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Blow Off Valve

mrfai

By mrfai,
in Four Door Family & Wagoneers

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SMOKEYV35 Mentor

SMOKEYV35

Posted
Posted
an atmo bov is also more likely to make an auto stall as the gears are not constantly meshed (same reason you can't push start an auto)

who fed you that line?

anyway, it will give you no advantages over your stock BOV other than sound.

i have a GReddy plumbed back and it is plenty loud enough.

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pipster11 Grand Master

pipster11

Posted
Posted

atmo bov = really rich on bov vent

manual box = gears constantly meshed, clutch in revs drop, clutch out brings revs back up

auto box = lift off for bov to vent, back on the gas, car is over fueled to bov release, stall out and fail

doesn't always happen but quite often will

if it doesn't, you will get black smoke on bov activation and you'll get a dirty rear bumper

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kidafa Veteran

kidafa

Posted
Posted

Smokey he's correct aftermarket BOV on an auto increases stalling and car running shit at low speeds. Why do you think certain controls are on airflow computers for if you have a BOV installed it adjusts voltages on sudden throttle let of to decrease the chance of stalling.

Of course it will give him gains over stock that's not just sound improvement. It will hold boost stronger that the stock oem Nissan jobby made for 7psi with a 10+ year old spring in it.

-1 for incorrect technical advice on forums.

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SMOKEYV35 Mentor

SMOKEYV35

Posted
Posted (edited)

the driveline is always engaged in an auto, the momentum of the drivetrain keeps the engine turning over - it won't stall. it might overfuel, but it won't be any worse than on a manual which drops revs dramatically when you snap throttle shut and clutch out which drops revs to idle speed within a matter of milliseconds.

i dont disagree that atmospheric BOV's cause spikes in AFM readings - i have always run plumb backs. my disagreement was that 'they are more likely to make an auto stall'

not withstanding the fact, that i you read his statement closely, he says 'because the gears are not constantly meshed'.......which is the exact opposite of how an automatic transmission works anyway. the car is in D - the gears are engaged with the torque converter acting as cushion.

and there is nothing wrong with the stock bosch BOV's from nissan. i had twin bosch GT-R bov's setup on my 30ET - which are proven to hold 32psi and nearly20 years old. proven performers.

so you keep your 'technical advice' scorecard, i'll keep mine. :blush:

Edited by SMOKEYC34
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QWK32 Veteran

QWK32

Posted
Posted (edited)

sorry but auto's are complete p1gs to drive with an atmo or even no bov when compared to a manual. its not the high rpm changes that are the problem, its when you back off at low rpm, say under 3k, that the stall convertor lets the rpm drop back to idle speed making it easier for the engine to stall. at least with a manual you can let the revs run down slowly with the gears when you back off, or give it a quick kick in the guts to stop it stalling without the car lunging forward.

i know this from personal experience of having to put up with no bov on my car for a couple of months after i did my turbo upgrade until i sorted out a replacement. only reason i was running no bov was the stock stagea bov, which in my opinion is complete rubbish for anything other than stockish sort of boost pressure, couldn't even hold 14psi.

the first time it stalled on me was at a really really bad time, turning right across a busy intersection, i accelerate quickly, but not going over 3000rpm, and back off as i'm at my desired turning speed, car stalls halfway into the intersection, then the mad panic to get going again. this is how it was:

car stalled --> f**k --> steering too heavy cant finish turn, f**k --> turn key to crank engine again, hang on, it wont start, f**k, panic --> oohhh, its gotta be in park or neutral to start (this is the last thing on your mind when you stuck in the middle of a busy intersection)

after that i found myself sometimes riding the brake and accelerator to keep the revs up and prevent a stall. a manual would have been instinctually easier to restart after a stall, car stalled --> clutch in turn key and off we go.

edit: to the OP, if your car is an auto, weather it be S1 or S2 it will have a bov, if you have a stock airbox it will muffle out the sound of the release and you will hardly hear it. but dont worry, it will be there.

Edited by QWK32
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d1_drifter Community Regular

d1_drifter

Posted
Posted (edited)

^^^ I get the same problem across intersections when you stop at the island.

I don't run a bov because I'm too lazy to source a GTR item, so I need to heel-toe to blip the revs back up so it doesn't die.

Edit: I have an auto.

Edited by d1_drifter
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Bronx Mentor

Bronx

Posted
Posted

wait, just let me get one thing clear, the stock BOV is not atmospheric, but rather flows back to turbo right????

so even if it only holds 7psi or 15psi etc. doesent it mean your air still gets to run at 7/15 psi??? since it just sends it back to its original starting place????

not like atmospheric where that certain pressure is lost and vented to air?

kinda hard for me to explain without a diagram.

but basically even with a stock BOV you wouldnt have any power loss what so ever since it just circulates the air???

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QWK32 Veteran

QWK32

Posted
Posted
wait, just let me get one thing clear, the stock BOV is not atmospheric, but rather flows back to turbo right????

so even if it only holds 7psi or 15psi etc. doesent it mean your air still gets to run at 7/15 psi??? since it just sends it back to its original starting place????

not like atmospheric where that certain pressure is lost and vented to air?

kinda hard for me to explain without a diagram.

but basically even with a stock BOV you wouldnt have any power loss what so ever since it just circulates the air???

it is released into the intake just before the turbo compressor inlet. it dumps the pressure from the turbo compressor outlet side.

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