Wednesday, July 3, 2013

The SPT Adventure

I don't get many questions about my Impreza... but when I do, it's usually about my exhaust.  The one that seemed to turn the most heads was my first attempt.  The whole goal was to get a Subaru Performance Tuning (SPT) Catback Exhaust installed on my '12 Impreza.  The SPT parts were designed to fit on a 5-Door WRX or STi, not my 4th Generation Impreza!  Thanks to the creative minds at Russ' Garage, we did some testing, assessed what would need to be done, and spent a day getting it all set up and installed!

The biggest thing that needed to be changed were the hangers.  On the 3rd Generation design for the Impreza/WRX/STi 5-Door, the hangers point forward and backward.  On my 4th Generation Impreza, they point side to side... so in order to fit 'em, we needed to redo that system.  Russ cut the original hangars off, sanded off the rest, and actually used the parts he had just cut off to start making the new hangers!  It's a stainless steel system, so things were a little tougher to work with, but RG did not disappoint.  To complete the fitment process, we added 2 inches to the mid-pipe so the tips could be revealed a little better under the bumper.  This also allowed us to clear the rear sway bar, which was in the way at first.  Because of this placement, and since there wasn't any cutting done to the bumper to accommodate it, the bend in the mid-pipe to go underneath the rear suspension lowered the ground clearance a bit.

Once it was finished, I took it for a spin right out of the garage into a snowstorm.  The snow was deep, fluffy, and in need of some shredding, so I found an open parking lot and went to town on it.  The sound was great!  Just what I had been hoping for!  I was a little worried about the sound inside the cabin, but didn't think much of it.  After a few weeks of driving with it, that interior noise was starting to bother me and my passengers, especially those unfortunate enough to sit in the back seat.  Without a resonator on the exhaust (since the SPT Catback doesn't have a resonator) all the sound that a turbocharged engine would usually help muffle was now roaming free in my eardrums.  I hadn't taken all the variables into consideration.  Still, the car sounded great, the SPT quad tips off the back end looked fantastic, and I found myself turning quite a few heads.

It was a tough call, but after just 2 months of running around with this fantastic sounding exhaust, the Pros were not outweighing the Cons.  While it looked and sounded great on the outside, the cabin noise was getting more annoying by the week and I felt bad offering rides to folks, knowing the assault their eardrums would endure if they dared take a seat in my Impreza.  Adding a resonator to the SPT Exhaust would've probably helped with the interior noise, but it wouldn't have solved my power issues.  As it turns out, N/A engines rely on back presure from the exhaust system to help retain power.  With the larger diameter of the SPT Catback exhaust, there wasn't enough resistance to create sufficient pressure and my low-end torque was dropping out.  With less power, I was having to apply more to the accelerator, which was then sapping my gas mileage.

In the end, I ended up removing the SPT Catback Exhaust and built another system based on my stock exhaust and a BRZ stock exhaust.  Again, Russ' Garage went to work on another crazy idea of mine, but I'm much happier with this new system as a whole.  I still have the SPT Exhaust stored away, so I might revisit this idea if I can figure out how to solve the issues I had with it, but for now... my car just can't handle it!


  1. what size piping were you using on the spt exhaust?

    1. Well, since I used the entire SPT catback exhaust, I'd imagine it's the same as that. Trouble is, I can't remember the diameter on that system. Just search for 2011-2014 SPT Catback Exhaust for a WRX Hatchback and get the specs on one of those.