Tial F38 boost creep?

[Smilinjay]

Whats up guys, I've been having an ongoing boost creep issue with my 2 bolt style tial 33mm ewg. It has a 1 bar spring (thats what i ordered, haven't opened the wastegate to confirm) and the boost signal is sourced from my lower intercooler pipe. The turbo is a tdo6 20g with billet ett compressor wheel,ported wastegate hole, and wastegate mounted off the o2 housing. Exhaust is a 3" straight pipe with the wastegate dumped to atmosphere. I am seeing nearly 25 psi on the 14 psi spring with no boost controller. The wastegate seems to start to open at 14psi under part throttle, but judging by my data logs, It seems to increase at a linear rate all the way to ~25 psi. I have a feeling this is going to cause some serious tuning issues down the road as the car is running pump 90 octane (yes, we have trash gas here in alaska). There is no knock to speak of but it only has from -1 to 3 degrees of peak timing at wot, which makes the car feel rather sluggish. Anyway, i would be happy if i could get the boost under control somewhere around 18 psi. Any suggestions? This is not a problem i thought i would encounter with a quality ewg.

 

[Smilinjay]

No one has had similar issues? I pulled apart the wastegate and verified that it does have a 14 psi spring. I also replaced my leaky stock bov with a new one and the creep got much worse. Now seeing nearly 30 psi at wot.

 

[96dsmftw]

Is it a used wastegate? Try using a compressor to see if it is truly opening all the way or not. I had gotten a 40mm and still had boost creep and it turned out it was only opening a little bit because the previous owner somehow managed to bend the shaft in it. The creep got worse because you had a boost leak. Check for boost leaks especially listening to where your boost source comes from and the wastegate itself. If you lose air before the wastegate, the actual boost and the pressure trying to open up the wastegate obviously won't be the same.

 

[Smilinjay]

Is it a used wastegate? Try using a compressor to see if it is truly opening all the way or not. I had gotten a 40mm and still had boost creep and it turned out it was only opening a little bit because the previous owner somehow managed to bend the shaft in it. The creep got worse because you had a boost leak. Check for boost leaks especially listening to where your boost source comes from and the wastegate itself. If you lose air before the wastegate, the actual boost and the pressure trying to open up the wastegate obviously won't be the same.

I bought it new like a year ago. I'll pull the gate off and make sure its opening all the way tonight. I guess it couldn't hurt to do another boost leak test either since i have changed a few things.

 

[Smilinjay]

This doesn't look right... Shouldn't the wastegate be opening more than 1/4"?

You must be logged in to view this image or video.

 

[DSMPT]

That size is maybe not good for your setup, possibly you need a bigger one. Small port wastegate is not good at controlling low boost.
I had a very similar issue with a customer's car. the car had a 38mm HKS wastegate with 1 bar spring. the wastegate was working well but didn't hold the boost at 1 bar at all and hit 25+ psi, then switched to a 44mm tial wastegate. The issue was perfectly solved.

 

[biglady112]

Turn the boost up. It will stop creeping then. Not enough wastegate for your situation to run so low. More boost=less creep

 

[Smilinjay]

That size is maybe not good for your setup, possibly you need a bigger one. Small port wastegate is not good at controlling low boost.
I had a very similar issue with a customer's car. the car had a 38mm HKS wastegate with 1 bar spring. the wastegate was working well but didn't hold the boost at 1 bar at all and hit 25+ psi, then switched to a 44mm tial wastegate. The issue was perfectly solved.

The wastegate hole in the turbine housing is still smaller than the 38mm wastegate even after porting. Correct me if i'm wrong, but wouldnt that still be the choke point? I could see having a larger wastegate make a difference if it were off the manifold, but not sure about off the o2 housing.

Turn the boost up. It will stop creeping then. Not enough wastegate for your situation to run so low. More boost=less creep

25 psi is not exactly ideal for pump 90 octane... Though it's starting to look like i don't have any other viable options. Probably would have to run meth to dial in any reasonable amount of timing.

 

[DSMPT]

It is normal that the wastegate hole in the turbine housing is smaller than the inlet size of external wastegate.
I don't know how much ported the hole but yes it could be a choke point if it is not sufficient.