EVO8STI

iTrader: (2)

i have a external o2 dump so when the wastegate opens everyone knows it. well a few days ago my car stopped building its normal 30 psi and is only hitting 21 and the waste gate seems to be stuck closed or so i thought. anywho while idling i put my hand on the o2 dump exhaust and i can feel exhaust air coming out of it for sure. so im thinking my wastegate is stuck barely open just enough to not build proprer boost. has anyone heard of this before? whats the fix? is the actuator the problem?

sparky

iTrader: (1)

This sounds bizarre. Tell us what turbo and what wastegate actuator is on there. How do you manage the boost level(controller, or ECU)?

EVO8STI

iTrader: (2)

stock turbo and wastegate, grim speed electronic boost controller.

sparky

iTrader: (1)

Given an unwarped flapper valve and a functional WGA, if you can feel exhaust gases escaping out through an atmospheric dump at idle, then the flapper valve is lifting off its seat way early due to insufficient spring tension to counteract turbine inlet (exhaust) pressure.

The tired internal spring in that stock 12 PSI actuator has taken a set. Just like saggy old suspension springs do over time. The first few mm of travel on your actuator spring get taken up by the exhaust pressure in the turbine housing even while the compressor is still in vacuum and no boost is even being produced. So, the flapper is lifting way early.

I still don't understand how people expect to be running a turbo at over 30# peak on a worn out wimpy stock actustor spring with zero preload if the flapper is already cracking at idle BEFORE the compressor has even crossed over from vacuum to positive boost.

At best, even when new, that stock actuator goes full open by 12#. If it is full open by 12# then by definition it started opening(cracking pressure) way earlier than that. Since you have an atmospheric dump then we know from the fact that you feel exhaust flowing out the dump that the flapper is cracking at idle.

Think about it. At idle a turbo is not even producing atmospheric pressure. At idle since there is no positive manifold pressure then the WGA diaphragm is not what is impulsing the movement of the actuator rod or lifting the flapper valve. In this case, exhaust pressure alone is the only force acting on the flapper valve to push it up off its seat. So you have zero preload and a tired actuator spring. So wimpy that they cant keep the flapper on it seat at zero boost.

EDIT: This is a prime example of my classic boilerplate rant. We will try to purge this type of knee-jerk schlock of mine right now during New Year resolutions. LOL

sparky

iTrader: (1)

I just realized that there is another possible explanation that could cause exhaust to exit out the dump tube even at idle and with the flapper valve closed. It could depend on the design of the OP's O2 dump. If for example, the main turbine exit chamber or area, is not totally divorced from the wastegate exit chamber/ dump tube as when there is not a complete seal due to an undivided gasket then there can be exhaust crossover taking place which would be measurable at idle. That is the OP might not be feeling exhaust flowing out past the flapper. But instead, it is turbine exducer flow at idle crossing over into the dump tube due to faulty design or an undivided aftermarket gasket.

Freddie: Are you out there dude? I think I flipped out totally. It must be the excessive holiday cheer!

AreSTG

iTrader: (4)

lol

WikdEvo

iTrader: (8)

What o2 dump are you running? That way we can figure out if your wastegate is leaking or if it's just exhaust gas out of the turbo.

Spec-Ops1

iTrader: (38)

If it just started doing it one day it is possible that the special divorced O2 housing gasket blew out or the wastegate actuator is not seating the flapper correctly due to improper preload or a tired worn out spring... if all that checks out take the wga arm off and make sure the flapper are is moving smoothly...

EVO8STI

iTrader: (2)

alright guys, its a map o2 dump. you guys seem to be stuck on the fact that it is leaking air at idle, but no one has explained why im not building proper boost and it is NOT opening at all while boosting. is there a way the flap could be jammed for some reason or maybe the actuator froze up?

Spec-Ops1

iTrader: (38)

did you take off the arm to make sure the flapper moves freely like I had suggested? Is it leaking air out of the dump at idle since we never got a good answer on that?

EVO8STI

iTrader: (2)

yes i have and it moves freely. i also pressurized the actuator to see if it moves and it does. while the actuator was off i held the flapper completely shut and still got exhaust coming out so i think i have a undivided o2 dump as someone stated before.

"Is it leaking air out of the dump at idle since we never got a good answer on that? " i answered that in the first post if you read it completely! i said "while idling i put my hand on the o2 dump exhaust and i can feel exhaust air coming out of it for sure" hope that clears things up.

EVO8STI

iTrader: (2)

i guess what i need to work on now is why am i only building 21psi instead of 30.

EVO8STI

iTrader: (2)

bump