Ok, BAC is the cylinder shaped object, on the outside of the upper intake manifold which has a vacumm going to the hotside of the intercooler pipe and a connector from the wiring harness.

I searched without much success, plus i dont have to much time.


I need to know if that is called a BAC, WHat that object does, and if you could block it off without coausing any problems.

 

It controlls the idle speed under engine loads (A/C, P/S, etc.) It can cause idle problems if you block it off. You can take off the connector to see what it would be like without it, but its generally not recommended to do this. It causes no losses in HP and can hurt the drivability of the car.

 

thanx. thats all i wanted to know.

I will not remove it like i was planning to.

 

For future reference, all of this is found in the Haynes and Factory service manuals.

The Factory Service Manual can be found in the FAQ For FC thread. It contains all this information and more, and is an essential tool for any sort of service work that needs to be performed on these cars.

Additionally, the Haynes service manual for the 1986 thru 1991 RX-7 (both turbo and NA) can be found at most local auto parts stores or purchased from any good bookstore (ISBN number 1 56392 007 7). It is only about $25 and is a great quick reference for things like this. Not only does it contain most of the information in the FSM condensed into an easy to read format, but it includes full wiring diagrams as well.

These manuals will answer 99% of service related questions for the car and if you intend to do your own repair work, you will need at least one of them. Preferably both, since the FSM is a free download.

 

so why exactly would blocking off the bac cause bad idle problems? im not sure if mine was blocked off when i had the block off kit isntalled or got rid of emissions ....

but can you explain it to me (i have to go check my car in a few minutes)

 

https://www.rx7club.com/forum/showth...ght=photobucket

http://www.wankel.net/~krwright/fil.../parts_manuals/

http://wombat.sevarg.net/RX7/RX-7_Training_Manuals/

http://www.cochran-racing.com/FSM/index.html

 

Ill keep the bac and the thermalwax thingy. evrything else. will be gone.!@

can anyone tell me if the thermalwax thing goes bad? My car acts like it doesnt have it.
WHen i start it. it wil rev to 3k or so and then drop to normal idle for a second before it dies.
I have to keep giving it gas till it warms up enough

 

Adjust it to the FSM

https://www.rx7club.com/forum/showth...ght=photobucket

http://www.wankel.net/~krwright/fil.../parts_manuals/

http://wombat.sevarg.net/RX7/RX-7_Training_Manuals/

http://www.cochran-racing.com/FSM/index.html

 

I find it funny how some classify the BAC and fast idle thermowax as emissions junk. So does that mean when I remove mine and have to hold the throttle at times to compensate for the power struggle at idle, my foot becomes emissions junk?

 

The ECU uses the BAC valve to control engine idle. Without it, the ECU has no way to compensate idle speed for varying engine loads.

 

Yes. Cut it off and zip tie what's left to your other leg. This cleans up the crew compartment. Gets rid of clutter. Please send picture of the modified crew compartment when you finish so we can archeive it. humor, please.

And as for the original thread starter:

The question about the BAC can be explained if one downloads the TRAINING manual that I attached a link to. Look in the Fuel and Emissions sections, I think.

 

As a supplement, you might find this idle system overview, and specifically the BAC section helpful:
http://howto.globalvicinity.com/gv_w...i=60&co=1&vi=1

I was going to do this, but got lost trying to find my "other leg"; when I choose my right one, all of a sudden my left one becomes the "other leg", but when I choose that, it goes back to my right! I'm lost.

 

Well. Interior Mods are a little more complicated than Mods in the engine bay, so don't worry about your confusion.

The main thing to consider is this: Which ever foot is keeping the idle up, is the foot that needs to be removed. Once that foot is removed you'll notice how the other foot needs to be used to keep the idle up. Remove this foot also.

It's all a part of the interior idle Mod. Once both feet have been removed, you'll find the idle speed to be the least of your problems. In fact you'll find that you won't even be thinking about the idle for some time to come. And if you don't zip tie the area that was removed, you'll be taking that eternal dirt nap a little sooner than was scheduled.

I'll stop here. This sort of thing can go on for too long.

 

I mostly need help repairing my car from all the dumb crap the privious owner did. plz bare with me here. Im not experienced with rotaries. And all the crap they rely on to run.

Where is the thermal wax thing located? Is it the mechanism on the inside of the LIM above the oil injectors? What is this mechanism? and can that be blocked off with out causing problems?

That "mechanism" seems to be blocked off at 2 of the 3 nipples. I think one of the nipples actually has a hose that goes to the UIM where emissions vacums used to go.

 

Don't hesitate to get the FSM (as linked above), it will answer most all your questions past, present, and future! The thermo wax is rear-facing on the throttle body. Above the oil injectors - are you talking about the vacuum spider? Fuel rail? EGR?

 

theres really no point if you dont have AC or P/S, I know I blocked it off for a week to see if it was causing idle problems

 

No not the vacum spider for the oil injectors. Bolted to the inside of the LIM (above the oil injectors)with total of 3 nipples for vacuum.What is it? Is that the thermo wax?
WOuld anyone have a picture showing the thermo wax?



I know its a little off subject but. I FOUND OUt the previous owner has n/a 460 injectors in the primaries!!!! Im pissed. I gotta buy some now.=/

 

https://www.rx7club.com/forum/showth...ght=photobucket

http://www.wankel.net/~krwright/fil.../parts_manuals/

http://wombat.sevarg.net/RX7/RX-7_Training_Manuals/

http://www.cochran-racing.com/FSM/index.html

--------------------------------------------------------------------------------

 

About the only thing you'll find on a rotary that you won't find on piston engines is the OMP system. The FC's idle speed controls systems are similar to what you'll find on any other car of similar age.

The thermowax is on the firewall side of the TB. See the FSM for pics.

That's the sub-zero start assist system. It injects coolant into the manifold when starting in temps below ~3degF. You can remove it with no problems; in fact Mazda recommends you do just that.

 

I will remove the sub-zero start assist system.!! ABout the thermo wax thing. It is what helps you car stay on on cold starts? Cause mine dies till warm. I need one of these thrmo wax things. I might actually need the whole s4 tII TB. Does anyone have the TB with all the factory crap on it? (in good shape of course n including thermo wax)

 

Correct, the lack of a functioning thermowax will cause your symptoms.