Auxiliary Air Regulator Questions...

Switchblade · Post by **Switchblade** » Sat Aug 10, 2002 12:42 pm

What is the best method for testing the AAR? I read that it shouldn't let any air through it when the engine is warm (aprox. 8 min). Is this true?
How do I test the connection (I currently get no voltage reading when the key is on, does the engine need to be running to test this?)

Where can I find a replacement? Pelican has it listed as NLA... ARG...

I am experiencing an 1,800 rpm idle and my MPS tested out good... any other suggestions?

thanx,

Dominic · Post by **Dominic** » Sat Aug 10, 2002 8:02 pm

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Switchblade:
<B>What is the best method for testing the AAR? I read that it shouldn't let any air through it when the engine is warm (aprox. 8 min). Is this true?
How do I test the connection (I currently get no voltage reading when the key is on, does the engine need to be running to test this?)

Where can I find a replacement? Pelican has it listed as NLA... ARG...

I am experiencing an 1,800 rpm idle and my MPS tested out good... any other suggestions?

thanx,

</B><HR></BLOCKQUOTE>

Check for Vacuum leaks, also check the deceleration valve for leaks or get rid of it all together. You may want to try disconnecting the crankcase breather line that goes to the air cleaner and plug the air cleaner hole to see if that fixes the Idle problem. It happened to me on a 1.7 that I was working on. Good Luck

Dave_Darling · Post by **Dave_Darling** » Thu Aug 22, 2002 8:58 am

The AAR power wire taps into the fuel pump circuit. So it should get +12V whenever the pump is running, which means for ~1.5 seconds when the key goes to "on", plus when the starter motor is cranking, plus when the engine is running.

You can jumper the fuel pump relay to check for voltage at the AAR connector.

Two things make the D-jet motors idle too high--air leaks (vacuum leaks or leaks through components like the AAR), or overly-advanced timing.

--DD

------------------
1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

Switchblade · Post by **Switchblade** » Fri Aug 23, 2002 4:34 pm

Dave,

First thanks for the information.

What I don't understand is that when I turn on my key the fuel pump runs constantly. It doesn't presurise the system and then shutoff. You can hear the fuel recirculating back to the fuel tank if it runs for a minute or so and the tank is fairly empty.

I have a '70 1.7ltr, where can I get a replacement AAR??

Dave_Darling · Post by **Dave_Darling** » Fri Aug 23, 2002 7:14 pm

If that's what your pump does, then someone has hooked it up differently than the way the factory did. If the original wiring has been hacked-up, that may explain why you don't get power to the AAR (if that is the case).

You get AARs for the 1.7 and 2.0 cars by going to the wrecking yards and getting lucky...

--DD

------------------
1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

Switchblade · Post by **Switchblade** » Fri Aug 23, 2002 9:05 pm

So basically I'm screwed!

Isn't a AAR just a cold start device? What would happen if it was removed and that port plugged? Are there substitutes that can be used? What was used on the 1.8?

Dave_Darling · Post by **Dave_Darling** » Sun Aug 25, 2002 9:35 am

1.8s used a similar valve, but it was configured a little differently. It had two pins in the plug (I think), and was shaped differently. Still had one vacuum hose in, and one out, and a little heater to warm up a bimetallic element to close a valve.

The 1.8 part is NLA, evidently, and has been superceded by a 944 part. I haven't seen this part myself...

They are all ways to get air from in front of the throttle plate to after the throttle plate, raising the cold idle. (Or keeping it from sagging too far.) With the hoses closed, your idle will probably be too low for the first 5-10 minutes the engine is running. You may have to tapdance with the throttle pedal to keep the motor running when you are stopped.

Are you sure the AAR is dead? It sounds like you were not getting voltage to it...

The AAR can be opened up and often repaired. If the electrical element is dead, you can solder up 13 ohms' worth of 1-Watt resistors and use those in place of the resistance wire. If the valve itself is stuck (the more common failure mode) you can often unstick it with penetrating oil and using a screwdriver from the underside of the valve (once you have opened it up) to twist the valve open and closed.

--DD

------------------
1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

[This message has been edited by Dave_Darling (edited 08-25-2002).]

Switchblade · Post by **Switchblade** » Mon Aug 26, 2002 8:54 am

Dave,

My AAR is bad. I tested it on the "bench" by hooking it up directly to a 12volt source and it doesn't close. I know the valve isn't stuck because when the engine gets good an warm the valve closes part way (this test was done by blowing through the valve before the engine was warm and then after driving the car for 30 minutes and blowing through the valve again - increases resistance).

I actually bypassed the valve yesterday, and you are correct I do have to tapdance on the throttle a little for about five minutes, but it runs so much better and idles where is is supposed to.

Does Pelican have a tech-article on repairing the NLA AAR? If not that would be a great new edition...

Thanks for all your help!

Dave_Darling · Post by **Dave_Darling** » Tue Aug 27, 2002 6:01 am

Not yet...

You can check the heating element by measuring the resistance from the electrical connector to the AAR's case. It should be right around 13 ohms. (More for the 1.8 version.) 0 indicates a short in the resistor or the wire, infinity indicates a broken resistor or wire.

The short version is that you can pry back the lip that is bent over the lid of the AAR. That will let you pull the lid off and pull the working "guts" (the valve and bimetallic spring) out.

...You should be able to figure it out from there.

--DD

------------------
1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

ray greenwood · Post by **ray greenwood** » Tue Aug 27, 2002 6:20 am

Wait...we always get definitions messed up when we talk about parts. YES, the auxiliary air regulator is a cold starting device...BUT...define cold starting? You absolutely need that piece of equipment even in warm weather. Remember that temperature is a relative thing. In July, a cold FI engine even in 90 degree weather will need the AAR device to run properly or else your baseline fuel mix will have to be too rich...causing all other ranges to be too rich.
Be absolutely sure you have the correct part #. There are literally DOZENS of models that all look and fit the same. They have different opening speeds and closing temperatures. Many will work fine...some...are designed to be partially open, or have some by-pass when fully closed. Look for milled notches in the plate or drum (depending on your configuration) with a flashlight, when fully closed.
Contrary to much factory literature, the AAR is not designed to augment or modify the idle point outside of the warm-up phase. It responds to slowly. In fact, on most injected type 4's, it does not change the idle range at all while the engine is cold (if its properly tuned)...UNTIL...the engine is warmed up slightly and IF the valve is not closed yet. The correct explanation for its function is, additional air to mix with fuel that has condensed in the ports and manifolds once the car has turned off, and the excessive fuel that is commonly added during warm-up phase both with the cold start valve, and without the cold start valve...by the ECU in response to the temperature sensors.
The original round type 4 AAR are still available from dealers. About $100. You can also use the later more common model...the "witches hat" shaped one with either the two wire D-jet or L-jet plug...but you have to get the little sheet metal bracket that allows proper mounting to the case/sheetmetal. Also it makes using the little "T" fitting that feeds the decel. valve difficult...but there are ways I have found.
The decel. valve is necessary in D-jet...in some cases. For best performance I disconnect wire # 17 at the throttle valve switch. This gets rid of the overrun shut-off feature, makes the throttle valve switch less sensitive to "bucking syndrome" and allows quicker throttle transition adjustment. BUT...it also leaves excessive mixture at overrun. The decel valve gets rid of this.
TAKE NOTE: On D-jet, you must have the decel valve. If you take it out, and your engine is closelyu or highly tuned, without this valve bleeding a little air into the manifold, the high rpm with throttle closed on overrun will re-vacume the MPS...leaving you very lean...causing pinging on overrun...ALSO because...your vacume advance will have you at very high advance rate while you are lean...which is why a properly adjusted vacume retard to bring you back to idle timing (7-10 in my case) is also a necessity. Think carefully before you get rid of components. Ray

rich2481 · Post by **rich2481** » Tue Aug 27, 2002 6:38 am

I sprayed the hell out of my AAR with carb cleaner, and bench tested it, I think it read 30 ohms too across the terminals, it takes about 5-10 minutes to fully closed you can look through it and see, at least on my bus I could.
Good luck, I wouldnt get rid of it though

Switchblade · Post by **Switchblade** » Thu Aug 29, 2002 7:21 am

Ray, just a note 70-71 1.7l 914's don't/didn't have a decel. valve.

Also I am confused by your statement "that the AAR shouldn't affect RPM's", how can it not affect the RPM of the engine since when it is open it lowers the overall vacume pressure within the manifold, which in turn is measured by the MPS which signals the ECU to richen or lean the fuel mixture(resulting in an RPM change).

If Type-4 AAR's work then why isn't anyone selling them as a solution for NLA AAR's on the 914??

I love this Forum, so many knowledgable people!! Thanks to everyone for answering my questions!

jeff

ray greenwood · Post by **ray greenwood** » Thu Aug 29, 2002 1:15 pm

Dave you are correct in the workings of the AAR. But... In 23 years of type 4's though, I have never seen a correctly tuned engine get significantly higher rpm from an open AAR...here is the catch...when COLD. They are designed to idle about normal when set correctly BUT...if you reach over and plug the hose when the engine is cold...they stall. That won't happen once the engine and the CHT reach normal operating temp, you will notice and is evidenced by the fact that the engine doesn't stall when the valve is closed....if you are tuned correctly. That is how it was designed to work. It bypasses the extra air necessary to keep idle in the normal range when the engine is cold. When the AAR is slow to close due to age of the element, extra cold ambient, or gummed up valve...and the engine warms up faster than the valve closes ...thats when you see the increase in RPM from an open AAR.
The type 4 AAR I am speaking of..for 411/412 IS the same as the 914. I bought one last year at the dealer for $89 + tax. They are still available, but you have to order it. It takes about a week. Not all dealers have the correct #'s to even order the part...so that is why some say its not available. As it was explained to me, just the part # is not all that is necessary to order obsolete parts. There is a constantly updated log of order codes that must be used. Not every dealer has that log. The other AAR...that was commonly used on type 4 powered buses, is also the same configuration used on many water cooled cars, but has a different part # denoting differnt operating temp settings on the bimetallic strip. It will bolt up just fine...but a little differnt hose configuration. The decel valve I was speaking of uses a connection that looks like a hose junction with a rubber "tee" for a 3mm vacume line to a decel valve. Not all cars used them. California 914's always used them with the 1.7L. This tee is about an inch long and mounts between the AAR and the plenum. Its a bear to get in straight and dies from heat and cracking. It is a dealer only part, and still available at about $12. To understand why the AAR does not cause a higher idle, you have to remember that the CHT is keeping you lean and the ambient air sensor is keeping you rich. This is why frequently, D-jet starts up very rich in the winter. You have two enrichment functions at the same time. Without the AAR...it would be very hard to start at all. If you do get more than 100 rpm or so of raised idle...there is a large chance that your entire mixture range, across the board, is running lean. Ray

Switchblade · Post by **Switchblade** » Thu Aug 29, 2002 3:05 pm

Do I order the AAR for the 411/412 or the same year and engine size? Do I even bother giving them the part number?

Dave_Darling · Post by **Dave_Darling** » Thu Aug 29, 2002 11:39 pm

Anyone tried to get a Type IV AAR lately? When the parts guys at Pelican looked up an AAR for a 1.8 Type IV, the number that they got back was a 944 part...

BTW, just for the record--I think all of you are wrong...

Changing the mixture doesn't change the RPM, changing the amount of air going into the motor does. Letting more air into the motor (the AAR being open) does not change the mixture. Rather, it simply acts like a throttle valve that is a little more open tha it actually is.

In an L-jet system, the AAR bleeds metered air from in front of the throttle plate to the manifold. Since the air is metered, the FI knows to put more fuel in for it. If the FI is working correctly, the mixture should stay right around stoich--but there will be more air going in so the RPMs should be a bit higher. (Higher meaning higher than they would be if the AAR were closed; not necessarily that the cold idle should be 2000 RPM.)

The D-jet bleeds air into the manifold; this extra air is seen as a higher pressure in the manifold. The EFI interprets that as more air, and adds more fuel to go with it. Just as if the throttle were open a bit. If the FI is working correctly, the mixture stays around stoich, but the RPMs go higher. Just like in the previous paragraph.

Or at least, that's my interpretation of what happens.

--DD

------------------
1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com