UsfDr

What are you talking about. You might want to do some homework or something. The only thing wrong about my post is that on rx7's the BACV doesn't bypass the turbo, but thats besides the point. Everything else is accurate.



And yes the ECU does control the opening and closing of the BACV which I failed to mention but assumed it was common sense. and yes it does bypass the throttle body, but it bypasses the a lot of other items too. However, in general just bypassing the throttle body would be good enough to achieve the effect.



So yes it manages idle, as I stated. I was also stating how it does this to educate those who might want to take it off thinking its only for emissions and might hinder the engine in some way.



UsfDr

UsfDr

The BACV cannot lower the idle, its purpose again is to raise the idle under high load low rpm conditions. If you want to lower your idle turn the screw on the throttle body next to the throttle cable or TPS until you reach the desired idle speed. The only way the BACV will lower the idle is to shut off.



UsfDr

pengaru

read your post, it has nothing to do with the turbo, intercooler, manifolds, any of the crap you mentioned other than the throttle body.



Thats what i'm correcting here, show me a car that has an idle air control circuit that bypasses the things you mentioned. They bypass the throttle, thats all it has to bypass to do it's job, for packaging reasons, this is usually done right on the TB with the circuit integrated into the throttle body casting itself on production vehicles. Some implementations bypass more than the throttle body, but I believe this is usually for other packaging reasons specific to the car, or costs.



What am I talking about? I'm talking about idle air control only needing to bypass the throttle to do it's job, and generally being implemented in this way.



I would especially like you to manifest an implementation that bypasses all you mention and leads ' directly to the combustion chamber ', thats an interesting statement considering most multicylinder engines will have runners leading to a plenum or individual throttles, so your idle air control only leads to one combustion chamber? what about the others? Perhaps now you see how it would not make sense to bypass the 'upper' manifold, as this is usually the plenum. Or maybe you think there are multiple IAC circuits, one per combustion chamber? right...



your statement didnt make sense to me, you're welcome to clarify if you think it should have.

UsfDr

First of all if your talking about a 3rd gen RX7 then yes the ACV is right under the throttle body just as it is on a 20B. However on a 2nd gen RX7 the BACV is mounted on the lower intake manifold meet and moves air straight from the intercooler to the lower intake manifold. Thereby bypassing some piping, the rest of the intercooler, the throttle body and most of the upper intake manifold.

UsfDr

well ok so its mounted where the upper and lower intakes meet





UsfDr

pengaru

you asked for it, heres my homework:











how many more references do you want me to come up with that do not mention bypassing anything other than throttle with regards to idle control?

UsfDr

Ok dude, read my post. I've stated that bypassing the throttle body is what you would need to achieve the desired effect. I understand that all you have to do is bypass the throttle body, however look at the picture of the 2nd gen.

The 2nd gen does exactly what I said and I dont have to manifest it Mazda already did. You must be getting hung up on my choice of words using combustion chamber. I should of just said Lower intake manifold. Don't just regurgitate words, try and understand them. The qoute you posted says that the air bypasses a closed throttle. That doesn't mean that it has to bypass it right at the throttle body. Air just has to get to the combustion chamber without going through the throttle. My picture of the 2nd gen clearly demonstrates this which you thought was non existent.



What you are failing to understand is that the only way the IAC can lower the idle is if its already open and letting air get in. Once its off idle is controlled by the mechanical setting. In other words if you have mechanically set the idle to 800 RPM while the IAC is offthe IAC cannot lower the idle anymore.

UsfDr

What do you have to say for the fact that the 2nd gen doesn't have the IAC on or near the throttle body (relatively speaking)?

1988RedT2

Peng and UsfDr:

It's clear to me how the IAC (or BACV) thing works. Clearly, what the bypass air needs to get around is the throttle, regardless of what else is bypassed and regardless of the device's physical location on the engine. I think you guys are basically saying the same thing, just in a different way with an emphasis on two different aspects of this particular IAC.



BTW, the BACV will remain on my car!



Thanks for all the info! Feel free to carry on this discussion.

UsfDr

Good, I think you will like keeping it on the car. It does make a big difference.



UsfDr