nowt as queer as folk

so still using the OE BOV...?

 

Darn pc!

 

And this is exactly the reason why I chose to only type the short initial comment, which imo 100% supports the context of the original post and subsequent posts being made.

Trails - Re-read the OP's post. There is no mention that we're talking about a standard engine, MAF based system or a VTA BOV (with regards to the "The general consensus on dump valves is this:"). Hence why I disagree with the statements being made...... total lack of context.

Your reasoning is based on assumed context. Which maybe correct, but I never assume much these days..... it can lead to egg on face.

thenewgalaxy,
Me a troll!

Upgrading or changing them leads to NO DISCERNIBLE performance gain at best, but is more likely to cause a performance DEFECIT. The best you can hope for is a "psssshhht" noise inbetween gear changes.
It can lead to a performance gain if your standard OEM valve leaks due to a weak spring - this can and does happen. A DV with a better spring and shim can ensure better control of the diaphragm, aiding boost ramp.

Loud dump valves are antisocial and not part of the image most of us as enthusiasts wish to be associated with.
Subjective to say the least.

The OEM recirculating valve is best. It is what your car engine is mapped to deal with and what the engine is designed to be used with.
Subjective and as per first item above, not always the case.

If you replace the OEM one with an aftermarket part it will most likely need remapping especially if it is VTA.
Simply not true as stated - replace "most likely" with "may" - I'm not aware of any recirc replacement DV that requires a remap (assuming correctly set-up)

Tidgy has hit the nail on the head as the appropriate wording all along should have been "could/may" etc.

 

Coolio

So you are saying you should run a wideband AFR meter if you want to run a VTA BOV to ensure you aren't putting your engine at risk?

 

Not assuming Shaun, just applying what I believe to be the most appropriate scenario...the vast majority of engines on this site are unopened and are going to be subject to to phase 1 type bolt on mods, which will not benefit from a VTA BOV...unless we make the assumption the OE BOV is leaking.

The real point here is this; why would you want to change a perfectly good piece of kit that offers no benefits (up to a certain boost threshold-and at that boost threshold 99% of OE builds will go pop), to something that could cause you issues?

Horses for courses of course, and personally I like a VTA (on other peoples cars), because they make me chuckle

 

Oh and just to add.... I still run my OEM DV, on MAF, with 1.8bar of boost on a GT30 sized turbo. Just to quell any discussion of trolling. But its all about whether the cap fits.

 

Trails you really are missing my whole point. The OP never stated the context of the performance statement and its absolute reference to a VTA DV - my point made reflects that succinctly.

I'm sorry but if something is not clearly stated you are assuming.

 

Sorry, to be precise, I meant what pressure the spring inside the OE valves are rated for (may differ between classic/blob/hawk/whateverthehelltheuglyhatchesarecalled)before they leak/dump boost. With the likes of Forge Recirc valves you can buy different rated springs and just "plop" them in.

 

No sorry correction again, I did mean AFM as I said in first post, it's not ideal to run one using AFM/MAF but it's ok to run one if not using them 2

Most folk run them using the AFM/maf and it's why they have idle issues etc

 

to the first bit

Yep, though I have a GFB thing sitting around in the garage. I may or may not remove my intercooler to fit it one of these days, it is quite big so unfortunately a necessary thing to do to fit it!

I cannot say I can see any justification for adding a VTA system but there would appear to be something in it for the recirc types.



Lack of context or not, we're getting somewhere and this is the knowledge I wanted coming in

I have to say I gather the point you're making but it isn't very often that we get someone coming in saying "Hey guys need some advice, I've just built a fully forged engine I'm competing at the Rally of Finland next week and intend to run it at 400000 psi was wondering whether or not I should go anti-lag or uprate the dump valve".

Unfortunately we more often get a badly written post something akin to "I've got a classic Turbo 2000 / Bug WRX what dump valve should I run they said on swap shop I could get another 20bhp from running a VTA eBay one, kthxbye".

Agreed but I have uprated radiator caps, in fact Subaru themselves sell us 1.3 bar ones when the coolant tank has a 1.1 bar fitted. We all like to add our own engine bay bling as it looks nice, but you don't usually see such vehemence towards them as you do our dump valves.

Forge are a name I hear a lot, their recirc valves can have springs uprated.

Here we have a kit from Forge themselves and if recommends green or yellow for a 26psi system.

http://www.forgemotorsport.co.uk/con...duct=FMDVSU110

I would imagine the higher rated springs could cope with some serious pressures.

But wouldn't a lot of people going for high pressure builds do away with a dump valve completely?

 

Not missing your point Shaun, perhaps you are missing mine...there is a difference between an ignorant assumption and stating your assumptions when establishing a baseline and I'm happy that mine is going to be a pretty good match to your average VTA aspiring owner. Which was why I mentioned the unopened engine. These 'discussions' are hardly targetted so I'm merely attempting to follow a single scenario that applies to the majority of site members. Perhaps I should have added a mission statement but this is suppossed to be fun not work...

 

Yes or do what I did; I run a HKS fmic and there was already a boss for a SSQV...so I converted it to recirc

 

+1

Sorry to be slightly off-topic, but I'd also mention forged internals for the 2.5 engine?

 

Read my reply to Tidgy...

Do you mean why don't Subaru offer uprated engine internals as an option? If that is the question, why would they?

 

Joke answer - they do and I went for their forged option with uprated brakes but apparently need my head examining

Serious answer - because a lot of Subaru's market are people who buy the car ahead of those of rival manufacturers do so for aftermarket tuning potential, and they have refused to uprate the 2.5s because they appear to think they can do a combination of hoping it won't fail under guarantee, sweeping it under the carpet and not worrying about it because it isn't affecting their home market.

Someone mentioned figures earlier. We can back up uprated brakes (even if that is a contentious issue among some!) and we can back up forged internals with a remap.

Apart from some spring strengths and monster builds which we don't see very often, there appears to be little going for an uprated recirc and nothing at all going for VTA.

 

I posted before reading the lot (thought at the time iot would be better to wait).

His comment was that 'just because Subaru didn't fit (certain parts) as standard doesn't mean that they (the parts/mods) are bad'.

He mentioned fmic, ceramic pads etc to support his argument, and I supported his support of his argument by citing forged internals.
They aren't OE and they aren't a bad enhancement.

I understand your question, and I bet we both agree on the answer.

Edit: Aahhh!, Tng has provided it for us.

 

Just waiting delivery for my ebay win of £15 all in standard dump valve to turn up... car is a 2004 sti with a bailey vta and is awful... Makes car feel laggy and sometimes makes the noise and sometimes dont

 

He's OK considering he owns one of those crappy Cossie hatches

 

And you are remarkably adept at using your keyboard for someone with a classic Impreza turbo

 

Now, now butty.

I don do sniffy lah-di-dah grammar policing.

Weem all human beings.

It's just that my English teacher(s) got through to me more than my mechanics ones did.

And as one (teacher) always told me - the art of communication is that the receiver ends up with exactly the understanding that the sender wanted to convey.

Hence smelling, punktueayshun and grammuh izunt impotunt.

Anyway, can I make a suggestion regarding a 'sticky' for the subject of BOV's ?

Basically - put this one up.

Reasons?

* It's got lots of technical information;
* It's got lots of examples/experiences;
* It's got lots of subjectivity er.... personal points of view; and
* It demonstrates perfectly how a simple question from a new member can become a free-for-all and a nightmare.

In other words, it's got just about everything anyone would ever want to know about BOVs and their effects, in both the car and threads.

Oh - and it should prevent many of us repeating the same thing over and over again.

 

RAOTFL...that's because I chose a classic because I preferred it rather than it being an economic descision...lets not get into what I could have bought with the money I've thrown at it

 

I could have bought all sorts of weird and wonderful things (most of which leave me cold tbh) for the price I paid for mine too. Don't regret my decision in the slightest! I'm not one of the crowd and never will be.

As with these dump valves, it is anyone's choice as to what to do. However I want people to be able to know why they need fitting, what they are for and what to expect out of them.

I do think it is important for newbies coming on here to avoid a flaming by being able to look at this thread as ultimately a lot of them think of the dump valve as a first port of call for tuning because of the amount of bad information out there.

 

I was be facetious; I like the Cossie hatches...I was seriously considering a 330S for my daily but know I won't be able to resist the urge to modify a blown car

Be interesting to see how many people read the stickies...I predict almost the same number of threads on BOVs even with the sticky

 

I know, but that is part of the Scoobynet "banter" which I think is what makes this forum a good place. We all own the best car out there and everyone else's is second best, at best.

I think we would certainly see a decrease in them and at least have a link to post right away. I also think for the good of those coming via search engine that we would have a hit that would bring people in.

I have edited the opening page to reflect the way this is going.

Edit - I have approached some people on here with monster builds and experience of building them for opinion that will hopefully get us some good answers that will move us away from "general consensus" and more towards "those with much experience" and "the leading authorities on building competiton winning engines"

 

I'd agree with you there

 

The Lord and tubbykins will be along any minute with their stick-on fake carbon to slag of the dump valvers.

 

ahhh my stalker greetings.


i got bored with dump valve threads ages ago as you may have noticed by my lack of comments

 

Pity (seriously).

As per my post above, a thread such as this would be very informative to new members, not just technically but it would give them a very good feel for the 'community spirit'.

This is how Wimbledon's dressing room must have been like in the days of The Crazy Gang.

 

its pointless, no matter what advice etc is offered the outcome is always.

" i dont care bruv its my car and im fitting one innit"

 

I suspect that with this thread we'll not have so much of the trolling, or at least I hope not. I want opinions and examples please!

It would appear from what I have learned that a VTA is actually worse for your car than weighing it down with the same weight of stick on carbon, and that a high-end third party recirculating one is little more than engine bay bling, like fake carbon.

At risk of going off-topic, it would appear that those that champion these devices tend to be keen on the other massively divisive paraphernalia.

Either way, we all tart our cars up with various bits but I want to know if these things have any arguable performance advantage or whether they deserve the bad press they get on here.

Not a single person has advocated the use of VTA and only one person has provided a cohesive argument that sticks in favour of aftermarket recirc - albeit for limited applications beyond many of us.