EJ25D intake whistle and exhaust whistle

[torxxx]

Ok, now that the wicked stereo system is done in the Outback, its time to get rid of the annoying noises I can hear when the bass isn't pumping.

 

Air intake whistle on the 2.5 DOHC engine, Someone has to have found the cure for this annoying noise. Would running a bigger air intake helps solve some of the problems? I'm not real worried about pulling warmer air from the engine bay (if it quiets down the engine) because living in Alaska, we only have another month of weather above 45F+ and then we go into the deep freeze.

 

I know once the inner fender airbox is removed the noise gets worse. If my understanding is correct about airflow/pipe size, smaller the pipe = higher pressure = higher chance of whistling from the air sucking in the entrance of the pipe. So if I got rid of all the plastic air intake stuff, kept the factory filter box/MAF location and made my own aluminum airbox that fits up inside the fender (not sure on size, once I get the front bumper off and start fitting the tube bumper I figure that would be a good time to build the new air box.

 

I was thinking about putting a 6 inch hole on the top of the airbox (will fit where the stock inner fender box sits) and covering that intake hole with some form of pre filter just to keep the crap out of the box. The box should be big enough to stop the "short ram air intake" issues that occur from running too short of air intake.

 

So has something like this been done? Or am I pissing into the wind with my eyes shut?

 

As for the exhaust, we jacked her up last night and took a peep at the system. 2 cats, 2 resonators? WTF subaru?? I'm thinking of chopping the system behind the second cat and running 1 7/8" pipe from there back. This way the ODB2 still sees its cats/o2 sensors and the 1 7/8" single tube from there back will create backpressure lost by removing the muffler.

 

So what does everyone think about this idea? I can't stand this "simulated turbo" noise the 2.5D makes..

[Legacy777]

The smaller pipe just means the air is going to move faster, not necessarily that the pressure will be higher. It may be slightly, but nothing you could measure.

 

Do you think the noise is coming from the bottom side of the airbox or topside (after the filter)? You could remove the bottom side of the airbox and just drive up the street to see if the noise is there or not. If it's gone, then you can likely modify the bottom part of the airbox. If the noise is still there, then you'd have to modify the top of the box or the piping after the MAF, and I'm not sure if you wanted to do that.

 

If you modify the bottom of the box, I'd suggest drilling a hole in the bottom and using some pvc pipe to connect that additional hole to inside the fender. You can see what I did in these pics:

 

http://www.main.experiencetherave.com/subaru/images/linkinstall/10/DCP_9035.JPG

http://www.main.experiencetherave.com/subaru/images/linkinstall/10/DCP_9036.JPG

http://www.main.experiencetherave.com/subaru/images/linkinstall/10/DCP_9037.JPG

 

As for the exhaust, the original muffler on my 90 Legacy had a whistle under full throttle. Replacing the muffler made it go away.

 

My 97 Impreza 2.2 has a similar whistle under full throttle, but I think it's engine/intake related. I haven't been able to find it, and have kind of given up.