OK so I needed a wastegate actuator to build boost fast, hold it and run a base pressure of only 4-5 psi while bolting up to the stock mounts on a toyota CT26 turbo. Tall order? Not so much, here is how I made it work;
1. I used a stock wasegate actuator off an MR2 turbo. I tested it with a boost gauge and found that it wouldnt even begin to move until 8 psi. I want to run 4-5 for safe daily driving. (it can always be turned up). The way a actuator works is it is a can that is sealed in the middle with a diaphragm. As boost enters the top part of the can it pushes down on the diaphragm and moves a rod out to work the wastegate flapper. A spring resists this boost until around 8 psi when the boost pressure is enough to begin compressing the spring and pushing the rod down. I said before that the rod could be extended to lower base pressure and this is true but the problem with that is that the flapper will be opened slightly at the start and that leads to slow spool and that is a bad thing. This way allows for the flapper to be held tightly shut until boost reaches 4-5 pounds so there is no sacrifice in spool time.
This is the beginning part.
2. Begin by removing the rubber seal on the bottom. (three screws) Next, we simply want to cut the bottom off the can as low down as possible and use a hand saw to avoid heating the metal up and damaging the diaphragm. (it does live next to the turbo though so it can take some heat!) I choose a hacksaw blade and chucked it up in the vise, the whole unit is under tension so when the bottom comes off it will really come off! Make sure before you do this you mark a line to show how to line the two halves up again.
3. With the can bottom off the spring comes out and the parts can all be seen. Now we either cut the spring shorter, or find a new softer spring. I choose to cut a coil and a half off teh spring. (eliminating the preload.)
4. I now replace the spring and realign the two halves of teh can with the mark I made earlier. I used my good old arc welder to rejoin the halves. I found that the old 80 amp welder lworked perfect with 3016 electrodes.
I cleaned the metal up with a grinder, tacked one side, tacked the other, then removed the clamps. With the clamps off I cleaned all around the cut with the grinder and welded the seam shut with a thinner electrode again.
5. Going slowly with the welding so as not to melt the diaphragm I finished in about 1/2 an hour. Let it cool awhile and then clean up the welds with a grinder. I just ground the welds down flush with the rest of the can and used sandpaper to clean up the rest of the can so I can repaint it later.
6. Here is the finished actuator:
Post test results show that the actuator now holds the flapper shut tight with a little preload but begins opening right at 4.5 psi and is fully open at 9 psi. If I ever want to raise that pressure all I need is a boost controller now. (4-5 pounds is fine for now IMHO)
Linear Mode
