Tuning tips for the Subaru Impreza WRX and STi

"That does Impreza me much!"

With their phenomenal success in rally, Subaru have really carved out a niche and created a truly easy to own practical high performance car.

A few of our members have been completely converted to Impreza ownership after driving one.

The power and handling is really something special.

There are many aftermarket parts around for the Impreza from suspension and handling kits to turbo conversions, stroker kits and off the shelf performance flowed heads.

The WRX and STi both appeal to those with family obligations as they are such good all round cars. The engines are very solid and can tolerate a great deal of tuning.

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One of the highest performing "family friendly cars" around. Ideal for those who still want a sports car but have to be a bit sensible!

Impreza Model History.

In the 1950s, Subaru started making cars as a small company in Japan. At the beginning of the 1980s, they decided to make their name known around the world by entering the World Rally Championship (WRC). At first, there was no success

But when the gears started turning, Subaru began to win races. In 1992, Subaru got rid of the larger Legacy and put out the smaller, rally-styled Impreza. At that time, Japan was selling the first generation of WRX (World Rally Experimental) cars. Users like how quickly WRX gets going and how fun it is to drive.

In 1988, Subaru Tecnica International (STI) was made by Fuji Heavy Industries. Then, in 1989, Subaru teamed up with the British motorsport company "Prodrive" to compete in the sports market, and in 1994, they released the STI model.

This version of the STI that was faster and more sporty did very well in rallies. It became popular because its engines, suspensions, and transmissions were tuned to perform well based on a blueprint. It had pistons made of forged metal, a better intercooler, and strut tower braces made of carbon fibre.

In 1994, Subaru took part in the World Rally Championship with its new, sportier WRX STI model. Subaru won its first WRC championship in 1995, and then won two more in a row. In 1998, to celebrate the hat-trick, Subaru made the Impreza 22B, a car that can't be beat. It had a working hood scoop, covers for the fog lights, gold wheels, flared fenders, and a huge rear wing.

When the Subaru WRX finally hit the American market in 2002, it changed everything about the car business there. Tuner culture also made these affordable turbo cars one of the most popular cars. In 2014, Impreza WRX models were separated from the rest of Subaru's productions. This was a big step forward for the company's reputation.

Both the way they work and how they use gas are different between the Subaru WRX and the Subaru WRX STI. The STI is more performance-oriented and costs $5000 to $10,000 more. It has a bigger engine, unique BBS wheels, a rear spoiler, a different set of bumpers, and better brakes. The STI variant can make 290 hp and 310 lb-ft of torque, while the WRX variant can only make 258 hp and 268 lb-ft.

Impreza is now in its 5th generation. Before we get into our newest Impreza WRX model, let's learn about the first four generations.

First Generation

From 1992 until 2000, seven distinct variants of the first generation were made available.
Both front-wheel drive (FWD) and all-wheel drive (AWD) versions of the first Subaru Impreza World Rally Experimental (WRX) were available to the public in 1992.

Later on, the Impreza's FWD was taken out of the equation, thereby making it an all-wheel-drive model only. For its first eight years on the market, the first-generation Camaro came in a wide variety of body styles and body types. Choose from 1.5L EJ15 H4, 1.6L EJ16 H4, 1.8L EJ18 H4, 2.0L EJ20 H4, 2.2L EJ22 H4, or 2.5L EJ25 H4 naturally aspirated motors. Both the 2.0 L EJ20 H4-T and the 2.2 L EJ22G H4-T were turbocharged options.

Second Generation

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.

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.

The third generation Subaru Impreza

Available with either a gasoline or diesel engine, made its debut at the 2007 New York Auto Show. A hatchback was chosen over the waggon. This generation includes the GE (narrow sedan), GV (wide sedan), GH (narrow hatchback), and GR (wide hatchback) in addition to the thin and wide variants of these vehicles from the previous generation (2007 and 2008, respectively) (wide hatchback).

WRX variants were available with a variety of gas engines (1.5 L EL15 H4, 2.0 L EJ20 H4/H4-T, and 2.5 L EJ25 H4/H4-T) and a diesel engine (2.0 L EE20 H4-T), as well as automatic and manual gearboxes (4/5 speed). Both the gasoline and diesel engines were rated between 107 and 170 horsepower.

Third-generation diesel turbo performance model can reach 60 mph from rest in 5.8 seconds. The new and improved WRX-S model was released in the UK in response to complaints about the previous generation's mushy suspension.

The output increased to 265 horsepower, while the 0-60 mph time dropped to 4.7 seconds.

Fourth Generation

Subaru's fourth-generation Impreza is now available as 2012 models in both sedan (GJ) and hatchback (GP) body styles.

When compared to their predecessors, new cars use less gas because they weigh less and are more aerodynamic.

Its roomy cabin is comparable in size to that of the Subaru Legacy thanks to the sedan's wheelbase being lengthened.

There were five different gasoline motors to choose from: Diesel 2.0 L EE20 H4-T and gasoline 1.6 L FB16 H4, 2.0 L FB20 H4, 2.0 L FA20F H4-T, 2.5 L EJ257 H4-T, 2.0 L EJ 207 H4-T, and 2.0 L FB16 H4 engines.

In 2014, a new model of the VA series WRX was introduced in Japan under the moniker WRX S4.

To the Fifth Generation

In 2017, Subaru debuted its fifth-generation lineup, which is based on the brand-new Subaru Global platform. A 4-door sedan (GK) and a 5-door hatchback (GH) were both offered (GT).

A 5-speed manual CVT was paired with either a gasoline engine (1.6 L FB16 H4 or 2.0 L DAVC FB20D (152 horsepower) H4) or a hybrid engine (2.0 L FB20D e-Boxer Hybrid H4). The hybrid version made its way to Europe in March of 2020. 2016 "Car of the Year Japan" title went to the Subaru Impreza.

2022 Subaru Impreza WRX

The Subaru Impreza WRX is a sophisticated sedan that was designed with flexibility in mind. All the way from $29,605 to $42,395 may be spent on one of four different models (Base, Premium, Limited, and GT).

All contemporary Subaru Impreza WRX models are powered by a refined and economical 2.4 L DOHC turbocharged Subaru Boxer 4-cylinder engine. With this engine, you can expect an output of 271 hp and 258 lb-ft of torque.

The horizontally mounted direct-injection engine provides superior balance and increased performance. Since the pistons move laterally to balance out vibrations, the power transmission is maximised.

All three lower models come with a basic 6-speed manual transmission that is completely synchronised, while the GT comes with an 8-speed manual transmission, auto vehicle hold, and paddle shifters as part of Subaru Performance Engineering.

Owning an Impreza

There was a problem with the early fuel pickups which would cause fuel starvation on long fast sweeping bends. A new design pickup/pump will address this issue.

The owners say that the Subaru Impreza has internal engine failures, but considering the power output they are pretty reliable. Some of its weak spots are the rods, pistons, rod bearings, piston bearings, and other moving parts, which tend to be expensive to replace or fix.

Leaking oil and gaskets usually hurt engines in the long run.

Wear and tear was also blamed for some turbo failures in newer WRX models. The turbocharged cars were put through a lot of stress by tuning.

The throttle shafts aren't stable, and the STI suspensions aren't smooth. When the road was bumpy, there were sudden, hard hits that made the ride uncomfortable. Even though some models had the problems listed above, Impreza has won many awards since it was first made.

The Impreza Boxer engine

The flat four boxer engine is certainly one of the most distinctive sounding engines around, and the engine configuration means that the weight is carried low down in the engine bay which helps the handling characteristics.

Due to the engine shape the exhausts are a work of art and the various twists and bends allow equal lengths of pipe from each cylinder. Performance exhausts cost a fortune and we suggest you get a good quality exhaust as some cheap upgrades are inferior to the OEM setup. A decent exhaust really enhances the sound of the engine.

The early (1992) WRX came with an impressive flat four 2.0 H4 engine block. There were quite a few revisions over the years and we see power steadily increasing with various limited edition tuning packs from Prodrive.

From around the year 2000 JDM models received regular revisions and cosmetic enhancements, with a few handling mods thrown in like the 2003 Transmission upgrade and the 2005 WRX being fitted with the better viscous rear slip differential. Other markets followed the Jap Spec upgrades and had various limited edition models introduced.

Most limited edition cars were produced in very small numbers of around 400 and in most cases these were customisable by the buyer with various performance, handling and styling packs. It does pay to do your research before buying and decide which options and year model you really need rather than buying a car at random and spending your way to the spec you want.

Tuning Mods for an Impreza

TorqueCars would recommend the following tuning modifications for the Subaru Impreza WRX and STi. Firstly the turbo can fairly easily be upgraded with one which has re-machined internals.

A remap will yield large power gains but this is best left until last so you can wring out the benefit of all of the other modifications you have. If you increase the power you will certainly benefit from an uprated intercooler, indeed many owners of standard Impreza WRX and STi report a power increase from adding a front mounted intercooler.

Impreza Tuning

A sports cam profile will lift the power in the upper part of the rev band, however this will affect the smooth tickover of the engine so this is only really recommend for serious track day use.

If you fit a lighter flywheel your engine will be more free revving and will feel more powerful. You will also certainly want to uprate the clutch although the original clutch should be good for 350 bhp, unless it is particularly worn.

The engine capacity can be increased to around 2.5 litres. This should not overly affect the reliability of the engine but we would recommend a thorough testing of your block for fatigue. A sports catalyst and sports exhaust will help the breathing of the engine. Fitting the later 2.5 turbo engine is another option in your Impreza tuning project and provides a good solid base to work on.

If you are increasing the power by a significant margin you should also uprate the fuel pump and injectors to keep the air to fuel mixture within their optimum parameters.

Alloy wheels of over 18 inches seem to compromise the handling so stick with the 17's or 18's unless you are not too concerned about this and want the looks of a large wheel.

Read our tuning articles for more details on the many Impreza modifications available. It would certainly be worth you joining our friendly Impreza owners forum where we debate all types of modification and tuning for the full range of Subaru engines.

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