thxone

Hey guys and gals, I just bought a cheap BOV and I have a question. The BOV says it is good from 6-17psi which should be good for me at 10-11psi of boost. It has a simple hookup that is 1" (25mm) on the bottom. Now, I have a 1" hole in my intake from the emergency Pop Valve...can I put it on the intake or does it have to be before the TB? The pic is of the BOV I bought.

thxone

Crap...I just remembered how the BOV works....I haven't converted to a Z31 setup so I would have to put it before the TB...if I do the Z31 setup there is no TB so I could put it on the intake. Damn butterfly valve on the TB

thxone

The final solution: I am going to use a stepped drill bit to drill a hole in the intake pipe from the turbo to the TB. I will then tap this hole to accept a threaded one inch pipe that I will then screw into the pressure pipe (it will be cut to length) I will then use a thick hose and sturdy hose clamps to connect the BOV to the smooth (exposed) side of the threaded pipe. I may also have the pipe welded by a muffler shop before the BOV is installed. I can see it all in my head....but as we all know I am not mentally stable (see my post on my female relationships)

NismoPick

Of course there is a TB on the Z31... 99.99999% of all cars have a TB.

entropy31

mine has 2 .

thxone

I don't think there is a day that will go by that I don't have some kind of a brain fart, malfunction, oversight, or lapse in judgment

veyenyl

Your BOV has to be recirculated until you switch to the Z31 setup. A 1st gen DSM BOV is cheap and works well at 10-12psi.

NismoPick

It really doesn't need to be recirc. It will run fine w/o. Many 280zxt'ers have run it vented to the atmosphere (including Bleach & myself).

lww

Yes, but it messes up your fuel map by conflicting with the position of the AFM and the actual amount of air being forced into the motor since the BOV is bleeding off air that would otherwise go into the combustion chamber.

Granted, as primitive as our ECU's are, it doesn't make that much difference, but it will result in the car running overly rich during the time the BOV is activated. Since this is usually on decel, it's not disruptive to overall performance.

I still prefer a recirc system since it keeps the turbo spinning at optimal speeds between shifts.

SHADY280

im gona put a bov on my na, for all that extra pressure it makes.

thxone

I don't follow your logic on this...the AFM is before the turbo and the BOV is on a pressure pipe after the turbo, before the TB. On deceleration (lifted foot from gas) the butterfly on the TB is closed whether there is a BOV present or not, the BOV is simply venting that surge and keeping it from retreating back in the direction of the turbo. The injectors will continue to spray when the TB is closed with or without a BOV present so a car without a BOV should still go slightly rich on deceleration.

The air that is still moving from the air filter through the turbo is moving faster than without a BOV but is only doing this for as long as it takes to shift...usually under a half a second when the driver is in "race mode" if you know what I mean. So if the car is going more rich than normal it is only for a split second. Ergo, this should have no bearing on ones choice for Vented or Recirculated BOV's. I think the choice is, do you want a loud Pssssstt or not?

Did I just stump the Head Muckraker?

lifegrddude

The surge is being vented, that's correct, but that air has already been metered by the afm. The ecu thinks that air will still get to the combustion chamber and will have the injectors fire the amount needed for that air. No air plus too much fuel = rich. Which is why on some occasions you can shoot flames out the rear from running too rich. It's not detrimental to vent the blow off valve to the atmosphere, it'll just have you running rich for a split second or so.

thxone

I agree...but let's remove the BOV now....the air just sits there with nowhere to go cause the TB is still closed...still not in the combustion chamber....still rich...still shooting flames.

Did I just stump lifegrddude?

lifegrddude

The air that's surging will still reach the combustion chamber man. It's not being vented so it will eventually reach the chamber. The tb is not 100% air tight or else it'd stall the motor at idle. All the air will do is oscillate back and forth until until it smooths out enough to enter. So you won't run rich without a BOV.

thxone

I see your point. Still, it will only run rich for a split second with a BOV so it's my opinion that it is not enough to not run a vented BOV.

snwbrderphat540

that split second is enough to kill the motor though. thats the only real detriment to a non recirc. valve unless its a 1G DSM then it will run like crap since teh MAF gets improper readings.

NismoPick

Huh? None of that made sense... Why would a 1G dsm vented bov make the car run any different than any other vented bov?

Like I said earlier, I as well as Bleach run a vented bov w/ no probs. My first bov was a 1G dsm one that at first I had it recirc'd. Then I removed the recirc hose & I felt no difference at all (also no difference seen w/ my a/f gauge). Huh... that's weird.

Bleach

you've made no fewer than 72 lapses in judgment.

I run the atmosphere venting BOV and I still get about 22 city and 27 highway so it doesn't make that much of a difference on gas milage. If I got maybe 17mpg I'd wonder about it.

lww

No, you didn't...

snwbrderphat540

ok, go get a 1G dsm unplug the recirc and you let me know that it doesnt run like ****. it wont hold idle very well if at all after driving it the slightest bit hard. i dont know why you would think i would make that up, kinda only experienced it first hand on more than one occasion. but W/E im probably just a habitual liar right? trust me.... it makes a HUGE difference, thats why they can run open BOV's until it was either you use a 2G MAF or a reflash cant remember which. nad im not being pissy im just saying, this time, you dont know what your talking about and i yah kinda called me out to be a liar or stupid there so i jumped on it. lol. and some/many cars if you go full boost (this is on an atmospheric vented BOV) and clutch in no throttle and dont put it back into gear it will die. are ECU's are yes to primitive to show much if any of a difference, but its what other cars do which i.e. leaves ours to have a possibility of this phenomena to happen. SUCK IT G!!!!

entropy31

probably.....

veyenyl

When I tried venting my 1G DSM BOV with stock electronics, it didn't run as smooth and half the time it would run rich enough to kill the engine. I guess you can run one vented if you don't mind black smoke on upshifts and crappier gas milage. It also depends on what BOV you use. A better quality BOV like a HKS SSQV will probably do a better job of not stalling than a cheap DSM BOV.

Heat Rave R

So is everyone in agreement that switching to the Z31 ECU conversion will make it so that you can run an atmospheric BOV vent without ill effect?

lifegrddude

Umm, it's still a maf setup so an atmospheric bov will stall the motor at times. When I switched from the stock efi to the Z31 setup, my Z was more prone to stalling from the vented bov. The stock efi didn't seem to be affected as much as the Z31 was from metered air being released.

thxone

So these cars that run like crap when vented to the atmosphere, how much boost are they running, were the injectors swapped for larger ones, are they running higher volume fuel pumps??? Unless the BOV is leaking or venting at an idle all the time I don't see how it's going to stall an engine because as it was stated before the valve on the TB is still partially open at an idle or it would in fact starve for air and stall. I am sure there are other factors that is causing those engines to stall...maybe they can't drive a stick...it could be many things causing the engine to malfunction, but with 6 pistons and only a split second that the BOV would vent, I just don't see that being the cause of the stalling problem.

Bleach, I am with you on the good gas mileage thing....my '79 5-speed just got 53 miles (10-12 mpg est.) on a quarter tank whereas my '82 Turbo gets 112-115 miles (22-24 mpg est.) per quarter tank in the city with me getting in the boost often, my window sticker states an EPA estimated 20 mpg Hwy, and that's the only one it gives. Weird.