What are BAC and ACV?
 

I see these acronyms tossed around all the time, but don't know what they are/do. So what do they stand for? And would someone mind giving me a jist of what they do?

ACV is the air control valve- a valve located under the upper intake manifol that controls the flow of air through the secondary air injection system.

Found on the FAQ's of the 3rd gen forum.

Not sure what the bac is though.

The ACV is for the 3rd Gens, BAC is for 2nd Gens (IIRC).

The ACV controls the secondary air injection from the airpump.

Ahhh cool. I will be taking my airpump off soon since my cat is toasted. So it's actually connected to the UIM?

The ACV is bolted to the LIM.

So if I have the UIM off, are the ACV components easily accessible to block off?

The site 2751engineering that sells block off plates, lists BAC and also the split air valve in the FD3s section.

I got their AWS plates and removed it last weekend. I only need one of their plates though and couldn't figure out what the other was for. I left the solenoid on the UIM and blocked off the pipe. I plugged the nipple on my stock elbow.

You'll be able to see the ACV easily with the UIM removed. Getting it out is another issue. The two 10mm bolts on the bottom are a pita.

As for the block off plates, you need 2 plates to remove the system completely. One is for the ACV, the other is for the hard line that connects to the LIM and runs down to the cat.

You need the plate listed as "Air Control Valve" and the "Air Control Valve Pipe" plate should be the other one (IIRC).

2nd Gens have an ACV also. It does the same thing. As for the BAC it is the Bypass Air Control. It routes air bypassing the AFM. Basically, helps the idle when an accessory is turned on. Like the A/C or the headlights.