wanted to see it for ourselves.  We put this to the test by measuring turbo inlet vacuum generated on the stock airbox and with a COBB Tuning SF Intake system fitted to the car.  Garrett refers to vacuum in the turbo inlet as “depression”:  “Any restriction (caused by the air filter or restrictive ducting) will result in a “depression,” or pressure loss, upstream of the compressor that needs to be accounted for when determining pressure ratio.” (http://www.turbobygarrett.com/turbobygarrett/pressure_ratio)

By comparing the depression created by the factory intake against an upgraded intake, we can actually “see” if we have removed a restriction or not.  If the depression is the same, well, all we’ve done is added a noise-maker to the car :)

To complete this test, we first gathered boost and depression data on the stock airbox using a stock-hardware 2015 STI (tuning only), first on wastegate boost pressures only, then at ~17.5psi peak via our Stage1 93 OTS map in “S#” mode.  Next, we gathered the same data on the COBB SF Intake, with no calibration changes other than for the different MAF curve required.

What did we find?  Results!  The stock airbox creates depression levels of a bit over 1psi on wastegate boost at redline, and well over 2psi on the Stage1 boost levels!  What does this mean?  Here in Austin, where the elevation is ~800 ft, the barometer was ~14.21psi for the testing day.  With the stock airbox at redline, the turbo was only being fed with approximately 12psi of pressure due to the depression.  For comparison, this would be the same as running the car at 5500 ft of elevation if there were no depression!

Here is the boost and depression (intake pressure) data for wastegate and for 17.5psi, shown in gauge pressure relative to ambient atmosphere:

Boost and Intake Pressure – Wastegate Spring Only


Boost and Intake Pressure – 17.5psi Setting

As you can see, thanks to the reduction in depression with the upgraded intake, boost is a bit higher on the wastegate.  At 17.5psi, we can see that spool has improved and high RPM boost is held out better on the same WGDC settings.  In each case, the depression created by the COBB SF Intake system is roughly half of the factory airbox.  What does this mean?  Simply put, we’ve reduced restriction in the turbo’s inlet path, as shown by the reduction in depression.

I also decided to take this data one step further, which is to calculate the turbocharger’s effective pressure ratio for each case.  One caveat is that we’re looking at post-IC pressures, not pre-IC, but because the intercooler has not changed at all between tests, it shouldn’t skew the results too greatly.

Here is the pressure ratio for each scenario (again, baro in Austin was ~14.21psi on testing day), calculated using Garrett’s methodology here: http://www.turbobygarrett.com/turbobygarrett/pressure_ratio

Pressure Ratio Comparison – Wastegate Spring Only


Pressure Ratio Comparison – 17.5psi

On wastegate boost pressures, we can see that there isn’t too drastic of a difference — perhaps a tenth of a point at very most.  However, at 17.5psi, we can see the COBB SF Intake really start to separate itself: pressure ratio is decreased by about two full tenths across the board after spool.  What does this mean?  The turbocharger compressor is now operating more efficiently, at least in terms of the demanded pressure output (boost) again the amount of pressure available at the input.

So, at the end of the day, here’s what power looks like between the two.  COBB SF Intake are the solid lines, stock airbox are the dashed lines:

Stage 1 vs Stage 1+SF Intake Dyno Comparison

Long story short?  On the 2015 STI, even in otherwise-stock configuration, the COBB SF Intake system (and others that have the same or better airflow capabilities) help the turbo breathe easier and in turn, make the same boost more efficiently or more boost at the same efficiency when compared to the stock airbox.

Thanks for reading along! Hopefully you found this data interesting and helpful. We plan to keep providing results like this as we dig in further on the 2015 STI and WRX, so stay tuned :)


The COBB Subaru Expert Group

Suspension – Yes, you should probably upgrade that too!

We can all sometimes get a little caught up in making power…and that’s great!  But what good is all of that power if you cant put it to the ground?

Check out our latest video for a little insight into what suspension modifications you can make to improve Contact, Comfort, and Control of your car.

Then, head on over to our website to check out what suspension parts we offer for your specific vehicle!



Subaru Tuning – A Quick Look into Boost Creep


Boost creep is something we tend to address quite a bit during the winter months.  Below we will go over the causes of boost creep, why you should be aware of it, and solutions to keep your boost levels in check.

Boost creep is defined as a condition of rising boost levels past what the predetermined level has been set at.   For example, if your target boost level is 15psi, you would see the boost levels increase beyond that as RPMs increase.  The short explanation for boost creep is that the wastegate is not able to flow enough air to bypass the turbocharger’s turbine housing.  When the volume of air flowing through the turbine housing continues to increase, boost will also continue to increase.  Boost creep is most commonly observed in areas that have very low ambient temperatures as well as high atmospheric pressure.  This often encompasses those in the Pacific Northwest as well as New England and East Coast.


Boost creep is undesirable for a number of reasons.  When a car exhibits a large amount of boost creep it makes controlling the boost level next to impossible for a tuner.  A car that is on the edge can exhibit highly variable boost response under different environmental conditions.  For instance, if you have your car tuned during warmer months, the change in weather going into winter may be enough to cause a significant increase in boost.  Once the flow limit of the wastegate has been reached, exhaust gas back pressure will increase.  This is very inefficient and will cause temperatures to increase and introduce more detonation-prone conditions.

Boost Creep is not a condition that can be corrected solely by making tuning changes as it is a mechanical limitation.  The two easiest ways to address boost creep are to either port the wastegate housing of the turbocharger in order to allow it to flow more air or to switch to an external wastegate style uppipe.

If you’re looking for answers to other tuning related questions, head over to our Knowledge Base!

COBB Releases BMW Stage 1+ Front Mount Intercooler and Stage 2 Downpipe with OTS Map Support

COBB is proud to announce the release of our BMW Front Mount Intercooler and N55 Downpipe along with off-the-shelf map support!

COBB BMW 1 & 3 Series N54-N55 FMIC Kit

COBB N54/N55 FMIC – One of the best power modifications for your BMW 1 or 3 Series – Click here for more pictures and details.

COBB BMW N55 Downpipe Kit

COBB BMW N55 Downpipe – Take your N55 powered BMW up to Stage 2! Click here for more pictures and details.

Tune your ECU for these modifications using our off-the-shelf maps!


COBB Releases – January 2013

COBB is proud to announce performance and suspension part releases for January, 2013!

COBB BMW 1-Series Springs – The best first step to a better handling AND looking car! Click for more pictures and details. COBB BMW 1 & 3-Series Anti-Sway Bars – This perfectly balanced kit reduces body roll, sharpens turn-in response, and reduces understeer. Click for more pictures and details.
COBB BMW 3-Series Spring Kit – An easy way to enhance your stance and improve handling! Click for more pictures and details. COBB Ford Focus ST and MS3 Rear Motor Mount – Improve traction and reduce wheel hop while minimizing NVH with a unique bushing design. Click for more pictures and details.
COBB Nissan GT-R Sport Spring Kit – Improve handling and appearance while reducing coil slap. Click for more pictures and details. COBB Nissan GT-R Anti-Sway Bar Kit – The easiest way to minimize body roll, increase turn-in response, and balance your body rotation. Click for more pictures and details.
COBB Subaru 08+ Anti-Sway Bar Kit – The perfectly balanced kit reduces body roll and improves turn-in response! Click for more pictures and details. COBB Mitsubishi Evo X Oval Tip Exhaust – A long time favorite is back! Click for more pictures and details.

COBB January 2013 Releases – New Nissan GT-R Support and Features


COBB is excited to announce the full world market support for the latest generation of the 2012 and 2013 Nissan GT-R (2011-2012 World Market). This support will be rolled into our existing Nissan GT-R Accessports, part numbers AP-NIS-005 and AP-NIS-006. Our Accesstuner software has also been updated to allow custom tuning of the 2012 and 2013 Nissan GT-R by both professional tuners and DIY tuners alike. Read on for more details about the work COBB is doing to make sure the Accessport is the most comprehensive tuning solution for GT-R performance enthusiasts.

Off the Shelf Map Improvements

Along with the application support, COBB would also like to announce the most comprehensive set of Off The Shelf COBB GTR calibrations to date with features directly requested by COBB GTR customers.

  • Map support for different fuel types translating to the perfect tune for your region’s fuel type.
  • 100 octane performance maps available for free download from the COBB website.
  • Up to 4 boost levels (13, 15, 17, 18 psi) and valet mode per calibration – easily accessible from cruise control buttons.
  • Popular mechanical configurations supported including stock (Stage 1) and exhaust modifications (Stage 2) in addition to 2.75” and 3.0” diameter COBB SF and BigSF GT-R intake kits.

Supported Vehicles:

  • 2011 ADM GT-R
  • 2011 East Asia GT-R
  • 2011 EDM GT-R
  • 2011 Gulf Spec. GT-R
  • 2011 JDM GT-R
  • 2011 South Africa GT-R
  • 2012 ADM GT-R
  • 2012 East Asia GT-R
  • 2012 EDM GT-R
  • 2012 Gulf Spec. GT-R
  • 2012 South Africa GT-R
  • 2012 USDM GT-R
  • 2013 USDM GT-R

Map Revision (version 404):

OEM Intake/COBB SF Intake (2.75”):

  • Stage1 91 OCT or 95 RON v404
  • Stage1 93 OCT or 97 RON v404
  • Stage1 100 OCT or 102 RON v404
  • Stage1 ACN91 OCT or 95 RON v404
  • Stage2 91 OCT or 95 RON v404
  • Stage2 93 OCT or 97 RON v404
  • Stage2 100 OCT or 102 RON v404
  • Stage2 ACN91 OCT or 95 RON v404

COBB BigSF (3.0”):

  • Stage1+BigSF 91 OCT or 95 RON v404
  • Stage1+BigSF 93 OCT or 97 RON v404
  • Stage1+BigSF 100 OCT or 102 RON v404
  • Stage1+BigSF ACN91 OCT or 95 RON v404
  • Stage2+BigSF 91 OCT or 95 RON v404
  • Stage2+BigSF 93 OCT or 97 RON v404
  • Stage2+BigSF 100 OCT or 102 RON v404
  • Stage2+BigSF ACN91 OCT or 95 RON v404

New Features!

The Nissan GT-R Performance mapping for v404 includes:

  • Real -Time map switching with the cruise control buttons.
  • This Accessport firmware enables users to switch between real-time maps on-the-fly using cruise control controls. The v4.04 calibrations contain 4 to 5 active map slots targeting 15, 16, 17 and 10 psi (valet). Some high octane calibrations contain map slots targeting 18+ psi. See the map long description for specific details. Peak boost levels will vary with altitude and exhaust modifications.
  • Heads up display based engine knock warning.
  • Knock monitoring with the Heads-Up-Display is not available for MY11+ GT-Rs during this initial release. Knock activity can be observed by monitoring the “High Det. Flag” and “Dynamic Timing Advance” monitors on the Accessport

Please see individual map notes for additional information and instructions for use. And as always, if you have any questions, just contact COBB Support: support@cobbtuning.com

COBB AccessPORT for the 2013 MAZDASPEED3, WM Axela and MPS


COBB is proud to announce the immediate availability of the 2013 USDM MAZDASPEED3 AccessPORT support! In addition to 2013 US models, we’ve also added Mexican and Japanese MAZDASPEED/Axela/MPS ROM support so more people can enjoy the simple plug and play power of the AccessPORT.

The 2013 US MAZDASPEED3 support includes our full array of Off The Shelf (OTS) maps for a variety of intakes and other common modifications. We have also updated the World Market maps to optimize fueling in all conditions and performance can now be monitored in the fully functional Dyno, ¼ mile, and 0-60 performance metrics.

AccessTUNER has also been updated with new vehicle support and added tuning tables. Load tuning strategy table updates include Engine Volumetric Efficiency (VE) – VVT Comp. (BETA), Load Target Comp – High RPM (BETA), and Load Target Comp – Injector Base Offset (BETA). More information on these tables is available in the revised tuning guide.

All of these updates are also available on existing AP-MAZ-002 AccessPORTs by completing a simple firmware update using AP Manager. Start your 2013 modification process with the best tuning available in the AccessPORT, available from your local COBB dealer or directly from us at www.cobbtuning.com.


COBB AccessPORT for the 2013 Ford Focus ST

COBB is proud to announce the AccessPORT for the 2013 Ford Focus ST. The AccessPORT is the industry leading OEM ECU flashing, managing and monitoring assistant. Unlock power hidden within the ECU by replacing conservative factory settings with more aggressive calibrations. The result is impressive gains in torque and horsepower while maintaining a high degree of safety. The AccessPORT comes with pre-installed maps that are optimized for common performance modifications.

The AccessPORT currently comes pre-installed with Stage 1 maps for a 7% increase in peak horsepower and a 20% increase in peak torque. The area under the curve is also massively increased with maximum power gains of 12% in HP and 25% in torque when using 93 octane fuel. Mapping is also available for 91 and 87 octane fuels to accommodate your local pump. Stay tuned for more map and feature updates as Ford Focus ST research and development continues! Click the link below for more information and to get yours today!

2013 Ford Focus ST AccessPORT: AP-FOR-001

COBB AccessPORT for the 2011 BMW 135, 335i and 335xi

COBB is extremely happy to announce the release of the AccessPORT for the N55 powered 2011 BMW 135, 335i and 335xi. We have been cranking extremely hard to get this out – with our best engineers working on making this a terrific product.

This is a Beta release – which means that although the support and tuning are 100% complete and, frankly, bad ass – we don’t support every single ROM on the road right now. As most of you know (but your friends might not), a ROM is an individual calibration file that makes small tweaks to the Engine Control Unit from the factory. Usually these changes are small and completely imperceptible to the consumer – however, we always want to support the latest the OEM has to offer so that all of the safety and reliability that BMW engineers into its vehicles stay there. It takes more work to do it this way – but we think it’s best for you and your car.

As such, during this Beta release of the AccessPORT, it is expected that several customers will need to send in the ROM data collected by the AccessPORT before the installation can be completed. Typically, new ROM support can be added in only 3-5 business days and is as simple as emailing your ROM information, and then completing an AccessPORT update on your home computer. As we collect more ROMs, the chance of having an unsupported ECU software revision goes down significantly and the sooner you can enjoy the added power!

The AP-BMW-002 will come pre-loaded with Stage 1 Sport and Stage 1 Aggressive power maps, as well as a Stage 0 map and Valet mode for reduced power when needed. Using the Aggressive map, you can expect an 11% increase in peak HP and a 25% increase in peak torque. The area under the curved is also massively increased with maximum power gains near 18% in HP and 26% in torque. Stay tuned for more maps (Stage 1+COBB FMIC) and updates coming soon as N55 development continues! Click the link below for more information and to get yours now!

BMW N55 AccessPORT: AP-BMW-002

COBB 2008+ Nissan GT-R Hard Pipe Kit

COBB is proud to announce the immediate availability of the Nissan GT-R Hard Pipe Kit. The COBB 2008+ Nissan GT-R Hard Pipe Kit replaces the OEM piping from intercooler to throttle body and from turbo to intercooler. The factory piping consists of small aluminum and rubber tubing that limits the vehicle’s ability to produce significantly higher power levels. The COBB GT-R Hard Pipe Kit utilizes 3” cold side and 2.75” hot side aluminum piping to ensure peak performance under all boost conditions. The custom mandrel bends optimize airflow and the larger diameters minimize turbulence between the turbos and throttle bodies. The wrinkle black coating is more durable and provides a subtle engine bay enhancement that any enthusiast would recognize. High quality 5-ply silicone couplers are included to eliminate crushing under pressure and stainless steel worm drive clamps prevent even the smallest air leak.

Squeeze the most performance out of your car with the COBB GT-R Hard Pipe Kit, available with blue or black silicone. Click the link below for more information and pictures.

COBB 2008+ Nissan GTR Hard Pipe Kit
Part Number: 7C1500