Help me understand the AAR please.

[FastWoman]

Tomo, I have an AAR from an '81 ZX. It came with a thick rubber boot that surrounded the entire part.

Captain, I'm impressed with your AAR modification. How did you get the clam shell open? How long does the thing go between cleanings?

[TomoHawk]

that's odd. The boot doesn't appear in any of my catalogs, or on eBay. Can you offer any more information? Can you offer a photo?

[Captain Obvious]

Hi FastWoman, I used a lathe to cut the crimped over lip off and after that lip was removed, the the two halves just fall apart. You could use a file to do the same thing. Wouldn't be as fast or as clean of a cut, but it would work. I usually try to take pics of projects like this just in case, but for whatever reason that I can't remember, I didn't take any of this one. I was probably in a hurry to get it back on the car or something.

I've been meaning to take it back off the car and take some pics of it opened up. Maybe this week as the weather isn't Z driving weather anyway, right? So if I don't have to spend the whole next week bailing, I'll take some shots for you.

Anyway, I cleaned it out maybe 500 miles ago, and I have no reason to believe it needs it again yet.

PS - Glad to see you active... Been wondering where you been. :ninja:

[FastWoman]

Tomo, the boot is in the attic over a flooded garage in another town. I suspect it may be a while before I can get you a photo. (It's not currently installed on my car.) I assumed this was standard equipment for the ZX, but a search of images suggests it might not be. There are other makes and models of car that use essentially the same AAR, so perhaps it's not even from a Nissan.

Thanks, Obvious, and glad to be back! I just haven't had much time on my hands lately, and my Z has been behaving very well for me. Well, it behaved well until a couple of days ago, when the starter died. I was literally in the process of moving the car to high ground. At least it was a quick repair. Good luck in Philadelphia!

[TomoHawk]

FWIW, I looked to a picture too, but I found a sale for one that can be disassembled!

http://www.rhdjapan.com/nissan-oem-auxiliary-air-valve-ca18-57582

Also: http://www.partsgeek.com/catalog/1993/nissan/pathfinder/air_intake/auxiliary_air_valve.html

It's a pathfinderor "CA18" part, I think. http://www.partsgeek.com/catalog/1993/nissan/pathfinder/air_intake/auxiliary_air_valve.html

Edited October 29, 2012 by TomoHawk

[Captain Obvious]

TomoHawk, That's too funny... Back when I was messing with AAR's, I grabbed one of those Pathfinder AAR's from a junkyard because I saw that it was held together by screws! I was considering using it on my car, but I decided against it because it's designed for a different intake manifold design. If you look at it, you'll notice that there is only one place to connect a hose instead of two hoses that are used on the Z's AAR. That single hose is the air into the valve. The air OUT of the valve comes out the O-ringed hole in the bottom and passes directly into the intake manifold without using a hose.

I'm considering drilling a hole in my intake manifold and adapting that single hose style. Would remove one hose from the system and clean it up just that little bit, but that project is further down on the priority list.

[TomoHawk]

I noticed that too. I also saw there was one for two hoses.

There is also one for a Porsche that has a square body, and the connector is right on the part with the shutter, instead of on a long tube. http://www.autohausaz.com/porsche-auto-parts/porsche-air_mass_meter_boot-replacement.html

[Captain Obvious]

I see the two tube variety now too. Cool, I didn't see that before. The junkyard AAR I have is the single tube style with the exit hole on the bottom.

The only other thing I can add about differences is that the Pathfinder one has a phenolic shutter while the stock AAR has an aluminum shutter. Don't know if they changed to phenolic as a cost reduction or for some sort of performance improvement.

[Captain Obvious]

Been a while, but I haven't forgot about this thread. I got the opportunity to pull my AAR off the 280 to take some pics of the modifications I made. Unfortunately I didn't take any pics of the work in process, but I took some of the finished product. To recap... I used a lathe to cut off the crimped over lip that originally held the two halves of the clamshell together, cleaned everything up, and made some improvements while I was in there.

Here's a shot of the inside. My calibration notes W = "Warm", R = "Room":

While I had it apart, I didn't like the way the shutter blade wobbled on it's retainer pin and didn't always align properly to make a good seal against the inside of the housing. This can result in an incorrect high idle, so I pulled out the original pin and drilled and tapped for a screw instead of the original retainer pin. I countersunk the shutter blade to accept a flat head screw and screwed the shutter in place with very little play. Here's a shot of the screw, and I am holding the original pin:

Then to put it back together, I drilled and tapped three small holes to accept screws to hold the clamshell back together:

Here's a closeup where you can see how the screw is installed:

I also drilled a hole for a retainer screw to keep the bending element in place:

Used a little RTV silicone on the bending element and also between the two halves of the clamshell and then tighten up the screws. It works much better than new! No binding, no leaks, and I can easily take it apart again if future cleaning is necessary.

And just for illustration, here's a pic of the components:

[TomoHawk]

Thanks.

I had the thought of putting a little spring under the center screw to put some pressure on the shutter and make an even better seal. Maybe just one of those flimsy little bent washers. But yours isn't panhead screw.

You might want to consider stamping or engraving your reference marks into the metal, because if you use a solvent (like carb cleaner) to clean it, you'll lose your marks.

Edited November 13, 2012 by TomoHawk

[Captain Obvious]

Using a small spring washer under the original pivot pin would work in a pinch, but the problem is the additional friction that it would provide. You don't want any stiction in the pivot as the resultant hysteresis could cause in unpredictable operation. The flat headed screw makes it such that I can tighten the screw to jussssssst a thousandth or so before it starts to bind. That way, I have good tight fit, but still no additional friction.

I also noticed that the original pressed in pivot pin had a tendency to loosen up after the blade moved around a few times. I wanted something with threads so that I could threadlock it in place and not have it loosen up by accident.

Speaking of the calibration marks, you can see how I have my AAR adjusted:

Once it's warm, the window is completely covered (as it should be), but as you can see, at room temperature the window opening is pretty small. Because of that, my idle doesn't shoot high when the engine is cold, but pretty much stays constant. In other words, the additional flow through the AAR doesn't actually RAISE my cold idle, but in fact makes my cold idle the same as my warm idle.

I need to open it up just a little more. I was fighting a high idle condition because the AAR was sticking open, and I overcompensated a little.

[FastWoman]

Nice, Captain! Thanks for the tour of your AAR. When I have a bit of time, I'll be doing the same.