How do you shim a wastegate?

[BLKMGK]

A question not directly related to a Z but I've heard th eterm "shim the wastegate" more than once and I'd like to know exactly what that entails. In my particular case the wastegate isn't strong enough to hold closed at full RPM and shimming it is supposed to help this. How ya' do dat'?

[Guest Cusp]

The wastegate actuator rod on my T3/4 has two holes on the end. The inner one puts more preload on the flapper, the outer less. It's just a cauter pin holding it on there, if your's doesn't have two holes, you might try finding/ordering an actuator rod with two holes, it may be an easy fix. Maybe even drill your own if there's enough room on the flattened area of the rod.

[DAW]

The wastegate actuator diaphram is mounted using a curved two-bolt flange that acts like the other retainer flanges holding the compressor housing to its baseplate. Using a curved plate (like a spare retainer plate) under the actuator mounting plate would reposition it slightly ("shim" it) in the direction of its opening action on an L28ET...which would weaken its closing tension and allow it to crack open at lower boost; not higher. Since there's no way to shim it in the beneficial direction, the external mod needed would be to add a supplemental extension spring between the wastegate lever and the actuator bracket, along the axis of the rod. This is best done incorporating an "S" hook/link in the attachment so that longer or shorter of this link can manipulated to get the desired additional preload.

 

There may be other car mfgs that afix the actuator to their turbo which allows shimming of the actuator such that it displaces the diaphram further from the wastgate lever pivot and in this case shimming could be used...but not in the L28ET. DAW

[Lockjaw]

If it is a stock nissan one, you can bend it towards the front of the car, in the direction that keeps the rod centered in the opening of the actuator. This mod is kind of like Kentucky Jelly, a little goes a long way. A little trial and error will get you where you want to be.

 

There is another option too. You can get a deal at a hardware store that is like a long hollow bolt aproximately the same diameter as the rod, and cut the rod and thread it and use that to manipulate boost.

 

You can also search for the mod using the grainger valve and use that to manipulate the boost, or buy a manual adjustable boost controller. You could probably hunt around on ebay and find one cheap.

[BLKMGK]

As I said, this isn't actually Z specific. This is for my Supra Someone has mentioned that shimming the wastegate will allow it to hold closed longer. Apparently the wastegate on the Supra, even with the hose pulled, won't hold boost because the darned flapper blows upen! Not too cool Mind you it still runs like 1.5BAR but I'd like a little more spring pressure so I can hook the wastegate hose back up and actually get some use out of the silly thing. Mind you it's only got the one wastegate for both turbos so it's really a funky setup

 

P.S. Oh cool - the guy posted how he did it!

I am not sure what the hpf mod is. I unbolted the wastegate and installed three washers in between the wastegate and the turbo on each bolt. As far as blowing up the turbo a friend of mine had his shimmed and ran over 23lbs for over a year