Over the past weekend, with the help of our good friend chuck who is a bit of a Subaru guru I embarked on putting a new exhaust on my Subaru. This may seem like a simple task as it is on most cars such as Derek’s Mazda where the installation of a full racing beat exhaust system including long tube headers took less than 2 hours. But my car, and turbocharged vehicles in general are a bit of a different animal.
By removing obstructions and restrictions from the exhaust of a turbocharged vehicle you are reducing back pressure. Therefore putting more force via exhaust gasses into the turbo. The larger amount of force makes the turbo spin up faster meaning the car will get more boost or get boost earlier. This has to be tuned for. In addition to the tuning required to accommodate the unobstructed exhaust. The exhaust also has to mate up with said turbo at some point in its path. this can often create strange or cramped routing requirements, as was my case.
Now Subarus of the turbo variety have the turbo mounted fairly high in the engine bay on the right side (that’s USDM passenger side). Therefore the exhaust must extend upward from the headers to meet the turbo in what is referred to as the up-pipe and come down back underneath the vehicle in the down-pipe. The up-pipe was what gave us trouble. In my particular car there is a pre-cat in the up-pipe, a catalytic converter in the down-pipe and another immediately after the downpipes. Being that we live in Indiana, a state that does not require emissions testing or checks of any kind. The main purpose of the new exhaust system was to remove all three of these catalytic converters to allow for more power and better fuel economy.
I had started the process by removing the front piece of my cat-back exhaust that was previously installed. I reused the Cobb muffler from the catback system so it wasn’t necessary to remove it. Then Chuck arrived and things started moving along a lot more quickly. We soon got the down-pipe and the remaining parts of the exhaust after the turbo off. Then the turbo had to be loosened on its mounts to allow the up-pipe to be slightly moved. The up-pipe was then unbolted from the turbo and the passenger side header was removed.
We began attempting to remove the up-pipe. Removing the stock up-pipe proved to be quite a process. First we tried taking it out through the top between the turbo and firewall. But our attempts proved fruitless. Then we tried removing from underneath the vehicle. This seemed promising but we just couldn’t quite get it to slip out. In order to get the it out many say to loosen the motor mounts. This is the route that had to be taken to remove my up-pipe. First we tried taking the up-pipe out by having Chuck lift up on the motor from underneath while I tried to pull the up-pipe out. This proved frustrating and I’m sure it was tiring for Chuck. At this point we realized we had no other choice than to lift the engine using a hydraulic jack. Neither Chuck or I was a fan of this idea because it involved lifting my motor by the oil pan. But this was the route that had to be taken. Finally we hit pay dirt. The stock up-pipe came out through the bottom. The Perrin aftermarket up-pipe had a much smaller outside diameter being that it doesn’t have a catalytic converter contained within. The engine was re-secured to the chassis and the installation of the new exhaust components began. The up-pipe went in easily unlike its factory counterpart with the turbo being bolted back down to its mounts and the gasket from turbo to up-pipe being torqued to specifications.
Headers and corresponding gaskets were installed and the portions of the exhaust before the turbo were in place. Then it came to the Turbo XS exhaust that was to be installed between the turbo and muffler. This all went together easily, I can’t say enough about how well all of the parts installed went together. Sometimes with aftermarket parts I’ve run into issues with quality or mounting locations, There were no such issues this day. Soon enough the exhaust was fully installed and it was time to tune to compensate for the changes we had made.
For tuning I went with a local guy, Mike R. Who had been recommended to me by the Indiana Impreza forums (link here) and Stuart parts manager at Fort Wayne Subaru. Now tuning to some seems like just a magical thing where a laptop is plugged in some keys are hit and magically more power is unlocked. Unfortunately that’s not actually how it works.
Tuning went easily enough with just one minor hiccup. When we began tuning, the car was pulling IAC counters meaning it thought something was wrong so we had to stop tuning. So Mike put a safe tune on it so I could drive it until I figured out what our issue was. I checked the car up and down for anything that could be causing it. I ended up removing a couple of heat shields that were loose and may have been rattling again the exhaust headers causing the car to think that there was something wrong like a valve rattle or spark knock. Additionally, I replaced the PCV valve for good measure because I had noticed a bit of a burning oil smell in the now cat-less exhaust.
One of those things must have been the cause because when we went to tune it again everything went smoothly. Mike is a very skilled and experienced tuner and the whole tuning process would have probably taken less than an hour had we not gotten caught up talking about anime.
After the modifications were completed the car felt much different and sounded like nothing else. The turbo makes a lot of good noise even at low speeds and light throttle input and goes into light boost even under normal driving conditions. As far as the amount of noise from the exhaust itself it isn’t all that much louder than it was with the three inch cat-back. But what was truly drastic change was how it feels under full boost. I’ve been driving this car every day for over a year now and I had become quite accustomed to the amount of power the car was previously making. That’s not to say that the car was by any means low on power but I just knew what to expect when I put my foot down. Now, running higher boost and going into boost even faster in the rev range it feels amazing.Words cannot describe the feeling of heavy acceleration in this car as well as many others I’ve driven and been a passenger in. Now I know my mostly stock WRX isn’t what some would consider fast but it is fun. And it’s fun that is important. That’s why some cars such as a Miata are great. Because, they are just fast enough to make that platform fun. That’s where I feel that I’m at now. So if you’re out there and you’re a car enthusiast like myself I encourage you, don’t be afraid to make your car your own. Modify it, use quality parts, do your research and above all have fun.