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iTrader: (1)

I am interested in buying a dump valve for my MY01 can any 1 recommend any and are there any pros and cons in having one

corradoboy

Pro's - Sounds like bus doors opening every time you change gear.
Cons - Sudden drop in air pressure fools the AFR sensor which can lead to failure, the drop then causes the ECU to overfuel, which causes the pops and bangs through the exhaust as some of the unburnt fuel ignites in the exhaust. The rest of the unburnt fuel gets pushed by the compression through the piston rings and dillutes your oil, reducing engine lubrication and potentially causing major bearing failure.

You've already got a dump valve. It's just a recirculating one that doesn't confuse your engine with potentially catastrofic and expensive results. I'm not saying this happens to all engines with VTA DV's, but it can and does.

I'd recommend spending money on handling enhancements and driver tuition. There aren't too many drivers out there who can fully utilise 220+bhp on the road (inc. me).

wakeboardar

did you know you already have a decent dump valve

topoff

iTrader: (1)

thanks, I did not know I suppose I just like the large whooshing noise and presumed it didnt have one

decent makes out there HKS, Blitz i suppose

chris singleton

I've just ordered a HKS BOV from www.stiracing.com

The general consensus would appear to be that vta's do cause overfueling. If this leads to diluting the oil, presumably more frequent oil changes will help reduce problems?

Chris

RLE

iTrader: (2)

Would be interesting to poll and see just how many people had had engine problems due to the dump valve (and by problems I mean failure).

I appreciate that there will no doubt be instances out there but it surprises me that so many tuning companies have them on their own cars.

greasemonkey

It's virtually impossible to attribute the cause of failure directly to a dumpvalve. Bore wash/oil contamination tend to be gradual processes, and thus the only way to accurately measure the consequences would be to build two identical cars, one with a recirculating DV and the other with a VTA, put them on identical driving cycles and periodically strip the engines and measure cylinder and general wear, as well as oil condition.

You can't see the underlying logic behind tuning companies fitting their show cars with the products they sell?

WRX Wannabe

FOR: sound more like rally car

AGAINST you WILL use more fuel as you KEEP changing up and down through the gears to get your woooooosssshhhh

Have a look in HERE come along to a local meet and have a chat with some of the guys who have them fitted to their cars

greasemonkey

Lol at the clueless comment. The proper Impreza rallycars don't have dumpvalves, so if you want yours to sound "more like" one, the thing to do is remove the dumpvalve and blank the connections, not waste a load of money on something that impairs the proper running of your engine.

WRX Wannabe

MEANT as general comment that IMO sound MORE like rally car

So if they are so bad WHY do so many SUBARU drivers have them?

greasemonkey

Presumably because either

a) Those who have them think there's a performance advantage to aftermarket dumpvalves (and many old wives tales surface here to that effect)

b) Those who have them just want the noise and either don't know about or don't care about any potential downside

Brun

I'm a B then

WRX Wannabe

Yep me too(B)

Mine is coming from Japan next week

ChungsterSTI

I'm a B too.

And i#ve managed to get over 240 miles on the last tank of fuel.

So its about the same as before on the std dump valve.

But I do find myself boosting up and changing gear more often just so that i can get that whoooooooooooooosh!

16vmarc

I dont have an aftermarket DV, but i notice that aftermarket recirculating DVs are available. What benefit are these over the oe item?

greasemonkey

No benefit at all in most circumstances. Most of them are nice and shiny so would have some "bling" value, if that's the thing that floats your boat.

Some of them may also work better in situations where the standard valve leaks under boost, although you'd need to be running lots of boost for this to become an issue.

Some of them are user-adjustable so you can preset the level at which they open, but largely though, they're just an excuse to separate you from your hard-earned.

16vmarc

At the nd of the day if it was meant to have a VTA it would have one as standard!.

greasemonkey

Correct, to a large extent.

OllieC

What an absolutely ridiculous thing to say. Presumably you’re joking? Should we all keep our cars as standard?

I’d be very interested in hearing some more justification based on science rather than assuming that car manufacturers are logical…

greasemonkey

Jeesh Ollie, there's plenty of technical explanation why recirculating valves are preferable, further up this thread, and elsewhere around the various forums.
Either have a quick browse, or, now it's working again, click the Search button.

MR Fusion

An interesting thread, as there's an identical one that keeps coming up on the MR2 forums, which also mention the possible long-term damage to your engine due to 'confusion' from the ECU over unmetered air, etc.

I had a dump valve on my last car, and loved it. There's a certain generation that still finds the word 'Turbo' macho for cars, and I guess the sound of the dump valve going off just keeps reminding the owners that they're driving a 'blown' car. Also the 'Look at me! My car has a turbo!" factor. Guilty as charged, m'lud.

Would I put one on my Scooby? Hmmm...still undecided...

MadGrip

I think it all depends on the kind of person you are. I think the borewash theory IMHO is a bit OTT although understandably it could happen over a long period.

so your either

A: a person who wants there car to run the best it possibly can , regardless of sound & image. (MODIFIED CAR/STANDARD VALVE)

or

B: someone who knows no different and isnt any kind of enthusiast. (STANDARD CAR & VALVE)


or

C: Someone who likes to show off and say "look at me " (VTA VALVE)

All IMHO you understand

OllieC

Sorry gm - didn't mean anything by it - your comments have been by far the most informative... I just think that the "if that's the way it's meant to be, that's how it'd be made" argument is funny. (I shouldn't fly as I don't have wings, If I wasn't meant to eat meat, why am I holding this burger, if I was meant to walk, how come I can drive? etc...). I was mainly criticising that method of discussing/arguing/explaining...

The thing I don't understand (from this thread) is why having a DV that releases to atmosphere is so much worse than one that releases to that big fat chunky hose that seems to be connected to the turbo... is there a signifacant difference in rate of pressure drop and if so, how different is this? I admit that I haven't searched yet (will in a mo) as I'm a tad out of the habit...

Off to watch a bit more about Thalidamide now (something about releasing stuff to the mass-market before the full consequesnses were known and the subsequesnt damage that was caused... ahem).

greasemonkey

Admittedly it might have more humour in it than Marc intended, but in this case his line of argument is correct. A recirculating dumpvalve is the best choice for a metered airflow based ECU.

The rate of pressure drop isn't the issue. The real crux of all this is that with a metered air system, the ECU's fuelling calculations will only be correct if all the measured air actually gets into the cylinders. You achieve that with either a recirculating dumpvalve, or no dumpvalve at all. Switch to an external venting DV, and the whole fuelling applecart gets upset.

Aren't we all? Still, at least the search works the way it's supposed to now!

pslewis

Come now ...... what do you all HONESTLY think when a car comes past you with a Dump Valve to Atmosphere???

You think, "What a complete and utter *******" don't you?

WHY would you want to join the Nova boys anyway??????????????

Keep It STANDARD Strategy ( KISS )

Pete

OllieC

Uh-Oh - Time to run, Pete's joined in... bye-bye interesting thread...

Pete - have you ever posted with the aim of being constructive? Even when you're funny you're still a bit irritating.

Jay m A

iTrader: (2)

Although Pete does have a point

I snigger as a VTA gear change goes by irrespective of vehicle manufacturer, in the same way that I snigger at people wearing sandels

Having said that I purchased my car last weekend, with a dreaded VTA attached. Christ did I cringe on the way home LOL

I actually BOUGHT an OE recirc and stuck it on today. I'm sure there are loads of free ones knocking about in peoples garages, but I couldn't wait a minute longer to get rid of the thing.

So who wants a VTA dump valve? Its of unknown origin but looks the part. Its great, really shiney and goes psssst

SCOOBY TOWERS

iTrader: (7)

If its free - I'll have it .
I'm sick of the kids in our street saying " get a dump valve mister !" and me having to reply " its got one that recirculate air thats why you can't hear..................."


huh where have they gone ?


I'll stick it on and tell them I've removed the "ultra flow foo foo valve" - that'll give em something to discuss in the playground.
I can see it now - "impretza's come with foo foo valves - not like them cr4p cossie 's !"

Dan J

Hi all, very interesting thread this. When I bought my MY00 last summer it had and still has a Forge VTA dumpvalve on it. Personally I'm in the camp that isn't bothered about the pssst, in fact I occasionaly find it a little embarassing, so now reading that it can if anything harm the running of the engine I think I'll def be looking to take it off and try to source an OE one to replace it with.

It is a bit Max P isn't it, whenever I hear a car go by my office and psssst it's inevitably a Max P'd motor!

Dan.

ChrisB

Guys - please keep the thread on topic. If you want to trade insults, do it else where like Fight Club.

Chris.