Love the sound of a bov

But doing a little research found this article

 

Any truth, I can understand logic behind what is said but quite often see them fitted

 

"Z32: Don’t install blow off valves on a 300ZX

 

Tech Article: Don’t Install a BOV on a 300ZX

Composed by:*300ZXttZman

By: Greg @ Specialty Z

 

Here’s why you won’t want to install BOV’s on a engine with a MAF sensor: When you make any positive boost and you close the throttle without a BOV or recirculation plumbing, the pressurized air will stop moving and stall the turbo.

 

Blow off valve:

What a BOV does is open a valve when you let off the throttle by way of engine vacuum, this allows the air to be released into the atmosphere. This is better for the turbo than nothing in the system because it allows to turbo to keep spinning.

 

The problem with a blow off valve in a MAF sensor set up is that because the turbo is still spinning, new air is being pulled into the turbo from the air filter and is being measured by the MAF sensor. So the ECU believes all the air coming into MAF is going into the engine that is now being pushed out into open air. So when you hear that sound of air rushing, the engine is pumping fuel in for all that air you hear coming out. This causes the engine to want to stall, because it is being flooded with fuel.

 

The engine wanting to die is one thing, the other is that all the unburned fuel going into the cylinders will not burn and this washes the lubrication off the cylinder walls and the engine rings, creating premature engine wear.

 

The plumbing on a Z with MAF’s is not designed to work with a BOV and you can not tune it out. A MAF measures the air being drawn past the air filter to allow the ECU to calculate the fuel needed. The MAF needs to be measuring the air and the ECU has no way of knowing when you’re blowing some of the air outside the engine.

 

What a MAP sensor does is measure vacuum and pressure in the intake manifold to tell the engine management how much fuel is needed. So it does not matter what happens in the pipes before the throttle body with a MAP system, as the MAP only measures what happens in the engine and not what is happening BEFORE the manifold. BOV’s work fine on MAP set ups, but a recirc valve is always better, as it is helping to keep the turbo spinning by feeding the turbo air.

 

Recirculation Valve:

The stock Nissan recirc valve is larger than most aftermarket BOV’s. The stock Nissan BOV is also stronger than most aftermarket BOV’s. The stock recirc’s can handle more than 40 PSI boost pressure. What a recirc valve does is similar to a BOV, but better. Just like a BOV the recirc valve opens when it gets a vacuum signal – the difference is that instead of allowing the air to be blown off into the atmosphere, the recirc valve blows the air back into the front side of the turbo.

 

What this does is let the air out from the pressure side of the turbo and blows that air back into the suction side of the turbo. The air pushing back into the front side of the turbo is helping it keep spinning because it is recirculating the air. The air simply goes out of the turbo and right back in.

Because the air that is coming out of the turbo is going right back into the turbo, no new air is being pulled in through the MAF because the air is going in a loop.

 

Removing the stock recirc makes zero sense and will only cause issues with stalling and filling your crankcase with fuel. As long as you run a MAF you should never install a BOV.

 

Now, the reason some BOV’s cause less problems is that they come with different springs, a heavier spring requires more vacuum to open the valve. The problem with too stiff of a spring, is the valve is not opening enough, this will cause compressor surge and is hard on the turbos."

I have this work in a better way than a regular after market valve with it being Sequential

http://www.hks-power.co.jp/en/product/blow_off/sqv/

They essentially replace the existing recirc valves and in the process add a very cool 'pssshhhh' sound when shifting.

If you think that pshhhh is a very cool sound and don't mind fitting a less-than-optimum solution to a problem Zeds don't have, then go ahead.

Another FAQ on BOVs is here http://www.twinturbo.net/ttnetfaq/FAQpages/bov.html

In conclusion: You could always disconnect your stock re-circulating valves (which you have to do to install blow off valves) and spend 500-600 bucks for blow off valves and what will you get? better performance? No, basically you do get the cool sneeze sound though you aren't going to be any faster than you were before (but you might sound like you are). If by chance you are running boost levels that exceed the airflow capacity of the re-circulating valves (~600+ hp?) then you've probably spent enough money and have enough experience and knowledge to know where the benefit reverses.

My car came with AB Flug Bovs, not only did they sound like scania air brakes but they made it run like a pig. I have driven David1846291's car and that had 2 bailey valves I think. They squeaked a bit but weren't quite the need for speed spaceship noises you may be after, but it ran absolutely fine.

 

It is true that it's not ideal but clearly you 'can' run bovs and get away with it.

 

I had stock recircs for a long time that honked. I now have BDE Goose honk killers that have sort of reconditioned and uprated my stock valves.

 

These are great, no running issues but they sound awesome. I get some compressor surge and some hissing and sound just right. They are silent under normal driving, or partial boost, but giving it full throttle they chirp beautifully.

 

Remember the sound isn't the recircs alone it's:

16psi

Recircs

dual intake with apexi filters

2.5 inch intercooler pipework and bigfer intercoolers

Big exhaust

 

All of that stuff will change the way the air moves and how quickly and audibly it does so.

they sound like scania air brakes

 

Oi! That's my saying! :wack:

 

I totally agree though. I've been saying that BOVs are useless tat for years, even before reading Greg's report into them on TwinTurbo.net. Back in the early 2000s, a mate of mine bought a Cavalier Turbo and fitted one against my suggestion. After having it fitted for a few months, he wasn't impressed with it and reverted back to the standard recirculating valve, he found that not only did it run better, but that responsiveness was also better.

 

As much as they are down to personal taste, they have plenty of negatives. Spunking out £220 on a pair something that does nothing just leaves me bereft. A willy waving McDonalds car-park modification if you will. :)

 

IMO, never has there been such a good case for something being so utterly pointless. :) Hell, not one single manufacturer the world over has fitted one to a production car, that probably tells you something. :rofl:

Edited August 28, 201411 yr by Funkysi

mate has bov on his evo no probs atall

Still better off without it! :rofl:

 

Mitsubishi's own WRC Rallyart cars don't even have them. ;)

each to there own. while you are hi si were did you get your car aerial from as mine is going in the same place

My car came with AB Flug Bovs, not only did they sound like scania air brakes but they made it run like a pig. I have driven David1846291's car and that had 2 bailey valves I think. They squeaked a bit but weren't quite the need for speed spaceship noises you may be after, but it ran absolutely fine

 

Be nice if you could type my name right tom its not like its difficult tom az északi anyway as tom said my car did have dump valves and ran with no issues at all and to be honest I quite like the sound too but could live without it with a nice note from the exhaust as my car did sound like a sick aeroplane cruising up the motorway headaches all round i think it was lol

if you are using the car all the time then I would not bother but if like me you only go for a blast for hour a week then I like the sound adds to the fun

an hour a week that wouldn't be enough for me though at the moment it would be lol I think when I get my next one Planning driving it almost every day during summer miss my car though I am in two minds whether the dump valves should go on new one or be left off its a tricky ish one as yeh it adds to the whole fun treat experience gives you a little cheeky smile like opening that remote control car you wanted for xmas when you were a kid ok 14 :)

every fast car I have had have just been for a thrash round for a hour or so on a week end I have my work van I use most days and a x5 I use that 3 times aweek

A willy waving McDonalds car-park modification if you will. :)

hahahahahaha bonk

 

IMO, never has there been such a good case for something being so utterly pointless. :) Hell, not one single manufacturer the world over has fitted one to a production car, that probably tells you something. :rofl:

+1

Atmosphere bovs only cause problems on cars with air flow meters (afms). This is because measured air is being dumped to atmosphere instead of ran through the system. This can cause rich mixture and lumpy idle when lifting off throttle.

 

I would only run atmospheric bovs on cars without afms.

 

I think they sound ok, a bit boy racer but not offensive.

Funkysi seems to have a phobia of atmospheric dump valves.

Its because he lives in scotland The air is clear lol and some of them can sound like your in a computer game haha

each to there own. while you are hi si were did you get your car aerial from as mine is going in the same place

 

Just ordered 3 or 4 different styles from a number of places and fitted the one that fitted the best. Sorry, can't be much more help than that.

 

Funkysi seems to have a phobia of atmospheric dump valves.

 

Correctamundo! It's no secret that I can't stand them. There should be a better collective noun for automotive detritus, under its description would be 'atmospheric dump valves' in addition to LED washer jets, aluminium tax disk holders (why do you need something made out of aluminium and machine screws to hold a tiny bit of paper to a windscreen?), seat belt harness pads for regular seat belts, under car neons, large aluminium type razor blade spoilers, fake rear disks, Lexus lights and ANYTHING made by Rickbrook or Foliatec! :rofl:

Edited August 28, 201411 yr by Funkysi

They have no benifit or use, you could also blank the recirc and get the chatter noise as a few have done, read up on it first. Recircs give the best performance and that's why they are fitted stock. I do personally have a set of baileys they cost me about £50 and I have them purely for novelty. We call them the angry budgies. When I pick my mates up they all love the wahhhhhhh putush noise of my car, its childish but it is a toy, the noise makes me smile so stay they will.

Every time I hear them Steve, say 'Oh no' to myself! :rofl:

My new car has them already.bluuuugh putushhhh.lovely.oi Si your going to love my new thread.its just for you.

I can see you ruining that wide arch! :(

New front end.smothed out arches so that hole on the side is going.type two rear spoiler.and 99 rear spec lights.hope that pleases sir?oh and loads of bling under bonnet.

Every time I hear them Steve, say 'Oh no' to myself! :rofl:

 

Lol, time I see blue smoke waft out I say oh no, when I hear it hit full boost as I exit the corner followed by the bov I say oooooooh yes. Like I say it's a toy I just like having fun the bov currently is fun. My recircs are on the shelf just incase I get bored.

New front end.smothed out arches so that hole on the side is going.type two rear spoiler.and 99 rear spec lights.hope that pleases sir?oh and loads of bling under bonnet.

 

Sounds pretty good! Worried about the 'new front end' though. :(

I'm hoping he's going to say stock or 99, I never like the storesk one it had personally, it's my second least favourite over the basking shark.

Correctamundo! It's no secret that I can't stand them. There should be a better collective noun for automotive detritus, under its description would be 'atmospheric dump valves' in addition to LED washer jets, aluminium tax disk holders (why do you need something made out of aluminium and machine screws to hold a tiny bit of paper to a windscreen?), seat belt harness pads for regular seat belts, under car neons, large aluminium type razor blade spoilers, fake rear disks, Lexus lights and ANYTHING made by Rickbrook or Foliatec! :rofl:

 

Oh dear, your gonna hate my 1.2 Nova SR then :laugh: