Where should BOV get its signal from?

[Grega]

Folks

Interested as to where the BOV should get its signal from?

Before the throttle body or after the throttle body?

Logic tends to suggest the BOV's purpose is to vent pressurised air in the inlet tract post the supercharger/turbocharger but before the throttle body.

Any thoughts/comments/what do factory cars do here?

All replies appreciated.

Cheers
Grega

[DQIKST]

doesn t make sence to me grega,

you BOV is always going to be before your throttle body isnt it??

[The Real Roadrunner]

bov goes between turbo and TB but the signal should be after the TB on the plenum.

cheers
linden

[JustCallMeOrlando]

Linden has it on the nose. The BOV opens on vacuum from when the throttle is shut. It lets pressurised air go from after the turbo to before in the case of a plumbback.

[Grega]

thanks guys, i know where the BOV goes and what it does. i'm just questioning where the signal for it comes from.....but thats answered and makes sense.

[Hash_ra23]

um dont mean to sound stupid, but whats this signal you speak of?

[Grega]

hash when i say signal - i mean vaccuum or pressure from the inlet manifold dude.

[The Real Roadrunner]

um dont mean to sound stupid, but whats this signal you speak of?

the small vac line that runs into the top/side of the bov,
its what makes the bov work ie if there is boost press it closes the valve, if its got vacuum it opens the valve.

cheers
linden

[Boostbitz]

From the post title i thought you had an electronic BOV for a sec.... hehe

[Andrew162]

indeed, had me quite a bit confused too... a 'signal' tends to suggest something electric/onic, where a BOV has nothing of the sort. how the BOV works (and I had to find this out the hard way) is by the vacuum line getting enough pressure to pull the piston on the BOV in order to get it to release the charge air either to the atmosphere (atmo) or back into the air intake route (plumb-back). mine, a GFB StealthFX, was supposed to be working quite well but it wasn't, and the only way I could get it to work was by talking to the dudes at GFB and having them suggest to me the proper route of the vacuum lines, because neither the BOV nor the wastegate were working.


about 1m of silicone hose and a couple of T-pieces were needed to set things straight again, and for the BOV and wastegate to actually function in the correct way. if you shifted gears before, it sounded like a bird-fart which was rather unimpressive... but sorting out the vacuum plumbing was the cure to all the ills.

[Ribfeast]

There should be a vacuum line running from your plenum/intake manifold (after the throttle body), across to your BOV. What motor are you running? If running a 1JZ, you'll have a small metal air line that runs along the back of the motor near the firewall.

[o_man_ra23]

indeed, had me quite a bit confused too... a 'signal' tends to suggest something electric/onic, where a BOV has nothing of the sort.

Signals have been around since long before electricity was discovered. You have signal flares, signal flags (used in semaphore etc). A signal can be anything that indicates something, whether it be an electronic signal telling the ECU how far open your throttle is, or a vacuum signal telling your BOV to open. Could be a kettle wistling to signal that the water inside is boiling (for those who grew up with gas stoves)

Back OT... I thought that there would be two signals coming in, before and after the TB, indicating a pressure differential... obviously I am wrong... so thanks to those who asked the question, and those to answer. Goes to show theres no such thing as a stupid question (other than "how do I make my XD foulcan look sexy"... cause that just cant be done )

[Grega]

OK, flame away
I actually have something a little different.


Believe it or not its actually a Toyota Lexcen

Now, the reason I asked is because I wasn't sure on how the BOV actually works. I knew it vented excess pressure from when the throttle butterfly closes between the supercharger and the butterfly ; but ; i thought it only did this thru a pressure signal (theres that signal word again) which in turn caused the BOV to expel the pressurised air. I was wrong. Its vaccuum in the plenum thru the closed butterfly which opens the BOV to expel the pressurised air.

Andrew ; thanks for your pic. Now for the 68 million dollar question.

With a wastegate ; where does the signal for that come from? Plenum or pre throttle body?

[YLD-16L]

Wastegate signal: from the compressor housing or close to it.

[Grega]

YLD......even for an external HKS gate? its got two ports on it ; one on the side ; one on the bottom...

[YLD-16L]

Never used an external gate so I will await someone more knowledgeable to answer that.

Edit, looks like you'd still reference from the compressor or near it. See pic below:




It got me wondering if I was right after you mentioned it

[Dale]

OK, flame away
I actually have something a little different.

Believe it or not its actually a Toyota Lexcen

Now, the reason I asked is because I wasn't sure on how the BOV actually works. I knew it vented excess pressure from when the throttle butterfly closes between the supercharger and the butterfly ; but ; i thought it only did this thru a pressure signal (theres that signal word again) which in turn caused the BOV to expel the pressurised air. I was wrong. Its vaccuum in the plenum thru the closed butterfly which opens the BOV to expel the pressurised air.

Andrew ; thanks for your pic. Now for the 68 million dollar question.

With a wastegate ; where does the signal for that come from? Plenum or pre throttle body?

If it's a toyota why do I see the letters HOL and half of a D on the front grille

[Grega]

holiest of holies dale

[Andrew162]

Signals have been around since long before electricity was discovered. You have signal flares, signal flags (used in semaphore etc). A signal can be anything that indicates something, whether it be an electronic signal telling the ECU how far open your throttle is, or a vacuum signal telling your BOV to open. Could be a kettle wistling to signal that the water inside is boiling (for those who grew up with gas stoves)

yeah thanks for pointing that out dude, I could go into the fact that I was a 'Signalman' with the Army (not to be confused with signaller), which is someone that does communications and networks and shit, but that's just one other example in teh off-topic section.

[LeeRoy]

Wastegate signal: from the compressor housing or close to it.

This is where the positive pressure is and is the same as teeing it into the intercooler piping before the throttle (although you wouldnt). The actuator is pre set to open at a certain psi meaning you can buy 7psi actuators, 10psi, or whatever tickles your fancy.

Once positive pressure reaches the actuators set opening psi it will open and once it falls below this it will close. This happens continuously and it was regulates your boost levels. Keep in mind that whatever your wastegate actuator is set at is the lowest boost level the car will run but if you wanted to run more you could through the use of a boost controller.

Edit: just found this dodgy pic