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Cold starting and Auxiliary Air Regulator questions
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furgo
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PostPosted: Tue May 30, 2017 11:37 am    Post subject: Cold starting and Auxiliary Air Regulator questions Reply with quote

As I'm starting to troubleshoot my cold start issue (need to crank for a while whenever cold starting, bus won't start without depressing the gas pedal a few times), these are some of the things I'll be looking at:

• Cold start valve and Thermo Time Switch
• Engine temp sensor (TSII)
• Auxiliary Air Regulator (AAR)

I believe I've got a good understanding of how the first three work and what to look for when troubleshooting. However the AAR is a bit of an unknown to me and had some questions:

ECU control of AAR heater

When looking at the manuals or online articles that deal with the AAR, there is one thing that is never mentioned: looking at the circuit diagrams, and if I understand it correctly, the AAR heating filament is grounded via an ECU output. Unlike the Termo-Time Switch, which is also bimetal+heater based, and always grounded.

I've also read some statements regarding to how long the AAR will stay open and thus let extra air in:

Quote:
From the coldest, the valve will close in about 8 minutes.


From this, I had initially assumed that the heating filament was always hot, but it seems there is some ECU logic that controls the heater.

Has anyone observed the AAR ECU line to shed some light into this logic?

AAR replacements

I'm looking preemptively at replacements in case I need to swap the AAR (admittedly, also to have a spare).

The original VW 022-906-045A (corresponding to Bosch 0 280 140 101) is pretty much NLA here in Europe (as are most of the FI parts anyway, FI buses here were a rarity!), and I was wondering if I could use a Bosch replacement from a different FI vehicle of around the same age, which seem to be much easier to find.

I started by looking at the Bosch datasheet for Auxiliary Air Regulators, and compared the original part with some others I can more easily source. Here are what the specs look like:

Bosch 0 280 140 101, VW 022-906-045A (original part):
• Curve: for air flow <unknown>
• Heater filament resistance: 30 Ω

Other alternatives:

Bosch 0 280 140 112:
• Curve: for air flow 9.5 m3/h
• Heater filament resistance: 49 Ω

Bosch 0 280 140 114:
• Curve: for air flow 12 m3/h
• Heater filament resistance: 49 Ω

Bosch 0 280 140 121:
• Curve: for air flow 11 m3/h
• Heater filament resistance: 49 Ω

I'm not sure if the resistance is too critical, other than meaning that a lower resistance will heat and close the AAR quicker. The air flow is probably the key characteristic, but unfortunately neither the rating nor the full curve for air flow are given for the original VW part. The alternatives do list their rating,

Has anyone had any experience with AAR swaps and air flow rates?

Thanks.
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PostPosted: Tue May 30, 2017 12:15 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

When I had cold start issues on mine it was traced directly to a bad cold start valve (CSV, Fifth injector). The CSV itself not the stuff controlling it.

I think you mentioned it but not sure if you checked it.
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PostPosted: Tue May 30, 2017 2:18 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

Thanks. Indeed, I mentioned what I'm going to look at. The time I can work on the bus is limited, so I tend to do my research beforehand. The CSV is on my list, but the AAR is a part I'm not familiar with, hence my questions.
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PostPosted: Tue May 30, 2017 2:19 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

I know that the shape of the opening varies with the application.

Haven't a clue how the ECU might effect the opening rate and whether it eventually cuts off the ground.
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PostPosted: Tue May 30, 2017 3:09 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

pressing the gas pedal does nothing... placebo effect. if you think the CSV is leaking or you are starting rich, start the car with the pedal fully down and release it when it fires
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PostPosted: Tue May 30, 2017 3:36 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

aerosurfer wrote:
pressing the gas pedal does nothing... placebo effect. if you think the CSV is leaking or you are starting rich, start the car with the pedal fully down and release it when it fires


I might be way off here, but if the AAR were stuck closed, would pressing the gas pedal to open the throttle and let some more air in to compensate not help?

I'm just thinking out loud, as I'm not sure if that's a common failure mode for the AAR, either.

I could swear I've had (cold start) occasions where the engine just fired, and if I didn't press the pedal briefly it would then immediately die. But thinking about it, and as you say, it might have well been the placebo effect, happy to learn new things!
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PostPosted: Tue May 30, 2017 4:07 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

furgo wrote:
aerosurfer wrote:
pressing the gas pedal does nothing... placebo effect. if you think the CSV is leaking or you are starting rich, start the car with the pedal fully down and release it when it fires


I might be way off here, but if the AAR were stuck closed, would pressing the gas pedal to open the throttle and let some more air in to compensate not help?

I'm just thinking out loud, as I'm not sure if that's a common failure mode for the AAR, either.

I could swear I've had (cold start) occasions where the engine just fired, and if I didn't press the pedal briefly it would then immediately die. But thinking about it, and as you say, it might have well been the placebo effect, happy to learn new things!


There are several common failure modes for the AAR. And....by the way the only control to the AAR by the ECU is to supply either ground or positive (depending on the car and system). As long as the engine is running....the ECU keeps supplying. If the ECU cuts off power.....the biemtallic strip cools and it opens back up. The AAR closes to a preset amount. Some of them are designed to close all the way....some not. Its qpplication specific.


And this is not bus specific.....but some AAR are adjustable by a small screw and some have a fixed amount of bypass via a notch or hole in the plate or vane that closes off the port.

As Wlldthings mentioned....many of the part #s are identical in every way except for the shape of the orifice or vane. Some have a rounded hole others an angled hole....still others with a notch.

I have sold off about 40 NOS AAR' on Ebay over the past year. I really should have photographed the different orifice shapes and sizes of the electrically heated ones. I only did this for the water heated ones as the BMW and Mercedes people needed to see it.

The common failure modes:

1. A fatigued bi-metallic strip. They will all die of this sooner or later if for no other reason. With many heat cycles and years.....the strip can still have the same resistance and heat up....but it does not bend as far. It can make it not close all the way or not open all the way or both.

2. Depending on how yours is put together.....some just have the plug and bi-metal strip pressed in.....and with age the joint between the heater core and body gets loose and the heater core rotates under its own torque.....turning the heater core instead of turning the vane/valve inside. This is usually not too hard to fix with a punch mark or a dowel pin.

Also....this type can be re-indexed to have a little more ability when old and fatigued...to close the valve....but they then usually do not open as far.

Others are put together by indexing the heater core to the right position....and then a hole is drilled and a roll pin is inserted. Ill see if I have enough varieties left to post some pics of these.

3. The most common problem even when they are not that old....is that the vane can get gummed and gritty and not open or close well.

4. Another age related issue is burn out of the heater core strip. This usually is found with aj open circuit. In the past....I have been able.....if its constructed right....to rob the heater core from a differnt AAR and insert in into the one I need. Calibrate by plugging it up to power and lock the core in place with a pin.

Its worth buying AAR even if they are different because unless the vane is radicwlly different you can usually tune them in a bit.

Ray
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PostPosted: Tue May 30, 2017 4:42 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

furgo wrote:
aerosurfer wrote:
pressing the gas pedal does nothing... placebo effect. if you think the CSV is leaking or you are starting rich, start the car with the pedal fully down and release it when it fires


I might be way off here, but if the AAR were stuck closed, would pressing the gas pedal to open the throttle and let some more air in to compensate not help?


I think Aerosurfer is referring to your saying you were pressing the pedal repeatedly. Holding the the throttle open does supply more air/fuel mixture, but the act of pumping the pedal isn't going to cause a significant volume of extra fuel to be delivered as it would if you have a carburetor.
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PostPosted: Tue May 30, 2017 5:03 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

furgo wrote:
From this, I had initially assumed that the heating filament was always hot, but it seems there is some ECU logic that controls the heater.

Has anyone observed the AAR ECU line to shed some light into this logic?


Not sure if this has been answered. The AAR is always grounded via the ECU and is powered via 88c on the double relay. If the pump is running the AAR is powered. No extra logic.
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PostPosted: Tue May 30, 2017 5:31 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

BayCreamPuff wrote:
furgo wrote:
From this, I had initially assumed that the heating filament was always hot, but it seems there is some ECU logic that controls the heater.

Has anyone observed the AAR ECU line to shed some light into this logic?


Not sure if this has been answered. The AAR is always grounded via the ECU and is powered via 88c on the double relay. If the pump is running the AAR is powered. No extra logic.

X2, in fact I even dissected an ECU and followed the circuit back directly to ground. https://www.thesamba.com/vw/forum/viewtopic.php?t=575435
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PostPosted: Tue May 30, 2017 7:10 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

BayCreamPuff wrote:
furgo wrote:
From this, I had initially assumed that the heating filament was always hot, but it seems there is some ECU logic that controls the heater.

Has anyone observed the AAR ECU line to shed some light into this logic?


Not sure if this has been answered. The AAR is always grounded via the ECU and is powered via 88c on the double relay. If the pump is running the AAR is powered. No extra logic.



Yes.
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PostPosted: Tue May 30, 2017 11:51 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

Every L-Jet bus I've worked on has a vane shaped like this; so something similar should work fine.

Image may have been reduced in size. Click image to view fullscreen.



They are somewhat testable by putting them in a fridge for a few hours, then watching them open as voltage is applied:


Link



Some tired fuel pumps/pressure regulators bleed the system down just enough that it takes a few seconds to re-prime. Next time your engine has sat for a while (overnight, minimum,) run the fuel pump for a few seconds before trying to crank the engine over. Do this by poking the AFM flap through the air intake [filter removed] with a dowel, or by nudging the AFM wiper open a tick. With the key on, either one of those methods will make the pump run enough to prime the system. Five seconds is plenty.

Good luck,
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PostPosted: Wed May 31, 2017 2:47 am    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

Wildthings wrote:
I think Aerosurfer is referring to your saying you were pressing the pedal repeatedly. Holding the the throttle open does supply more air/fuel mixture, but the act of pumping the pedal isn't going to cause a significant volume of extra fuel to be delivered as it would if you have a carburetor.


Oh, I see what he meant, that makes sense now, thanks!

I went the same route as busdaddy and followed the AAR PCB track on my spare ECU. Here are a couple of pictures to complement visually what him and BayCreamPuff already said: the AAR is hardwired to ground internally via the ECU.

Image may have been reduced in size. Click image to view fullscreen.

See the GND and AAR PCB tracks being the same one. Also, unrelated, but interesting, see the 4 injector drive lines next to the right being interconnected too (that's normal, as they are all driven at the same time, and it allows for a fatter PCB track that can carry more current than 4 individual ones).

Image may have been reduced in size. Click image to view fullscreen.

AAR highlighted in the '79 Federal diagram, showing the internal connection between the AAR and two of the ECU grounds.

That answers the first question nicely. Although I do wonder why the AAR wasn't just simply grounded externally via the harness.

Thanks raygreenwood and asiab3 for the awesome wealth of information on the AAR. That was extremely helpful.

What I'm taking from this is:

• There is not much info on folks having replaced the AAR with an alternative
• As I've got no way of testing the flow (and there is only limited info on ratings on the datasheet), the best way to test one of the alternatives will be to simply do the replacement and see if it improves things.
• The opening time(s) can be checked prior on the bench. For the bimetallic action via the fridge, for the heated operation via 12V through the pins and noting down ambient temp for reference.
• If the vane shape is the same as the original, the same opening time will mean same flow rate

Which brings me to: if I need to replace the AAR and I don't find the original part:

• Just get one of the alternatives
• Check out if the vane looks the same as in asiab3's picture
• If it is, tune up the opening time to match the original part's air flow if possible

raygreenwood wrote:
It's worth buying AAR even if they are different, because unless the vane is radically different, you can usually tune them in a bit.


... and that brings me to the follow-up question: what can be tuned in an AAR and how? That screw on asiab3's picture has the looks of either something you can calibrate or should leave alone...

From the A.F.C. manual, I also noticed this statement:
Quote:
[The AAR] is calibrated so there is little difference in the idle speed of a cold or warm engine


So I wonder if it is practical at all to measure the warm idle RPM and then calibrate the alternative AAR part's gate initial opening to match those RPM during a cold start.
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PostPosted: Wed May 31, 2017 11:28 am    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

A few things before I answer your question…

The easiest test you can do for an AAR on a cold morning is to start the car and immediately clamp off the AAR input hose that comes off the s-boot. The idle speed should decrease immediately, and then increase when you remove the obstruction. Horrible Freight radiator hose clamping pliers are great for this, because they don't damage the line, and you don't have to futz with plugging and unplugging hoses while trying not to kill the engine with a vacuum leak. If the speed doesn't change, your AAR is stuck closed and should be ministered to.

Image may have been reduced in size. Click image to view fullscreen.



The cold start RPM does not have to match the warm RPM. If anything, it should be a little faster. How much? I can't find a Bentley specification, but 1,200 to 1,400 on a warm summer day at sea level is what I usually get out of a stock bus with a clean and adjusted AAR. It allows for a clean cold idle with no misfires on even the coldest days at elevation, and who knows when you're going to make a spontaneous road trip to some desolate snowy mountain. "Hold on kids, daddy's gotta adjust his AAR…" No thanks… Laughing

furgo wrote:
...and that brings me to the follow-up question: what can be tuned in an AAR and how? That screw on asiab3's picture has the looks of either something you can calibrate or should leave alone...


The "gate" opening of the AAR can be adjusted, which gives you more air and a longer "open time." Time and flow are locked in their relationship, so a larger opening will allow more air and take longer to close.

Before you go adjusting, make note of your cold start RPM and warm RPM. That way you'll have a quantitative reference point.

As you saw in my picture, there is a 6 or 7mm hex nut that VW or Bosch paint-ticked. (I think it was an anti-tamper measure, for emissions laws, like the yellow paint on the dual carb linkages.)

The adjustment is outlined on this page, where the images disappeared but the text is still good:

http://www.itinerant-air-cooled.com/viewtopic.php?t=7834

Amskeptic wrote:
If engine is suffering a fast idle when warm, try first merely cleaning the mechanical end with GumOut carb spray followed by a nice bath of WD-40. Keep the electrical plug up vertical through this cleaning procedure.

If engine is suffering a doggy slow idle when cold, remove the AAR. Stick it in the freezer for ten minutes or so to get enough of the aperture window open that you can cram a 2 or 3 mm allen wrench through the window. If freezer persuasion is insufficient, try to pry the disk with an awl or small-bladed regular screwdriver. Once you have the allen wrench through the opening, loosen the adjustment screw's locknut. This adjustment is *not* about rotating the screw and watching the aperture open. It actually sort of slides around, so jam that allen wrench to get the aperture as open as you can, and harass the adjustment screw to find it's relaxed state with the aperture open, then tighten the lock nut down. There are intense leverage/fulcrum points going on between the bimetal and the disk, so if you get it right, it really does remain more open. There may be a little closure when the allen wrench is withdrawn, but if it springs back towards closed dramatically, repeat adjustment attempt.

Await the cold morning with great anticipation. You can hear that little sucker suck from the driver's seat as the engine fires up and holds a strong idle on the coldest morning. Then, in about 4-6 minutes, the idle will trend towards the normal warm idle.
Colin 12-13-10


Use the picture in my previous post for what a good-sized opening should look like for a nice and fast cold idle on a stock bus. Performance camshafts, big-valve heads, or new engines that aren't fully broken in will require extra diddling beyond the scope of the stock adjustment.

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PostPosted: Wed May 31, 2017 11:51 am    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

Furgo said:

Quote:
That answers the first question nicely. Although I do wonder why the AAR wasn't just simply grounded externally via the harness.


On some systems in other cars....L-jet, variations of L-jet, Digifant I and II, even some CIS cars, D-jet....it is run directly to switched power.

Meaning...some systems have the AAR grounded permanently at the pigtail...and supply power when the ignition is running just from the mains...with no connection to the EFI system at all. And still others as you see...that supply + all the time and use switched ground.

I have been wondering this for ages. Eons ago when I was taking the course at a Bosch Clinic that included L-jet and current derivatives....this was asked of the instructor and his crew by several mechanics in the audience.

The answer was less than definitive. It remember his answer was more of outlining the current philosophy of safety features that were being pushed at the design level of automotive manufacturers.....and was equated somewhat with the feature of L-jet that the fuel pump does not run until the flap in the AFM signal cranking and airflow....which I find just silly and really makes for more actual cranking than is necessary....whereas a simple fuel pump pulse like D-jet and many other systems....would pressurize the mains to the minimum pressure insuring great atomization on the first injections into moving air.

Meaning....why have the AAR powered until you REALLY mean to be running. Conversation went around that perhaps the engineers did not want the AAR heating while one just had the key on to do some other maintenance check. Not that its going to hurt it....but...sure...a short time later...it may be closed when it should be open for a cold start. Fair I guess....so we all took that as "an answer"...and moved on.

But....it would have been simpler to run the ground for it to one side of a relay...like one that is supplying power to the fuel pump or the EFI system....so when they are on its on....and no need to run it through the ECU.

The worry issue in my mind with running it through the ECU....is that once....and only once....I have seen that a shorted pair of wires or a bad heater element (never found out which one)....caused an overheat of the ground circuit in the ECU...as the AAR circuit is not fused. It damaged the ECU.
The ECU still functioned fine but the ground circuit trace through the ECU for the AAR no longer worked.

Quote:
What I'm taking from this is:

• There is not much info on folks having replaced the AAR with an alternative


Actually there is....but its not collated into a group of threads. In parts of conversations (usually parts of threads with other handles)....over the years on the STF for sure....there have been numerous examples. Also on the BMW, Porsche, Audi, Volvo and BMW sites there has been many conversations about this.

With early simple L-jet like the bus has....having an AAR that is different in flow rate and warm up time might make for occasional running problem because it is an air bypass...and if you bypass the flap with enough air when cold...it "may" cause enough of a pulsewidth variation to give a small amount of warm up issue.

On L-jet with an 02 sensor....maybe less so depending on how fast the 02 sensor warms up and the system lets it start affecting the fuel map (if at all during warm up).

On other systems in other cars....you can get away with murder with the AAR opening size and flow rate....because other systems like the 02 sensor and idle air controller are also working. Yes...there are a very few early cars with both idle air controller and AAR....which quickly ended when the ECU's starting actually controlling the idle air controller opening.

Other makes of classic car owners (Mercedes, BMW, Porsche, Audi, Volvo, Saab and VW)....have finally gotten wise to the fact that they REALLY do not have to chase the exact part number of AAR for huge 444...if they find one with the exact housing shape and hookups.
The difference may be that it supplies warm up air a few minutes longer or shorter...or idle may be a few rpms higher or lower....but otherwise its perfectly functional and allows a cold start.




Quote:
• If the vane shape is the same as the original, the same opening time will mean same flow rate


yes....it should...but also make sure it closes the same amount. Some are designed to not close all the way. On those AAR that have and adjusting nut...you "should" be able to adjust this.

Quote:
Which brings me to: if I need to replace the AAR and I don't find the original part:

• Just get one of the alternatives
• Check out if the vane looks the same as in asiab3's picture
• If it is, tune up the opening time to match the original part's air flow if possible


raygreenwood wrote:
It's worth buying AAR even if they are different, because unless the vane is radically different, you can usually tune them in a bit.


Yep.....really you just need to try some out....but I can tell you this....all of these in these pictures will "work" on a type 4 engine with L-jet or D-jet. They have some slight variations in idle and warm up length...but I have installed all of these at one time or another and they do the job.

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


These are the last of my NOS (except the one on the left). You can see that not only are they all identical inlet, outlet and chassis shape...they all have the plug indexed the same (some very small variation when you look at them)...and the roll pin installed

Image may have been reduced in size. Click image to view fullscreen.


they all have the adjusting nut

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


They have three different port shapes between them.

These parts are:

0 280 140 122: Saab-Peugeot various years (40.5 ohms)

0 280 140 132: Porsche 944 and Triumph TR-7 among others (40.8 ohms)

0 280 140 141: 83-84 Audi 4000 coupe, VW Quantum 2 and 4 door (41.5 ohms)

0 280 140 143: Audi 4000, 5000, VW Quantum all with K-jet (43.3 ohms)

0 280 140 169: Porsche 924 and 944 (41 ohms)


If you can wait a day I will freezer them and power them up and time them out for you. Sorry....I had about 20 part #'s of this type of AAR that were NOS...that I could have done this with until a few months ago but I sold them all off and didn't think about about cataloging them before hand.
Quote:


... and that brings me to the follow-up question: what can be tuned in an AAR and how? That screw on asiab3's picture has the looks of either something you can calibrate or should leave alone...


The nut changes the stopping point. and somewhat the starting point of the AaR. But.....the shape of the hole in the vane (if there is one) really changes the tuning. A slanted port hole.......slanted toward the direction and at a shallow angle is a slow decrease over the time/movement range. A large angle port in the same time range can cut off air faster. It matters how much of the hole passes out of range how fast.

Oddly...I have not tried to see if any ballast resistance between either positive or ground may help slow one of these down. I have to think about that for a moment...it may not make any difference...or it may put undue resistance load on the ECU ground circuit.

But...I have tuned one by adding a port restrictor inside one side or the other...meaning instead of feeding from a 10mm port....it feeds from say a 5mm port.
This helped with one years ago on my 412 when I needed one that closed all the way...and I had one that closed to still have a small hole peeking...that was correct for whatever its original application was.....but was bad for mine.
So I restricted the inlet port by 50%. I got a little less warmup air....and still had a small leak at full close...but was now even smaller in effect so I could tune around it.


Quote:
From the A.F.C. manual, I also noticed this statement:
Quote:
[The AAR] is calibrated so there is little difference in the idle speed of a cold or warm engine


Yes...in general thats how these are set up. They are designed...at least on some ...not all....systems....to allow the engine to run at "normal" rpm...not elevated. In reality that does not work across the board in early injection systems with very few enrichment controls.

The actual ambient temperature, available fuel due to effect of the temp sensors in the system, drag of the cold oil etc.....may cause the actual mixed produced by a fully open AAR to be lean enough to cause slightly elevated rpm or not.

Quote:
So I wonder if it is practical at all to measure the warm idle RPM and then calibrate the alternative AAR part's gate initial opening to match those RPM during a cold start.
[/quote]

Its possible...and I have tried a little bit of that and its harder than it looks due to what I listed above...the variability of engine condition, ambient...and even add in atmospheric pressure and altitude.

And once you tweak the adjusting nut....it adds or subtracts from the closing point...but also from the opening point.

I have been thinking about cracking one of these open carefully....to figure out a way to make something like a screw together "re-closing kit". Then it could be tuned either by spring pressure, snapping in tuning orifices in the disc etc.

I don't have an answer for the weak with age bi-metal strip yet. I can build heater elements easily....but I have never tried to make a bi-metal strip element. Ray
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furgo
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PostPosted: Wed May 31, 2017 1:13 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

Thanks Robbie and Ray again.

Quite a lot of helpful info to digest. I'll reply tomorrow with more time and perhaps with some findings on the status of my AAR.

Just a couple of quick replies for now:

To complement the ratings you posted for your AARs, and to get a feel for comparing them, here are the rest of the figures from the bosch-classic.com datasheet:

0 280 140...

122
• Peugeot 2.0l K-Jetronic
• as 115, which is in turn as 101 (original part), but with...
• Air flow: 14.5 m3/h
• Heating filament resistance: 40 Ω

Note: seeing this info on the datasheet (i.e. "same as 115, which is the same as 101") I would think this one has the same blocking plate shape. Also comparing Robbie's picture with yours and seeing that both have the axe-shaped opening would seem to confirm that.

132
• Rover/Triumph TR 7, 2.0l
• Air flow: 10 m3/h at 20°C (68°F)
• Heating filament resistance: 40 Ω

141
• Audi 4000, 5000, VW Dasher
• Air flow: 14 m3/h
• Heating filament resistance: 49 Ω

143
• Audi 5000, 200 T, Quattro, Alfa Romeo 3.0l GTV, Alfa 75
• Air flow: 17 m3/h
• Heating filament resistance: 49 Ω

169
• Porsche 944
• As 161, but with with different blocking plate and different heating filament
• Air flow: 12 m3/h at 20°C (68°F)
• Heating filament resistance: 30 Ω

raygreenwood wrote:
Oddly...I have not tried to see if any ballast resistance between either positive or ground may help slow one of these down. I have to think about that for a moment...it may not make any difference...or it may put undue resistance load on the ECU ground circuit.


I would think that adding the resistor would mean less current and thus less heat, effectively slowing down the closing time, as you're saying. It would be a series resistor, and it should not make a difference on which side of the heating filament it is. Given the small Ohm figures at 12V, it should probably be a power resistor.

That would be easy to test on the bench, but I think the tricky part would be to affect or even test the combined closing time (engine temp + "self" heating via the filament).

raygreenwood wrote:
I have been thinking about cracking one of these open carefully....to figure out a way to make something like a screw together "re-closing kit". Then it could be tuned either by spring pressure, snapping in tuning orifices in the disc etc.


If this helps, there was a guy on the Pelican Parts forum who did open one up and documented its inner bits with pictures:

http://forums.pelicanparts.com/porsche-924-944-968...tions.html

Image may have been reduced in size. Click image to view fullscreen.

The whole assembly, with the lid taken apart. Notice the broken hole on the left hand side of the blocking plate, which is probably where the spring was initially attached to. Not sure if it's a fragile point or if he managed to break it in creative ways.

Image may have been reduced in size. Click image to view fullscreen.

Air flow blocking plate detail.

Image may have been reduced in size. Click image to view fullscreen.

Bimetallic strip with heating filament.
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PostPosted: Wed May 31, 2017 2:48 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

Thanks for the internal pictures!

I have actually been inside of several of them. What I meant........was to try to take one apart with an eye toward being able toget it back together......in a manner that is reliable......can be taken apart at will for adjustments, repairs or calibration.

I have also thought.....about replacing the heating element on one of these.....with just a simple on/off solenoid. In reality......it does not matter much during say the 5-8 minute warm up period.....if the valve is "gradually" closing or not.

The most important item is that its open when you need the extra air for starting.....and when you reach the stage where bypass warmup air is no longer needed.....it is closed.
4-5 minutes in betweeen with a very alightly higher amount of bypass air is not huge.
As you note from the factory specs.....10-14 cubic meters per minute is not huge.

A solenoid on a timer or even with a temperature switch inline that breaks or makes contact can simply snap the shutter closed.
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PostPosted: Thu Jun 01, 2017 8:43 am    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

Fargo,

I love the indepth, if not long winded description of all the components you have been writing threads about lately. It's a battle of knowledge with Ray that really give the rest of us L-jet savants a great location to source all the info we always know and reference, but Can't always find in text. It certainly compliments and adds to what Colin and Ratwell have written over the years too.

Keep it up.
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PostPosted: Thu Jun 01, 2017 12:16 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

aerosurfer wrote:
Fargo,

I love the indepth, if not long winded description of all the components you have been writing threads about lately. It's a battle of knowledge with Ray that really give the rest of us L-jet savants a great location to source all the info we always know and reference, but Can't always find in text. It certainly compliments and adds to what Colin and Ratwell have written over the years too.

Keep it up.


X2.

I like it when other people dig into the little details of why and how various parts actually work.....what may or may not make them special for our applications....and therefore validate what may or may not be used as an alternate source for parts that are drying up faster than you can shake a stick at.
Ray
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PostPosted: Thu Jun 01, 2017 2:30 pm    Post subject: Re: Cold starting and Auxiliary Air Regulator questions Reply with quote

i suppose the day is upon us when we drool over NOS pictures of (sadly, consumable) FI components.

our vehicles certainly arent rare, especially compared with other models of earlier vintage and the components should be even less rare for how abundant they were used around the worldn but the challenges of time and interest to the hobby seem to be the real adversaries.


The long worded replies, as well as all the tutorials definately get appreciated by the masses far more than the author will ever know
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