BAC valve question
 

i have an s5 with a weird idle problem, after it warms up it sometimes stalls or gets close to it. i decided to check the BAC valve and it looks like its missing something. im going off the haynes manual with a picture, so im sure its the BAC valve located under intake tubing. i see the two coolant hoses, but no air hose. does that connect to anything? can anyone show a picture of where it connects to if it does? thanks.

You need to post information about your car. If you have an S4 NA, the BAC valve is located on the back side of the plenum, in plain sight. Its air source is a metal hardline that is attached nearby. The hardline connects to a rubber hose on the black plastic intake tube.

its a 91 S5 NA

Your profile says "s4 rx7."

On an S5 NA, the BAC valve is underneath the plastic intake duct, and also connects to a hardline near the throttle body. It will be obvious if the air inlet is not connected and open to the air. If it is open for some reason, it will be sucking in unfiltered air, and you may have a big vacuum leak where it is supposed to connect.

i had an s4 and sold it. just picked up the s5 little over a week ago. guess i was right about the placement of BAC. the air inlet is completely exposed, so it would cause my idle problem. know anywhere i can get a pic of the hardline?

Er...no.

The S5 BAC gets it's air feed from one of the two elbows on the bottom of the intake duct, after the MAF and before the throttle body elbow. There is no hard line and it's not anywhere near the throttle body proper.

I don't own a series five non turbo, but the FSM seems to show the air nipple on the BAC connects to one of the TWO nipples on the intake duct that attaches to the throttle body. See jpgs.

Edit: Corrected me before I could do it myself!

Actually, it looks like it just connects directly to the large metal nipple on the intake duct. Page F1-34 of the S5 manual has a diagram.

Ya'll posted a minute before me.

A mute point, H2.

what happened to H1?

thanks for all the help. love this site. should be metal elbow and then hose to intake right?

Yup.

should it matter if elbow and hose are from s4? should be pretty much the same?

The S4 version only has 1 smaller nipple on it. It's considerably smaller than the opening on the BAC, but it can work if you clamp it in place. I did this when I had an S5 manifold on my S4 NA engine.

thanks

H1's computer died a quick death.

H1 got a new used computer.

H1 forgot his RX password.

H1's originally logged in using AOL (mistakes will be made in life).

H1 has ATT.NET and hiiiii spppppeeed internet. The girls in the porno sites move faster now ...humor

When H1 askes for his password to be sent to him.......it goes to a non functional AOL site I guess. RX site only recognizes H2.

It matters not. I lost count of posts sometime ago. It's not worth the trouble to get H1's password back.

I'm pretty sure that the orientation of the inlet nipple is different.
Functionally they're going to be the same but it will be more difficult to route the hose.

The S4's electrical connector is also different, both in shape and location.

All in all, it's much simpler to just use the correct part.

how did you clamp it? found a possiible s4 elbow and hose.

With a hose clamp. It wasn't perfect, or pretty, but it sealed. The nipple on the inlet tube will rotate, so you can move it around and make it fit with an S5 BAC.

just to be sure, the elbow is the same size on s4 and s5 na?

On my T2, i run my BAC with a standalone (no AFM) and I just have my BAC opened to the atmosphere (air does not need to be metered) and no coolant hoses. it's basically two bolts and a plug.

Yeah, they're the same size.

But you have a filter on the inlet, right? If not, you'll be sucking all sorts of crap into the engine.

nah i don't have a filter on it. i couldn't find one at autozone that fit on there easily, and i'm feeling kind of lazy about fabbing something. I may figure something out later, but right now i'm not that worried about it. A lot of cars with bigger turbos don't even run a filter on their turbo inlet. Besides, the BAC doesn't even open unless you are idling or decelerating.

A crankcase vent filter would fit nicely. I had one on my air pump inlet at one point. K&N sells them in all different sizes.