boost problem

[ydg27]

hiya
i have got a 1.7tdi in my nova (isuzu) and i have got a bleed valve in the actuator pipe, i have got a problem that my boost will not increase past 17psi (1.2bar)
i want to run 1.5bar and no matter how much i turn the bleed valve it will not go up - any ideas why?
i have had fuelling increased already so it isn't that.

any help will be greatly apprieciated

[Aragorn]

well either there's sonme kinda overboost protection built in OR the turbo simply cant push that much pressure

[Ste_Nova]

there is a valve that dumps any boost over 1.1 bar.... it's under the air filter

[ydg27]

yeah i know about that and its been removed and a blanking nut made up,
i have managed to get it up to 1.3 bar but it wont go much higher and the turbo can push out 30psi - so why will it not go any higher?

what is 1.3bar in PSi

[mikeoxford]

is the blanking nut etc sealed up well? not leaking precious pressure?

[Dicko]

is it possible the waste gate is leaking?

[ydg27]

i dont know anything about actuators and wastegates - all i know is that they control the boost - so it may be possible yes

and the blanking nut is 100% air tight

[Stuart]

1 bar = 14.5037 Psi

and dont forget that the turbo isnt 100% efficient

[Aragorn]

the problem is even tho the turbo can push 30psi its not designed to run 100% capacity

you will be putting extreme pressure on the wastegate valve and will over time fuck the valve seat causing leaks

the problem here is to get more boost people tend to simply fit a stronger wastegate spring - unfortunately this has a side effect - the overboost is increased

lets say your current spring cant hold any more than 1.3bar sustained, your prolly still overboosting to 1.5bar

u fit a stronger one and manage to get 1.5bar sustained

the overboost however could be well in excess of 2 bar at this stage which will FUCK the engine over time

i know this applies to the LET engine and i'd guess its the same principles for the turbo on the TD

[ydg27]

would the over boost show on the boost guage? it goes to 1.1 bar really quick and then slower to 1.2 bar and only when revving hard 1.3 bar. and how would i uprate the actuator/waste gate