as it says, ok me being dumb, but would like to know which is the best for certain cars and for me to know what to buy.

VTA, recirc. or standard??

At the mo, I'm standard running a full decat and 15-16psi of boost on a MY01 WRX

Rice Rocket

 

Standard is best unless it is leaking or you want noise, jerkiness, crap idle or flames, poor mileage and degraded oil quality.

At this level of boost, only a rice boy would change it

In terms of what they actually do - they relieve the boost pressure from between the compressor and the throttle plate to prevent compressor surge. They therefore prolong the life of your turbo, and some would argue they increase lag between gearchanges. Conversely some would argue they stop the increase in lag you get from stalling the turbo.

They have a pneumatic feed from after the throttle body which acts against usually a piston or diaphragm which has pre-throttle body boost pressure acting against it. The strength of the spring determines how much the piston moves with the pressure difference across the throttle body. A stronger spring is more like running no dump valve, a weaker spring vents or recirculates the gas more easily.

Recirculating the gas into the intake increases the pressure before the compressor wheel so the effort put in by the turbo is not totally wasted and causes a reduced pressure ratio across the compressor wheel for a short time, so less exhaust back pressure, charge temperature, better spool up in the next gear. Venting the gas causes a noise, and the MAF sensor signal causes the ECU to continue to fuel (excessively) because it has metered this leaked air, so there is a transient overfuelling which causes pops and bangs, sometimes flames. It can also dilute the oil quality which could potentially reduce its protective effects on your engine. The upside is that the backside of the MAF sensor is not shot with a hot jet of oily gas.

Some of these effects are controversial, based on my opinions, and the effects I assert may not be measurable or important. You did ask

[Edited by john banks - 2/23/2003 11:29:39 PM]

 

Thanks John,

Back at standard at the mo


Ricey

 

On that note John, I went from stnd to Bailey to stnd to APS recirc.

With resonator removed from airbox and an itg panel inserted the 'noises' I was hearing varied.

Bailey sounded like a bus. Stnd with res. removed sounded like wastgate flutter with a lot of noise coming from airbox. APS sounds loud under load but airbox noise has gone. APS pops and bangs like mental though!!!

Did experience idle problems at first with APS, however samcos have helped.

Check airbox and MAF all the time with no adverse effects so far!

So what people want to hear is, being a tart won't kill yer motor??

KH on the 8th???

 

this is the reason that im debating weather or not to actuly fit one to my new car

from what i read they basicaly make them run crap and give u a noise!

but this over fueling could be usefull to stop the car running to lean? would that help with det??
excuse my crappy scooby knoweldge lol this is my 1st one and my first turbo petrol car

my current car is a vectra diesel running about 1.35bar boost and its NOT runing a dump valve (no point what so ever!!

help
would there be any benifits in a uprated recirculating one or maybe a piston type vent one (shouldnt give any leaks and stuff?)

i pick my my97 wrx up tomorow and have been offerd a load of bits including airfilters (dont want one will break the maf i belive) dumpvalve (still aint sure on them) tracker system (ill be having this fella me thinks lol) and other bits and bobs

what do u think
yay or nay, dont really want one if all ts going to do is makea noise and make it run crap lol

i have a mate who swears his boost pick up was much better with one instaled

 

VTA DV more likely to carbon up your piston crowns and make it det that way. More fuel on the over-run will not stop detonation on full power, and the degradation in oil quality is more likely to increase engine wear.

 

OK then, what will a recirc. DV do to the car then?

Sorry for being thick

Ricey

 

Ricey

John is, as usual, right. A VTA dump valve does cause noise, overfueling, and hence (on a full decat) pops, bangs and flames. Only a big kid would fit one - like me .

However, any recirc DV will put some oil through the MAF, but will increase the effectiveness of the release.

The next issue is whether the standard valve is good enough - it can (with suitable plumbing) be used either as a VTA or recirc. However, it is difficult to adjust and is on the edge at the sort of power you must have. Choice past then is down to your trust of manufacturer - I'll not get libellous by suggesting which is better.

Duncan

 

Thanks again guys.

looks like the Turbo XS ones for sale then!!!


Ricey

 

Jesus John

Every time i read one of your excellent, and detailed tech explenations, I always feel like I need a lay down afterwards to let my brain recover.

ps I have now removed my dv, and replaced it with a Flux Capacitor.
This has cured the lumpy idle over fuelling, and is excellent for short trips to other parrallel dimensions.

Welll.. It is 6 in the morning and Ive been at bloody work all night.

LM

 

Lan Man

Are you running the full 21.1 Jigawatts through your FC?

Paul

 

"1 . 21 Jiggawatts where will we find that sort of power"

 

John,
So are you saying that fuel economy will go down with a dump valve?

 

With a VTA it will go down a little.

 

bbbhhssssss !!!!

 

I take it a VTA DV makes a noise on every gear change,does it work any different on an auto box, as the revs don't drop that much as the box goes through the gears, also the turbo does not spool down and there is hardly any lag.Some or all of the above may be wrong as I'm a bit af a novice ! I have just got my hands on a HKS super SQV sequential blow off valve, would you recommend fitting this or leave the OEM DV ?

 

<quote> Standard is best unless it is leaking or you want noise, jerkiness, crap idle or flames, poor mileage and degraded oil quality. </quote>

Yes, there are side effects but we want noise don't we??... There is _nothing_ more satisfying than that PHSSST... in between gears... louder the better to scare the **** out of poor unsuspecting pedestrians eh??

Take a look at this fantastic new product, and save $$$ on the cost of a new BOV! http://www.sunamiturbo.com/products.htm

_AND_ it has an overide so you don't even have to wait for a gear change.... Every rice boy should have one!!!

-- BarkingMad is not employed by and has no affiliation with Sunami Products!!

 

OMG I seen it all now!!!

 

From my experience of changing from standard valve to a HKS SSQV was that it imporved driveability - given practice.

It does NOT cause any of the idling probs ive heard about.

It also is not just about noise. I happen to like the sound but even if I didnt I would still use the SSQV with a silencer.

Also as already mentioned it does add the rally pop n bangs.

Remember...standard parts are made to a cost...read the descpirtion below and ask yourself if the standard valve provides the same quality.

(sorry didn't know how to do clicky thingy)

The HKS Super Sequential Blow-Off Valve (SSQV) is a dual stage pull type relief valve. Unlike other blow off valves that are push type, the SSQV will not leak under high boost conditions nor under vacuum at idle. Being of a pull type valve structure, the SSQV can not physically leak under any level of boost because boost pressure also keeps the valve closed against its seat. The SSQV is actuated by pressure alterations only, not by the rate of pressure or vacuum in the line, which ensures a quick valve response and complete closure during idle. On typical blow-off valve designs, a large valve is utilized in order to accommodate high boost / high horsepower applications. However, these large valves tend to react slowly and require high activation pressure to open, therefore are not able to activate and prevent compressor surge at light-load conditions. On the other hand, smaller, fast reacting valves do not discharge the airflow capacity required for high horsepower applications and tend to creep open and leak as the boost pressure overpowers the spring on these push type valves. For maximum performance, the HKS SSQV incorporates both a small primary valve for ultra quick activation, along with a larger secondary valve for additional discharge capacity. The SSQV is engineered to initially open the small primary valve at light throttle and load conditions, then sequentially opens the secondary valve for additional relief capacity under high boost and load conditions. The SSQV is constructed of polished billet aluminum, which ensures long-term durability and visual appeal. The mounting base utilizes a circular mounting flange that provides exception flow and complete secure mounting via a C-clip snap ring and O-ring gasket. The triple-fin discharge port design produces a powerful and unique aggressive blow-off sound along with added visual distinction.