23 replies to this topic

[SuBrat84]

AND WHY IS IT SO DAMN LOUD?
If I plug the end where the hose goes it quiets up just fine.. and everything sounds GREAT on this motor until I unplug the hole and this thing starts making all kinds of noise... any ideas? (84 brat EA81)

[moosens]

Well,at least the reed valve in there won't burn out if it's sucking cold air.


ASV?
Air Suction Valve?

[SuBrat84]

I have the hoses and stuff for it.. i just have them unhooked right now to try and figure out why the damn thing is so loud...

[Snowman]

It's the ASV (air suction valve). It allows extra air into the exhaust so that the cat can work better. Remove the four screws and take it apart. There will be some reed valves in there that allow the air to only flow one way, which you should inspect as they tend to get dirty and/or break. They do make some noise even when working properly.

[ruparts]

AND WHY IS IT SO DAMN LOUD?
If I plug the end where the hose goes it quiets up just fine.. and everything sounds GREAT on this motor until I unplug the hole and this thing starts making all kinds of noise... any ideas? (84 brat EA81)

If you look where the large metal pipe leads you can see it is exhaust pipe (noise)

[SuBrat84]

It's the ASV (air suction valve). It allows extra air into the exhaust so that the cat can work better. Remove the four screws and take it apart. There will be some reed valves in there that allow the air to only flow one way, which you should inspect as they tend to get dirty and/or break. They do make some noise even when working properly.

I took it apart and cleaned it. Everything seems to be in good working order... but this thing is still making a ton of noise.. before I pinpointed this thing I thought I had bad rings... but it's definately the ASV.. if I plug it the motor sounds SO GOOD. Could it be making this noise because i don't have the O2 sensor hooked up (no wire)? Could the reed valves be bad even though they look good? Can you get new reed valves or do i need to replace the whole ASV?

[moosens]

THe big problem is that when the reed valves break apart on the tips they allow too much heat through.That heat goes into the black plastic flying saucer (silencer) and melts it to poop.The poop ends up in your carb and when the molten poop cools it hardens and you see hard little doo doos in your carbie.You may also find some deposits inside you valve/rocker covers if you have some misfires.

[Snowman]

Hold up....oxygen sensor? I've NEVER seen an ASV system on a FI soob, or one with a feedback carb. Wouldn't the extra air give horribly false readings?

The only worry I would have about plugging them is that the cat might get loaded up with unburned gas, causing it to melt and plug.

[SuBrat84]

Hold up....oxygen sensor? I've NEVER seen an ASV system on a FI soob, or one with a feedback carb. Wouldn't the extra air give horribly false readings?

The only worry I would have about plugging them is that the cat might get loaded up with unburned gas, causing it to melt and plug.

What!?! I'm not supposed to have an O2 sensor on my cat?! It's carbed... I just dont want it making so much damn noise... it sounds sooo pretty with that valve plugged BTW, I have this ASV in my lap right now if you want to see pics of it apart... i am thinking.. would it make less noise if i bend that metal piece so the reed can't open as far???

[GLCraig]

O2 sensor and ASV are pretty much a given with the carter weber, I've seen a few dozen Subaru like that. Some 2wd models even have a ASV going to the second Cat.

[Snowman]

Does your car have an engine computer under the dash? If it does, then the oxygen sensor should be there. If not, the Y-pipe was probably replaced with one from a car that had an oxygen sensor.

If you've got the little black plastic muffler things and all the tubing to hook the ASV back up, it really shouldn't make much noise at all. I would just be scared to disable it because the cat might melt.

[SuBrat84]

Could you please describe better what the computer would look like / location of said computer? (84 brat)

Here's pics of inside of the ASV:

[Snowman]

The computer bolts to the bottom of the steering column, right above the pedals, underneath the dash. I'm not sure exactly what it would look like on your car, but most of the older ones were a black rectangular box maybe 6" by 8", with a bunch of wires going to it.

[SuBrat84]

Okay.. i see where a computer would mount.. and MAYBE even some wires that would plug into one.. but there is no computer... wtf? What do you think of my idea of not letting the reed open as far?

[SuBrat84]

Well I tightened down the reed limiters.. it still lets lots of air through but is much quieter.. It would seems that most of the noise is being caused by too much air getting through .. or even the exhaust sucking the air through (more likely)... which I can only assume is being caused by improper or leaky vacuum hoses somewhere.. a lot of this rubber looks like it's original and thus 21 years old... I'll be replacing it all as soon as i can afford to.. so hopefully that will improve the noise too... Also, should this Brat (84 GL EA81) being having a computer in it? The cat does have the O2 sensor.. I was going to buy a new one so it would have the wire (the old one is cut at the nub) to plug into... well I dunno where it plugs into. Thanks for your input.

[Snowman]

Some EA81 cars had an ECM, others didn't, depending on whether they had a feedback carb or not. Your "underhood emissions junk" sticker might tell you if it has a feedback carb.

[NorthWet]

My 82 with Hitachi carb has an O2 sensor, cat and ASV. I believe someone has said that this was the way California cars were setup. My ASV functions only for the first couple of minutes after startup, presumably while the O2 sesnor is too cold to function. It is rather loud during that time (maybe I should check my reed valves, eh?) The ASV is not there to help the catcon, but rather to allow oxidation of HC and CO in the hot exhaust pipe environment.

[SuBrat84]

Anyone know how much a computer for an EA81 costs??

[ShawnW]

Check out the USRM article.

http://www.ultimates...rticle.php?a=72

[ShawnW]

Anyone know how much a computer for an EA81 costs??

Pretty cheap if I have the same one you need.

[SuBrat84]

This is the only thing that might give a hint about needing a computer for this...

Engine Family: EFJ1.8T2AFD3 (109 CID) EGR / AIV / OC
Evaporative Emissions Family: NU

Anybody know what all this means? Was this thing a turbo at one time? Maybe this hood is off a turbo??

Is there different computers for the EA81? Thanks.

[SuBrat84]

My first *bump*

[VaporTrail]

What!?! I'm not supposed to have an O2 sensor on my cat?! It's carbed... I just dont want it making so much damn noise... it sounds sooo pretty with that valve plugged BTW, I have this ASV in my lap right now if you want to see pics of it apart... i am thinking.. would it make less noise if i bend that metal piece so the reed can't open as far???

I have mine plugged off in my 87 wagon with a ea81/weber dropped in it....

[SuBrat84]

I have mine plugged off in my 87 wagon with a ea81/weber dropped in it....

Yeah.. Junkie told me to stick a 20oz soda bottle cap in the rubber hose... but then should i block the hose coming from the air box too?? And then just take those plastic "muffler" things out??