Category Archives: Tuning

XRT COBB 2007 MazdaSpeed 6 Stage 4

2006 Mazda Speed 6, fully built, still breaking in!

  • XRT Cobb Mazda AP v3 Stage 4 Tuning (Altitude: 4269 Ft)
  • Corksport Stg 2 Cams
  • Keyed timing, Forged rods and pistons
  • Upgraded pump valve and injectors
  • CorkSport MazdaSpeed CST5 turbo
  • Cork sport C5 turbo header and tail wastegate
  • Perrin EBCS
  • Front-mount intercooler
  • 4-inch Corksport cold air intake to turbo
  • Complete 3-inch turbo out exhaust

The car had been sitting since 2021, but came to us in late December 2025, where tuning was successfully completed in January 2026.

https://www.facebook.com/XtremeRacingTuning/posts/pfbid022EbLCpojFVdD268dK9skxjbRDTHqEn73quYSF3w7TMbwPyCmz632nSJrYCMQbgmdl

Recommended alternative Turbo: Xona XRA55xx_X3C or XRC64xx_X4C

2013 Crosstrek FB25 6MT Turbo (XRT-XVT08)

2013 Subaru Crosstrek
2015 Subaru Outback FB25 intake AVCS, stock block housings, stock rods, stock pistons,
– ring gap
— #1 Ring .21mm
— #2 Ring .60mm
King Race Crank and Rod bearings,
Port matched FB25 heads, stock 2015 Subaru Outback cams.
2014 STI 6-speed manual, 2008 sti lsd rear differential
OS Giken pull-to-push conversion twin disk clutch

Altitude:
– 7000 ft (2133.6m)
– Estimated power at sea-level: 332whp

Turbo setup:
Garret Gt35x (3582 turbo)
Tial 42mm wastegate (10psi spring)
Custom Equal-Length exhaust manifold
ETS 2.5 inch FMIC, 2.75 inch intercooler piping
2013 Crosstrek throttle body

Fuel system:
Walbro 255 in-tank fuel pump,
Aeromotive Fuel Pressure Regulator
Stainless -6 AN-Lines
STI Injectors

Misc:
Catch can, pcv delete, billet aos valve,
2.5-inch core triple row half radiator.
No air conditioning.
NGK ilkar8h6 spark plugs, stock 2013 coil packs

What you need to know about turbo modifications!

The article outlines the proper methods for modifying your car, ensuring money is well-spent, and collaborating with skilled tuners and tuning shops.

Choosing the right modifications for your car should be entrusted to a skilled tuner who can offer technical support and visualisation maps to assess the impact of parts on your power requirements, particularly in scenarios you encounter over 75% of the time. The remaining 25% or less pertains to your desires, which dictate the available efficiency for an occasional spirited drive.

Reference car:
Altitude: 3740ft (1140m)
Modifications:

– EJ25
– Manley Pistons 99.75mm C.R 8.5
– Blouch 1.5xtr 10cm
– Process West Verticooler
– Grimmspeed Cold Air Intake
– Perrin Turbo Inlet Hose
– HKS Equal Length Headers
– Grimmspeed Uppipe
– No name Downpipe
– Greddy Supreme SP Cutback

Determining the final performance of a car cannot always be accurately done on a dyno. Cars tuned exclusively on a dyno often do not perform as well on the road due to different load conditions and untested areas of the engine map. Consequently, dyno-tuned cars may excel in straight-line acceleration at full throttle but may not handle as well in other real-world driving conditions. It’s common for owners to be surprised by the initial performance, especially when compared to another car of similar power that’s been fine-tuned on the road, outperforming their ride in all areas. Moreover, these cars can suffer from inconsistent fueling, exhibiting areas that are either too lean or too rich, with optimal performance only achieved at full throttle.

Sometimes, relying on forums, other people’s experiences and dyno charts can be misleading. This can result in installing parts that are not optimized for your altitude and other requirements, leading to a waste of time and money. The following information will demonstrate cases where individuals become their own (google) tuners or rely on tuners with little knowledge of tuning. Standard modifications in the community or forums are then added and dyno-tuned with overinflated numbers, leading to further complications in the future for those who seek advice or want to experience more power.

Below is data taken from a car highlighting the incorrect decisions made when all parties have limited technical capabilities, previewing the creation of a performance platform.

Wastegate-boost to high-boost
Midrange-boost to high-boost with no gains
3rd Gear Dyno road pull shows increasing intake temperatures into the engine, reducing power and ignition
1/4 mile drag pull shows rising intake temperatures into the engine

The data shown highlights the mapping is way off the charts of a turbo’s compressor map, thereby demonstrating the need for compressor maps and the technical knowledge to calibrate the car with respect to the modifications and performance goals. As one can see, increasing boost did not lead to increasing torque and horsepower

Understanding the above, the key attribute, especially in boosting a car or enhancing the boost system, the following is a good visualisation when mapping a car’s performance with respect to the turbo used in achieving the performance goals:

Mapping at 18psi – 4000-6400rpm
Mapping at 23psi – 4000-6400rpm, showing reducing compressor efficiency the higher you rev
Mapping at 23psi – 4000-6400rpm, showing a broad range of efficiency for continuing boosting at higher revs
Mapping at 28psi – 4000-6400rpm continues to show a broad range of efficiency for continuing boosting at higher revs

Please remember that higher engine revs lead to lower efficiency unless cams are installed. To achieve optimal performance, aim for an efficient zone in the compressor map that suits 75%+ of your driving style and usage.

700whp+ Subaru Club – 2011 USDM STI 2.5 6MT

Mods
IAG stg 4 extreme block
14mm headstuds
Fire ring headgaskets
Pinned mains.
Garrett GTX3582R Gen 2
Ported heads, valves
Springs and Bc 280 cams
Ams intake manifold
TGV deleted

Exhaust
Full turbo back 3inch
Perrin big tube equal length headers
External wastgate 44mm
Grimmspeed 3Port boost controller

Fuel
Injector dynamics 1700x
Radium in tank dual pumper
Dual AEM 340s Fuel Pumps
Perrin fuel rails regulator
PTFE line throughout
Radium -8 feed and return lines
Radium FPR 48psi base pressure

4bar map sensor -OMNI
Gm IAT sensor

Videos – https://www.facebook.com/XtremeRacingTuning/videos/381216840855791/