Shall I BOV-ver?

[colVR4]

To BOV or not to BOV? That is the question. :scholar:

I like the idea of having the extra response that many of the BOV manufacturers claim, but is it worth it? I don't want anything too noisy, but do want something subtle to get that nice schnikk sound. /Steeringw

Can you get BOVs that you can turn the noise on and off? or at least increase and decrease the volume. Also, what are the advantages and disadvanages of recirc over dump-2-atmosphere?

Finally, how easy are these things to fit and set up? What are the best buys (cost vs performance)?

I have just ordered a boost guage, which should be arriving in the next couple of days (may have to pop over to see Glenn to get it fitted) so I can monitor the boost. Would that help setting a BOV up properly or should I take it to someone who knows what they are doing?

Ta

[Nick Mann]

Your car has a re-circ. I believe you can get BOV's with a volume control, but I'm no expert!! I don't think they need setting up, and I don't think they make much if any difference to performance. I think a good exhaust/intake/de-cat/boost controller will add more horses per £.

[pezza]

There are hybrid valves which recirc and VTA too.. think BDA has one...

Then there are adjustable VTA ones where you can adjust the volume of
the *exhale* ...

TurboXS do a performance recirc valve which have a quiet sound but you can adjust the amount of air recirculated etc..

These shouldn't cause a problem to fit yourself...

[michaeli]

is a dump valve and a BOV the same thing??

[d3x]

is a dump valve and a BOV the same thing??

yup, dump / blow off all the same.

One other thing I reckon needs to be made clearer is that VTA stands for: vent to atmosphere

[SGHOM]

Col......... a dump valve is compulsary !! and it needs to be loud......... VERY LOUD !! :thumbsup:
I have the Turbosmart supersonic. Both mine & Dave's make grannies drop their shopping, & little children cry !!


It's a must have !! :smug: /Steeringw

[colVR4]

Thats what I thought Derek. :D

However, I want something that I can turn down when I have the missus in the car....if you know what I mean. The dump valve on my car is noticeable when suddenly lifting off the throttle after heavy pressure is applied to is so I am wondering if it may be an aftermarket one.

[Kieran]

I must admit I prefer a re-circ only one.... I like the stealth factor. No-one need know it's turbocharged unless I decide they should!

[Dan_G]

To BOV or not to BOV? That is the question. :scholar:

I like the idea of having the extra response that many of the BOV manufacturers claim, but is it worth it? I don't want anything too noisy, but do want something subtle to get that nice schnikk sound. /Steeringw

Can you get BOVs that you can turn the noise on and off? or at least increase and decrease the volume. Also, what are the advantages and disadvanages of recirc over dump-2-atmosphere?

Finally, how easy are these things to fit and set up? What are the best buys (cost vs performance)?

I have just ordered a boost guage, which should be arriving in the next couple of days (may have to pop over to see Glenn to get it fitted) so I can monitor the boost. Would that help setting a BOV up properly or should I take it to someone who knows what they are doing?

Ta

Not sure about any more response but they do sound good.

You can get BOV's that adjust the volume, the easiest way of acheiving what you're after would be to fit a fully adjustable BOV (eg a GFB Stealth FX). WIth these you can decide how much air is dumped to atmosphere or re-routed back into your intake system. The more air you dump to atmosphere the louder the Psssschht! :leer: if you decide you want no noise then you can set it so that all the vented air goes back into the intake which is the standard set-up of the car.

Very easy to fit. undo 2 Jubilee clips and remove the actuator pipe. and just swap with your old one.

To set up a BOV all you need to do is make sure the pre-load is set so that the BOV will fully close once you are at idle. This is usually done by screwing in a screw or turning the endcap. if the bov does remain open on idle it will usually stall the engine or have a rough idle.

Here's a piccy of my Stealth FX... I'm sure you can get others like it though:-

[colVR4]

Great piccies. Where abouts is that fitted in relation to the rest of the car though? Where would my standard re-circ valve be located? More piccies please

[Dan_G]

Great piccies. Where abouts is that fitted in relation to the rest of the car though? Where would my standard re-circ valve be located? More piccies please

I'm at werk so not many piccys here.... here's one showing the approx location of the BOV. Its behind the cross. The standard valve is located in the exact same place and its just a direct swap for this type of BOV.

[colVR4]

Do you have to take the under tray off to get access to it?

[colVR4]

Anybody know if this would fit our cars? I am interested in this one because it is still a re-circ valve.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7986990390

or this one

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=72205&item=7987375472&rd=1&ssPageName=WDVW

[Nick Mann]

Not sure I understand the point of fitting the first one. Will it do anything extra other than look shiny? The second one looks like a better bet, although you can't adjust it.

Surely pretty much any DV will fit on any turbo car?

[ako]

Okay...


The reason that fitting an aftermarket BOV to a VR4 gives such noticable results, is because the stock one is so CRAP.

Not only will they stop you from exceeding around 14psi, but they also partially open under half and even full throttle conditions, due to the very soft spring they have in them. This is a sort of safeguard measure on mitsis behalf, and probably also a bit of stingyness as well.

Fitting the top one (the recirc one) will net the same gains as any other, just without the "pishhh" noise. It can still be vented to atmosphere though, if you want.. It just has the facility to be recirculated.

Hope that helps :)

[colVR4]

Thats what I thought. I think that the recirc valve that I have fitted IS leaking, leading to low Psi. I am not bothered about getting one that vents to atmosphere to give the psshhhtt sound, as much as I am bothered about getting one that works!!

I have also found out that with some cars (don't know if it applies to the VR4) that if you replace a recirc valve with a DTA then you can have overfuelling problems. Not something that we want in a car that overfuels anyway.

Anybody know how true this is?

[Nick Mann]

Didn't realise the standard one was cr@p. Sorry! I thought the only reason to change was to get the pisshhhhh sound.

Overfuelling is right, I think, with a VTA. If I rev and dump mine on the drive a couple of times it leaves a big sooty mark on the garage door!! That is with an HKS SQV.

[Kieran]

/Adds 're-circ' valve to the ever-growing list of cunning plans ... /STP

I think my valve is struggling too.... With the gauge attached, you can see the pressure falling steadily. That and the fact that the standard re-circ valve 'hishes' sometimes - and if it's okay, well...... Err /Hmmm , we'll move over that one!! :embarasse

[colVR4]

Okay, heres a question for you.

If you take the recirc pipe off a recirc valve and bung it up (as you would with a DTA valve) would the recirv valve just act like a Dump valve? Anybody tried it to see what it sounds like?

[ako]

Okay..

The only difference in an aftermarket BOV between a recirc one, and a VTA one, is the trumpet, or lack thereof.

I used a recirc BOV without recirculating it (just like a normal VTA BOV) and it worked exactly the same. Because it is!

If you try this with the factory one, it wont work. The slight leak it has will cause all manner of issues - in a nutshell, dont bother, it just doesnt work :p

But any other dump valve, go for it.

[colVR4]

What problems can the leak cause other than loosing boost. As far as I can see, any leak will just lose any pressure that could be going into the throttle body.

Are you saying that the leak will cause the turbos to produce too much boost? If this is the case won't a leaky recirc valve cause this anyway whether it is recirculating or not?

[colVR4]

Somebody mentioned using a recirc valve from an EVO FQ-340. Are these a better valve and if so are they a straight swap?

[pezza]

Somebody mentioned using a recirc valve from an EVO FQ-340. Are these a better valve and if so are they a straight swap?


/wave twas me /yes

I am running with a 340 DV at the mo and it is a recirc device,.

I have run a stock recirc valve with the recirc connection venting to atmosphere and it was fine, I did not have a problem, it sounded the same as the aftermarket VTA BOV. I did not, however, have the return pipe blocked and so the car sucking in, what I believe to be, unmonitored air. :uhoh: (this was unintentional as I needed a new part) the car was on the verge of stalling and idling very roughly as this pipe was NOT blocked and ECU was not very happy!

Sounded great induction wise tho :thumbsup: but not really recommended due to the car running leaner /help . The big increase in pickup /response with the extra air was very noticeable though and proved to me the difference that the extra air made.

the 340 unit is made out of metal and a sealed unit. i believe the piston is sprung at higher tension than the stock plastic VR4 device and was advised that it could withstand (ie. stay shut at ) higher pressures . it works a treat and is a straight swap.

Hope this helps

Cheers

Pezz

[ako]

Pezz - did you try it at all with the pipe blocked off? I'd say with a fair degree of certainty that it would still have had idle issues, and its far far from a perfect solution - if anything, the car would go slower due to the excess air being bled off.


ColVR4 - your correct. For a graphic demonstartion, try and raide your boost above around 15psi or so, if it doesnt fuel cut first. In most mitsis pre - evo 4, you just wont be able to. I could even freeboost my car with the stock BOV and still only see 14 psi at the manifold.

It wont cause problems as such, apart from running richer than it needs to, and reduced response. Remember, the mitsi engineers aren't stupid, the leak was put there as a safety measure more than anything, a lot like the overly agressive fuel cuts on the 6A13.

And like someone mentioned, it will give overfuelling on a full throttle gear change or lift off - great for backfires :D



Like Pezz said, finding another factory BOV is a perfectly good alternative. A lot of people down here opt for the factory BOV from a lancer evo 4 or newer, they have proven capable of holding 25psi + and at about 1/3 the price, you cant complain.



One point to note as well - AllBeItMine, another guy on these forums, found that his factory BOV was the cause behind his car hitting fuel cut (and running massively rich the rest of the time) at 8psi and being quite flat on the road. I also found the same problem with my first VR4, couldnt get over 13psi.

Trust me, it gives you a lot more than just a "pissh" noise, its one of the few cars I know where it genuinely is a performance improving device!

[pezza]

Pezz - did you try it at all with the pipe blocked off? I'd say with a fair degree of certainty that it would still have had idle issues, and its far far from a perfect solution ....




I would have to agree it was not a perfect solution but the plastic intake pipe the recirc pipe connected to was broken and was genuinely waiting for replacement... /help I did not have the opportunity to block off the pipe as the pipe was being replaced in a matter of a few days.

I did enjoy lifting off the gas and *dumpin* next to potential prey like type - Rs, and the like, to antagonise them into some fun and games :evil2: Or just being plain anti-social /pan

Col I think I would go for a hybrid valve if I planned to upgrade this device...

[bradc]

just a thought that you are all going to think is really dumb and probably won't work, but what if you had a VTA blow off valve, and had a tube running into the cold air box. it would pump a whole lot of extra air into the cold air box. I'm sure it would stuff things up, but would it work?

[Kenneth]

just a thought that you are all going to think is really dumb and probably won't work, but what if you had a VTA blow off valve, and had a tube running into the cold air box. it would pump a whole lot of extra air into the cold air box. I'm sure it would stuff things up, but would it work?

you would be running it double rich!!! Not only will the ECU think it USED the air, it will see the air it thought it used a second time.

Its pretty simple really... if you want noise, VTA. if not, plumb-back. if you want a compromise of both, get a hybrid. Taking the DV out can sound cool too.

[colVR4]

Loads of great information here, I am glad that I started the thread :D

However, I want a replacement for the rather ****ty standard valve but don't want to pay the £200 or so for a HKS SSQV or similar. I just want something that is going to do a better job.

Are there good hybrid valves around for a reasonable price? How much would an EVO valve cost?

Ta

[Wodjno]

Colin are you at the JAE .. If so you can take a look at my GFB Stealth(like DAN G's) Full Chrome .. This can vent to atmosphere fully or set to as little or as much as you want. Or set to recirculating. As far as i know the only place you can get these in the UK is Graham Goode Racing up in Leicester. He does mail order.. They originate from Australia and you can source them from the USA to, but it isn't any cheaper.. www.grahamgoode.com

Also you can check the spec out on this page..

http://www.newdimensions.com/2003/gui/04_pro/gfb_fx.html

[colVR4]

I may try and pop over and have a look some time. I am still looking at the option of getting a direct replacement but with stronger valves.

[Wodjno]

I may try and pop over and have a look some time. I am still looking at the option of getting a direct replacement but with stronger valves.

Look forward to seeing you again.. Just let me know when. The spring is adjustable on the GFB to. :thumbsup:

[wcur008]

i've got a mate who blocked up his factory recirc with a screwdriver to make a pisht noise but he ended up with no boost limit, so obviously decided it was not the smart track to go down

[Smokinmasta2]

Loads of great information here, I am glad that I started the thread :D

However, I want a replacement for the rather ****ty standard valve but don't want to pay the £200 or so for a HKS SSQV or similar. I just want something that is going to do a better job.

Are there good hybrid valves around for a reasonable price? How much would an EVO valve cost?

Ta


My hybrid one cost £40 off fleabay!!.................all metal with nice brass piston.


http://img.photobucket.com/albums/v732/Smokinmasta/DSCN1066.jpg


Smokin.............

[pezza]

Smokin' that device sounds gud mate... do you still have that grin of yer chops? :evil2:

So Col have you decided between recirc fully VTA or hybrid? ... When I changed back to the 340 recirc valve from the stock unit, noticed how much more the revs are maintained plus faster pickup between gear changes... (This is with .9 bar boost)

Wouldnt there be a difference in performance (not sure how negligable) with a fully VTA or hybrid unit if that air is not recirculated? Just a thought, an unimportant one tho ... :thinking2

[colVR4]

I have bought a replacement metal recirc from ebay to replace the plastic one that is fitted as standard. I am going to get it fitted and see if it makes any difference, should get it done some time this week.

[caishanvr4]

Does your car need to be running a higher boost setting to get the best from these VTA's or hybrid bov's /Hmmm
COLvr4 did you buy the same one as smoky masta, if not how much, any pics

[colVR4]

AFAIK even on standard boost you will be better off with a replacement for the Bosch plastic recirc valve on our cars, as they are DESIGNED to leak by Mitsubishi as a safety feature. This means that you will get better sustained boost with a replacement valve.

The valve I bought is a direct replacement for the Bosch recirc valve and does not VTA. I will dig out a picture for you when I get the chance.

[Axeboy]

I just fitted a Bailey DV26... sounds great & feels great so far.

[caishanvr4]

whats the best way to bring the noise /Hmmm auto or tiptronic

[ako]

Put a manual box in it :D

Only time it will vent is when you back off the throttle.

[Wodjno]

Put a manual box in it :D

Only time it will vent is when you back off the throttle.

Makes no difference whether you have a manual or auto, or use it in Auto or Tip.. Just lift off the gas on after acclerating and hear it TSSSHhhhhh.. :evil2:

[caishanvr4]

colvr4, have you fitted recirc valve yet, has it made any difference and where,s the site :thumbsup:

[colVR4]

oh,yeh...I haven't got round to it yet, but I think that this afternoon is looking favourable as I have just decided to bunk off work :D

As for the site, here is the link to ebay:

http://cgi.ebay.co.uk/Bosch-Recirculating-Turbo-Dump-Valve-Upgrade-Gain-BHP_W0QQitemZ7992205017QQcategoryZ72205QQssPageNam eZWDVWQQrdZ1QQcmdZViewItem

[colVR4]

Right, fitted it tonight. First thing to mention is the fact that it was a lot easier than I thought. Once you have taken off the under tray (extremely filthy and oily) there are only three pipes that you need to be concerned about.

The OEM recirc valve is quite obvious; on the right hand side at the end of the radiator. There is a little pipe that goes in the end and two larger pipes. There is a compression clip on the little pipe that you squeeze with a pair of pliers and it comes off dead easy. The other two have jubilee clips, easier with a spanner than a screwdriver to undo them I found.

Then its a case of just replacing the old with the new. The openings on my replacement recirc valve are quite a bit narrower, but I just tightened the jubilee clips to squash the original pipework to fit (still forms an airtight seal as far as I can make out). Then its just a case of replacing the undertray.

Took it out for a test run and although I couldn't tell if there was any significant performance difference it does now make more of a noise when its recirculating, a kind of low whistle. I thought at first that this was a leak so I tightened everything up a notch but I think it is just due to the smaller opening in the replacement valve and the fact that the new valve is metal and old one was plastic. Dunno!!

My boost gauge isn't showing any greater boost so I am starting to come to the conclusion that maybe it is my gauge that is faulty rather than the original recirc valve leaking. However, I still think it was worth replacing the OEM valve after hearing about how it wears out and there is a leak built into it as a safety feature.

I just need to borrow a boost valve now :D

[colVR4]

UPDATE

Okay, bought a NEW boost gauge since it appears the one that I got off fleabay is SHIIITE!! Bought it from......erm......hal.....erm...frauds!! Okay, I know but it was only £25 and it looked better quality than the previous one.

So I fitted it and immediately it gave better results. The boost now peaks at about 0.8 and settles down to about 0.6-0.7 when "giving it some" (technical term). That seems a lot nearer to what most people were saying before about the figures I should be getting.

By the way, the recirc valve gets better and better. I definately makes a dump-valve sort of noise but much more 'refined' in my opinion. I can still get heads turning in my direction without it being so in-your-face as some of the dump valves that you hear.

I would definately recommend this mod.

[Kieran]

....The boost now peaks at about 0.8 and settles down to about 0.6-0.7 when "giving it some" (technical term). That seems a lot nearer to what most people were saying before about the figures I should be getting.

By the way, the recirc valve gets better and better. I definately makes a dump-valve sort of noise but much more 'refined' in my opinion. I can still get heads turning in my direction without it being so in-your-face as some of the dump valves that you hear.

I would definately recommend this mod.

Hmm.... Your boost results are interesting. Mainly because they match what I get. :inquisiti :thinking: :book: :lost:

Regarding the re-circ valve... Have you noticed any difference to how quickly the car comes on boost, or how well it holds boost? :inquisiti

[colVR4]

It comes on boost quickly, spikes a little and then holds boost all the way through to read line without any noticeable drop off. Don't know how this compares with the factory valve, but looks good to me.

[koala]

I have also found out that with some cars (don't know if it applies to the VR4) that if you replace a recirc valve with a DTA then you can have overfuelling problems. Not something that we want in a car that overfuels anyway.

Anybody know how true this is?

Not on every tubo charged enginrs. I had DTA on my skyline, because of this I had stalling problems due to measured air dissepearing from the intake and overfuelling BUT I used to get HUGE flames with every gear change :evil2: Once I was stopped by police. (they thought my engine was on fire /pan ) /Hmmm

I have no idea why I sold the B u g g e r .

[bernmc]

Not on every tubo charged enginrs. I had DTA on my skyline, because of this I had stalling problems due to measured air dissepearing from the intake and overfuelling BUT I used to get HUGE flames with every gear change
This is exactly what ColVR4 was saying - overfueling, so lots of unburned fuel in the exhaust which ignites. Impressive, but expensive, inefficient and loses power.

[bradc]

but there is flames!!!!!!!

I quite like the idea of getting a hybrid one, where it can dump to atmosphere as well as recirc. You just turn a knob to determine how much air goes either way.

[koala]

This is exactly what ColVR4 was saying - overfueling, so lots of unburned fuel in the exhaust which ignites. Impressive, but expensive, inefficient and loses power.


Hmmm thinking cap on again.
Expensive!!!
I have learned my lesson by buying a VR4 so word expensive has different meaning to me after gearbox pulleys etc etc(I now live in the dark side)

So I dont think loosing £0.012 every gear change will ever get me to the day light!!! /help




Inefficient???

I will dissagree ???

This is my theory and there are setups for this.

"Little overfuelling will keep your internals cooler.
"Its better to burn(ignite)fuel to athmosphere then dump it in unburned form.
So its environment friendly and looks the Pupys little balls

Loses Power,

"Overfueling done after you lift of throttle. So When you flooring your mixture as good as your ecu settings timing spark etc etc.
"You ll gain maybe little couse your internals cooler.

So DTA is for me.

HKS Idle stabilisier will cure any problems you might have with having DTA. and it costs around £90.

E rEgarDZ/pan

[Quail]

Just on a side; is anyone actually getting any natural flames from their VR4s?

[bernmc]

Hmmm thinking cap on again.
Expensive!!!
I have learned my lesson by buying a VR4 so word expensive has different meaning to me after gearbox pulleys etc etc(I now live in the dark side)

So I dont think loosing £0.012 every gear change will ever get me to the day light!!!

Inefficient???

I will dissagree ???

This is my theory and there are setups for this.

"Little overfuelling will keep your internals cooler.
"Its better to burn(ignite)fuel to athmosphere then dump it in unburned form.
So its environment friendly and looks the Pupys little balls
These cars do overfuel to aid cooling - by decreasing the burn efficiency and also absorbing extra heat energy. This is needed under boost though, not on lift-off, so you're not achieving anything with the BOV. As to burned vs unburned fuel being more harmful, try sniffing your exhaust!



Loses Power,

"Overfueling done after you lift of throttle. So When you flooring your mixture as good as your ecu settings timing spark etc etc.
"You ll gain maybe little couse your internals cooler.

You might want to read BDA's emanage post to see just how much power overfueling loses you. As you say, it's mostly on lift off, so the effect may be minimal...

[marsh]

Sortry to drag up this thread again, but I was wondering if a boost gauage was required to go alongside the purchase of a replacement/upgraded dump valve?.

[bradc]

it isn't needed, but then I guess that when most people are modifying their car, they will buy a boost gauge anyway.

[marsh]

Cheers, much as I'd hoped :scholar:

[pezza]

Just to touch back on this old thread...

I lent my 340DV to a pal with a FQ340 as his one was suspected of malfunction. Especially as it dropped 60 HP on dyno between 6000 and 6200 rpm /Hmmm
In fact the dump valve was fitted with the plumb back and main air feed connected the wrong way round as delivered from SMC Mitsubishi in Uxbridge :furious3:

ANYWAY...

I replaced the 340DV with the stock plastic one on my car and noticed the difference in days with a considerable rise in fuel consumption and that rich rich rich rich (ok point made /pan ) fuel smell came back.

Just for testing purposes, I then disconnected the plumb back hose and blocked it off... Hmm that loud piiiissssht sound...BUT..... 30 quid of petrol almost gone in 60 odd miles or less?? :shocked: and almost high on tesco 99 RON fuel vapours... /Hyper

I get my 340DV back tonight... not before time /yes :rolleyes4

[Trojan]

Hey ako,
I recently bought my legnum vr4. It was already lowered but i cant figure out what brand of spring / shocks they are, the springs are orange. Do you or anyone know what brand these are... and how i can tell what brand shocks i have without major dismantling. :evilgrin:

[ritch_w]

I replaced the 340DV with the stock plastic one on my car and noticed the difference in days with a considerable rise in fuel consumption and that rich rich rich rich (ok point made /pan ) fuel smell came back.

Just for testing purposes, I then disconnected the plumb back hose and blocked it off... Hmm that loud piiiissssht sound...BUT..... 30 quid of petrol almost gone in 60 odd miles or less?? :shocked: and almost high on tesco 99 RON fuel vapours... /Hyper

I get my 340DV back tonight... not before time /yes :rolleyes4

Hi derek, just cottoned onto this thread (thinking about getting a DV), anyway - what was the prob with your car - was refitting the OEM DV (faulty??) that caused excessive fuel consumption - or the after market one?

[Axeboy]

http://www.camskill.co.uk/products.php?plid=m7b11s192p1069


I fitted one of these.

[Eurospec]

With reference to the over fueling issue you guys are mentioning with atmospheric dump valves.

The issue is that the air flow meter, vkf, is right at the front of the intake system. Behind it are the turbos, all the i/c pipework and the throttle body etc.

With a VTA dump valve, the air, which has passed through the vkf and thus been metered and has had the fuel calculated by the ECU, is dumped to atmosphere. Hence, when a VTA valve dumps, the car runs rich for a short period of time. The ecu is expecting the air that came in via the meter to be ingested by the engine, and thus the pulse of the injectors at that moment in time has taken account of it. If you dump the air externally with a VTA the result will be a split second blip of rich running. Possibly enough to cause a pop in the exhaust, or a spit of flame in extreme circumstances.

A recirc type valve recirculates the air to the low pressure side of the turbos, but after the VKF, so not causing the 'problem'.

Without sticking one of these on a datalogger and seeing the effect its not really possible for me to say how rich it goes or for how long, and as you can imagine it would depend on how much air was dumped anyway.

If you get an atmoshperic dump valve and it leaks, you can guarantee the car will over fuel, where as with a leaking recirc, the fuel pulse will be correctly calculated and you will just lack boost.

In my oppinion, you pays your money and takes your choice. Personally i have been running a recirc on my own car for a couple of years and its been great. It works the way the ecu is expecting and i have no 'rich shift' issues. However, it isnt particularly loud and it wasnt cheap! A lot of people will trade the 'rich shift' for a nice loud psssssht, and they have run for years that way.

Cheers,

Ben.

[Kenneth]

With reference to the over fueling issue you guys are mentioning with atmospheric dump valves.

The issue is that the air flow meter, vkf, is right at the front of the intake system. Behind it are the turbos, all the i/c pipework and the throttle body etc.

With a VTA dump valve, the air, which has passed through the vkf and thus been metered and has had the fuel calculated by the ECU, is dumped to atmosphere. Hence, when a VTA valve dumps, the car runs rich for a short period of time. The ecu is expecting the air that came in via the meter to be ingested by the engine, and thus the pulse of the injectors at that moment in time has taken account of it. If you dump the air externally with a VTA the result will be a split second blip of rich running. Possibly enough to cause a pop in the exhaust, or a spit of flame in extreme circumstances.

A recirc type valve recirculates the air to the low pressure side of the turbos, but after the VKF, so not causing the 'problem'.

Without sticking one of these on a datalogger and seeing the effect its not really possible for me to say how rich it goes or for how long, and as you can imagine it would depend on how much air was dumped anyway.

If you get an atmoshperic dump valve and it leaks, you can guarantee the car will over fuel, where as with a leaking recirc, the fuel pulse will be correctly calculated and you will just lack boost.

In my oppinion, you pays your money and takes your choice. Personally i have been running a recirc on my own car for a couple of years and its been great. It works the way the ecu is expecting and i have no 'rich shift' issues. However, it isnt particularly loud and it wasnt cheap! A lot of people will trade the 'rich shift' for a nice loud psssssht, and they have run for years that way.

Cheers,

Ben.

I HAVE done the data logging... its nothing to be worried about, just a rich spot when you lift off the accelerator.
There is of course the idea that you get worse fuel economy... I found I could get maybe 20km per tank more with the recirc valve... not enough extra for me to give up the VTA

[matt mowbray]

mines completely standard. I like the stealth mode ( no noise ). would i notice any difference with a bov pereformance wise

[Kenneth]

mines completely standard. I like the stealth mode ( no noise ). would i notice any difference with a bov pereformance wise

Depends on if your standard recirc valve is buggered. They are known to leak at high boost and apparently start failing when they get old. I think dickytim found that replacing his standard one with an aftermarket recirc valve upped his boost a couple of PSI.

so long as your BOV operates correctly, there is not likely to be any difference between recirc and VTA performance wise.

[AderC]

Was reading this thread last night - I hadn't realised how bad the stock BOV was. Just completed a "buy-it-now" on Ebay for an evo FQ300 BOV for £18.00 :happy:

aDe

[T-Tech]

Does VR-4 use airflow/airmass meter or MAP-sensor? Cause the problem with Dumb/BO valves is WITH airflow/airmass meter, that when the airflow/airmass meter has measuret the air that is "heading" to engine and you change gear, bov/dumb throws some air of it to outside of intake system BUT your ECU has already calculated needed fuel to that air what airflow/airmass meter gave it info and now it injects to engine too much fuel.
This results then lots of black smoke, idle troubles, engine struggling, in worst cases catalytic converters have been destroyed and lambdasensors too.

That is the biggest problem if car is equipped with airflow/airmass meter and your using valve that diverts to atmoshphere. Sounds are cool of course but aint my choice ever to MAF equipped cars, only MAP equipped.

Best is circulating valve so your ECU stays up with the info all the time.

Also about that what colVR4 asked: Yes you can take of the pipe but sounds arent really that great that its worth it.

I use Bov/By-pass valves mostly just to decrease the pressure hit towards turbo's compressor wheel. Not cause it decreases lag(actually when measuret this, its 0.1-0.2secs difference with, and without by-pass. so not much)

Why they use bov/by-pass? because on changing gear situation(hard acceleration) you have full boost and when you change gear, you usually lift leg from accpedal and pressure plate on throttlebody closes.
Turbo is still spinning fast and pushes air towards intake but now the air stops on pressure plate and rapidly runs back to compressor wheel and there hitting plates. This pressure hit can damage compressor plates and I have seen on own projects too this happen. Also usually it makes this loud stall sound what you hear on WRC cars often, like the car "giggles"

There just some basics to ppl who dont know why its really there, mostly its to protect, not to decrease lag.

[TAR]

OK so I've just read this long post and I have a question...


The valve opens to vent pressure to stop the turbo being damaged when the throttle is closed - so what actuated the valve?

Is it just pressure equalisation using a spring and if so, wont it cause a problem if a stronger spring is used??


Probably a very simple answer but I'm feeling stupid today
/duh

[Kenneth]

OK so I've just read this long post and I have a question...


The valve opens to vent pressure to stop the turbo being damaged when the throttle is closed - so what actuated the valve?

Is it just pressure equalisation using a spring and if so, wont it cause a problem if a stronger spring is used??


Probably a very simple answer but I'm feeling stupid today
/duh

The valve is opened by a combination of boost pressure pushing against the piston and vacuum pressure from the intake manifold. When you close the throttle the engine is starved of air, this causes the intake manifold to go into vacuum.

The intake manifold is connected to the BOV, so when the intake manifold goes into vacuum it causes the BOV piston to rise. (it gets sucked upwards)

Theoretically, the spring in the BOV should only be necessary to stop the BOV opening when the turbos are not creating boost.
In high boost applications you may need a stronger spring to overcome any difference in boost pressure in the pipe-work vs pressure in the manifold.

Thats about it really... the BOV is supposed to actuate when there is unequal pressure between the intake manifold and the intake pipe work.

[TAR]

Thanks Kenneth, that is a good explaination.:happy:

[spm01]

has anyone completly taken their BOV off and blocked up all the pipes? the reason i ask is that i did this to a evo i had and the sound was awesome, and when my evo was tuned the tuner actually said he runs all his cars without them.
is this possibly with the vr4, if so are there any of you running without that can make a comment? is this a good move or a bad one?

[Kieran]

Axeboy did this- can't remember what he thought.

The argument against it is there's nowhere for the compressed air to go when the throttle snaps closed.... The sound being caused by the 'backlash' as the air collides with the turbo blades and stalls them - I can't imagine this being good for response or condusive to long turbo bearing life....:inquisiti

[Kenneth]

I did that for a while on my old car. Yep, it does sound cool :D

Apparently it can lead to thrust bearing failure though... so for longevity of your turbos, you may want to avoid it :P

[spm01]

ah well, thought i would ask the question. thanks for letting me know anyway guys...

[snickells]

Fantastic amount of information here everyone, it's been quite an enlightening read.

[Marklar]

Really good info

Recently I had noticed I was not getting quite 8psi (after finally checking what the boost should be) and found slight leak in a vacuum line, fixed this, boost level returned to normal but the drop off in pressure was quite noticeable.

Never realized that the standard valve was so rubbish, and I am definitely looking into an after market valve before playing with the boost at all. I like re-circ too.
I have recently put in an electronic valve controller (plumbing in progress) so hope this will help with the pressure stability also.

Great Thanks.

[AderC]

A lot of evo owners (pre evo-IX) are replacing the plastic BOV's with the JDM Evo IX/MR BOV. It's an all-aluminium one and a direct replacement. Mitsi part number is 1545A001.

aDe