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Power upgrade guide for MY08 Turbo Subaru WRX 2.5 litre engines

We get many calls for upgrades on this model, as a guide to assist you we have created this list to save your time, guarantee your money is invested correctly and most of all give you maximum value!.

SUMMARY
Search over 40,000 parts!
A huge parts info list for this car can be displayed here by choosing your exact year model or choosing a key word search
http://www.mrtperformance.com.au/search

Typically this car is a "Subaru's error" but it has HUGE potential and is a high performance car effectively detuned when compared to the STi model of the same year and later!. 
There are some great features of this car, stealthy looks (compared to past models), 4wd, turbo 2.5 litre and most of all, a sensible budget with some well planned upgrades and it turns a great car into a STi beater!
(Editor note, this model is a very detuned option (power and suspension) that Subaru effectively "stuffed up", but some simple mods makes this bargain model  much better than the later model at a much lower cost)

ECU
Can be converted and fully tuned, using EcuteK Software for almost any improvement, ECU is same design as previous (MY07) models and allows solid results with correct settings and allows good improvement.
The ECU in this model can also be upgraded to "EcuteK Race Rom" for added features that were never included in the Subaru ECU

ENGINE WEAKNESS's
Bottom end and mid range performance can be dramatically improved with ECU tune. The engine is very detuned (as subaru dont want it to beat the STi and it was targeted to a more "soft" market in 2008) and also limited due to emisions requirements when delivered by the factory.
Poor durability with the factory standard pistons can be troublesome although not as obvious as the STi model it should be kept in mind. 
Poorly designed upgrades only magnifies the risk of piston failure. 
Run too much boost or too much ignition advance and the result will inevitably be piston failure
Boost and VVT cam maps, can be improved. 
Car MUST be run on 98 Ron Fuel unless a custom (ecuteK) map is done.
The turbo is reliable, (but was small compared to the 2009 model) but if over boosted with boost controllers etc will result in costly turbo failures.

ENGINE SENSORS
On this model the aif flow meter sensor is more reliable than previous model, but can suffer contamination and in turn this will effect reliability and performance. (see MRT for this solution)
The twin rear exhaust O2 sensors if located incorectly related to modified exhaust can cause problems, if old can also dull the cruise performance of the car and increase fuel use.
Crank, cam  and Knock sensors are reliable, but with age can fail.

INTERCEPTOR ECU OPTION
Not worth considering as the intercptors simply do not have enough options to tune and modify the latest technoplogy control inputs.
ZERO VALUE

NEW (replacement) ECU
Factory ECU retune is best value unless a really serious engine rebuild is chosen. 
See notes above

INTERCOOLER
Factory fitted unit is good, dont fit a FRONT mount.
Use a better replacement top mount, but choose carefully.

INJECTORS
Bigger injectors empty your wallet and add no power unless part of a E85 fuel retune or major engine rebuild. 
Save your $$ for suspension and get some GOOD improvements.
OEM Injectors are big enough unless you do a major engine rebuild.

FUEL PUMP
More than adequate up to 50 kw at the wheels after that a 500 hp pump can be retofitted

EXHAUST
(Some traps for people here, unless carefully chosen.)
Single scroll turbo engine pipes with split collector to fit wastegate is necessary and will add throttle response and is good value, with the correct complete design. High flow ceramic cat in the downpipe is best.
Flex joint is needed as well, with correctly located O2 sensor.
Get this wrong and the car will suffer CEL lights, deactivate the Cruise control and cause poor fuel economy.
On hatch models the single rear muffler is not that restrictive and on the and adds no value in just replacing this and should be completed as a part of a whole turbo back exhaust kit.
Consult MRT for this.

AIR INTAKE
Other than a intake noise no power here. 
MRT used to supply and fit ram pod style intakes, but with technology and recent testing and on the later models these were made redundant. The positive intake pressure with the factory intake is best kept in place.
A replacement panel filter in the std airbox will save on future servicing but give no power improvement.

ENGINE ANCILLIARIES
Items such as aftermarket plug leads, high capacity discharge ignition systems etc all will ad very marginal if any improvement.

A GFB alloy pully kit will fit some models, but this varies as this model now has stretch fit belts and no adjustment like earlier models.
If fitted a kit or alloy crank pulley will result in snappy throttle response.

TURBO
If you have the budget a turbo upgrade will add power, heaps on this model as the turbo was really poor, but be careful the OEM turbo is best kept in place unless you have the right other parts to match a new turbo upgrade (such as a STi unit). As the limit becomes close to the engine depending on your choice turbo and will give no value unless you plan carefully. 
(meaning if you fit a bigger turbo you can use its benefits but be careful as the extra boost will need to be tuned carefully )
If you want big grunt and big torque then ok, this is an option here, then you need to plan a engine rebuild.

ENGINE INTERNAL
Like above if you have a solid budget, then a rebuild will give some great and huge benefits, but a rebuild will cost over $7k and then you need to choose carefully there are many options, but only if you REALLY want to.
Best value here first and foremost is Pistons and Rods.

OTHER OPTIONS
Is the car serviced correctly? Because often a service by a workshop who really knows subarus will be your best choice for first place for power and reliability.

IE:

  • Upper engine cleaner and in tank fuel additive. (when was this last done, its a subaru suggested option).
  • Good quality low friction engine oil such as Mobil 5 w 30 will give around 5 kw and better fuel economy over a non synthetic oil.
  • Fuel system service, MRT offer this and often get good results, cleans the EGR "gunk" out of the intake and combustion area.
    Also injectors as well as inlet manf and exhaust as well as fuel pump, lines and sensors.
  • Synthetic trans and diff oil, again like engine oil this adds up in benefits.
  • Timing belt, fuel filter are again areas that should be checked and renewed.

SUSPENSION
Check out the performance / suspension section for REAL gains and benefits.
If I owned this WRX suby, I would invest first in the MRT XB kit as it will then have more power than the later 2009 model, and then some of my budget in brakes and suspension as this is guaranteed BEST VALUE!
more here http://mrtperformance.com.au/performance/suspension

FREE CHECK
Refer the MRT vehicle service section here and take advantage of our free 78 point check to ensure your car is in top shape!

PRIORITY LIST

  1. Check service history.
  2. Check the O2 sensor
  3. Check brakes
  4. ECU upgrade and re tune.
  5. New brake pads and discs if needed
  6. Front and rear sway bars.
  7. Complete (quality) exhaust.
  8. Front and rear sway bar links
  9. Positive shift kit
  10. New Top Mounted Intercooler.

OTHER RESOURCES

Select Tune Level

EcuTek

  •  Want More Power?
  •  Want More Torque?
Find out why your Mitsubishi, Subaru, Mazda car is detuned by the factory Learn More ECU

MRT Big Brake Kit

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