Upgrading your Subaru

Continuously Under Development

It is very rare that a Subaru Impreza is bought and left at the standard spec for very long.  Due to it's Rally pedigree the Subaru Impreza WRX and particularly Subaru Impreza WRX STi are bought by keen rally and performance enthusiasts and have a huge following around the world.  Because of this there are a plethora of parts suppliers and performance centres supplying everything from Hayward & Scott de-cat exhausts through Exedy multi- plate clutch kits front mount intercoolers, Whiteline suspension kits and Xenon Headlight Conversion Kits, a complete A-Z of performance parts.

Although some modifications are made to the body styling it is what is under the bonnet, under the car and under the wheel arches that counts.  One of the most common upgrades that is carried out is replacing the standard exhaust with an aftermarket one such as a Hayward & Scott.  Ranging from a simple upgrade of replacing just the back box to give a nice shiny look and sound and a slight increase in bhp to a complete turbo back performance de-cat system (everything behind the turbo replacing the catalytic converters with a through pipe) to give an increase in performance and sound level.  An alternative to this is to fit a hi flow cat system which will still provide performance increase at just below a decat system but has the added advantage of keeping it street legal.

The real enthusiast however will be looking to really push up the performance from the standard 218bhp.  (All newer UK spec. STi models now come with a 265bhp engine, a six-speed gearbox, inverted suspension struts, Brembo brakes, front and rear limited-slip differentials, a faster steering rack, satellite tracking and a full body kit with high-rise spoiler). 

Upgrading the air filter to a Green Cotton panel filter to provide an uprated air flow can increase performance by a few horsepowers at relatively small cost.

Replacing the exhaust system with performance upgrade high flow cat and decat would give around 20-25 bhp increase.

Replacing the standard injectors and fitting an uprated fuel pump help to boost performance but at this stage remapping or replacing the ECU and fitting something like a Pipercross, Green cotton or Powertec induction kit & front mount intercooler and ceramic coating of the exhaust headers, up and down pipes and turbo to keep the heat down becomes desirable.

Further performance upgrades involve replacing the turbocharger for a larger aftermarket version, fitting parallel fuel rails to avoid any lean running, equal length exhaust headers and further remapping of the ECU.  With all of this extra power comes additional torque.  The wise upgrader will also fit an uprated aftermarket clutch and maybe even change the gearbox, pistons, conrods, crank and shells and even having the block converted from open deck to closed deck.

With all of this exra power comes the need to be able to stop efficiently.  Other common perforrmance upgrades come in the form of uprated suspension and brakes.  Manufacturers such as Eibach and Whiteline produce enhanced performance adjustable suspension in the form of adjustable shock absorbers and anti roll (sway) bars and lowered springs.  Companies such as Brembo, Compbrake, BlackDiamond and Mintex produce a vast array of uprated products from drilled, grooved and combination brake discs to race track large 4 pot brake calipers and race track sport 6 pot professional calipers and brake pads of a varying degree of hardness.

Whatever performance upgrade you are thinking of doing to YOUR Subaru we suggest you do it incrementally rather than throw a lot of money at it all in one go.  If you upgrade something and don't like it you can reverse engineer but if you add a number of performance upgrades all in one go and do not like one of them you may have to reverse engineer more than one such as exhaust and remapping if you decide to reverse the exhaust you may need to have another remap.

Commonly asked questions.

Will performance upgrades void my warranty?

Warranties are peculiar things with grey areas and be prepared to have a fight on your hands with your main dealer.  Having said that there is such a thing as the Magnuson-Moss Warranty Act.  This basically states that your warranty cannot be deemed void because of an aftermarket part (this would include performance upgrades) unless the aftermarket part caused the problem that the warranty claim is about.  For example, if you fit an aftermarket back box to the exhaust and your shock absorber failed then the manufacturer should not deny your warranty claim because a back box should not affect the suspension.  However if you fitted an aftermarket high flow performance exhaust and a remapped ECU and your turbo failed the manufacturer could claim that the extra stresses caused by the remap and high flow of air had caused the failure.  The grey areas come in the form of possible links such as if you fitted the above exhaust and ECU and then you had shock absorber failure the manufacturer may try to claim that the additional performance of the car put additional stresses on the suspension.  The law looks at what is reasonable to expect and while the law may be on your side, the dealer service department may or may not be.

How does a turbo work? 

The following diagram created by Matt Randolf simply explains this.  Click the image to enlarge.



What is a blow off valve?

A "blow-off valve" (BOV) and a "compressor bypass valve" (CBV) do the same thing, which is to release compressed air in the intake tract when the throttle closes, so as to prevent high pressure from smacking back into the compressor wheel of the turbo. If the valve vents the relief air to atmosphere, it's a blow-off valve,  if it sends the air back to the intake, it's a compressor bypass valve.

Octane Boosters
ALL NF products contain an upper cylinder lubricant and fuel stabiliser which gives EVEN fuel burn, reduces vibration, pre-ignition, pinging and overheating.
 

For high compression and performance engines
Up to 6 RON increase
Treats up to 6 tank refills