S40 t4 twin piston dump valve open at idle. Boost drop.

[Volvulate]

Dv24 is single dv26 is twin. Apparently single only have one spring where as twin has two springs. Well ive stripped it n there definatley two springs. So what goes to vacuum pipe on throttle body if not dump valve? This is my first turbo, so bare with me. And that ptcshhhhhhh never fails to put a smile on my face, and I have no problems besides the boost drop. Alot of ppl say dv is meant to be doing what its doing. I am a mechanic by trade, altho not very long, bout a year, and we rarely do anything like this, its all servicing and replacing. Never ever ever modifying lol

[Volvulate]

Djx said he had full boost right to the line....

[Volvulate]

If the turbo is capable of boosting higher surely it can sustain boost pressure at high revs. Ive heard you can turn them wayyyyyyy up, obv at cost of killing it.

[m1tch1987]

The higher you boost the higher the gas pressure on the wastegate flapper - basically the exhaust gasses get to a point where they just push the wastegate open after overcoming the spring pressure. Massive boost on a smaller turbo isn't ideal as it will be working outside its efficiency island, it would be producing a massively increased amount of heat meaning that the intercooler must try and cool the intake charge down more before it goes into the engine.

[Volvulate]

First things first ill do a boost leak check. See if im leaking anywhere. Also going to change all the tie wraps holding vacuum pipes to jubilees (after leak test, so I know that I actually had a leak). But does tinkering with actuator make boost last longer, or give more boost? I have enough boost, just need longer. Lol its like driving an extremley quick turbo diesel

[Volvulate]

Bigger intercooler?

[malteser]

Might also be worth checking if the actuator holds pressure, pump it up to 20 psi and see if it holds or if the pressure drops

[Volvulate]

Thought they were 0.3 bar?

[malteser]

I think that is more to do with when they start to open, If the car used to boost 18 psi the actuator should hold that without dropping pressure. I've done this to my own car to check the actuator and mine holds it without dropping.

[m1tch1987]

Actuators are rated to the minimum they open eg the minimum boost level you can have before it opens no matter what you try to do - some have interchangable springs, some are fixed. Example is that you can't boost to only 0.5bar with a 0.8bar actuator. The weaker the spring the less likely it is to be able to hold pressure at higher boost levels.