AAR hose re-routing

[Captain Obvious]

Correct' I don't use the AAR at all.

Hmmm... I've got my AAR adjusted such that I don't get much of an idle boost when first started, but I don't think my engine would idle stone cold without it. My idle settles out to 700-800 once warmed up, but I think if I cut it out completely, I'd have to sit there with my foot on the pedal for the first minute to keep it from stalling.

Maybe I'll try that and see what happens.

[TomoHawk]

I just let mine idle while I clean the windows. But first, I push the tail out of the door. If I need to, the foot presses on the gas pedal for a minute.

IMO, the AAR had a bad design and use. It only really closes if the car is not moving and the engine is warm, and as soon as you turn off the engine, it opens, no matter how warm the engine is, unless you have the warming plate installed with all the associated coolant hoses. It really needs an insulating cover.

Edited October 23, 2013 by TomoHawk

[siteunseen]

I sure don't believe the solution is to post stupid non-technical pictures of "loosely related"? situations simply in order to make a point.

Sorry, I couldn't help it but you hit the nail square on the head.

Edited October 23, 2013 by siteunseen

[TomoHawk]

The modern IAC units are interesting because you can control them to open as much as you like, or not at all. How do you control those? Can I assume there's a stepper motor inside? If so, a small circuit that is temperature-activated or switched by by the driver would work well. You hit the switch before or just after you start the engine, and it idles high for 60 seconds or so, then closes completely. My AAR takes a few minutes to close.

The only thing I don't like about the modern ones is that they're so BIG. A 12V solenoid valve is smaller. It ought to be small like the Datsun AAR is.

[Zed Head]

The Megasquirt site is informative - Idle Control

Looks like many ways to use a modern valve.

[TomoHawk]

Why not just remove the inlet hose altogether? Just put a small air filter on that nipple. The outlet hose is only a few inches long. It would probably work, but just make a hissing sound.

Edited October 23, 2013 by TomoHawk

[TomoHawk]

Since we'd like to see something small for the IAC valve, let's see what small fuel-injected engines use. Small engines like on a motorcycle. Outboard engine?

[Captain Obvious]

I'm no expert on the topic of idle air valves, but I believe it goes like this:

• If the valve has two wires, it's a PWM control with one field coil fighting against a spring. Simplest, but not the fastest response time.
  
• If the valve has three wires, it's a PWM balancing between two field coils. More complicated, but faster response.
  
• If the valve has four wires, there's a stepper motor inside. More complicated, but stays positively where you left it with no input signals. Example is GM.
  

I thought about the concept of just having two idle speeds "cold" and "normal" and just using a small simple solenoid valve to open up a bypass around the throttle plate. I've seen some really nice small solenoid valves used for EVAP can purge functions on cars. Maybe I'll grab one of those and mess around.

[TomoHawk]

Considering the size of the opening inside the valve (it's NOT a motor, like techs will call it :pirate: ) then you could just use some small solenoid-operated water valve, and plumb it directly to one of the unused vacuum ports on the intake manifold using small-diameter hose, instead of the big hose that comes from the manufacturer. You only have to plug the unused hole near the throttle.

[Captain Obvious]

And that concept of using a solenoid valve instead of the AAR came back to mind just this evening as a matter of fact.

It's gotten cold enough here that my idle crept up a little. My assumption is that my AAR (which doesn't have the warming plate underneath) isn't generating enough internal heat to close completely. I'm planning to take the car down for the season shortly, so I probably won't be driving much more until spring, but I thought of you and your AAR issues.

[TomoHawk]

The (problem) with using something like a solenoid valve is that you need a switch or timer to control it. A timer shouldn't be too tough; you can use the same circuit as the AAR itself for power and build a simple timer from an IC with some kind of a temperature sensor (a thermister switch?) Closing the valve slowly would be nice, hence the stepper motor in the Idle Air Controller, but if you have a long enough wait, a sudden close should be tolerable.

BTW-

It should be made to fail in the closed state, just in case, IMO.

[TomoHawk]

I made a quick sketch of the solenoid-operated AAR. It gets fresh air directly from what's under the hood, through a small filter. I suppose you'd hear a little sucking noise from it. The wires go to an electronic timer or switch/relay.

Edited November 21, 2013 by TomoHawk