Jump to content
SAU Community

Unplugging Bov Plumb Back

Samuel Leonard
 Share

Recommended Posts

Samuel Leonard Rising Star

Samuel Leonard

Posted
Posted

i am addicted to trying to get loud pops and cracks from my RB20. the very light tapping of the accelarator whilst decelerating is a lot of fun. it's fun to try to scare people walking along the foot path with a massive (flame, or possibly just a black cloud and loud bang) am i alone here?

anyway, from what i can see, my blow off valve has a thin hose running back into the intake. when ever you decelerate the ecu dumps fuel in to compensate for the extra oxygen from the blow off valve. if i unplug this will it cause any other problems than loud pops at the time you let off the accelerator?

any opinions would be sweet!

Link to comment
https://www.sau.com.au/forums/topic/325077-unplugging-bov-plumb-back/
Share on other sites
jrm Veteran

jrm

Posted
Posted

I'm guessing the hose you're talking about is the vacuum tubing at the top of the BoV that acts as a pressure source with the internal spring that ensures that it is closed under normal conditions, and then opening when under pressure differential. This is how BoVs work.

If that's what you're talking about - then removing that will basically screw the operation of the BoV (and car) completely - it'll just be held closed by the pressure of the internal spring, and would leak under any boost conditions. What are you actually trying to achieve? The ECU shouldn't be dumping fuel into the system from the BoV unless you have it plumbed back before the AFM (kinda stupid) or you're using an atmosphere venting BoV.

Anyone else have any comments?

Samuel Leonard Rising Star

Samuel Leonard

Posted
  • Author
Posted
I'm guessing the hose you're talking about is the vacuum tubing at the top of the BoV that acts as a pressure source with the internal spring that ensures that it is closed under normal conditions, and then opening when under pressure differential. This is how BoVs work.

If that's what you're talking about - then removing that will basically screw the operation of the BoV (and car) completely - it'll just be held closed by the pressure of the internal spring, and would leak under any boost conditions. What are you actually trying to achieve? The ECU shouldn't be dumping fuel into the system from the BoV unless you have it plumbed back before the AFM (kinda stupid) or you're using an atmosphere venting BoV.

Anyone else have any comments?

that sounds logical. i just didn't understand! how do i delete a thread once it's no longer needed?

.:: GimpS-R34 ::. Grand Master

.:: GimpS-R34 ::.

Posted
Posted

Yeah, i also like my car to look like i'm a bogan that has a POS car.. I think i look so cool.. goes extra well with my mullet..

PS. you can't delete threads, Its left for the rest of the SAU community to laugh at you..

mad082 Grand Master

mad082

Posted
Posted

you can block off the bov so it doesn't let any air out, but while you may get some extra popping, you will also find that the car may stall a lot everytime you push the clutch in to stop at an intersection.

if you want pop flames, etc on deceleration, put a few cracks in the exhaust manifold worked well on my mates falcon after his extractors started to crack at the welds. would backfire and shoot ouf flames. just expect to lose some power

Samuel Leonard Rising Star

Samuel Leonard

Posted
  • Author
Posted
you can block off the bov so it doesn't let any air out, but while you may get some extra popping, you will also find that the car may stall a lot everytime you push the clutch in to stop at an intersection.

if you want pop flames, etc on deceleration, put a few cracks in the exhaust manifold worked well on my mates falcon after his extractors started to crack at the welds. would backfire and shoot ouf flames. just expect to lose some power

nah :thumbsup: happy to leave it like it is lol wouldn't want to compromise anything for a silly pop! :)

and to the other guy, you seem like a massive dick. We all make mistakes. I know I'm still learning. I'm 17.

.:: GimpS-R34 ::. Grand Master

.:: GimpS-R34 ::.

Posted
Posted

LOL i have a name.. Just chill it's the internet dude.. no one really cares what people say on here.. I was just having a laugh.. at your expense yes.. but unless some meaningless words offend you.. don't worry about it..

Samuel Leonard Rising Star

Samuel Leonard

Posted
  • Author
Posted
lol at complete wrong ness of OP

"ecu puts in fuel for the air that comes in the blow off valve"

i may have worded it bad but yes, that is correct. as a result of a plumb back system, the air that get's recirculated through the turbo, some of that gets back into the intake. the ecu expects this so if you block your blow off valve you get loud pops when you decelerate. the ecu still compensates for the non existent excess oxygen and to stop this you would get a tune. i rushed my wording before but i still stand by this statement.

mad082 Grand Master

mad082

Posted
Posted
i may have worded it bad but yes, that is correct. as a result of a plumb back system, the air that get's recirculated through the turbo, some of that gets back into the intake. the ecu expects this so if you block your blow off valve you get loud pops when you decelerate. the ecu still compensates for the non existent excess oxygen and to stop this you would get a tune. i rushed my wording before but i still stand by this statement.

actually that is wrong. what happens is that if you block off the bov, when you lift off the accelerator the butterfly in the throttle closes. this leaves a heap of pressurised air with nowhere to go, so it goes out the only opening in the system. this is back through the turbo. this is why you get the "tu-tu-tu" sound. this results in 2 things, 1: your turbo slowing down, and 2: all that air then continues out through the AFM. now since the AFM doesn't know which direction the air is traveling, it thinks that the air is going into the engine, not out of it, so it starts putting in extra fuel. this results in the car stalling, or almost stalling.

in the case of an atmo bov, something slightly different happens. when you lift off the bov opens and vents the pressurised air. this air escaping then sort of sucks more air through the afm. the ecu doesn't realise that this air is just going to vent out of the bov rather than actually go into the engine, so it adds in extra fuel, thus making the car want to stall.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Dose Pipe Sutututu
      NC MX5

      By Dose Pipe Sutututu · Posted

      The German place in Cabramatta was rock solid, fresh pretzel cooked to order back then. Then it went all quiet, after all the poker machines were removed, then I believe it closed for good. I did drive past the other week and noticed outdoor lighting a big screen, but no idea what is there now.  
    • joshuaho96
      R33 GTR running -9 with no tune

      By joshuaho96 · Posted

      Yeah I suspect even if you hold airmass per cycle/cylinder constant if you get too far away from stock you're still going to have problems running the factory tune within the bounds of the factory load scale. Cams, different displacement/rod ratio, etc. I'm just lucky that the GTIII-SS with wastegate boost + CA compliance cats is pretty much equivalent to stock turbos. When I have actual space I can finally get it tuned and modify the fuel system for flex fuel to 100% handle any detonation concerns when cranking the boost to whatever those dinky turbos can put out.
    • The Bogan
      NC MX5

      By The Bogan · Posted

      I would say no, why, because my daughter, who also lives in Goulburn, hasn't recommended us going there Pity, as we miss all the German joints around in Sydney, actually, the restaurants are the only thing I really miss about Sydney, and a special mention to Ishibanboshi at Bondi Junction, their Kara-age Don is heart cloggingly deliciousness (always added a special boiled egg...or 2) 😋 
    • GTSBoy
      NC MX5

      By GTSBoy · Posted

      Does that German restaurant still exist in the old place out the NW end of Goulburn? When I say "out the NW end of"...I am really being vague. It was 1997 when I was last there, and the only point of reference I can recall is that it was on the opposite side of the main drag from the big merino. And when I say "opposite side of the main drag", I don't mean "on the main drag". It was either a couple of streets back from there, or might have even been out in the sticks a bit further. Was an old farm building or mill or somesuch. And when I say "the big merino" I might actually be thinking of a completely different part of town, because I just looked on maps and the big bugger is not where I remembered him to be! The food was good, consisting largely of various German mystery-meat sausage/loaf things and kartofflen.
    • GTSBoy
      R33 GTR running -9 with no tune

      By GTSBoy · Posted

      So while the second sentence is completely correct and the whole point of the conversation, the first sentence bears consideration. If this bloke is just hoping to throw big turbos on and drive it around, because there are no helpful facilities at all in his tropical paradise** then he likely has zero chance of even knowing what the TP is on the last column in the stock maps, let alone know whether the ECU is operating anywhere near it or past it. So the point is very very moot. And, per what I said before, at stock boost on those turbos, you may well be off the end of the map. **I'm just back from Vanuatu, so I know exactly what small Pacific nations can be like wrt paradise without requisite facilities. But it's not even that simple. I put a high flow on my car and had to drive it around without a proper tune because of the lack of opportunity*** to put the bigger AFM and injectors into it to allow it to be tuned. I had to turn the boost down to less than I had before, and back off the boost controller's ramp, because it was exploring parts of the map that it didn't drive in before, and really couldn't access for tuning on the dyno either, and so was pinging. It was still well within the last column, because when I first**** set up the Nistune on the Neo I rescaled all axes of the maps to give some more space to explore. ***Family dyno was broken ****This was 13 years ago, and the TIM thing wasn't a thing then and so TP would definitely grow when pushing past the stock tune's limits.
×
×
  • Create New...