External spring for w/g can?

[Tony Hanna]

Anybody ever fooled around with using an external spring connected to the w/g arm to aid the spring in a weak w/g can? I know you can shim the can to increase the tension, but only up to a point before you limit the w/g travel and run into creep.
Here's an idea I've been kicking around. I thought I might post about it to get some feedback.
Why couldn't a person make a bracket to bolt on with the stock w/g can. The bracket would hang off the side of the turbo and have a hole in it with a nut welded on. A piece of all-thread with a nut welded on one end and a swivel on the other would be threaded through the nut on the bracket. A spring would be connected between the swivel and the w/g arm.
Backing the all-thread out would tighten the spring against the w/g arm, and turning it in would loosen the tension. Depending on what size spring you use and how much preload you dial in with the all-thread, you should be able to set a weak can to hold whatever boost you want without limiting it's travel by using shims. In theory it should work just like changing springs in an external wastegate.
Any thoughts?

[supercrackerbox]

I don't have too many details to offer, but I do know that 86Shelby had an auxilary spring on the wastegate on his Spirit R/T (formerly owned by JayLo) for that exact reason. Made a lot of difference I was told. I'll PM him a link to this thread so he can elaborate more.

[86Shelby]

Yup, I had 2 on there actually. My setup wasn't quite that elaborate, nor did it have any adjustment like that. The two springs were attached to the swingvalve arm and then achored to a stud on the firewall. It worked pretty well and allowed me to run 24psi. My motor mounts are all pretty close to solid, so there was very little engine movement to mess witht he tension on the springs.

[Tony Hanna]

Cool! That sounds alot like the setup I had when I was running the small can on the Daytona. I had a spring connected from the arm to the vacuum barb on the w/g can. I kept having problems with the spring popping off, so I eventually switched cans but it started the idea for the bracket/all-thread/spring rig. I'll have to pick up a piece of plate and a spring assortment when I get the O2 bottle filled on my torch and see if I can fabricate something.

[CSX321]

It should work well, I would think. The SRT4 guys have been adding a spring almost from the beginning with those cars, but without the adjustability. The shape of the actuator arm makes it easy for them.

[1985ShlbyChrger]

Why not use something designed somewhat like a valve spring. Use a retainer type thing that sits on a small area machined(or a small lip welded on the wastegate rod) with the other end of the spring sitting on the diaphragm on the wga. It would be like a lawn mower valve spring kind of retainer. Do you think this would work? I may experiment with this. I'll let you guys know how it works.

[Tony Hanna]

Why not use something designed somewhat like a valve spring. Use a retainer type thing that sits on a small area machined(or a small lip welded on the wastegate rod) with the other end of the spring sitting on the diaphragm on the wga. It would be like a lawn mower valve spring kind of retainer. Do you think this would work? I may experiment with this. I'll let you guys know how it works.

If I understand what you want to do correctly, I don't think it'll work. The wastgate rod pushes to open the wastegate, so you'd need to set your spring up for tension not compression. I may misunderstand how you want to do it, but it seems to me like it would actually be working against the spring in the can instead of with it.

[Tony Hanna]

You guys think a swivel designed for a dog chain would be strong enough?
The reason I want to add the swivel is so the spring doesn't have to be disconnected just to make a preload adjustment with the allthread.

[puppet]

Great idea ... why use a WG can at all? Make a plate with the spring held in a craddle and the actuator rod down the center of the spring. Bolts that hold the craddle pass through the plate. Boost adjustments to the craddle could be made with a nutdriver .... no more grainger valve.

[Tony Hanna]

I'm sure that would work great. In fact, for a race only car (especially something that I wanted to keep consistant) I'd probably go that route.
The Sundance is going to be pulling daily driver detail with the ocasional trip to the track, so I'd like to keep the can so I can build a 2 or 3 stage switchable boost control out of vacuum solenoids and bleed valves.

[GLHSKEN]

ASK CSXTRA he has lots of experience with that.

[contraption22]

I used it on my horizon. Basically i drilled a hole in the wastegate actuator bracket, and another in the flat part of the arm close to where it snaps onto the swingvalve. I went to the parts store and bought a pack of extension springs i found in the HELP! section. Found one that was somewhat tight and stretched it till it hooked into the holes i drilled. Worked very well!

[Tony Hanna]

I used it on my horizon. Basically i drilled a hole in the wastegate actuator bracket, and another in the flat part of the arm close to where it snaps onto the swingvalve. I went to the parts store and bought a pack of extension springs i found in the HELP! section. Found one that was somewhat tight and stretched it till it hooked into the holes i drilled. Worked very well!

That's it exactly! The only difference will be the adjustable preload.
I bet the spring assortment I've been looking at (help section) is even the same as what you used.:thumb:
I may simplify this a bit and instead of building a bolt-on bracket, just weld a nut to a washer and weld the washer off to the w/g can bracket.
I've got loads of mitsu w/g cans to play around with.:)

[csxtra]

Tony,

Your idea should work well, I didn't try the all-thread approach because I came up with a different approach before I figured out a way to keep the springs from turning when tightening/loosening the all-thread.

Here's what I did when I had my old hybrid turbo with a stock Turbo II compressor housing. With 2 external springs, I got the small stock can to hold 29psi of boost (I can't find my old pictures, so I'll have to try to explain it):
1. Cut the Wastegate arm about 1" in from the flat spot where it attaches to the swingvalve
2. Using a tap, thread both cut ends of the rod, threading the part still attached to the can down about 2 inches or more (to give adjustment room).
3. Get a small piece of strong flat metal and cut 3 holes in it (one to go over the rod-in the center of the piece of metal, and 2 holes on each end for the springs to hook into).
4. Drill 2 small holes into the bracket that mounts the can to the turbo (one on each side of the can. The idea is that there will be 2 springs stretched the same amount on each side of the rod to eliminate side loads on the rod).
5. Thread a nylock nut onto the part of the rod still attached to the can, then slide the 3-hole piece of metal onto the rod. Attach 2 identical springs between the holes in the metal piece and the holes in the bracket.
6. Turn the nylock nut in or out to decrease or increase the tension on the external springs.
7. Use a coupling nut to re-attach the 2 threaded pieces of the rod back together.

Now you have an adjustable WG can that has the full stock travel and can be adjusted on the car.

I hope this description makes sense. Unfortunately, I can't show pics of this because I took parts off of my old can to add external springs to my current WG can.

I hope this helps.

[Tony Hanna]

Warren, that sounds exactly like what I'm wanting to accomplish, except the adjustment will be in a different place.
Do you think side loading the rod would be cause for concern?
I don't think my rig will have a problem with it as I intend to attach the spring to the w/g arm itself instead of the rod, but it's something I hadn't considered.

[csxtra]

Do you think side loading the rod would be cause for concern?
I don't think my rig will have a problem with it as I intend to attach the spring to the w/g arm itself instead of the rod, but it's something I hadn't considered.

Tony,

If you are using the stock can and attaching the spring to the swingvalve arm, I don't think you'll have any problems. I was concerned with the springs pulling the arm sideways where it goes into the can. And, by going with dual springs, I was able to get enough pre-loading to get my boost where I wanted it (a single spring didn't give me enough pre-load).

I currently have an aftermarket can (with a weak spring inside and a bent arm) on my hybrid turbo, and the diaphragm inside the can doesn't quite seal up right if there is side-loading on the arm (hard to avoid with external springs, given the way the arm is bent), but I never noticed that problem with my stock WG can, so you will probably be alright.

Take some pics of your setup and let us know how it works for you.:thumb: It is definitely cheaper than buying a big stiffly-sprung can.

[Tony Hanna]

That leads me to another question. What effect does the physical size of the can have on the range of pressure it will work in? I'm guessing the larger the can, the wider the range due to the increased surface area. I've worked with a couple small cans recently one was a stock TII can and the other was off a Holset hx35. Neither one seemed to be able to work in a very wide range of boost. The TII can would work in the 7-14 psi range and the holset can would work in the 18-28 psi range. That's one of the reasons I want to fool with the mitsu can. They are pretty large compared to the holset or small TI can, so hopefully with the right spring/tension I'll be able to keep the boost below 10 psi with the can hooked up straight, and get to 30 with it unhooked.
I know that's a pretty wide range, but it would allow me to run whatever I want at the track and still keep it reasonable on the street.