How tight should Wastegate Flapper be - T25? Dont boost past 8-9

[dacowgod]

I finally got the new"er" engine put in my car and have been playing around with the boost and I get a spike to 9 and levels off at 8. It spools up to this very fast like 2500 RPM.. but this is the max boost regardless whether the BCS is hooked up a MBC is hooked up or nothing is on the actuator at all. I put pressure to the actuator and it seems to function like it should and I replaced the UICP with a Dave Brode special and have a 1g bov mounted to it because that was the only real leak i was noticing when I did the Boost Leak test. other than the Idle screw but I havent got a new O ring to replace that, But i would not think it would be leaking so much boost that i cant go pass 9. So i've come to think maybe the flapper in the turbo is being blown open at 8-9 .. or something else is wrong with the turbo. The flapper is not stuck but it is very loose and sloppy without the actuator hooked up. I dont know if it is supposed to be springy and hold any pressure on its own or if its just that easy to move and relies on the pressure from the actuator to keep it closed. Oh yeah... Also already checked the Timing...its perfect... Can any body throw me out any more ideas? Thanks in advance

 

[DSM90AWD]

But i would not think it would be leaking so much boost that i cant go pass 9. So i've come to think maybe the flapper in the turbo is being blown open at 8-9 .. or something else is wrong with the turbo. The flapper is not stuck but it is very loose and sloppy without the actuator hooked up

I'm assuming you are measuring boost with an aftermarket gauge, but from where are you measuring it (manifold, turbo outlet, other)?

With the actuator diconnected the flapper should freely "flap" back and forth. With the actuator connected, the wastegate valve should be seated against the WG hole with a moderate amount of preload.

Also, you should not be using a BCS in conjunction with a MBC unless you are deliberately trying to run a high/low boost setup. The boost source to the MBC/Wastgate should also be as close to the turbo outlet as possible (e.g. not from the intake/BOV line).

Note also that a stock T25 is not a very big turbo, so don't expect alot of boost/airflow from it

 

[dacowgod]

yea reading a calibrated aftermarket gauge .. mbc and bcs are not hooked up at the same time..they are just merely examples of boost not changing at all .. .and neither are relevant if the actuator is not hooked up to anything....my flapper flaps freely but it maybe it isnt sealing? is there any easy way of checking that? also my vacuum on the car is between 11 and 12 .like i said the boost leak test found only a leak at the biss and it is a very small leak at that.and putting my thumb in front of the hole to seal it up doesnt effect the vaccuum one way or another .. anyways thanks in advance for any more ideas..

 

[DSM90AWD]

and neither are relevant if the actuator is not hooked up to anything....my flapper flaps freely but it maybe it isnt sealing?

To be clear are you saying the actuator is not connected to the valve or it is connected but there was no boost/vacume source connected to the actuator? If the latter, you should see at least a momentary spike well past 9psi if the turbo/wastegate is in good condition and have no significant boost leaks. It's possible that the wastegate "puck" is not sealing well or there is not enough preload on it to overcome the exhasut pressure pushing from the other side.

also my vacuum on the car is between 11 and 12 .like i said the boost leak test found only a leak at the biss and it is a very small leak at that.and putting my thumb in front of the hole to seal it up doesnt effect the vaccuum one way or another .. anyways thanks in advance for any more ideas..

Unless you are running big cams or are at 5000ft altitude, that vacumme reading is an indicator of either a loss of compression (headgasket/valves) or possibly a slipped timign belt (mine read that low when my exhaust cam was off a couple teeth)

 

[dacowgod]

Well my vacuum is right around 12 ... I am actually at 2800 Feet... never thought about altitude being a factor...not sure if that is my problem or not ... car runs fine .. Oh and Thanks for your replies.. I did fix my problem today...switched to another T25 I have that had more Play in the shaft..and I wasnt sure if it was any good. .. when i put it on though it boosts like crazy and the runs great .. i guess it was something to do with the wastegate on the other turbo... thats to bad too because the thing has almost no play whatsoever... oh well anyways thanks for replies..

 

[forcefed4]

If you think is was a problem with the wastegate, just change turbine housings. Put the good turbo with the housing from the one that has shaft play.