I've got a tial mv-s 38mm wastegate off the o2 housing. The turbo is a td05 16g with the evo3 turbine housing. The problem I'm having is the wastegate is not controlling boost levels at all. I bought brand new tial springs from extreme psi. I bought the 1 bar(14.5psi) springs. But yet when my turbo starts to spool I see my boost gauge spiking to 20-25psi and I immediately let off the throttle.

I have the plugs on 2 of the bottom ports and the vacuum fitting on the other. Both top ports are open. Only think I can think is, I replaced the aluminum crush washers with copper ones and maybe they aren't sealing completely, creating a leak. Any way I can test to see if its opening at all? The diaphragm looks fine also.

You can do a boost leak test and use some thing like pencil held in the port on the top of the wastegate. once the waste gate starts to open it will push the pencil out. Disclaimer if you drop or lose something in the top port you will have to disassemble the waste gate to retrieve it which will be a pain. Also you don't have the top port plugged correct?

xiteamxi said:

You can do a boost leak test and use some thing like pencil held in the port on the top of the wastegate. once the waste gate starts to open it will push the pencil out. Disclaimer if you drop or lose something in the top port you will have to disassemble the waste gate to retrieve it which will be a pain. Also you don't have the top port plugged correct?

Click to expand...

Yea thats what I was thinking also. And I know I've already changed springs a couple times and it sucks haha. Yup both top ports are open.

Or Just simply hook up and apply air pressure to the wastegate line. Be aware it will open at a different pressure then when the car is running do to exhaust pressure working in the turbos favor. Also do you have the " fire ring" installed it seats at the bottom of the valve but that would normally cause the boost to just build slower.