SOURCE FOR AN AIR CLEANER FOR MY SUBY EJ-25 & AN ENGINE SERVICE MANUAL

Bruce,

I suggest that you determine the engine type EJ25? and serial number before you order a service manual.  Google Subaru engine identification marks.  They are both punched in, one on the rear top, near the flywheel and one on the crankcase top near the front.  Once you determine model #, there are many companies online that sell manuals, some hardbound, some digital.

Naturally, you want the service manual to be specific to your model, and there are LOTS of EJ 2.5 liter models, such as EJ251 through EJ257.  Regarding an air cleaner, there are many opinions on what brand to use, as discussed on Subi enthusiast sites.  You may want to check out www.nasioc.com. 

The inlet volume is useful, but that's just one of the measurements you will need.  There are online formulas designed to provide ideal air cleaner size, dependent on HP produced.  Besides inlet diameter, you can plug in different heights, widths, and air cleaner types (foam, paper, oiled felt) to see how much HP you lose with too small a filter flow area.  That filter flow area is as important as inlet size.  Of course, the formula may call for a height x width that we can't use due to limited space. One or two HP loss is considered acceptable.

I would think your builder would have the complete solution including the K&N cone type or other so that when he programs the ECU he will make sure the air fuel mixture is appropriately adjusted ... you don;t need a situation where you change the air filter system and lean out the mixture with disastrous consequences. Just saying.

Got  new Miata a couple years ago - the days of buying a $300 dealer tech manual are over.  I found the same info online - some you can subscribe to and download too.  Here's link to some sources for the EJ25 engine.

https://1pdf.net/subaru-ej25-e...8d7ce12e8959372f0b8f

Thanks much guys....found the serial # 20968601337.

K & N says 51 sq inches, minimum, of effective air cleaner surface area. I think double that should be sufficient. Their formula seemed a little nebulous though. The builder is  off-road oriented so larger is better but I do have somewhat of a space restriction as Jim mentioned.  I have used K & N products since they came out in the late 60s and have never had an issue with them so I will stick with them. Thanks for the link Wolfgang.................Bruce