Boost creep with tial 38mm

[Ondonti]

Went for a scary ride. 2 4th gear pulls.

#1 pull it was way to lean and boost was creeping badly. 3000 rpms and we were at full boost 5 psi. boost then crept up to 9+ psi near redline and the car leaned out to 15:1 a/f. EGT's got up to 1725. Not good. Glad I had a datalog of that. Cranked up the rising rate regulator.

#2 pull 3000rpms = 5psi. Creeps to 6ish psi and then above 4800 rpms it creeps up to 8-9psi. My guess is the engine really is moving air at those rpms and the tial 38mm is not able to handle it. Only leaned out to 13:1 but that was a blip it was more like 12.7:1. Added a little bit more fuel.

This is with the custom intake manifold fixed and cams advanced 4 degrees.

So my question is this. When if turn the boost up, is it going to creep even higher or will it probably creep to the same numbers as before?
I dont want to turn it up to 8-9 psi and then have it creep to 13-14 cause I dont have enough fuel for that.

Wondering this question because if its going to be a POS and creep that high, then I might as well run the same boost number throughout the RPM range so tuning the a/f is a bit less weird.

Is my camshaft timing complicating boost creep or shouldnt that be a non issue above 4800 rpms where the creep gets really bad?

One thing I am going to try is giving a dedicated vacuum line to the wastegate as its currently sharing with a lot of other stuff.

[xtrempickup]

sounds like you are creeping more because of the wastegate or could be the size of the exhuast housing on the turbo maybe even. thats a low amount of boost but trying to run soo little, i dont know how free flowing your exhuast or intake manifolds are would contribute to the problem because the motor is making enough to support probably 15psi all day.

[bn880]

Agreed, the BOV won't help until you close the throttle plate some. This is a Turbocharger exhaust side issue.

[Ondonti]

Well its a P trim t4 in a .63 a/r t3 turbine housing. 3" downpipe to 3" exhaust with 3" mufflers.
2.0L dsm's dont spool this turbo until 5000 rpms but I think they go with the .82 housing.

[bn880]

That's weird, maybe your wastegate actuator arm is bent up or the thing is shimmed up? You could try bypassing the wastegate solenoid to the actuator, see if you can stop it from boosting that way. Make sure there is always some vac/boost reaching the actuator when testing or you will overboost.

[Akromix]

Do you have manifold pressure holding the wastegate closed until target boost (5psi?)

Also, what are you using for boost control or are you just running a 5psi spring?

the 38mm is plenty for a 3.0 boosted.

[Ondonti]

38mm Tial external wastegate with a .4 bar spring (5.8psi).

I just have a simple vacuum hose going to the side port on the Tial (nothing installed on the top port since I dont even know what thats for).

Im going to try to make a new vacuum line from the compressor housing to the wastegate. The current one is referenced to the intake manifold and its on a cobweb of Tee's that are all sharing the same vacuum port on the intake manifold.
Hooking to the compressor will cut about 3 feet from the line and should hopefully behave a little better.

I thought 38mm was enough but it sure doesnt seem like it with my new batch of mods.

[Akromix]

Yes, you need the side port to be hooked up close to the turbo outlet.

[Kevin]

Your wastegate just cannot flow enough exhaust out of it.

It's possible the boost will creep beyond the 9 psi you're seeing if you set it to 9psi to start with. When it starts to creep it spools, holds a pressure for a second, and then continues to climb, correct? OR does it stop at 9psi and hold that up till 6k?

If it continues to climb you're going to have problems if you set the boost pressure higher as it will just continue to climb up and up.

There's also a possibility that the wastegate positioning has something to do with it. Where is your's mounted? Right off the #2 runner? That could also be contributing to the problem.

That wastegate would probably be fine for running 10psi... but IMO it seems a little small if you're only planning on 6psi.