How to Install a Mid Pipe on a 2015+ Subaru WRX and STI
By Aftermarket Car Parts -Private Label Mfg | Published: 2026-11-05
Category: 사용 방법 가이드
A step-by-step guide to swapping the mid pipe on a 2015+ Subaru WRX or STI, including how to fit a PLM resonated mid pipe and avoid common install mistakes.
Quick answer
For a 2015+ WRX or STI, install the mid pipe by raising the car safely, unbolting the factory or existing mid pipe at both flanges, transferring or fitting new gaskets and hardware, and torqueing the connections with the system aligned. If you are adding the PLM resonated mid pipe to an existing PLM non-resonated kit, confirm you have the correct mating section before starting.
Why the mid pipe choice affects fitment and sound
The mid pipe is the link between the downpipe or Y-pipe and the axle-back section, so its length, flange angle, and resonator design determine whether the exhaust sits correctly and how loud the cabin gets at cruise. A resonated mid pipe adds a chamber that can take the edge off drone, but it also adds bulk that must clear heat shields and subframe braces.
On 2015+ WRX and STI models, the factory mid pipe is a single assembly that often seizes at the flange bolts. Soak the hardware with penetrating oil a day ahead, and plan for replacement nuts and studs rather than assuming they will come apart cleanly.
Resonated vs non-resonated: what changes during install
A resonated mid pipe is not a complete exhaust system; it is a section that replaces or converts part of the mid pipe. If you already run a PLM non-resonated mid pipe kit, the resonated pipe is a direct swap for that straight section, but it will not bolt to an OEM Y-pipe. Check what the pipe connects to on your car before you remove anything.
If you are replacing a factory mid pipe on a otherwise stock car, confirm the new pipe is designed to mate with the factory downpipe or Y-pipe flange. Mixing brands at the flange can leave gaps that no amount of gasket maker will seal.
Step-by-step mid pipe installation
- Lift and support the car safely: Raise the vehicle on jack stands or a lift so you can work under the mid pipe. Common mistake: using the jack only, which is unsafe when you need to pull and twist the pipe. Shake the car before crawling under; it should not move on the stands.
- Spray the flange hardware: Apply penetrating oil to the bolts at the mid pipe-to-downpipe and mid pipe-to-axle-back flanges. Let it soak while you gather tools. Checkpoint: if a nut rounds, stop and use a nut extractor rather than forcing it.
- Disconnect the rear flange first: Support the axle-back or rear section, then remove the rear flange nuts. This gives you room to swing the mid pipe down. Common mistake: removing the front flange first, which lets the heavy mid pipe hang on the downpipe studs.
- Remove the front flange and hanger: Unbolt the front flange and slide the mid pipe out of its rubber hanger. Inspect the hanger for cracks. Checkpoint: keep the factory gaskets as templates if the new pipe did not include replacements.
- Test-fit the new mid pipe: Offer the new pipe into position without tightening anything. Confirm the flanges meet flat and the pipe clears heat shields, subframe braces, and the driveshaft. Common mistake: forcing a flange to close a gap, which preloads the exhaust and causes cracks later. If the flanges will not meet flat, stop and verify you have the correct pipe for your setup.
- Install gaskets and start hardware by hand: Fit new gaskets at both flanges and thread the bolts or nuts by hand until snug. Checkpoint: use the correct hardware for the flange type; mismatched bolts can bottom out before clamping the gasket.
- Align and torque the system: With all hardware snug, check tip alignment at the bumper and clearance at the resonator. Torque the flange fasteners to the specification for your hardware, then recheck clearance. Common mistake: torquing one flange fully before the other, which pulls the pipe off-center. Recheck all flange bolts after the first 50 miles of driving.
Product facts
- PLM Subaru 2015+ WRX & STi Mid Pipe - Resonated Pipe Only: This is the resonated mid pipe section only and does not include or bolt to the OEM Y-pipe. It is intended as an upgrade for owners who already have the PLM non-resonated mid pipe kit, not as a stand-alone replacement for a factory system.
PLM Subaru 2015+ WRX & STi Mid Pipe - Resonated Pipe Only
