Subaru Impreza WRX Gen2 Tuning

"All you need to know about performance tuning the Subaru Impreza WRX Gen2 engine!"

A site visitor emailed and posted questions for more information on the Impreza WRX Gen2 and how to tune it up and modify it, so we've put together this web page to take you through what we feel are the main modifications that we find are the optimum enhancements you can do to this engine.

The Subaru Impreza WRX Gen2 provide a fun base for your project and with the ultimate parts like a remap, turbo improvements and camshafts you will definitely maximize your driving experience.

This pages aim is look at Impreza WRX Gen2 tuning and outline the optimum modifications.

We have articles covering tuning, mods and upgrades for the following models.

Subaru Impreza tuning, Impreza WRX STi mods, Impreza WRX Gen1 mods, Impreza WRX Gen 2 mods, Impreza WRX Gen 3 mods, Impreza WRX Gen 4 mods, Impreza WRX Gen 5 mods, (VA) WRX Mods

History of the Impreza WRX Gen2 Engine

Subaru produced its second generation Impreza from 2000 to 2007. Two body styles were introduced: a 4-door sedan (GD) and a 5-door wagon (GG). Four naturally aspirated and two turbocharged engines include 1.5 L EJ15 H4, 1.6 L EJ16 H4, 2.0 L EJ20 H4/H4-T, and 2.5 L EJ25 H4/H4-T. In 2000, Impreza won the overall ‘COTY’ award in Australia. In America, it won the ‘Best Sport Sedan’ award in 2002 and the ‘Best Performance Car’ award in 2004.

Both WRX and WRX STI versions got two facelifts: one in 2002 and the other in 2005. Subaru produced three STI versions with the same engine but different torques. S202, S203, and S204 were produced using an EJ207 engine capable of generating power of 315hp but the value of torque increases due to increased weight. Another car ‘Spec C Type RA-R’ was derived from S204 with the same engine and output but reduced weight.

Tuning the Subaru Impreza WRX Gen2 and best Impreza WRX Gen2 performance parts.

Best Impreza WRX Gen2 modifications

The prime Impreza WRX Gen2 parts on an engine are usually the ones that give the biggest return for your cash.

We won't be sidetracked by the most popular Impreza WRX Gen2 parts, they need to work out to be cost effective.

Please watch our video which covers the 5 principles of tuning your Impreza WRX Gen2. Be sure to keep up with our latest YouTube content and subscribe.

Best mods for your Impreza WRX Gen2

• Impreza WRX Gen2 Suspension Tuning - Upgrading your suspension greatly enhances your Impreza WRX Gen2 road holding and cornering. Adjustable coilovers and better bushings are what is needed here.
• Engine Tunes - A remap gives the biggest gains for the money, aftermarket ECUs, and Tuning boxes are all alternatives.
• Flywheel lightening - a reduced weight flywheel will improve the engines free revving nature. But not always suitable for all Impreza WRX Gen2 engines.
• Intake Upgrades and Exhaust - Please be warned on their own these mods won't ADD TORQUE in most applications, but they enable you to release power after other mods by minimizing the restriction.
• Sporty Profile cams are generally the biggest mechanical mod upgrade, but should always be installed by someone who can fine tune the cam timing and it is often hard to find a suitable cam near you but you might have a local firm to regrind a stock camshaft .
• Turbo upgrades - A New Turbo is the most efficient approach to improve intake air supply, this means you are able to use more fuel and make power gains. Typically one of the most expensive mods it offers big gains.
• Brake Mods - Improve your Impreza WRX Gen2's stopping power needs to be near the top of your Mods list.
• Internal engine mods - crank, pistons, conrods & compression ratio including balancing and blueprinting

Impreza WRX Gen2 Tuning Stages

Typical stage 1 mods often include: Performance Brake Pads, Fast road camshaft, Suspension (mild drop), New Bushes, Remaps/piggy back ECU, Panel air filters.

Typical stage 2 mods often include: induction kit, high flow fuel injectors, Fast road cam, Ported and polished head, Sports catalyst & performance exhaust, Brake Discs (drilled/slotted or grooved.

Typical stage 3 mods often include: Competition cam, Internal engine upgrades (head flowing porting/bigger valves), Crank and Piston upgrades to alter compression, Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Twin charging conversions.

Impreza WRX Gen2 Handling/Suspension Upgrades

Upgrades to the Impreza WRX Gen2's suspension and handling

When it comes to modifying your Impreza WRX Gen2, one of the most often stated reasons is to enhance its handling. However, we repeatedly witness the same mistakes.

We would choose a set of Coilovers that allow set a ride hight to set the cars handling to your preference

Is there anything I should keep in mind while deciding on suspension upgrades for my Impreza WRX Gen2?

Uprated Bushes

Enhancements to the bushings: Things you need to know

It is possible to connect the Impreza WRX Gen2's suspension components to the chassis of the Impreza WRX Gen2 using poly bushes, which are direct replacements for the original rubber mounts. The rubber ones usually deteriorate with time and need replacing anyway so why not upgrade.

Installing new OEM rubber bushings may dramatically improve the performance of your car.

Because polyurethane bushings are stiffer, the ride may be more harsh, but the bushings will last longer and maintain the car's handling for longer.

Increased vibration and play may also quicken the decay in other suspension parts.

A new set of polyeyurothane bushings might help to lessen the excessive play associated with rubber bushings.

You may struggle to find a full set of polyeyurothane bushes, but most regions have the primary mounts available. Often, custom Impreza WRX Gen2 polyeyurothane bushings may be manufactured to your requirements.

A common misconception is that a non-adjustable suspension system that lowers the vehicle by70mm from a franchised component shop is the best option. But suspension design and setup is quite complex.

Vendors may assert that their Impreza WRX Gen2 suspension kits are compatible with any or all of the Impreza WRX Gen2 model years.

For a vast variety of vehicles, a 'one size fits all' approach is obviously incorrect.

How low should you go on the Impreza WRX Gen2?

According to TorqueCars research and testing, the maximum amount of suspension drop for most road vehicles is 30 - 42 millimetres, whereas hot hatchbacks with lower OEM sport suspension have a maximum suspension drop of 21 millimetres.

These tolerances may be drastically lowered if the wheel size is changed. Even with 16 or 17-inch wheels and conventional suspension, lowering the vehicle may create a a slew of new complications.

Impreza WRX Gen2 Camshaft Upgrades

Sporty camshaft profiles raise the top end power which makes it a best mod for NASP and turbo petrol engines, but not so much on diesels. We've always seen peak power gains through performance camshafts on most engines

The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake and exhaust durations will alter depending on the chosen camshaft profile, so large bhp gains are on offer for camshaft upgrades.

Fast road camshafts usually raise the torque over the rpm range, you may lose a little bottom end bhp but the top end will improve.

Race camshafts, raise the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

For a road car you should ideally to match your power band to your driving style.

I would be surprised if you have ever asserted that a Impreza WRX Gen2 Race cam is a pleasure to live with when in heavy traffic. This is because a competition cams causes very lumpy idle, and makes the car more prone to stall or jerk along in stop start traffic, sadly though many ignore this and end up spoiling a perfectly good car and having to revert back to a fast road, or OEM cam profile.

Each engine responds differently depending on how well made they are, when cams are fitted depending on the cam being more aggressive cam durations and cam duration as unique due to manufacturing tolerances and quality variations so check your engine on a rolling road.

The ECU mapping and fuel delivery and fuel pump and injectors also have an effect on the bhp gains you'll achieve.

A longer valve duration can alter the bhp range, and on most engines there are some advantages to extending the intake or exhaust durations and valve lift.

ECU Mapping Improvements for the Impreza WRX Gen2

A tune/remap will help release the full potential of all the upgrades you've done to your Impreza WRX Gen2.

(Sometimes flashing the ECU is not an option, so an aftermarket ECU is the route to take, and most of these exceed the specs and performance of your factory ECU's but make sure it has knock protection and that you get it correctly setup.) It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NA (naturally aspirated) engines, but the end result often vary depending on the upgrades you've fitted and the condition of your engine.

Air Flow improvements on the Impreza WRX Gen2

It is the main goal to any tuning job to feed more air and fuel into the Impreza WRX Gen2 engine

Air Intake manifolds flow the air from the intake filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

Design and flow rate of the Intake can make a noticeable effect on to fuel engine efficiency on the Impreza WRX Gen2.

I usually find intake manifolds are in desperate need of motorsport parts, although some makers provide decently flowing intake manifolds.

Larger valve conversions on the Impreza WRX Gen2, getting port work and head flowing will also improve torque, & importantly will allow you to get increasing the torque increase on other parts.

Impreza WRX Gen2 Turbo upgrades

NA (naturally aspirated) engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your Impreza WRX Gen2

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes excellent power gains.

If an engine is fitted with a turbocharger mods are simpler to install and you'll see that turbo engines will have stronger components.

However you will find engines have weakspots. Discover these restrictions and install higher quality components to survive the power.

We see many people spending lots of money on turbocharger upgrades on the Impreza WRX Gen2 only to suffer the humiliation of seeing the Impreza WRX Gen2 explode when it's been finished.

Big turbochargers will usually suffer low end lag, and smaller turbochargers spool up quickly but don't have the top end bhp gains.

Thanks to new tech the range of turbochargers is always evolving and we are seeing variable vane turbochargers, permitting the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbochargers divert the exhaust flow into a couple of channels and flow these at differently angled vanes in the turbocharger. They also increase the scavenging effect of the engine.

You'll commonly see there's a limitation in the air flow sensor AFM/MAF on the Impreza WRX Gen2 when considerably more air is being pulled into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp at a much lower level.

Adding a supercharger or additional turbo will make large torque gains, although more difficult to setup. We have this in depth look at twinchargers if you want to read more.

Impreza WRX Gen2 Fuelling Upgrades

Don't overlook the need to raise the fuelling when you are increasing the performance - it makes the car more thirsty. Boosting the fuel pressure can provide a better the acceleration responsiveness.We would recommend you to be generous with your injector capacity.

As a rule of thumb add 20% to the flow rate when buying an injector, which takes into account injector deterioration and allows a little spare capacity should the engine need more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

Impreza WRX Gen2 Performance Exhausts

You should look to boost your exhaust if your current exhaust is actually creating a restriction in flow.

On most factory exhausts you'll see the exhaust flow rate is good even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Sports exhausts can usually air flow from the engine but avoid an exhaust that is too big or you will stuff up your flow rate. Keep the exhaust pipes to around 1.5 to 2.5 inches for best results.

For road going cars mods such as a sports catalyst pretty much remove this restriction, mainly due to it's larger size and surface area, and will effectively raise the performance to levels you would expect without having a catalyst installed, but keeps the car road legal. And will better flow due to it's higher internal surface area and design. The alternative catless mod or cat removal should be considered an off road only mod, as removing a catalyst is illegal in most territories and regions for road registered cars (and in some you can't even replace a working catalyst).

Weak spots, Issues & problem areas on the Impreza WRX Gen2

The Impreza WRX Gen2 engines are generally reliable and solid as long as they are regularly serviced.

Carbon build up in the head, particularly around the valves which will reduce power and smooth running, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon By avoiding short journeys where the engine doesn't warm up and using good quality fuel you can reduce this risk.

Regular oil changes are highly recommended on the Impreza WRX Gen2, and more importantly so when the car is tuned and will help prolong the life of the engine.

To find out more about mods and upgrades, or just get more pointers on Tuning your Impreza WRX Gen2 engine please join us in our friendly forum where you can discuss Impreza WRX Gen2 tuning options in more detail with our Impreza WRX Gen2 owners. It would also be worth reading our unbiased Subaru tuning articles to get insights into each modification and how effective they will be.

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This article is flagged for an update, so please pass on specific tips below that I can include. All articles, and content was written by me, Waynne Smith TorqueCars founder. Some outlines are just too general so I appreciate your feedback and suggestions. This entry was filed under Subaru. You can leave a response below or join our forum to discuss this article and car modification in detail with our members.

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