OK, I've read all the warnings of cars not running right, there being no benefits, keep the original recirc one on the car etc.etc.

But what experiences do people who actually have them on their car have?
Any running, reliablitiy or other issues?

Most of the advice seems to come from people who dont have them, then at NBO I notice a lot of cars run VTA dump valves - so are they really that bad??!

My cars a late MY98 UK turbo if that makes a difference.

 

I have a 50/50 VTA / recirc DV on my car, I was sceptical as to whether changing the OEM one would make any difference, but I went for a GFB Hybrid and was actully suprised at the difference that happened on my car (can't say about others) my car seemed to repsond a lot quicker, spoolup seemed quicker as if it was holding boost in reserve, the noise is a bit of a pain in the **** but I can live with it.

I am not an expert but to me changing the DV made a big difference to the cars response, maybe not performance but engine response.

but I am waiting to be criticised and told I am imagining it.

My car is an MY00 Impreza saloon.

 

what year/model do you have ?

 

You might not be imagining it, but it's not all good news.

There are two possible explanations for what you are experiencing:

1) The spring in the original valve had lost its temper and was leaking.

2) The new dumpvalve is adjusted in such a way that it stays shut when a standard one would otherwise be open.

In scenario 1, your car is now working properly again, whereas on the old valve it wasn't.

In scenario 2, you are gaining in terms of throttle response, but increasing the stress on your turbo, with possible consequences for its working life.

If all things (i.e. opening pressure etc.) are equal, an aftermarket dumpvalve can't possibly make your engine performance better. That is not the same as claiming that what you're experiencing is impossible, as illustrated in the two scenarios above.

That might be because most of the people you're talking about have had them in the past and taken them off!

As for many of the cars at the Northern Big One having VTA valves fitted, I'm not quite sure what you think that means. That probably says more about the type of owner who takes their car to a Subaru day out than it does about the plus points of VTA dumpvalves.

 

I have been running with a Bailey Motorsport VTA for over a year now on my WRX import MY93 (it was on the car when i bought it) and have not had any problems at all...idling is perfect and fuelling according to the AFR meter is OK.
I have had the car run on the rolling road and the fuelling did not cause any concerns,the car is used every day in all weathers and the MPG is 'normal'

I have been in the motor trade for over 20 years and have never heard of an aftermarket dump valve causing any problems....however i am sure i will be told the contuary regarding Subaru's

It's a bit like the 'Marmite' subject you either like them or hate them.

steve

 

Both me and my girlfriend have had Forge VTAs on our Scoobs - a 02STi and 99 Turbo. They did not appear to improve performance and just made a pssst noise and the odd pop from the exhaust on changing gear. After about 18 months we decided to remove them because of possible engine damage problems and we both remarked that our cars now seem to be running better with the original dump valves fitted, i.e. smoother when coming on and off accelerator.

I have just sold the new age VTA dump valve but the classic one is still up for sale!

Alan

 

i have a uk99 with a couple of mods and i have a blitz supersound dump valve, been on for 2 years

 

edited due to being the morning after the night before

I was a tad anebriated(sp), stressed and tired when I reacted to what quicksprint posted.

My apologies to all concerned.

Steve

 

Good grief! Here's some more bollox! I fitted a higher end of the market VTA dump valve to my previous MY03 WRX (curiosity got the better of me). When the novelty of the sound produced wore off (lets face it this is why it was fitted in the first place, with many justifications about theoretical performance enhancement), the standard recirc valve was put back on. The difference in performance of the car was quite remarkable on return to standard. This underlines the statements above that it is not a mod which enhances performance, but actually detracts. This is just one subjective example. A statistitian may require 20 or so to perform the same experiment with lots of fancy engine monitoring to come to a definitive conclusion, but i suspect the outcome would be the same. If it is an aesthetic motivation, fair enough.

 

Steady on old boy, you're getting unnecessarily aerated there. Don't think anybody has said that "any aftermarket part" is not good enough for these cars. There's plenty of non-OE stuff on mine. We're talking one specific part here, and in this one specific case, the standard one happens to do its job very well, to the extent where it is very difficult for any aftermarket part to actually function better.

Lol, companies all over the world make large fortunes selling you sh*t you don't remotely need, so why does it surprise you that the same thing happens in the motor industry?

Somewhere on this planet is the factory (no doubt several) that makes huge fork off Max Muppet spoilers. Does anyone remotely need such a thing? No. Do they have any positive aerodynamic effects? Usually no. Why do they exist? Because there is a market for them, simple.

Say again?

Eh? STi's come down the same regular Subaru production line as the "normal" Imprezas, and have the same DV as the non-STi models of the same year, so not sure what you're getting at there.

As far as Prodrive are concerned, it's probably notable that (I believe I'm correct in thinking) every limited edition roadgoing Impreza that Prodrive has ever had an input on has kept its standard dumpvalve. The RB5 and P1's were the same as fitted to the STi5 and 6, which was the same one fitted to MY99/00 Impreza Turbos. The WR1's is the same type fitted to all MY04 cars. If P. don't think it needs changing, then it probably doesn't.

Come again? I know you're not referring to me there Steve, but that comment seems more than a little unwarranted, especially in the context of this specific thread.

Of course all cars are built down to a price, and there certainly are areas where the Impreza can genuinely be improved. However, there are equally plenty of areas where marketing bullsh*t and peer pressure create more sales than anything else, and dumpvalves are a perfect example. The DV's Subaru have used over the years have tended to be very good, and there is basically no room for improvement. Something like headlights, on the other hand, are a completely different kettle of fish...

Most of the aftermarket Impreza DV's are sold either with a stack of marketing crap (step forward Blitz, HKS, Turbosmart etc.), or simply on the basis that they look prettier than the standard one. As for why aftermarket tuning companies sell 'em, well, that's because there's plenty of people out there prepared to waste their money on them.

If I owned a tuning shop, I'd probably stock some too. I'll tell the potential buyer what the consequences of fitting one are, but if he still wanted one, I'd happily take his money.

 

QUOTE:Come again? I know you're not referring to me there Steve, but that comment seems more than a little unwarranted, especially in the context of this specific thread.

Greasemonkey.....it wasn't me that made those comments

steve

 

Agree with what Lemmy has said above.
Fitted a VTA dump valve 2 my old 01 bugeye wrx yes i admit it was mostly down 2 the sound. Going back 2 OE valve for trading in showed it up.
Until then had been thinking about one for the WR1 but now i've got it i will be leaving well alone.

 

I have to say I've noticed 3 different depending on what's been used.

When I first changed to a vta (HKS marketing all the way) I did notice an improvement between gears, not nearly enough to warrent the cost mind you! Also the car never drove quite as smooth as it once did.

It's worth a mention I was doing around 500+ miles a week at this point, and I'm sure you know, you really get the feel for a car when you're never out of it!

When blanking the hole completely the car responded like the vta, yet was as smooth as with the oem (I soon returned to using the vta for safety).

Now with a much bigger turbo, using the vta gives much less lag through the gears than having the valve blocked (for other reasons) although anti-lag more than makes up for it .

Dave

 

Dave - warning - anti lag will kill your turbo......eventually ! Every pop and bang is like someone hitting the thrust bearing with a hammer, the oil wedge ramps will eventually cease to exist and the bearing will fail. May take some time to happen, who knows

WRT dump valves, it is worth remembering that the valve also has a part throttle duty in addition to its 'lift off' duty. The OEM dump valve is partially open during high speed cruise, this reduces the load on the turbo and ensures that the surge line on the compressor map is not breached.

Fitting an aftermarket VTA DV can do one of 2 things.
1 - It can open at the same or lower differential pressure as the OEM, protecting the turbo but venting previously measured air to atmo, this means the engine over fuels which may or may not be caught and corrected by the closed loop fuel control, depending on the engine load.
2- It can open at a higher diff pressure which will increase the backpressure on the turbo, this will run the turbo under more load and closer to the surge point even when you are not using the boost.

Andy

 

When people say they run "smoother" with the OEM DV, or after they take off a VTA dump valve - what do you mean?

Smoother accelerating, idling, cruising?

Cheers

 

Andy, my anti-lag is very mild, It hardly ever pops and bangs, just sort of gurgles. And works at a slight vacuum.

My only real concern was egt's not being able to recover off throttle. Should I be more worried? It's hardly ever used anyway to be honest.

Dave

 

If the pops n bangs are infrequent then you should be ok as long as the EGT's are not silly ?

Andy

 

Once again is an after market re-circ bov worth fitting over oe one,simply because it's alloy and not plastic.Have read all the recent thread's on dv's and come to the conclusion an atmo is no go for me (this time)can the plastic one start to wear out/leak quicker than an alloy one? not interested in bus noise's,just improving my car is what i'm after.

MIKE...

 

If it's not leaking yet, why bother? It should be ok at standard boost of just above, after all thats what it was designed for

Dave


Oh, and i cant be sure of egt's so it doesn't get used much.

 

Just dragged this up, come back Greasemonkey we miss you!

 

my 94 wrx was already fitted with the hks ssq dump valve when i imported it and ive never had any fueling probs. the car is very responsive and my power fc tells me everythings ok.

 

What about one of these - does the fact that is adjustable get around some of the problems as above ?
I've got one sitting here and debating wether to put it on my Foz..



GFB Stealth FX New Age Impreza
WRX Stealth FX is a direct bolt-on replacement for MY01 Subaru Impreza New Age models and onwards. Everything you need is supplied in the kit for quick and easy installation. Only the Stealth FX allows you to go from silent and unnoticeable to ear shattering in a matter of seconds!By utilising a unique air diverting system you control exactly how much air you dump to the atmosphere for noise, or the inlet for silence. By sending the vented air back to the inlet (rather than muffling it), there is no restriction and the valve still operates at maximum efficiency.For cars with sensitive air flow meters, the valve can be tuned to vent just enough air back to the inlet to prevent backfiring whilst giving the loudest possible blow-off noise

 

I'm fitting an STI8 I/C to my MY00 classic this weekend and my VTA won't fit so putting the 8s OE valve on.

Can't say I'm too bothered. I like the DV noise (sorry but I do) but I can't stand the jerky on/off throttle response.

 

My experience is almost the same - Had a Forge VTA on for a while - swapped back to the original and car felt much better. I think it comes down to thinking the car is better just cos you've spent money on a new part that goes whoosh!!!

 

got one and want to take it out

no running problems at all (idle is fine and all that)

i think i lost a bit of power tho

dont get the "rush" when boost is on full...