NOISY Subaru <Air Injection System (AIS)>

[fj401968]

My 1987 Carbureted GL wagon, sounds like it has an exhaust leak but it doesn't. After some inspection and a bit of research (HTKYSA page 248), I've discovered that the softball sized plastic muffler/silencer for the air injection system has been eliminated for some reason. It probably broke and so a previous owner just replaced it with a plastic union. Since this device is missing you can hear the rumble of exhaust noises and it sounds like I'm driving a beater that I'm too cheap to fix the exhaust system on. If I pull the cover off the air cleaner box and put my thumb over the inlet hole to the AIS, it sounds much better.

 

I'd like to hear suggestions:

 

Get part off junk yard Subaru and call it a day?

 

Engineer a homemade replacement from a lawnmower muffler?

 

Eliminate Air injection system all together?

 

Comments and ideas much appreaciated.

 

TIA,

 

Tracy

[GeneralDisorder]

Eliminate the AIS. Just block the valves with Quarters ($0.25), or cut the pipe and weld it up where it bolts to the heads. Don't need it anyway.

 

GD

[fj401968]

Eliminate the AIS. Just block the valves with Quarters ($0.25), or cut the pipe and weld it up where it bolts to the heads. Don't need it anyway.

 

GD

 

Thanks for the reply.

 

How is the air pump driven on an ea82 engine?

 

Many years ago I had a '76 Toyota Corolla that backfired all the time, I removed the belt on the 'smog pump' and it solved the backfiring.

 

With just a quick cursory look at my '87 Subaru, it appears the air pump is not driven by a belt off the flywheel. Blocking the valves will cause it to stop pulling air but is it more desirable to eliminate the air pump all together?

 

Tracy

[GeneralDisorder]

Actually, there is no air pump. The Subaru Air Injection System is passive. It uses the force of the exhaust pulse to open a reed valve and suck in fresh oxygen... so blocking the valve body where it connects to the pipe that runs to the exhaust is all you have to do. A quarter in each valve (usually there is one for each head) will solve your issues most likely. Almost always does in my experience.

 

You have to wonder why other manufacturers didn't figure this out... The air pump is such a complicated solution... not to mention uses HP to run it. Belts, pumps, lubrication, etc. Man what a waste huh?

 

GD

[fj401968]

Actually, there is no air pump. The Subaru Air Injection System is passive. It uses the force of the exhaust pulse to open a reed valve and suck in fresh oxygen... so blocking the valve body where it connects to the pipe that runs to the exhaust is all you have to do. A quarter in each valve (usually there is one for each head) will solve your issues most likely. Almost always does in my experience.

 

You have to wonder why other manufacturers didn't figure this out... The air pump is such a complicated solution... not to mention uses HP to run it. Belts, pumps, lubrication, etc. Man what a waste huh?

 

GD

 

That's cool... I didn't realize it was a passive system. I'm glad to hear it. I'm going to take your advice and block the AI valves this weekend. I'm looking forward to a quieter Sooby.

 

Thanks again GD.

 

Tracy

[Subarian]

The nice thing about using the quarters is that it's reversible if you decide for some unimaginable reason you want to open it back up. I used quarters and cut the pipes right at the flange.