If you followed a how to for the TB mod it says you must set the TPS once you are done. Dont remove the BACV or you will run into more problems. Set the TPS to one volt by voltmeter. I dont know how to set the AFM adjusting screw. I am still in the process of the mod on my S5 N/A but from what I read the downside to this is lumpy idle until the car warms up and you cannot romp on the throttle under 3k rpms or the car will bog a little. These 2 things are okay with me for time being because the TB is only a temp solution until I can buy a new TB. I have stock ECU with Racing Beat Road Race headers to OBX single exit and cone filter, thats it for now.

 

^ I believe there are absolutely no advantages to performing this modification on an N/A.


The information might possibly be in the Factory Service Manual. -> Foxed.ca - FREE Second Generation RX-7 FSMs


Who told you that the BACV is only used for the A/C? Where did you find this information??

You can remove the BACV, but you may have issues with your idle. Especially with the TB modification. If "Form over functionality" is your thing... Go for it.

 

earlier in this thread guy were talking bout how the BAC is for the load the AC puts on the motor... and i feel after i did the mod i got better throttle response.

 

The BAC is there to maintain the idle not only when the ac comes on. It works against all kinds of load.
You get better response because the throttle plates you removed are originally opening with a small delay. I guess Mazda let them open up with a delay to keep the engine from stalling because of too much air coming in.

 

Ah yes, I get what you're saying about the BACV helping with A/C load. The BACV is very helpful with other loads, too.

If you're pleased with it, that's all that matters. I eventually got sick of such sporadic idle and other issues related to the TB mod.

 

this should only be done with an aftermarket ECU. There is just too much crap that goes wrong. TB Mod should have been buried and port/polish is where the real benefit comes from.

 

yah when i did my mod i also port and polished and got a Greddy compressor tube elbow. ehhh i decided to leave my BAC on why f*ck with something that works right?

 

Exactly.



If you're still worried about cleaning up the engine bay, and you're thrifty... You can find a way to hide the BACV while still being able to use it.

This is Aaron Cake's custom upper intake manifold. As you can see, he mounted the BACV on bottom of his custom UIM.

 

Once again I must explain that I am not looking for an advantage or performance gain. I dont give a rats *** about that. Yes, my ECU is stock along with the engine ports. The only things aftermarket are exhaust and intake filter. I did the mod because my thermowax was not extended fully and my secondary plates were sticking or not set right. It was the cheapest way to get my car running again until I can buy a new throttle body. The only advantage is better throttle response and the aesthetics.

 

Yes, you had mentioned that it is a temporary solution. I originally made the "no advantages" comment so that N/A owners don't start performing this mod, causing issues with ther car, and giving up on RX-7's altogether.

I know of an '89 TB I may be able to sell you. Throttle bodies seem to pop up all of the time. If it is a money crisis, I fully understand... Happens to me from time to time.

 

I understand I just got tired of explaining it because I ask for info on it and not many people if any helped me but when I post that I decided to go through with the mod a whole **** storm of comments from people telling me how bad it is pops up. I am in a money crisis but what are you asking for the TB? I am interested in it.

 

This isn't entirely true. If you have a bad or dirty BAC your idle issue may be completely resolved by removing it. Then again you could just replace it. I don't really believe that the BAC is necessary if you bump up the idle a little.

 

If the BACV isnt working take it off and test it. If its just dirty clean it and put it back on it and try it out. It probably wouldnt hurt to take it off and clean it regardless. I cleaned mine and put it back on when I was trying to find the source of my idle problem. It will only help the engine.

 

so whats the verdict...Remove or keep the BAC?

I vote remove it for a clean throttle body look!!

 

That would make sense if the BAC were actually on the throttle body.
Which it isn't.
So, YAY!, I guess...your vote doesn't count.

 

I'm going to remove my throttle body entirely. I mean it just blocks mad turbo boost from getting into my intake manifold. I'm trying to be a drift king so I can't have that **** on my engine.

 

BEEFHOLE..you should not Post stuff like that!

You Know you NEED some way to control that air flow..LOL.

SO,Knock the turbo off there too!!!!
get a 12 volt leaf blower,attach it to the intake.
attach a variable switch to the gas pedal!

( since there is no TB and turbo any longer, Drift Kings can be assured that this Modification will cut down on excess weight!) :P

 

^ Actually there was a youtube show where some guys bought an old american car, think it was a monza, and put 5 husqvarna leaf blowers on the intake. They actually dyno'd it and it made a more power!

 

I can't think of a single legitimate reason to EVER remove/disable the BAC on a street car. Ever.

On a pure track car, sure, why not. But even then you save what, a quarter of a pound and lose the handy warmup idle function.

Why people continue to remove necessary and helpful parts from their car under any reason (mostly done under the excuse of "engine bay cleanliness" which I trans late to "I don't know what this thing is so I'll just tear it out") is beyond my thinking.

 

The BAC seems to be grouped with the much hated "emissions crap" and deleted when it's all removed for "better performance".

As to the "engine bay clean up" theory...well, it's bullshit.
My bay is as tidy as can be and I run the full (and totally functional) emission package as delivered from the factory.
If the only way you can think to clean up the bay is removing a bunch of parts, you just aren't trying very hard.

 

glad i keep all that stuff, for when the kids are done ******* up their cars i can put the back to stock when they all get crushed and become a rarity.

looking at this thread and all the other TB mods, they're a waste of time on most cars, only with a turbo engine does it make even a tiny bit of sense.

 

I've still got to get my bac valve working the ground isn't working ugh..

what would cause that?

I'm gonna try diagnosing and fixing it, I've already replaced the connector.

 

the ground is pulsed by the ECU(duty cycle/hertz), you won't see a direct ground signal to the BAC.

 

yes but when hooked up the bac will not function, if hooked up to a direct ground it will turn on but obviously isn't functioning like it would be if controlled by the ecu.

I'm wondering what's wrong, if my ground to it is bad or what... I really want to fix it.

I've got a multi meter so I can do electrical diagnostics.

 

the BAC valve is slow and clunky in its function unlike most modern idle control solenoids. if the idle is set too low the engine will stall before the BAC valve can compensate, this is true even on the FDs.

by shorting it to ground you're opening it all the way, which is more than it will ever do under normal conditions. so your test is probably just masking other issues like an improperly set idle screw on the throttle.

of all the cars i've worked on, the initial set coupler has never had an affect on the BAC idle function. i often wonder if they even work at all...


sometimes you simply have to correct for engine condition with the throttle body settings, if the engine has lower than ideal compression and vacuum then the idle screw has to be turned in to bring the idle to an acceptable level first before worrying about anything else. once the engine is broken in the idle can be brought back down since compression and vacuum have risen since the first start.

the BAC valve also has little control over idle functions on a cold engine, that is the thermowax's job.

technically speaking the BAC valve only makes very minor idle corrections and it takes a while to do them. so it may in fact be working perfectly fine, but most of the time you simply don't see it.

the BAC also has no memory in the ECU, since this is old technology. every time the engine idles down the BAC valve has no idea where the ideal range should be so it starts from 0 and works it's way up to bring idle speed to target. if this ECU was modern it would store the idle information and start from a target BAC setting before the idle dipped into stalling range.