BAC removal? 2nd butterfly on TB.

[L18M]

Just thinking whether to remove the bac or not.
any benefits? am running ap eng pfc.

if the bac is removed then what do you do with the tubes that go into the bac?

also i cant find the thread about 2ndary butterfly removal. any pointers anyone?
want to see what benefits there are to this removal.

thanks

[Prof]

The BAC controls engine RPM with respect to electrical loads and power steering - if you\'re Apexi can do the corrections then the BAC could be removed.  The 2 pipes that run parallel to it carry water - you can bypass them with a small tube, or find where they come from and blank off.
 
You need a small bit of metal to blank off the BAC air feed.
 
As to secondary throttle plates - these are on a cam that\'s fed from the wax device - it stops you hooning the beejasus out of the car when it\'s stone cold, and also prevents rapid throttle snap back - so taking them off may make the car more difficult to drive.
 
Some say it promotes better airflow - but when you are on full WOT, the thin blades of the throttle plate are in line with the air flow so offer virtually no blockage to the airflow.
 
If you\'re that worried about airflow requirements - go with a bigger throttle body. :Thumbs-up

[L18M]

cheers prof, i gues i\'ll leave it as it is then.

on another note, i mate asked if there were any way of making a DIY MAF to get rid of the stock maf, he is after a shorter pipe work and gettign rid of the S bend.
any ideas?
He\'s quite techi and hands on.

[Prof]

cheers prof, i gues i\'ll leave it as it is then.
 
on another note, i mate asked if there were any way of making a DIY MAF to get rid of the stock maf, he is after a shorter pipe work and gettign rid of the S bend.
any ideas?
He\'s quite techi and hands on.

Watch this space as I have a project on the go for a hotwire replacement, in theory allowing any hotwire device (they are normally shorter as well) to be used.  I will be testing my idea out on the vert with a Mazda B2500/B3000 truck MAF which seems to be a suitabe size and allows direct mating with an Apexi filter.

[L18M]

prof, is the nuts on either end of the bac just holding the bac together or does it serve another purpose and have to be set at a certain tolerance?

[Prof]

prof, is the nuts on either end of the bac just holding the bac together or does it serve another purpose and have to be set at a certain tolerance?

You got a piccy?

[yiug412]

i took the BAC out and from what i can see, the only adjustable bit is that screw thats always missing. Those two nuts are just holding it down, torque to the spec according to the mazda manual as i found those nuts in the engine bay pretty fragile.

Sorry Liam im gona hijack your thread :p
I have removed the pipe that connects to the stock cat. do i need to block that hole up on the engine?

[L18M]

Hope this pic helps Louis.



Hope theres nothing wrong with the above pic. I\'m guessing the bottom pipe on the bac just vents to atmosphere?



prof, the nut on the end where the round cylinder bit is, next to / behind the water pipe going into / out of the bac.

[yiug412]

um my bottom pipe is blocked by a huge wheel nut. and my car struggle to idle when i toke it out. does your car idle fine?

[Prof]

OK - answers:
 
Louis - that pipe is the \'split\' air pipe - under control of the ACV if you still have it (thing that sits on the side of the lower inlet manifold - on Liams car it\'s blanked off and he\'s pointing to the corner of it) it gets fresh air from the secondary air system.
 
If like Liam you\'ve removed the ACV, then you\'ve alreday blanked off one end - so you could just blank off small oval exit behind - as Liam\'s car.  If you don\'t, there is a slim chance of an air vac leak behind that blanking plate.
 
Liam - that bolt on the BAC itself - that holds the solenoid onto the actual valve - don\'t touch that one - to remove the BAC completey, you remove the 2 nuts that Louis mentioned - that come straight out of the engine manifild, and use them to hold the blanking plate on.  By the way - on your setup there - that BAC valve will be letting in unmetered air into the car, but I am guessing with the Apexi, you aren\'t using the AFM anyway.  It could use a small filter if you are going to keep it.  If you do blank it off, you\'ll have to get the Apexi to re learn the idle again.

[TiddlesRX7]

Yeah that pipe normally recirculates air back into the intake system doesn\'t it? I\'d be blanking it off if I were you Liam just incase it is letting air in that way.

[papercutout]

BAC is an abbreviation of what?


Liam, can you send me Mark/Mikes number (the guy I got the bumper off), just to remind him I want the exhaust. Also want some air pump blanking plates if anyone has any for cheapo? or a template? (I know John has a template, but I\'d rather have them ali instead of cutting them from 3mm steel with an angle grinder!)

[Prof]

BAC = Bypass Air Control
 
It\'s air bypassing the throttle body.  On TII engines it\'s normally fed from the turbo to intercooler pipe, so it\'s metered air.