Intake duct is meant to have an opening?

Posts specific to the 2.5 litre NA engine

Intake duct is meant to have an opening?

Postby luckcity » Mon May 24, 2021 4:56 pm

Hi,
Just got this car, and seeing in the (found) photo and diagram below
that the Intake duct has what looks like a box attached.
The red circles

but on the car is a open hole, no box,
and it opens to the engine compartment.
(red arrow bottom right,
arrow indicates the airflow.)

Is it OK to let this unfiltered air in, or should it be sealed?

2005 Subaru Liberty
White | 2005 | 5 Door Wagon | Semi-automatic | Petrol
Safety Pack B4 | 2.5 Multi-point injected | 4 Speed Semi Auto | 121kW | Four Wheel Drive | January Release
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Re: Intake duct is meant to have an opening?

Postby LibertyTragic » Tue May 25, 2021 12:09 am

Unfiltered air is never a good thing for an engine.

Head to a wrecker and grab a replacement would be my suggestion. Just sealing it may eliminate a purpose e.g. pulsation or noise dampening.
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Re: Intake duct is meant to have an opening?

Postby Yowie » Tue May 25, 2021 11:58 am

Agreed.

In the short term you could plug it securely with something about the right size/shape. The plug unlikely to be drawn into that larger pipe with the mild ported vacuum, but still be sensible about how you plug it up.

If you can find a replacement resonator to return the intake to factory spec the plug is probably ok long term, with the only consequences probably more noise and/or perhaps a slight loss of power.

Intake resonance tuning on a NA engine is a bit of a fine art by the factory. Usually it's to supress noise, but sometimes there are power benefits to sound pressure waves being managed in a certain way.
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