Project Introduction

Project 2005 Legacy GT
“STi Killer”

Objective: To build a reliable, powerful, and tight handling car that still offers the acceptable ride and comfort of a touring sedan. Project STi Killer will out accelerate, out corner, and out brake a stock STi.

Overview: The car being used for this project is a silver 2005 Legacy GT sedan. From the factory the Legacy GT offers 250hp from a 2.5L turbocharged 4-cylinder boxer engine. The block and engine internals are much the same as the STi, but the Legacy was equipped with a smaller turbo, different intercooler and intake manifold to fit the scoop and lines of the car. This difference in design poses some challenges for one trying to make significant power out of this vehicle. The biggest problem is the intercooler size and location. Due to the design of the hood a stock sized intercooler must be used or there will be little to no airflow through the intercooler at high speed when the intercooler is needed most. Possible solutions to this issue are going with a front-mount intercooler or an air to water type intercooler. Both have their advantages and drawbacks. That point is a ways down the road yet, but something to keep in mind during the build. This project will be recorded from beginning to end with at least two dyno graphs showing the increase in power over stock. Since we do not have access to a skidpad, no lateral grip numbers can be recorded but the results will be recorded by the driver.

Part 1: What is already there and prepping for power.

The most important part of getting the most performance out of any vehicle is making sure the car is in excellent running condition to begin with. Luckily, we purchased this Legacy GT with only 3000 miles on the odometer so we know that it has been treated well for the majority of it’s life. The only issue we have had with the car is the rear struts have been replaced twice under warranty. Occasionally the noise has been heard again recently so we will take the car back to the dealer to ensure the struts haven’t blown again. We intend to retain the use of the stock struts so they must be in top-notch shape before we put extra load on them by installing lowering springs. Oil changes have been kept up to date and semi-synthetic oil used to reduce engine wear. Full synthetic will be used starting at the next oil change, as the car will be about 20K and seeing more “spirited” driving.

The vehicle already has a couple aftermarket upgrades, none of which alter performance so we should be able to get a nice baseline dyno number that one would expect from a stock Legacy GT off the lot. The previous owner or dealership installed a STi gauge pack including a boost gauge, an oil pressure gauge, and a coolant temp gauge. I would have rather had an EGT gauge installed over the coolant temp, but we will go with what we have already until it becomes necessary to have one. The vehicle also has extensive clear bra installed covering almost the entire front end, blacked headlights, and a STi rear trunk spoiler from the JDM Legacy GT. Not much is in the plans at the moment to add to the aesthetic look of the car. Obviously, wheels and tires will be added but more to improve handling over the stock set. We will stick with a 17” rim for aftermarket wheels, but wider, as we intend to use the stock wheels and tires during the winter months if needed. This influences brake upgrade choices, as most aftermarket caliper/rotor upgrades are too large to fit under the stock 17” wheels. At this point we will try to upgrade the stock components or will be on the lookout for a brake kit that offers use of the stock wheels.

The car runs very well at this point, and maintenance will be kept up to or exceed the manufactures recommendations. The first thing that needs attention is the handling. To the average guy wanting to drive this thing to work everyday in comfort the stock suspension is probably ok, but the vehicle has way too much body roll and understeer for a performance enthusiast. The stock tires are decent, but not what we would call “confidence inspiring”. Power is not the first concern of this project, the Legacy GT puts down a pretty healthy horsepower number stock. We want to be able to harness the available horsepower better than the factory car. First thing is to start off with a baseline dyno graph and see what kind of power we are putting to the wheels. Then we will start to add parts with some lowering springs to get the center of gravity down lower as well as reduce body roll and add a larger tubular rear sway bar to reduce that pesky understeer. Then, it’s time to focus getting the car stopped quicker.

Stay Tuned!