If you look under the hood of a WRX, the intake path is a little convoluted. Air enters a large channel near the hood latch that funnels diagonally across the front of the engine compartment. It then drops down into the fenderwell, passes through a bulbous silencer and then returns via the main intake channel heading towards the manifold.

So, here's the question: is the silencer in the intake path too restrictive for the turbocharged engine?

You'll often see sites talking about a silencer delete procedure which will definitely make more noise. What's not at all clear is whether removing any of this piping has any effect on total airflow.

Note: I'm not asking about power, tuning or whether the sound is cool / less so. The question is whether removing the silencer components will remove a restriction and increase net airflow.

  • Seems like a scenario similar to the Lincoln Mark VIII. There's a silencer near the front-passenger wheel that does nothing but restrict airflow to make the engine quieter. Supposedly, the gains from removing it are very minor aside from the slight amplification of engine noise. Could this question maybe be widened in scope a bit?
    – Iszi
    Commented Mar 9, 2011 at 19:42
  • 1
    @Iszi, I don't think we can widen the scope - if we don't have a specific question, we can't have a specific answer. A follow-up / linked question is likely appropriate, though.
    – Bob Cross
    Commented Mar 9, 2011 at 20:19
  • @BobCross - I understand. I just wasn't sure if a more general "how do intake silencers affect performance and airflow" without a make/model specification would equally address your particular issue.
    – Iszi
    Commented Mar 9, 2011 at 20:30
  • @Iszi, I think that would get closed - according to the FAQ, the goal is to ask questions with answers rather than questions that spawn discussion.
    – Bob Cross
    Commented Mar 9, 2011 at 20:49
  • 1
    @Iszi, that's the problem - if it varies according to the car, there isn't a single question-answer pair that applies. The answer "it depends on the car" is less useful to a specific person asking about a specific car.
    – Bob Cross
    Commented Mar 10, 2011 at 1:43

1 Answer 1


Simple answer that all the forums seem to agree on, and that my garage also approves is that you will get better airflow to the manifold, however unless you also adjust your ECU, and potentially replace your Mass Airflow Sensor (depending on exactly what you are changing in the airflow path) then you may have problems.

I had the full Prodrive Performance Pack added to one of my Imprezas, and derestricting the inlet was only required for one of the performance boosts for the turbo. Without the PPP, this derestriction would not have given me any significant difference.

(I have had various modified Subarus over the years, so I chat to my local garage a lot :-)

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