Aux air regulator

[DJ]

Question for you guys with Beta FI systems knowledge.

After putting an aux air regulator in the freezer to test it's operability, how far open should the hole be?

Both of the ones I have only open up about a fourth of the way. I've seen references that say it should be completely open.

[rossocorsa]

as far as i know should be virtually fully open you can play with them by adjusting the tension on the nut that you will find on the outside however old air valves tend to be sticky and erratic you might need to find one new cheap off ebay to try

[davidb]

There's a thread from me way back under what topic title
I don't recall . I think Will was the one w/the correct
test . A good one should open up almost ALL the way .
Mine opened about 90% - 95% so it went back in .
Someone else said they almost never fail . Well then
why do all our vendors sell them ? It's mechanical +
exposed to fuel fumes so it might gum up .

[Will]

At room temperature, the AAV should be open far enough to look like a slice of pizza (clever comparison, eh?)
BUT- it's metered air, so open a little more or less doesn't matter much since it can be trimmed out with the throttle bypass screw.

As for why every vendor sells them, I'd hazard a guess that it might have something to do with the fact they can be purchased bulk for about $30/ea, carry a list of something like $220, and can be "rebuilt" by hosing with carb cleaner and beading the outside- a five minute (tops) procedure. I have seen them priced over $100. I have seen "rebuilt" ones (pulled from junkyard car and sprayed with Gunk) for $75. Most folks don't understand them/trust them/know how to test them so they go buy a new one to solve one of the most common problems in old cars- vacuum leaks. It doesn't take a whole lot of reading between the lines to realize brisk sales + huge margin = nice gross profit.

FWIW I understand these can be adjusted via the stud/nut on the back and Watson's book details this, but I don't think I personally know anyone that's ever had to do it ! It's a bimetallic strip, so not very failure prone, and if it's full of water and corroded no adjustment nut is gonna help IMO. Ditto on the electric heater, but some folks claim it'll close strictly from engine heat regardless (eventually). I don't know enough to ascertain whether this is true, or at what temps/speeds if any it ceases to be true. I assume this is true for normal temps, but I have noticed with winter temps (in my truck) that sometimes ice barely melts in the engine compartment, so I suspect temp and airflow may prevent the AAV from closing it real cold weather if the heater is not working.

[Gregory Smith]

Will: "At room temperature, the AAV should be open far enough to look like a slice of pizza (clever comparison, eh?)"

A clever comparison, except the valve should look like this when COLD (or taken from the freezer for testing). At room temp the valve's pizza-shaped opening should be closed or nearly so.

In most systems the valve is bolted solidly to the block or to a coolant cross-pipe as on the F.I. Beta. This assures the valve warms up with the engine if the valve's heating element doesn't close it first.

[Will]

Well, by "room temperature" I meant about 70F. If your temperature is 140-150F then yeah, it should be closed, or nearly closed. Else, it's probably a bit out of whack. When taken from the freezer (if you choose to do that) then it should be open far enough you can practically pass a pencil through it, i.e. almost completely unoccluded. I believe the spec for when it is *supposed* to close is approximately 150F, so 70F about halfway between fully open and closed assuming fair linearity in the bimetallic strip.

I believe there are several part numbers for various application sof Bosch AAV, so some may close sooner or later by design, rather than circumstance? Or maybe it's just so the Porsche guys don't buy and use the VW AAV!

Greg, you live in the PNW, I would have thought your response maybe suitable for one of the Aussies out in the desert or something, but I think maybe your AAV's need a tune-up?

[rossocorsa]

my experience is that even if you clean test and adjust an old air valve it still works erratically in practice you can probably use one that is not an exact match for the original and it'll be near enough

[Will]

I agree, the idle speed = the SUM of AAV + throttle bypass + throttle leakage, any one of the three can be adjusted to suit, although common preferred practice is throttle plate as close to sealed as it can get without sticking, AAV as stock, and throttle bypass screw to compensate. I can't really tell if backing off the AFM spring raises the idle, I haven't ever heard an L-jet that idled perfectly enough to tell. I'm told the experts can pick up the beat frequency of the falling idle and tune things very smopothly, I lack either the talent or ear or both! I'm happy if I can keep it running relatively flat at 850.

[DJ]

common preferred practice is throttle plate as close to sealed as it can get without sticking

Sorry, Will, but I have to disagree with you on this point. I just went through this. This is the way I initially had mine set and I found that the engine kept stopping when backing off the throttle to stop. It essentially chokes off the engine completely until the idle air circuit can move enough air around the plate to keep it running and there is definitely a small lag in this, especially with a remote adjustment screw.

My research (online reviews and actual correspondence with others) found that most people just follow the standard manufacturer's idle set procedure but with a couple of added things that aren't mentioned in the literature.

The FIAT manual says to first adjust the accelerator stop screw until the idle is at 700 to 800 RPM. This must be done with the idle air adjust screw turned all the way in.

Then the idle air screw should be turned out until the idle reaches 800-900 RPM. The Lancia manual says 950 +/-50 and this makes for a slightly better idle and smoother off-idle starts IMHO. Many of the FIAT folks seem to also use the higher idle setting.

All this must be done with the engine at operating temperature (once the radiator fan has actuated twice, according to the FIAT manual) and the TPS should also be disconnected or loosened. The TPS must then be set to actuate when opening from the new throttle plate position.

Just completed this tonight and it makes for markedly improved driving.

Now to just get the coolant system bled and an alignment done and she'll be completely ready for the road. Just in time for the first snow... :mad:

[Will]

You are absolutely correct DJ. As much air as possible should go through the throttle opening and not around. Unfortiunately, it's easy to get it open too far, and then you can't get the throttle down below 1000 even with the bypass screw wedged down- just like you experienced recently.

The Bosch implementation chart lists idle as 850RPM and 750RPM (automatic). This is also kind of a matter of personal preference, but if you are idling too high the motor slows down when the AC cuts in because the orifice on the electrovalve for the AC is too small in proportion to the total airflow of the motor.

I don't know what Bosch (or FIAT/Lancia) use to determine the *proper* idle speed, there are some bizarre and non-intuitive measurements used by Bosch (like why would you measure return line volume in cc/per 30 seconds??) and all the applications use slightly varying specifications in almost all areas, even on engines with identical displacements and injector sizes. I find that a bit confusing. It's almost like they got one running good by trial and error and then said "OK, use all these settings!".