I mean, there is not a mechanical linkage to hold the throttle slightly open, right?
So if it is all electronically controlled, what EXACTLY takes place? What does the ECU do to increase rpm? I mean, I can see it being able to tell the injectors to spurt more fuel in but...what about AIR?

 

I never really investigated how AWS works, but I believe it is just a valve operated by the solenoid to open a passage between the hose on the back of your intake elbow and bypass the throttle plate. That would be the extra air to raise idle. The ECU would just compensate with fuel for the air thats bypassed.

 

^ exactly right. It works the same as the TPS. It is an electronic solenoid that the ecu controls. The pipe that goes from the UIM to the intake elbow goes to the solenoid, and when the solenoid is open the vacuum pulls in extra air therefore raising the idle.

 

Awesome. Thanks, guys.
I was comparing to my Volvo, which is a total 'drive by wire' car. There isn't a throttle linkage, just a potentiometer for a gas pedal. In its case, I can see the ECU having total control

 

sorry to bring this back but does anyone know what the ECU uses as an input to decide when to operate the AWS. I was thinking maybe the ECT sensor and if thats so does anyone know up until what temp that the AWS is in operation?

 

^^What^^?

There is a wax pellet within the module. It holds open an air bypass until the engine becomes hot enough to melt the wax. Once the wax is liquified the air bypass closes.

Duh

 

The AWS system and the thermowax are 2 different systems.

AWS gives you the initial 3000 RPM startup when you start cold. The ECU uses the coolant temp sensor to determine if it needs to do the AWS process. There is a separate AWS solenoid on the intake manifold - it draws air from the throttle body and puts it into the upper intake manifold after the throttle plates. The AWS solenoid is a simple on/off solenoid, not duty cycled like the ISC. ECU turns it on, it opens, there's your extra air.

The thermowax is a mechanical item on the throttle body - it holds the throttle plates open a bit to allow extra air into the engine. This allows for the 1500 RPM idle when the car is cold that slowly comes down to 800 RPM as the car warms up. It's simply a wax rod that has hot coolant running by it - as the wax heats, it expands, pushing the rod up and pushing against the cam that holds the throttle plates open.

Dale

 

awesome...great info dale!

Got another question for you....does the airpump do anything special during cold startup besides cat operation. I don't know much about the ACV or "secondary injection?" ....but im trying to understand why my car has a rough idle for the first 10 secs of startup.....700-1100 back and forth and then smooths out to 750 after like 10 seconds.

airpump had been removed and I have a greddy elbow so the AWS hose is just plugged.(i ran a filter for a long time but have since ditched it) I always start the car in gear to bypass the AWS and would like to know which system to attribute this momentary idle fluctuation to. Car runs like a dream after its warmed up and idle is rock solid.

Does the ACV do anything special during cold start up?

thanks in advance

 

so essentionally if i get a block off plate for the aws and remove it and block it off i wont have the annoying high idle

 

if you have no airpump you have rendered the ACV useless, its job is to take the airpump AIR and CONTROL where it goes, either the exhaust ports, air cleaner, or the main cat.

what you might have, is that the ecu wahts to AWS, so it turns on the solenoid, and adds fuel, but the solenoids not there, so its just really rich.

 

the US cars are the only ones with the AWS. on a US car there are 2 things that bump the idle cold, the AWS brings is to 3000ish rpms, and when that shuts off, the thermowax is pushing the throttle open, to 1500-2000rpms

the thermowax is adjustable, you probably could have it cold idle at 1100ish or something. too low and it'll stall

 

correct except I dont know if my problem is because of AWS at all. It has been said that starting the car in gear should BYPASS the activation of the AWS all together. I still have the solenoid hooked up but it should be ruled out all together from the problem if i bypass it, correct?


Now i understand COMPLETELY that the ACV is useless without the airpump...I'm just wondering what operation the ACV has with cold start-up,idle, ect if there even is any.

I believe that air injection to the cat and exhaust ports has no connection to idle and I wouldn't think that putting more air to filters would affect idle either since its before the TB.

I guess what I want to know is if the ACV does anything POST Throttle Body and PRE exhaust port.....if that makes sense

 

and actually the cold start up looks something like this

immediate jump to 1400rpms then drops instantly to 900 and then fluctuates between 850 and 1100 for like 10 secs then drops to 750-800 and is completely stable.

like i said...its not even close to being a problem but I would just like to educate myself about the cause.....

my guess is the AWS but it has been said that is can be bypassed.....now does this mean total operation is bypassed or what

 

I just tap/blip the throttle to de-activate the aws system (immediately brings the idle from 3000 down to 1100-1400 rpms for a few mins, then down to about 850, then I get in and drive and don't boost until my water temps are up to 180F.

 

and this crap is why the Rx-8 is drive-by-wire. It eliminates a crapload of solenoids, sensors, and plumbing.

 

It's easy to bypass, just start the car in gear with the clutch pushed in. I do it everytime I start the car. I then put the shift in neutral, take my foot off the clutch, and let it warm up for a few seconds before I shift back into gear and drive off. I hate that 3,000 rpm from cold.

 

Good call. It is instinctual muscle memory for me now to hit the ignition and immediatly blip the throttle. I had forgotten all about the 3k run up crap! You're right, I was talking about the 1500 we all see right away.

Duh