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2G Wastegate Actuator Not Opening Until Like 25psi

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Will Kellermann

Probationary Member
24
5
May 19, 2020
Eagle, Idaho
Hey everybody,

The issue I am running into is that the turbo will not stop building boost as I can get to 20+ psi levels (I stop accelerating when it hits around 14lbs to be safe). I have a Evo 3 Big 16g TD05H installed on my '95 2G DSM. I don't know the internal wastegate brand/model and it is not the one that came with the turbo (mechanic worked on it before, not doing that again...).

I did my homework looking at other threads and I was able to isolate the fact that it is the wastegate itself:
  1. Pulled off Hallman MBC (new) and twisted the knob while blowing into the inlet side until air wasn't blowing through the outlet side of the MBC. Okay... not the MBC.
  2. Inspected the vacuum lines that lead to the MBC (inlet and outlet side vacuum lines) and they hold pressure just fine.
  3. Used an air compressor on the vacuum line leading to the wastegate actuator nipple. It hits 25psi before the wastegate opens and the dowel rod begins to move, and is fully open all the way around ~38psi.
So it's the wastegate. I need to be steered in the right direction, is the problem that the wastegate dowel rod is adjusted too tightly or because it takes 25psi to open that the wastegate actuator is broken? Just want to see if I can figure this out before I fully break in to the car again.

Thanks!
 
Is the wastegate aftermarket like Kinugawa or similar? If so they have internal springs that can be swapped in and out for different opening settings. Post a pic of what you have and that will help.
 
Is the wastegate aftermarket like Kinugawa or similar? If so they have internal springs that can be swapped in and out for different opening settings. Post a pic of what you have and that will help.
This is what the back of the wastegate actuator looks like. There's no branding or sticker but it also looks a lot like this eBay knockoff one.

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This is what the back of the wastegate actuator looks like. There's no branding or sticker but it also looks a lot like this eBay knockoff one.
Yeah I tried one of those once and before I even put it on the car I used a pump to verify opening pressure and it was waaaaay off from the normal numbers, and also didn't hold the pressure once the nipple was plugged and pressure removed. Plus I remember the arm was hitting the compressor housing too so I threw it in the trash and got a kinukawa one and matched the spring pressure chart they have to what I wanted on gate pressure. Worked like a champ. My advice is to either snag an oem one from one of the many part out guys or the kinugawa one.
 
Yeah I tried one of those once and before I even put it on the car I used a pump to verify opening pressure and it was waaaaay off from the normal numbers, and also didn't hold the pressure once the nipple was plugged and pressure removed. Plus I remember the arm was hitting the compressor housing too so I threw it in the trash and got a kinukawa one and matched the spring pressure chart they have to what I wanted on gate pressure. Worked like a champ. My advice is to either snag an oem one from one of the many part out guys or the kinugawa one.
Yeah, I'm looking at the Kinugawa wastegate right now, looks like the one I want to buy. Gonna get the 1bar (14.5psi) actuator, this is right around the minimum boost I want to start at. Thanks for your help man!
 
That's an aftermarket actuator head, likely from a Holset or something much more-durable than stock. The stock actuator is weak and has trouble holding a peak beyond twice the spring pressure (roughly 22psi) so folks will do this in attempt to hold higher pressure into the upper RPM range.
 
That's an aftermarket actuator head, likely from a Holset or something much more-durable than stock. The stock actuator is weak and has trouble holding a peak beyond twice the spring pressure (roughly 22psi) so folks will do this in attempt to hold higher pressure into the upper RPM range.
Ahh, ok good to know. Thank you.
 
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