Miller time

iTrader: (1)

Hello

Please can someone let me know if changing to an after market dump valve on an 04 STI Type UK will bug up the ECU or mess up the MAF sensor?

Can anyone recommend a dump valve? I am not looking for one that makes too much of a noise just after what it can do performance wise.

Thanks

brashy

hi fitting a dump valve shouldnt mess up your ecu or youe maf an i would recomend a hks dump valve ive got 1 on my car an they are good

Splitpin

If you change to an aftermarket atmospheric venting dumpvalve, you will confuse the ECU, yes. Probably not very much, but you will lose, not gain performance.

Sure, the standard one. They're excellent, and, most importantly, the one with the release pressure, spring tension and piston size that the ECU is designed to run with.

In which case stick with the standard one and spend the money you just saved on something which will actually improve the car. Simple.

midnight

iTrader: (10)

Standard recirculating valve are pretty good for up to 350 bhp,you can get a baileys or a forge quite cheap which will give you that bit of noise but wont improve the performance as they are vta 'dump' valves,which means they just vent the compressed air that normally flows back to the turbo,out to the atmosphere.
The hks,and blitz are' blow' off valves ,but are often called' dump' valves,because they operate in the same way as a dump valve ,but allow the turbo to freewheel between gearshifts which is a better solution.

RA Dunk

Happy searching, remember and report back with your findings

alcazar

iTrader: (2)

Hmmmmm, and you know this how?

It seems to conflict with advice from trusted tuners..........

Splitpin

ROFL. So what does the turbo do between gearshifts with a 'dump' valve then?

midnight

iTrader: (10)

Splitpin do you know the difference between the 2 ?. I knew what a dump valve was when i had 1 fitted to my cosworth back in 1987. I was a test driver for jaguar then so i liked to now as much about cars as i could, but being as you've asked i will explain:

A dump valve normally sits between the turbo outlet and the throttle body.When you go from a boosted state to a closed throttle state iechanging gear)your turbo still continues to pressure the air,but your throttle is closed, so it cant enter the engine,so the extra air puts pressure on the 'preset' spring on the dump valve and vents it to the atmosphere.Even with your dump valve the compressed air acts as a brake on your turbo(slowing it down)because the pressure on the backside of the turbo is higher than that on the front side (simple physics)

A blow off valve does the same thing as a dump valve,but when you close the throttle(change gear)it allows the turbine to freewheel which equalises the pressure on both sides of the turbo allowing it to spin up faster.Also blow off valves can be used at multiple boost settings without reconfiguration,where as most dump valves cant.

I aspologise for the 'geeky' explanation, but that is the difference between the 2,also some people use bov and have no running issues at all, i had a baileys on my car,then a forge and while both these dump valves worked,the car never felt any faster than with the recirc valve on,only thing i did notice was erratic idling,and sometimes a slight hesitation in pulling away.I have since fitted a blitz(which cost£100+than a forge) and have had no running probs at all and turbo lag is non existant.

Once again it depends on the car as some tuners say dont use them ,others map the car to the valve.

Hope this explains , I knew that that 'O' level physics exam i passed would come in handy 1day.lol

Splitpin

Strangely enough...

Lol, you honestly think that's how the standard dumpvalves on the Imprezas work, that the boosted air has to force its way past a "preset spring"? Why do you think there's a vacuum connection between the standard valve and the inlet manifold? What do you think it does?

S'alright, it was worth a laugh. You haven't got any left-handed spanners in your box have you?

It explains what you believed, yes. By "pass" do you mean a C?

midnight

iTrader: (10)

lol,mate i meant the preset spring in the dump valve,the vacume connection is to stop the pressured air from trying to flow through the turbo backwards(inertia) , ie ; once the throttle is shut the air has to go somewhere.On the recirc it also has a spring which opens and vents it back into the turbo.
No mate,was my best subject along with chemistry got straight A's lol

Splitpin

Rofl, what on earth are you on about? Did someone really tell you this stuff or are you making it up?

While you're at it could you explain climate change for us?

Splitpin

So, to recap, you're claiming that on a "normal" dumpvalve, the turbo boost has to blow past a "preset spring", and then goes down the vacume <sic> connection (otherwise inertia will make it go backwards). Also, the recirculating valves have an extra (in addition to the preset) spring that opens and vents back into the turbo?

Do I have this about right now?

merlin24

iTrader: (1)

Bet the OP is totally confused now

midnight

iTrader: (10)

I have just had a email of a mate of mine who has asked me to ask you : what is the most dedicated magazine that you can buy if you are a subaru impreza enthisiast ?

If the answer is : Total Impreza , then go to Issue No 6 Winter 2008 page 91,it is entitled : 'myth' busters and has all the tech guys explaining about the proclaimed gains and the real gains that can be provided by adding parts to your subaru.It deals with ,air filters,de cats,mapping,and dump valves.He also worked for turbo technics a good few years ago

Quote from total impreza magazine issue no 6 page 91

Sitting between the turbo outlet and the throttle body.When the transistion occurs from a boosted state to a closed throttle state (as in between gear shifts),due to inertia the turbo still continues to pressure the air,but the closed throttle prevents the compressed air from entering the engine.As the pressure exceeds the preset spring pressure in the dump valve,the excess pressure is bled of to the atmosphere.
However,even with a dump valve the compressed air acts as a brake on the turbo(slowing it down), because the pressure on the backside of the turbo is at a higher pressure than on the front side and the air actually wants to flow through the turbo backwards.
A blow off valve is a more elegant solution to this problem,by allowing the turbo to freewheel,when the throttle is closed,which equalises the pressure on both sides of the turbo.Unlike a dump valve, a blow off valve can be used at multiple boost settings without reconfiguration.Blow off valves are sometimes calleddump valves incorrectly,because they serve a similar function,but they provide very different answers to the same issue.

DOES IT WORK : It can do

DOES IT KNACKER ANYTHING: it can do and it may lead topremature meltdown in the turbo charger area. it may make a nice noise but it might notlast very long before some remedial work proves necessary within the engine.

DOES IT ENHANCE POWER:Not really,infact by itselfit may make a bit of extra underbonnet noise, but that is likely to be all.With a remap to ensure that all the various peaks and troughs in the system are being clicked on,its effects will be useful in a highly tuned power unit.

My explanation sounds pretty much like that,maybe not word for word ,but the gist of it is there,or maybe the people who write our beloved magazine make it up as well. pmsl
Dont know nothing about climate change except if everybody in the uk went out and bought petrol and gas guzzling motors like scoobs ,evo's ,range rovers ,etc ,we might see a temperature rise of 5 degrees by 2012 lol

Splitpin

Probably less confused than some!

midnight

iTrader: (10)

not confused,mate,i love banter,know bugger all about gear ratios,diffs,and gear boxes,but i do know the basic principle of how a turbo works,and have fitted a few as well.They may have different A/R ratios but they all operate the same, irrespective of what motor they are on ,even my old mg montego turbo with su carburetter, had a valve to release the excess pressure or the turbo would just blow up.

Wagwann

I have read that magazine and that is what it said. I have also read it some where else to. I read it in red line too and they tested it to. It had it + and -

good info midnight

midnight

iTrader: (10)

No probs louileach, i maybe a newbie on the forum, but i'am 44 years old and started messing around with cars when i was 20(changing the twin choke webber carb on my 2.0 ltr S capri for twin 40 dellorto's),i am now on my 39th motor and have had 95% of my cars have been performance motorsI joined this forum to get as much info as i could about the impreza,and i will only give information out that is fact - not my own idea's.

originally posted by splitpin;
Lol, you honestly think that's how the standard dumpvalves on the Imprezas work, that the boosted air has to force its way past a "preset spring"? Why do you think there's a vacuum connection between the standard valve and the inlet manifold? What do you think it does?

Yes mate thats exactly how a standard dump valve works on ANY car.


quote:Rofl, what on earth are you on about? Did someone really tell you this stuff or are you making it up?

Splitpin,Maybe you think it works like this: Quote Jeremy Clarkson...A 'turbo': exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.”

Not making it up like i posted beforehand simple physics, a turbo is like your mrs's hairdryer,but without the exhaust gases .pmsl

scoobiewrx555

The standard 'Recirculating Air Bypass Valve' as Suabru calls it is good for well over 400-450bhp and is a cracking bit of very relaible kit.

I've come across many aftermarket and expensive BOV/DV type valves both recirculating and VTA that do a pretty lousy job. They either down't allow the mapper to up boost due to the very weak std spring they come with or they are so loud when VTA it makes me cringe and want to hide out of public site, however more importantly they create a very rich state of AFR in between gear changes which is not good and can lead to detonation or cylinder wash. I advise customers to stick with the standard setup if they haven't already changed it.

There are arguments against recirc type valves like introducing heated up air back into the Turbo inlet pipe after the MAF sensor so the ECU can't measure the heated air and does that lean out AFR's significantly or contribute to det etc etc... You could go on all day for the Pro's and cons or both systems.

IMO for cars that are still using the standard ECU and MAF sensor the standard ABV (Air Bypass Valve) is best. The tuners i know cringe when they have to map a mildly modified scoob with an aftermarket Bailey BOV or Forge DV and tend to ask if the customer still has the original ABV to refit. I certainly do!!

midnight

iTrader: (10)

I have to agree with you scoobiewrx555,as both the baileys and forge dump valves i fitted only gave me problems, and did not appear to make the car any quicker at all.I fitted the blitz bov a couple of weeks ago ,and so far no running issues,but i have still kept the standard recirculating valve in case it does cause it to run rich,and if this should happen it will be straight back on for good.

Splitpin

Posting stuff you think is fact isn't the same as thing as posting fact. The understanding of the function of the standard air bypass/dump/blow off/ valves that you've demonstrated on this thread is fundamentally wrong, at least as far as they relate to the Impreza.

Some cars may have that arrangement but that's not how the system works on the cars that this forum exists as a result of. Your suggestion that the "vacume" connection to the manifold exists because the "air has to go somewhere" demonstrates that you don't understand it. That pipe is not an escape route for dumped air, as its small diameter should tell you.

The vacuum pipe exists to equalise the air pressure between the inlet manifold and the actuator diaphragm (or piston) at the front of the dumpvalve housing.

When you lift off the throttle, the sudden vacuum in the manifold travels along the pipe into the actuator and pulls the valve open. Your suggestion that the air has to force its way past a "preset spring" (with no other factors involved) is wrong. While there's a transient delay (hundredths of a second) while the vacuum forms, once that has occurred, the waste air doesn't have to force its way past, because the vacuum from the inlet manifold has already opened the valve.

Sure, there is a spring in the DV, but the ones in the Subaru valves are carefully calibrated so that they will hold shut only under idle vacuum. Lift off under boost and they snap open flippin' quick. You can try it yourself - just connect your (now spare) standard valve to the vacuum line and hold it in your hand while blipping the throttle gently. You will see it open all by itself without any air to push against it.

To use an analogy, you're comparing the function of these valves to a door with an automatic closing spring on it. You think that to open the door, you've got to push against the spring. In reality, there's someone on the other side waiting to open it whenever you need to go through.

You came in here saying that "standard" dumpvalves don't allow the turbo to "freewheel" because the boosted air has to fight against a spring to open it, whereas a "blow off valve" somehow does allow "freewheeling" (although curiously at no point did you explain the mechanism by which that works).

That distinction is wrong. The bottom line is that even with the bog standard recirculating valve fitted to every Impreza ever built the turbo can "freewheel", because it's the manifold vacuum opens the valve, not simply the force of the air acting against it.

Incidentally,

The idea that a recirculating valve "also" has an "extra" spring which opens up and vents air back into the turbo is also wrong. A recirculating valve is no more complicated in its basic design than an atmospheric one. The difference is that an atmospheric valve simply lets the dumped air out through a hole (or holes) into the engine bay. A recirc valve simply has a pipe connected to the hole which sends the waste air back into the inlet tract, just before the turbo. This is demonstrated by a number of aftermarket valves that can be converted from VTA to recirc just by taking off a trumpet and replacing it with a boss for the pipe.

Sure, there are plenty of expensive aftermarket valves around which claim to do all sorts of wonderful things, but the distinction you are making here between "standard" and the rest is built on a fundamental misunderstanding.

midnight

iTrader: (10)

I never said that recirc valves have an extra spring ,but you are correct in saying :
A recirculating valve is no more complicated in its basic design than an atmospheric one",whether it be the big black valve fitted on the early wrx's,or the ones bolted to the intercooler, they all have a spring concealed inside
I took your advice and fitted my std valve back on ,and blipped the throttle,and as you said it does as you say.I then fitted it on the intercooler,and instead of connecting up the inlet pipe i left the bung in the turbo inlet pipe and went for a drive,car was fine .Didnt quite whoosh between changes but it did vta.(poor mans dump valve,lol)

Anyway thanks for a very good discussion,with some very good points from both sides and like i said in the pm i like a bit of banter mate, and by the way : i am left handed ,and do use left handed spanners lol.

Scooby Arthur

iTrader: (2)

Just to throw another question into the equation, I am fitting a FMIC so obviously the standard DV has to go. I still want a re-circ as I dont want the noise, how do I get the feed back to the inlet? All the silicone pipes in that diameter are rigid so wont bend round the front of the inlet manifold.

06wrx

iTrader: (2)

SO TO RECAP DUMP VALVES ARE BAD ??? OR IS IT ME THATS READ IT WRONG. ONLY IVE JUST HAD ONE FITTED, SHOULD I REMOVE IT ?

alcazar

iTrader: (2)

Have you read ANY of the above?

Stick with the factory fitted recirculating dump valve, you won't go far wrong

mickywrx

iTrader: (29)

Use the search.

https://www.scoobynet.com/technical-...r-project.html

For a classic admittedly, still relevant in parts though.

I don't have a dump valve/re-circ/BOV fitted Still pops and bangs like a mo'fo.

scooby2004Lee

iTrader: (1)

What a fantastic debait, Split -pin really knows his stuff tho midnight!! Although you have a physics o level, split pin has a subaru masters degree in my opinion, but well done for trying to hold your own. Anyone you two just a personal note, i have a 2004 STI now running just 331BHP on the original TMIC. I had a HKS SSQV BOV (The best of the best, sir) BBBBUUUTT it was rubbish lol lol. It ideled funny, overfueled (Smell from the xhaust of raw petrol) and judddered on gear change) May just of been me but the original went back on and im laughing now!! Spend 280 pound on sumink worth while, WRX boys get a STI intercoller (£250) just a comparision!

Scooby Arthur

iTrader: (2)

Already read that, my FMIC is a Hybrid so the DV tee's off the fist bend before the inlet manifold.

I didnt see anywhere on that thread where a re-circ DV had been fitted?

So, back to my question, has anyone fitted a Hybrid FMIC with re-circ DV? And no, I will not run without one, thanks.

scoobiewrx555

I've just today mapped a V2 with a VTA BOV and a front mount, 440cc injectors + TD05. It ran as rough as a bears **** and popped it's head off before mapping. The noise it makes on lift off is just plain nasty but the judder on lift off was something else. Anyway it's mapped now and running sweet as a nut,pulling very nicely, and low speed running is as smooth as silkl!!. The judder isn't quite so bad now but that bloody noise is still there. I've advised him to modify the BOV and have it recirculating back to the turbo inlet. It will be a lot smoother on changing gear when he does that and switches to 99RON permanently!!

IMO aftermarket BOV's really are a waste of time unless you are making decent big power (over 400) and then it makes sense, but the standard OEM ABV does the job every time.

Don't be tempted!!

mickywrx

iTrader: (29)

1st page.

STAGE 7 RECERC DV FITTING

TOOLS NEEDED

1, 12mm SPANNER/SOCKET
2, L BRACKETS FROM B/Q
3,STI/WRX NEW AGE DV CONVERTED BY DA ONE
4,RECERC DV ADAPTER SUPPLIED BY DA ONE



I SENT MY STI 8 RECERC DV OFF TO DA ONE TO GET IT CONVERTED SO I COULD RUN THE PIPE TO THE ORIGINAL FITTING AND ALSO HAD A ADAPTER MADE TO THE SAME SIZE AS THE FRONT MOUNT DV OUTLET SO I COULD RUN ONE SINGLE SIZE PIPES TO CONNECT
FIND A PLACE TO MOUNT THE DV SECURELY I FOUND THE BEST PLACE WAS AT THE BACK IN THE MIDDLE BOLT THE RECERC TO THE DV ADAPTER WITH A NEW GASKET THEN GET THE L BRACKETS AND BEND INTO SHAPE SO THEY LINE UP WITH THE CAPTIVE NUTS ALREADY THEIR THE BEND TO SHAPE TO FIT TO THE 2 BOLTS HOLDING THE ADAPTER TO THE DV TIGHTEN DOWN AND ADJUST SO IT SITS CENTRAL