Buckrogers

Is there a difference or are the above the same?

Excuse my lack of knowledge!

TIA

flat4_ire

same thing man, americans just call em blow off valves!

corradoboy

"Blow off" is usually refering to a Vent To Atmosphere (VTA) type dump valve, due to the sound they produce. Scooby's are fitted with a Recirculating dump valve which has very little sound but is better for the engine.

JCScooby

does that mean my bailey dump valve that gives an almighty whooooooosh aint a recirculating valve and is bad?

corradoboy

There are some aftermarket recirc valves, but not many. If you hear a big whoooosh then you have a VTA, and yes, there are issues which are frequently hotly debated on here. By releasing air from the system, the car briefly overfuels which can lead to borewash (unburnt fuel being pushed past the piston rings removing the lubricating oil film) and oil thinning. The fuel will often then ignite in the exhaust (moreso in decats) causing the pops & bangs you sometimes hear. If you still have cats they can be damaged by either fuel contamination or shattered by the explosions. Also, the recirculated air is used to help slow the turbo in a controlled way. With a VTA, the turbo can be suddenly stopped by the drop in pressure and can shatter. Many people who have returned to an OE recirc valve after using a VTA report that the car runs smoother and seems more responsive. The only real justification for one is if you are running big power with very high boost levels and the OE unit leaks pressure. Oh, and they are very chavy

pnbond007

iTrader: (1)

I have a Blitz D/V on my 93 WRX-RA it's a bl--dy nuisance, being quick and geared to sprint it's always on the woosh, sneak drive is very difficult to achieve.

What would be the best solution to avoid this noise without compromising power, if power would be compromised by using original outlet...

corradoboy

As I said, if you're not running excessive boost for massive BHP, then the OE item will probably be the best solution. I don't think there's any power advantage to be had from any aftermarket DV unless you need one to cope with high boost pressures.

flat4_ire

hks ssqv, lovely sound, love em
get one if u aint got one

Buckrogers

Thanks for the info, very interesting read.

Buck

mgcvk

Nice reply Corradoboy. I think thats the most succinct answer I've seen on this recurring question. If you want fewer miles to the gallon and less performance go vta!

Aztec Performance Ltd

iTrader: (234)

Nonsense about less performance.

Usual scare mongering. Bore wash blah blah

corradoboy

Please explain ! If the OE unit is not leaking any pressure, and negates overfuelling issues along with allowing smooth spool down of the turbo, exactly where are the performance benefits of a VTA ? They are not increasing boost, benefitting fuelling or turbo performance, so where is the advantage ?

Aztec Performance Ltd

iTrader: (234)

First of all where exactly is the loss of performance?

corradoboy

The turbo stalling, the overfuelling and the backfiring.

So, where is the advantage ?

Aztec Performance Ltd

iTrader: (234)

Turbo stalling...how?

Overfuelling...how does this effect the performance?

corradoboy

I notice you aren't answering any of my questions

The turbo can stall when one side sees a sudden drop in pressure.

Overfuelling leading to ignition within the exhaust system (backfire in old money, pops & bangs in acceptable modern terminology) upsets the flow and backpressure of the exhaust gasses.

Come on Bob, justify the VTA performance increases

Aztec Performance Ltd

iTrader: (234)

If you look back and read you will notice that I do not state that there are any gains, only that saying there is a loss in performance is nonsense, which it is.

We both know its nonsense about the turbo stalling and overfuelling upsetting the backpressure of exhaust gasses.

corradoboy

So why do many people report that their cars run better after returning to an OE unit ? Do you seriously believe that efforts put into achieving a freely flowing exhaust will be enhanced by an explosion, which forces both out through the exhaust, and back to the exhaust valves ? Will a fan (which is all a turbo is) operate at its peak when there is a sudden and extreme variation in pressure in part of its flow ? Is dumping a disproportionate amount of fuel over air into an engine a sensible and mechanically sympathetic proposal ? Is making a noise like a bus opening its doors not a bit silly ?

Gridlock Mikey

I ran a VTA for about 4 years (about 75,000 miles) and all is well, you get used to it etc. I had a tek 3 done and to make the mappers job easier, it was suggested that I stick the recirc back on. When i drove it home the car seemed smoother and less frantic. It was a placebo moment. The car wasn't any bloody smoother just where my ears were expecting the whoosh it just didn't happen and it gives the illusion of your car being quieter inside ergo smoother. Like driving a renault laguna or something.
Anyway, did about 3,000 miles on the recirc, absolutely NO difference in fuel consumption, but I missed the VTA so I pulled over in a layby, spent 2 mins popping it on and Whoooosh hey presto, a car that pops bangs farts and hisses in ALL the right places. Is it quicker? Nope, smoother, Nope, more fun YEP
All this bollox about pressure drops increases etc, it's a TD04/5 for crying out loud not a Harrier Jump jet turbine. Now if they experienced back pressure, i'm sure it would be a problem

~~ Cal ~~

I have a TurboXS RFL and it's fantastic.......I dont care about MPG and I'm not too concerned about borewash although it might be an idea to increase the frequency of oil changes.........

All this chav talk is just bollox - whether we like it or not as far as the general public is concerned Scooby owners are the biggest chavs of all i.e garish spoilers, big scoops, vents, wheels, exhausts............if you love the sound of them then go for it ! The Baileys isn't particulalrly loud but does sound quite nice. The HKS makes a nice whistle like noise and the sound can be adjusted by using adaptors ( dunno there real technical term). The turbo XS is feckin' LOUD - I had to spin the trumpet of mine to 90° as it started blowing a whole in the underside of the bonnet material

Cal

Aztec Performance Ltd

iTrader: (234)

Faulty, badly set-up cheap d/vs


Exhaust valves?

Its not a fan and does not stall as a result of a vta.

How is that any different to running rich (which is how most cars are mapped)?



Clutching at straws?

Newbies dont need to be scare mongered into thinking vta's are bad for their cars and will result in a slower car, by this regurgitated nonsense.

I have run with and without for a few years and I know which one is best for me

WRX Blues

I think I am right in saying that dumpvalves incease HP much more than blow-off valves?!?! My dumpvalve added at least 20 horses!

corradoboy

Aztec Performance Ltd

iTrader: (234)

I think you missed the ''

WRX Blues

Spot on Bob'5!

Wmscooby

iTrader: (24)

I keep reading these debates about d/v's i fitted a Blitz to MY01 WRX and i can honestly say not being technically minded that no its not smoother but the pick up seems to be instant.
Hey you may not believe me but im just stating what i feel, coupled with my PPP it feels good

Mark

P.S. Kids love the sound

philthejuggler

FWIW - I bought a Bailey Motorsport DV12 for my new age (54 Plate, early '05). I had it fitted by the outfit that supplied it and immediately felt on the drive home that the car had lost its 'edge'. Felt as if I had filled up on tesco unleaded instead of optimax. I was also a little annoyed that the Bailey hissed on anything except granny-style driving.

I took the Bailey off as soon as I got home (replacing the original dv) and went for a burn - the performance was straight back to normal. I must stress that I had not read about any adverse effects of VTA's before and my Scooby garage had categorically told me that there would be no adverse effects so I wasn't looking for a performance decrease - it was just obvious.

I have since read countless tales of people putting the original back on and noticing a performance increase. One of these people is a reputable Scooby supplier (of DVs amongst other things!).

If there is some psychology involved, I suspect that it is this: People are so delighted by, and concentrating on the new noises coming from the engine that they don't notice the performance drop.

Final point - after my experience I'm dis-inclined to try another DV, but I have heard that there are some which both recirc AND vta, but only vta under extreme boost so perhaps they would not have the same negative affect on the performance.

Phil