Dump valve lettin by...

[oblark]

Just got back from Pompey where Dalhousie & myself pulled the engine out of his Gul Est.

On the way back I did so data logging :)

Gave it some beans to make sure she was boosting to the correct psi, well yes and no :confused:

I can hit 17 psi then I hear air escaping as if the dump valve has opened and as you see from the screen shot boost & TCV duty cycle drop but Rpm and speed are increasing then the boost & TCV increase.

24926

I`m pretty sure the dump valve spring needs to be stiffer to withstand the high boost pressures

I`m I right or I`m I barking up the wrong tree ??

You`ve got to love this data logging :)

[stribo]

You're a chav for having a dump valve :P, but yeah, sounds like boost pressure is opening it prematurely.

[T5frankie]

need a stiffer spring mate, is it a forge one?

[M-R-P]

Iirc it's a forge knockoff one.that doesn't open soon enough (giving a lovely chatter noise under normal driving) so I wouldn't be surprised if it needs a strip down and a new spring.

[oblark]

Iirc it's a forge knockoff one.that doesn't open soon enough (giving a lovely chatter noise under normal driving) so I wouldn't be surprised if it needs a strip down and a new spring.

I`ll let you Know it`s a copy (a poor one )

I`ll have a look on ebay tonight for a better make one :)

[cherry1809]

Forgive me, I'm squiffy again. Isn't there a fine line on how much pressure the spring puts on 'closing' the valve?
If you run more boost, then there will be more pressure holding it shut too, until you 'let off'

[oblark]

Forgive me, I'm squiffy again. Isn't there a fine line on how much pressure the spring puts on 'closing' the valve?
If you run more boost, then there will be more pressure holding it shut too, until you 'let off'

Good piont.

My thinking is the surface area on the spring side is smaller than the sirface area of the piston :)

[stribo]

Forgive me, I'm squiffy again. Isn't there a fine line on how much pressure the spring puts on 'closing' the valve?
If you run more boost, then there will be more pressure holding it shut too, until you 'let off'

Yes and no, the 2 sides don't have equal pressure as the surface area of the pressure side is greater than the side keeping it shut, so if you up boost pressure, although it raises both sides, it is not equal, so the pressure side overcomes the side keeping it shut. Hope that makes sense.

EDIT beaten to it.

[oblark]

Just a thought.

My dump valve is connected to the manifold by 3mm silicone.

Would 4mm be better and help balance out the pressures ?

[960kg]

Only my own opinion but all this spring changing to me is only a money maker!!

Yes, i have the Forge Recirculating valve with a yellow spring but i have seen boost on 26psi with no problems from the vent valve also before i fitted it and also on my V40 T4 my boost was way up 20psi and the standard valve still gave no problems!

Of course i am not saying you don`t have a problem as even a screw can be loose .........i never use silicon pipes at all as they pulsate and can play havoc with steady boost, i only fit the recommend Volvo sized pipe so i get what i am supposed to get.....


On a Standard Mitsubishi turbo recirculating valve the pressures or psi are equal as it works off a large rubber diaphragm, the reason it doesn`t leak is because the large spring assists it keeping shut......so it has psi + spring pressure as against just psi on the other side.