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bailes1992
Wednesday 18th February 2009, 23:36
Can a standard turbo with no dumpvalve still make a ptshh sound? Out drive is on a slope and when My dad reversed the T5 up it earlier he blipped the throttle and you could here the turbo spool and it went "Ptshh" and when he first had it he was climbing a hill down west wales and when he changed gear im sure I heard the same noise but thought I was hearing things.

T4FLY
Thursday 19th February 2009, 02:04
My golf 1.8T has always done the same thing, completely standard engine too

Dan850T5
Thursday 19th February 2009, 02:08
Could it be a boost leak or do the recirc valves split?

bailes1992
Thursday 19th February 2009, 10:37
We had an intercooler hose replaced under warrenty after there was a split but it was making a high pitched whistle! This only happens when my Dad seems to be going just as the turbo spools and pulling off the throttle although It did happened at about 6500rpm going up a hill?

bailes1992
Thursday 19th February 2009, 11:56
Sounds exactly like this...

http://www.youtube.com/watch?v=_Rc9140wdSk&feature=related

So im going to guess its normal?

Babybadger
Thursday 19th February 2009, 12:15
Can a standard turbo with no dumpvalve still make a ptshh sound? Out drive is on a slope and when My dad reversed the T5 up it earlier he blipped the throttle and you could here the turbo spool and it went "Ptshh" and when he first had it he was climbing a hill down west wales and when he changed gear im sure I heard the same noise but thought I was hearing things.

Mine does occasionally.

Niles
Thursday 19th February 2009, 12:23
dump valve releasing turbo pressure. Absolutely nothing to worry about. Mine doe's the same but a lot louder :pimp2:

bailes1992
Thursday 19th February 2009, 13:03
But it's standard so it wont have a dump valve will it?

CONDYBOY
Thursday 19th February 2009, 14:15
Yes mate but its called a blow off valve

daveforber
Thursday 19th February 2009, 20:22
I thought it was a recirc valve, but essentially I think it's just a dump valve that dumps to the intake rather than to atmosphere and is therefore substantially quieter.

But I could be wrong.

chris yeatman
Thursday 19th February 2009, 22:21
my 850 t5 does the same noise, changed all vacuum pipes near turbo, tho it boosts ok std at .6 bar,

bailes1992
Thursday 19th February 2009, 23:11
I thought it was a recirc valve, but essentially I think it's just a dump valve that dumps to the intake rather than to atmosphere and is therefore substantially quieter.

But I could be wrong.

Hmmm... Might explain one or two pipes I been a bit curious about :)

madhouse
Monday 2nd March 2009, 14:32
My T4 is a bit more 'vocal' after I removed the sound insulation from inside the airbox. The noise is more of a deep 'sigh' rather than a 'phtshhhh' of say an Impreza etc.

Having said that my daily motorway hack is a 1997 Saab 9000 turbo which has a factory dump valve and that - for a standard motor has a very loud 'phtshhhh' Sounds great in tunnels and quiet lanes.

Babybadger
Monday 2nd March 2009, 14:37
oooohhhh snake!

Wobbly Dave
Tuesday 3rd March 2009, 11:19
Can a standard turbo with no dumpvalve still make a ptshh sound? Out drive is on a slope and when My dad reversed the T5 up it earlier he blipped the throttle and you could here the turbo spool and it went "Ptshh" and when he first had it he was climbing a hill down west wales and when he changed gear im sure I heard the same noise but thought I was hearing things.
All turbochaged volvos have a dump valve. The fact that the standard one recirculates the air back into just in front of the MAF sensor is irrelevant.

I have noticed that on certain 850s it is more prevelant than others.

Now I stuck the SRT from IPD on my C70 I can hear nothing else! LOL

Still not sure if I like it or not.

bailes1992
Tuesday 3rd March 2009, 18:14
Can you stop it recirculating? Make it atmospheric?

dooby
Tuesday 3rd March 2009, 19:10
Not very easily IMO - if you want to do that, replace re-circ with a blanking plate and fit an atmospheric dump valve as close to the throttle plate in the boost piping as you can.

It might be possible to make a custom device which sits in place of the re-circ and covers the right holes in the the turbo compressor housing but it'd surely be more expensive to develop and manufacture than buying a plate and DV :-)

HTH, Pete

Wobbly Dave
Wednesday 4th March 2009, 13:30
Can you stop it recirculating? Make it atmospheric?
Why on earth would you want to do that?

t4 b4194t2
Sunday 8th March 2009, 22:16
if you want to hear the standard reciculating dump valve more just get a bsr optiflow induction kit like i've just fitted to my t4 and you can really hear the dump valve now,it sounds more like an atmospheric one now,i'm sure if you google t5 with bsr induction kit you will get an idea of what i mean

bailes1992
Monday 9th March 2009, 18:46
Why on earth would you want to do that?

I don't I just like knowing things :lol:

Alan M
Monday 9th March 2009, 18:54
The car will run like a right pig if you fit an atmospheric dump valve to a later model Volvo. The system is sealed and designed to run that way for a reason.

Wobbly Dave
Tuesday 10th March 2009, 11:59
I don't I just like knowing things :lol:
As Alan points out BOVs on later cars will cause issues - the only reason they can work on 850s and the like - is the system is not as clever. IMHO it is preferable to keep the same mass of air in the system after the MAF oitherwise the mass of air in the system it thinks it has is different to the reality.

And you need a dump valve to stop the turbo blades stalling during the back pressure that exists during those off power moments (e.g. changing gear).