Blow Off Valve - not working?
Turbo Mini Forums

I'm now running 12psi with the standard plenum and blow-off valve.

Should I not hear it opening and stabilising at around 10psi? (i've read 10psi is it's operating point)

However, I don't hear the turbine stall (as if by high back pressure when changing gear) so i'm confused as to what might be going on.

Edited by dan187 on 8th Feb, 2011.

1275 N/A Sprite, 998 T2 Turbo Mayfair
1275 EFi Turbo

??? i dont understand

Are you saying your using the standard built in blow of valve? (the one in the plenum)

And what actuator are you using? (plus a bleed valve if any)

The turbo will chatter/stall/flutter if your blow off valve isnt operating.

is your boost gauge reading 12psi?

Sorry for the confusion.

I am using standard plenum blow off valve (BOV).

I'm using a Metro T3 actuator on a Renualt 5 T2 turbo. Plus a bleed valve.

My boost gauge is reading 12 psi at maximum.

I don't hear the turbo chatter/ stall/ flutter - this makes me think the BOV is working.

I've read here that the BOV opens at 10psi.

Therefore my question is, how am i getting to 12psi?

I've not had the two plenum halves apart (but i can see the spring in there). Could someone have packed out the spring in the BOV to make it open later?

Edited by dan187 on 9th Feb, 2011.

1275 N/A Sprite, 998 T2 Turbo Mayfair
1275 EFi Turbo

dan whats wrong here is your gauge is reading wrong! ... where have you plumbed it in ?

The BOV in the plenum is a overboost saftey device which leyland place there to save the standard crapping out ............. so to speak at 10 psi ish you right, check its not blanked off ?

the standard T3 acuator opens at 4.5 psi so if you have just connected this to the actuator and not bled the signal line off its running at that 4.5 psi ...... i bet the car is a snail ?

you have to check the above ^

Edited by BENROSS on 9th Feb, 2011.

The gauge is correct i'm running 12psi. It's tapped off of the top of the inlet manifold. I'm bleeding off air to get to 12psi. I'll plug the laptop in to correlate my gauge to the Megasquirt sensor but i'm pretty sure they're close.



I'll have to check the BOV is operating next time i have chance but I don't hear any stall of the turbine.

1275 N/A Sprite, 998 T2 Turbo Mayfair
1275 EFi Turbo

As above, the valve you are referring to is an over pressure valve, not a dump or blow off valve. Normally people blank them off of fill them with 5pence pieces to seal them shut.

You'll have to take it apart to check, and fit a proper dump valve if the noise is what you want.

not bothered about noise, would probably recirculate a dump valve.
I was just curious why it wasn't operating.
Perhaps the turbine is stalling but I just can't hear it. The suction noise from the turbo is pretty loud.

1275 N/A Sprite, 998 T2 Turbo Mayfair
1275 EFi Turbo

i couldnt hear mine and when i blocked it off (after fitting a dumpvalve) it ran about 16psi boost, before that it was a steady 10psi in my eye it was dumping that 6psi
the turbine should not be stalling if the over pressure valve is working

Yes i moved to the darkside

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