Im collecting my 1st Impreza Turbo on Sunday and fancy getting a atmospheric dump valve. Its a standard 99T wagon. Which one should i buy and what do u think i should be paying including fitting ?

 

hks ssqv dump valve ive got one on my 99 turbo would cost over £200 brand new but you might get a second hand one for about £150 its easy to fit takes about 30 mins tops do a search for hks

 

Probably better off putting the money towards things that'll make a difference on an otherwise standard car, imo......the d/valve will just be noisy, nothing else! If you plan to mod it, buy a knocklink first.....not a very exciting first purchase, but for circa £150-£200, could save you thousands. Even a standard car can benefit from this.

 

Silly question, but why so keen to screw up a car you've only just bought?

Think you should spend the money on something that will actually make your car work better, rather than waste your money on something that will make it work worse.

If you must have one, it doesn't really matter which you get as they're all largely as bad as each other.

 

Didn't want to put as fine a point on it as GM, , but for future reference, if he answers your query, there's a vicious rumour going around on here that he may know what he's on about!

 

HKS

 

Shhhh, don't tell him that - I'm trying to sell him mine

For the record I haven't seen any activity on my new KnockLink because of the HKS SSQV, so I it's unlikely it will do any damage. But it won't contribute anything to the performance either.

S7EV3N, you have PM.

 

Eh? Excuse me if I'm missing the logic behind that comment BiJ, but is there any chance you could explain it?

A KnockLink only detects extraneous engine noise. It doesn't detect overfuelling, bore wash, plug fouling or any of the other symptoms that venting dump air out to atmosphere can cause. It would be somewhat surprising if a KnockLink did register any change in behaviour after the fitment of a VTA dumpvalve. An AFR meter, on the other hand, probably would demonstrate the differences, provided both it and the lambda sensor had sufficient range and display resolution.

 

I thought there had been suggestions previously about the possibility of det due to a VTA dump valve? Not initially when you get over fuelling but if the lambda sensor detects rich running and leans out the mixture just as you open the throttle again leading to lean running for an instant. I don't think this does happen as the KnockLink picks up nothing.

As for bore wash etc, it will happen to some extent, which there is no up-side to, but I have not seen or heard any evidence that it indeed causes long term problems. You might remember we talked about this before and you said you'd try and find out if there was any evidence of long term damage due to VTA dump valves. As you never came back to me I assumed you hadn't found any evidence.

If you have now found some evidence there are long term problems, please share with us. I'm not having a go, I am genuinely interested in knowing whether there is real damage being done or whether it is so trivial as to have no long term effect.

 

Not to my knowledge. The main downsides of this sort of modification have always been overfuelling, and the consequences thereof.

I don't think it happens either, which is why your observations of the KnockLink aren't really relevant.

Exactly. There's also reduced response on reapplication of the throttle, which is a direct performance demerit, so why bother? If you bought your Impreza because it's a performance car, why fit something that dulls the performance?

It's more the case that I'm not in a position to go looking for it myself, and that the people I spoke to about it don't have direct access to any figures that FHI have.

Unfortunately, scientifically accurate evidence is difficult to find. Whatever Subaru have done on the subject isn't available for public consumption, and it's not like the aftermarket dumpvalve manufacturers will devote large amounts of money to long-term independent testing.

My view on this issue is fairly simple. If you know that there's a downside (no matter how big or small) to something, and there's no actual gain involved, the downside clearly outweighs the benefit (because there is no benefit), so don't do it.

As mentioned in my original post on this subject, if the original poster wants a wheezy dumpvalve, it largely doesn't matter which one he chooses. The reason why I worded that post the way I did is to make sure that he asks himself the question of why he wants one, before he goes and wastes a load of money on a product that will, in all likelihood, make his new performance car perform less well.

 

So should i put the standard dump valve back on my car instead of the special dump valve Forge made me for my car

 

mind you come to think of it, it is a recirc!

 

i've noticed this, ever since i said i was going to fit a VTA d/valve to my scoob, i haven't had a single greasemonkey reply to any of my posts *sniff*,wipes away tear.

don't worry GM, it's coming off soon, had my fun, scared some elderly people and i'm now bored with it. roll on the reift of the std d/valve wo-hoo

 

That's absolutely correct if one's primary concern is performance, but there are clearly plenty of people who are happy to forfeit some performance to make a style choice, whether a wheezy sound effects, body kits which add weight and increase drag, or supersize wheels which increase unsprung mass. Each to their own.

If anyone wants to make a non performance style choice, I'm still flogging my HKS SSQV

 

That was only because I was paid to put you on my ignore list!

 

Has my initial comment about the KL been understood....it seems not. I only mentioned that the purchase of one was relevant with regard to ANY subaru, and that, as a first mod, it made more sense to spend money on that than a DV....no suggestion, as BiJ seems to think, that I would advise someone to purchase a KL as a safety measure after fitting a none-standard DV.
Bet you wished you'd never bothered asking now eh, S7EV3N?

 

a reply hurrah! and i've still got the dreaded VTA on the car at the mo your standards are slipping mate

BTW how much were you paid? free membership to muppets for life?

 

Correct, and as this is the technical part of the site, my focus was on performance and I approached the thread from that angle (as did MicaRed). If this was the styling forum, I'm sure the folk there would have approached the thread accordingly.

Of course, hence my "if you must do it, they're all as bad as each other" comment.

On the contrary, it's excellent advice, and, as you say, a far more worthwhile way of spending some pocket money on the car.

 

It wasn't misunderstood by me.

Totally agree.
No I was referring to a thread many months ago which I can't find now. I wouldn't have fitted a VTA dump valve to my car, it came with it on already. The novelty effect has worn off long ago so I'm making a performance mod to go back to the standard recirc valve. A KnockLink would be a good first step before any performance mod.

 

Fight......fight....fight !!!!!!!!!!!!!!!!

 

Lol, check out the newbie!

 

Have to agree with The mighty Greasemonkey about VTA Dumpvalves. I've owned a Scoob for a year now and always read scoobynet, but a few months ago I thought sod it and wasted a £140 on forge vta, sounded good for the first few weeks untill the missus pointed out that it sounded like a air brake on a bus after about a month the car started holding back and just didn't feel right, so I stuck the standard dv on and hey presto all back to normal.

 

Having had both VTA and recirc DVs on the car (now recirc) both types exhibit richness on lift off (logged by a wideband). I'd put this down to the same fact... the car fuels for a given amount of air (which is measured by the MAF) on lift off this air doesn't go into the engine. In the VTAs case it is vented to atmosphere and in the reircs case it goes back down the system to pre turbo. So as i lift off both types of valve show the AFR go richer and i get pops and bangs on lift off from both types too. Ok the recirc keeps the air in the system and so going on/off the throttle mid bend etc is smoother with the recirc (reason i went back to recirc) but i can't see why one is considered far worse than the other for overfueling, bore wash etc. My wideband logs show this not to be the case.... all IMHO.

Tony.

 

BiJ, fair enough, fight with you some other time?

 

Tony,

The recirc puts the air back in *after* the MAF, keeping the already metered air in the system. The change you're seeing is likely caused by the reverse direction shock wave of air the stronger spring in the Forge is causing (coming from the wrong direction, and confusing the hell out of the MAF ). Can be felt as a judder on sudden lift off from boost.

It gets much worse if you block the dump valve off altogether, but the benefits outweigh the drawbacks (for me, anyway!). The compressor blades make a bit of noise though Don't try this on a VF series turbo

Richard

 

I understand it goes in after the MAF... the point i'm making tho is it doesn't go into the engine at the point in time that the ecu has fuelled for. Whether it's in the system doesn't matter.... it's not in the engine where the ecu has just fuelled for. The reverse direction of air confusing the MAF will not cause the AFR to go instantly rich on lift off.... may have effects but not the one i'm seeing (plus at the moment i'm using the oem recirc and get no judder).

Tony.

 

Changed from a HKS VTA back to the oem and find the car to be much smoother and I get no judder when lifting off now either. I must admit I enjoyed the tsssching for all of a few weeks and soon found it getting on my nerves. However I have gone the full Hayward & Scott Nonresonated Exhaust....now that is a sound I like to hear

My advice forget the VTA and get yourself a decent Exhaust system if you haven't already

 

Fair enough Tony, my comments relate to MAF monitoring (and their results) rather than AFR.

OEM recirc doesn't cause judder because spring is very weak - do you still see the rich AFR's with the stock DV?

I assume that shutting the throttle closes the injectors unless (or because of...or a mixture of both) MAF signal suggests there's still flow (which requires fuel).

Richard

 

sorry you guys are going totally off topic with circumstantial evidance with that the vta would damage a engine. the question states "which one should i buy", its nice to know what the vta might do and help a newbie but if the guy wants to buy one then which one?

 

I think that the Baileys VTA is a good value for money VTA Dumper. I do believe JW Racing is doing a deal on the Baileys VTA at the moment ?

Sorry for going off topic by the way (wrists firmly slapped)