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bradself
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Joined: January 13, 2013
Posts: 167
Location: SF, CA
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 Posted: Wed Nov 26, 2014 3:43 pm Post subject: Alternative AAR?? |
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| Neither of the two decent ones I have any longer close all the way. I can open one up and do the rebuild routine described on the 914 fan site that replaced the heating element with resistors, but am curious if anyone has replaced these (expensive) regulators with something newer and a bit more common. |
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KTPhil 
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Joined: April 06, 2006
Posts: 34013
Location: Conejo Valley, CA
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| Posted: Wed Nov 26, 2014 3:56 pm Post subject: |
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It's not required to close all the way, as long as:
(1) it nearly closes, so you can adjust the idle speed correctly
(2) it gets to this nearly-closed point at the right time (5 minutes?) and consistently
The AAR is a controlled air leak, just like the idle speed screw.
You could also fit the non-electric version used on stick shift cars... I think it fits. There are more of those and they are more easily adjusted.
EDIT: Oops, I realized I'm in the T4 forum, not T3. I'm not sure the T4 engines ever used the mechanical AAR. So the second part of my answer is probably useless. |
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bradself
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Joined: January 13, 2013
Posts: 167
Location: SF, CA
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| Posted: Wed Nov 26, 2014 4:27 pm Post subject: |
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| We share these with 914s so they are stupidly expensive--wish there had been a mechanical version like the T3s, wonderfully simple design. Ours sit atop the engine, not within it. |
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raygreenwood
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Joined: November 24, 2008
Posts: 21519
Location: Oklahoma City
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| Posted: Wed Nov 26, 2014 4:54 pm Post subject: |
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| KTPhil wrote: |
It's not required to close all the way, as long as:
(1) it nearly closes, so you can adjust the idle speed correctly
(2) it gets to this nearly-closed point at the right time (5 minutes?) and consistently
The AAR is a controlled air leak, just like the idle speed screw.
You could also fit the non-electric version used on stick shift cars... I think it fits. There are more of those and they are more easily adjusted.
EDIT: Oops, I realized I'm in the T4 forum, not T3. I'm not sure the T4 engines ever used the mechanical AAR. So the second part of my answer is probably useless. |
No sir.....factory correct part # oc electrically heatedAAR for D-jet when brand new and working correctly is RRQUIRED to close all the way and should.
This is one of the problems with it in the first place. I have had several NOS in my hands a b d ran them. They WILL and DO close all the way.....for a while.
This seriously changes baseline tuning for the MPS. If your system is right in the middle of D-jet adjustment tolerance.....you only notice a small change. Many people dismiss this as antics of a 40+ year old car......I wont put up with it because I KNOW how they should run when the AAR is correct.
The problem is that very shortly after they are installed from new.....normal bi-metal sprjng fatigue makes it to where it no longer closes all the way. In a perfect world it would be like the original type 3 non-heated AAR......and you could simply adjust with the set screw.
You can, do this on the type 4 versio ....but you have to uncrimp the case.
If yours is not brand new....but will not close all the way and you open it to adjust it...go ahead and replace the heater wire inside because thats the next thing that goes out.
If yours is only staying open with about a 1/8" of the horizontal slot showing....you cancget away with it.....but you will need to adjust at the MPS.....NOT dirt simple.
You can also use one of the later 2 wire AAR that were used on late late buses and a lot of watercooled cars. It requires a small sheet metal bracket to bolt it down and you will need a short length of 12mm hose.
Those AAR are what many of us call the "witches hat" shaped model. They work really well but there were over 30 part #s used across everything from VW, Saab, mercedes, volvo, Renault, etc.
Personally....when my engine goes back together....I am, modifying mine to open and close with a oull, cable.
I tune my D-jet much tighter than factory. When you tune tighter...small vacuum leaks like the AAR and PCV valve not closing. ...make a huge difference.
Also.....if you dont want to rebuild yours....and want to go to the 2 wire witches hat model....I can find you the part # I was using on mine and it worked well. I also have a large collection of NOS Bosch AAR. I might have a spare. Ray |
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bradself
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Joined: January 13, 2013
Posts: 167
Location: SF, CA
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| Posted: Wed Nov 26, 2014 5:35 pm Post subject: |
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Oh yes, witches hat part # please Ray, thank you! I assume one of the two wires is a ground?
Turning the original into a manually operated device is also a very appealing idea, but might be past my workbench skills. -Brad |
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raygreenwood
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Joined: November 24, 2008
Posts: 21519
Location: Oklahoma City
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| Posted: Wed Nov 26, 2014 7:31 pm Post subject: |
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| bradself wrote: |
Oh yes, witches hat part # please Ray, thank you! I assume one of the two wires is a ground?
Turning the original into a manually operated device is also a very appealing idea, but might be past my workbench skills. -Brad |
But....KTPhil is a crafty and skill gent as well.
Everything he noted is correct in general. It is a controlled vacuum leak. But its not just important that it close enough for idle control.
The type 4 with d-jet...as compared to the type 3 with d-jet....has other systems like pcv and vacuum operated decel valve, the throttle modulator on the automatic etc....that make it more sensitive....and not just at the MPS adjustment.
But he is also correct that if the type 4 could somehow use the early non electric type 3 model.....it would be wo much easier to adjust and calibrate for.
I will get you part #s when I get home next week.....but I can also show you how to do the manual cable version for cheap and easy. And....there are already locations it would fit kn your dash like factory. Ray |
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