2G T28 won't hold boost at high rpm

[Rustic gst]

Ok so i have a mbc set to about 14 lbs but when i get to about 5500 rpms it tapers to about 9 lbs. I hold about 20 or 22 vacuum when my car is warmed up at idle. I have a little bit of side to side movement on the shaft on my new t28. And a tiny amount of oil residue, is my turbo going bad possibly?

 

[2gmitsueclipse]

Things you should try:

1. Boost leak test

2. Test/inspect waste-gate operation

3. Post back with results.

 

[pauleyman]

And yet another member without a profile page. Tell us what mods you have so we can help you.

 

[Rustic gst]

I have a t28 turbo, injen intake, evo 9 bov and a grimmspeed mbc. Stock everything else. I found a leak at my boost gauge sensor, i fixed the leak and will retest tomorrow in the morning

 

[pauleyman]

Get a bigger exhaust

 

[Tanro]

I'd redo the boost leak test, then upgrade your exhaust if you've fixed all the boost leaks.

 

[Vegas Smith]

May want to look into a better fuel if you're turning up the boost

 

[chrysler kid]

Turbo is fine, that amount is normal to find from the valve cover breather

 

[Rustic gst]

Ok so i did a leak test with soapy water and couldn't find bubbles anywhere. Although I can hear a hissing noise from my throttle body, and when I turn the plate by hand it changes in tone, could I be leaking from my shaft seals and i just cant see the bubbles because its leaking out from inside the throttle body?

 

[Dsmkauai]

Get a better wastegate actuator

 

[pauleyman]

Get a better wastegate actuator

Can you explain this?

 

[Dsmkauai]

Well like when I was running my 16g to the max it sucked with the stock actuator wouldn’t hold in high Rpms. So I switched to a holset actuator and it would hold 20-22 psi rock solid all the way to redline. Sounds like he’s on a stock actuator and it’s probably old and can’t hold up to the pressure. So the wastegate just blows open up top. Also sounds like his tb shaft seals could be leaking to. He’s got a good bov so we know it’s not leaking there. If everything else is good and not leaking that’s where I would focus. Port the turbine housing and upgrade exhaust. Can always check the actuator on it for proper function.

 

[pauleyman]

I could see a defective actuator but not the need for a "better" one. 9psi is easy.

 

[Rustic gst]

The actuator came with the new turbo, it's mounted to the turbo right?

 

[2gmitsueclipse]

The actuator came with the new turbo, it's mounted to the turbo right?

Here we go:

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[Rustic gst]

If my new actuator on my new turbo is just blowing open, what would be a good replacement? https://www.maperformance.com/produ...MIr_u6-rCG2QIVkqDsCh3ttQ4vEAkYBSABEgLC6vD_BwE would that one work?

 

[Tanro]

Yes it sounds like your throttle body shaft seals are leaking. You can remove the TPS and see if you feel any air blowing out around the shaft.

 

[pauleyman]

I doubt it's your actuator. Instead of asking about a new one test the one you have. Pressure it up. Boost is a function of pressure differences. Right now you have a restrictive stick exhaust and you'e asking it to flow more and it has to do so to make a turbo work. Guess what happens when it can't?

 

[chrysler kid]

It's not your actuator, that was the most generic basic response to a post I've seen in a while.

 

[pauleyman]

It's not your actuator, that was the most generic basic response to a post I've seen in a while.

A faulty actuator can fail on two ways. Broken diaphragm which would keep gate closed and build everything the turbo will make. Broken spring which would let gate open easily however is easy to test. Just pull on the arm. Throwing a new part at the problem isn't a good solution

 

[Archer Fabrications]

Oil is prob from valve cover breather into the Intake?