engine turbo airflow question

[SteveS]

ok, probably going to be hard to explain what im trying to get at here..

OEM DV, lift your foot up and it opens releasing the air.
forge DV, only opens depending on pressure, so only when higher boost does it open and release.

what action is better?

i was trying to find an engine diag so i could see for myself.

my questioning is, if the forge stays shut more of the time, then the air it DOESN'T release compared to the OEM valve causes build up in pressure back to the turbo?
OR
If it stays shut as above does that air go to the engine rather than back to turbo or released. i assume it does not go in and the intake in SHUT.

hope that makes sense? and if anyone has technical image/docs post it up. the manuals TT posted don't work anymore :(

[KRL]

The whole reason for the dv opening when you lift off during boost is for the unused air to be recirculated back into the turbos intake tract.

If the valve were not to open it would cause back pressure against the turbo and cause it to try and spin in the opposite direction.  This is of course bad as it will put extra stress on your turbo.  Hence why Turbo'd cars either have a valve that will dump the excess air to atmosphere (Dump Valve) or valves that ricirculate the air back into the intake part of the turbo (diverter/recirculation valves).

Dump valves may sound cool but my opinion is that recirculation valves are a far more efficient solution.

As far as the Forge recirculation valve goes for our cars - I understood that this was electronically actuated so does not rely on boost pressure to open it? 

[SteveS]

Yup, i understand that. 

Forge sure as hell doesn't open at lower boost as the OEM does. my understanding was it DID rely on the pressure. 

[KRL]

Here is the blurb from Forge's site:

Our valve and installation kit replaces the original unit with a pressure/vacuum operated piston valve that still also retains the desirable OEM ECU control over valve actuation.

Taken from here:
http://www.forgemotorsport.co.uk/content.asp?inc=product&cat=010202&product=FMFSITVR

So from that I understand that the valve is electronically actuated and not mechanically actuated (relies on boost).  Correct me if I'm wrong...

[SteveS]

that's what it says yea..

however, i have the spacer so can hear exactly when it does and doesn't open, i hear the air!
OEM will open and release sound on very little boost,
Forge only does at high boost

the forge piston has no electrics so completely relays on pressure to open it, the solenoid obv does something, but even if it wants it open it needs the pressure in the first place?

[Richn83]

Im no expert, but the ECU will have a reading on boost pressure, since this can be logged in vagcom, so the DV can still be electronically actuated based on pressure.  So you can both be right  

Ducks for cover........(waiting to be shot down for what ive written above)

[GTIjames]

i am currently running the forge dv (previously 'd' oem) and when combined with the itg intake you can hear the DV everytime I take my foot off the gas

does not matter whether at high boost or low boost I can still hear the cha cha cha sound, even after a short stab of the throttle you can hear it

how long have you had the forge on for? - may need servicing/re-lubing

and get the spacer off has no benefits or functions other than rice

[SteveS]

hum, well im pretty sure mine doesnt. its new, had two do the same thing.

the spacer i just for fun, but hay look on the good side, i dont have the hot air going back in :) but were not talkin about the spacer here!! 

[KRL]

I think you would be best to ask Forge Steve about how the valve actuates.  I would be interested in the answer as well as it would influence my decision on which valve to go for if my C revision DV tears.

[KRL]

i am currently running the forge dv (previously 'd' oem) and when combined with the itg intake you can hear the DV everytime I take my foot off the gas

does not matter whether at high boost or low boost I can still hear the cha cha cha sound, even after a short stab of the throttle you can hear it

how long have you had the forge on for? - may need servicing/re-lubing

and get the spacer off has no benefits or functions other than rice

How do you find the Forge valve compared to the D valve performance wise?  Did you manage to get any logs of both?

[SteveS]

I think you would be best to ask Forge Steve about how the valve actuates.  I would be interested in the answer as well as it would influence my decision on which valve to go for if my C revision DV tears.

Your probably right but i dont know how to put that in a simple and correct way. lol. feel free too :0

[chungster]

you're in the car driving...do you realise how much boost needs to be vented for you to hear it??

at low boost poodling along i'm not surprised u don't hear it. there's not enough air for it to make such a noise that u can hear over and above all the other noises around u. The forge spacer is also not designed to be full atmospheric and to make a noise such as a HKS SSQV or whatever.

I'm not really sure what you're trying to get at either.

Forge's spacer / full recirc piston/vacuum operated DV works with no problems on lots and lots of cars out there. 

[SteveS]

you read it all wrong.

i DO hear it at low boost with the OEM valve....
I know the forge dv isnt designed for atmospheric, hence the spacer.

it was just a general question....

[SteveS]

well i have put the forge back on and when lifting off the gas i hear no air being released though the spacer. infact all i hear is, what sounds like, the turbine, which i thought was a bad sound...
It must be releasing the pressure as my boost gauge drops...?

[KRL]

Boost would drop anyway as when you lift off the throttle the N75 will stop the turbo from boosting.  What sort of sound are you hearing from the turbine?  Is it a kind of fluttering sound?