Subaru Wrx Sti Parts Guide


Most Subaru owners love their vehicles. And while we are very satisfied with them in stock form, there’s something in the Subaru owner’s brain that makes them want to modify their vehicle. What would make a person take a perfectly running vehicle and mess with is a topic for another discussion though.

While each of us in our mind’s eye have a vision for our vehicles within our perspective budgets, this narrative is catered towards probably the highest percentage of Subaru owners, including myself. Power is nothing without power is the phrase I am fond of saying. While some people’s hearts flutter when considering brake upgrades, suspension components, driving schools, and the like, give me something that adds horsepower any day. With this in mind, I’d like to review what most consider being the very first power mods to their Subaru.

Step 1. Research. Before you perform ANY modification to your car, you must weigh the pros and cons of the potential modification. This is because there are very few “no downside mods” with our vehicles. When you think you’ve researched the mod to the ends of the earth, wait a few days and start over. The general rule of modification is 90% research and 10% purchase.

Another good tip is to ask yourself the following questions. These are only examples and should be tempered towards your specific mod(s):

a. Will this affect my neighbors? The really awesome exhaust your buddy has may be the genesis of sour neighborhood relations.
b. How will the law look at it? Realize that many states and localities frown on exhaust modifications with regard to noise and tampering with catalytic converters.
c. Will this affect other people who drive my car? No wife/husband/out of town visitor will think that your “pre-flight checklist” before starting your vehicle is as cool as you do.

Step 2. Installation planning. Right after you’ve made your decision, find out what is involved with the install. This rule applies even if someone else or a professional will be doing the install. What gaskets do you need? What are the torque specs? What parts should you buy just in case? The list goes on and on, but more than one install has been put off for a third hour run to the parts store. Remember, there’s nothing worse than to have performance parts sitting in your living room; prepare before you buy.

Now that you know the most important aspects, let’s cover the basic power mods.

Exhaust. This is one of the more expensive first mods. A typical full exhaust system can run around $1000 and add around 25HP. This is also one of the trickiest mods in terms of personal satisfaction. The reason for this is that most users select an exhaust that is simply too loud. You’ve read the online reviews that praise the quality, fit, finish, and cost effectiveness of say a Helix exhaust. You decide to pull the trigger. You spend the better part of 2 hours doing a textbook install and go for a spin, loving every minute of it. Then reality sets in. It drones at highway speeds, your wife hates it, your neighbors hate it, and you just got your second exhaust ticket….

When it comes to exhaust volume, you are limited as online audio clips that just don’t provide a physical realization of how loud it is. In order to do so, you need to find a local with this exhaust or rely on a trusted Vendor who will tell you a good comparison.

Also, don’t forget to search online forums for used exhaust systems. Used exhausts are a real bargain. Sure, it may have a ding or some scratches, but how long will your showroom exhaust stay looking that way anyway?

Intercooler hoses (for turbo Subarus except the STi). Real great bang for the buck mod with zero drawbacks. For around $150, you get a quicker spooling turbo and somewhere in the neighborhood of 8HP. This will replace the stock plastic accordion piece with a freer flowing unit. The other hoses are mainly for looks and do nothing; so many users give these away or don’t install them. Once again, used is perfectly fine.

Uppipe (for turbo Subarus except 2006+ turbo models and the STi). This is arguably the best first mod. Considering you will gain 10HP for around $200, it’s another great bargain mod. The big downside, other than possible legal issues with removing a cat from your system, is the installation. This install requires a lot of planning and a lot of time.

Much has been written about the horrors of this install, but as long as you have the correct tools, utilize the correct techniques, and allot yourself a full eight hour workday in case of problems, it can be done alone. The best way to perform this is to have a friend assist, preferably one with previous uppipe experience. It is within the realm of a shade tree mechanic though as most of the install consists of moving easy parts out of the way to access the uppipe. Used uppipes are perfectly acceptable though most owners generally do not swap this part back out once installed.

Intake. For naturally aspired Subarus, they are 100% fine as they are MAP based systems. For turbo Subarus, which are MAF based, this mod requires some knowledge. We all know that intakes are the first mod on most cars. Do not fall into this logic with a Subaru as it isn’t like other cars in this regard.

If you want an intake for your STi, there are several choices that require careful research on your part and are 100% fine. An example of a good intake is the K&N Typhoon intake which has been independently tested as providing good air/fuel ratios. Just because your buddy has an Apexi intake on his STi and it runs great does not mean it is doing unseen/unheard harm. Most aftermarket intakes, without tuning, will make your car run lean, which can be a dangerous condition or one that will decrease the reliability of your car.

If you want an intake for any other model turbo Subaru, there are a few good choices that require research as well.

Recently, SPT announced a new intake designed for the STi, but not other models. This is good news, but also begs the question: Data seems to point to fewer problems with intakes on the STi than other turbo Subaru models, so maybe other turbo Subaru models just do not work as well with intakes as the STi?

If you plan on tuning, any intake for any Subaru model will work. Some intakes are easier to tune than others though, so talk this point over with your tuner prior to purchasing. This can save you an extra hour on the dyno and at up to $200/hour + dyno time, it’s a 5 minute phone call work making. But, your tuner just might talk you out of an intake though. For that reason and many others, used Subaru intakes are plentiful.

Engine Management. For the 2002-2003 WRX owner this is not as big of a concern as it is for 2004+ turbo Subaru owners (minus STi). The reason for this is the EPA mandated engine tuning requirements in 2004 for manufacturers changing the transition for open/closed loop periods due to emissions & fuel economy reasons. Manufacturers are allowed to exclude one model and Subaru chose the STi. What this means is that 02/03 WRX and STi owners, with sufficient knowledge, can safely use manual boost controllers, air fuel controllers, and the like. For 2004+ turbo Subaru owners, your best bet is to discover the world of engine management. As well, for all Subaru owners, you are best served by engine management as there are hundreds of power variables that can be changed aside from say boost or A/F ratio.

Choosing an engine management system is a very hard process and probably the one that requires the greatest amount of thought for ALL mods. You want to ensure that the system you choose will accommodate your present and future desires. In the case of a local tuner, in might just be in your best interest to use their recommended system. This is because if you have problems or need a retune, they are better able to handle your system than say the “better” system you have your eyes on.

Used components are an outstanding way to go. Many users sell their system due to poor planning as they quickly outgrow their system, so you can find great deals on lightly used equipment. Ensure that the system will work with your vehicle though as many systems are year and/or transmission type specific.

Now that you have an uppipe, intercooler hoses, a full exhaust, and some engine management, you are at the “Stage 2” level of power. Stages are just a marketing tool, but to give you a better realization, it should mean you are putting around 50 more HP to the wheels than a stock car in a turbocharged Subaru; numbers will be slightly less with N/A models.

This is an amount of power that you can feel. Your car should be much more drivable and should reduce most of your low end/off the line sluggishness that you previously may have experienced. With this power though, you will also maintain a high degree of reliability and there shouldn’t be much of a change in your day to day mileage either. Total cost can vary, but the smart shopper will talk to locals, search eBay and the Subaru For Sale Forums, and save around 50% by buying used components.


Source by Unabomber