gating my secondary? eating up thrust bearings

[turbominivan]

i have an HX-40 / HT3B twin set up. up until tonight i have had the HX-40 ungated (gate held shut). ive boosted up to 94psi that i have seen but im sure it can do more (not that i need it to....)
anyways, my issue is that with that kind of boost and an ungated smaller turbo, i believe the large turbo is forcing enough volume/pressure of its own into the smaller hx-40, causing the hx-40 to get over spun, and/or the compressor is being 'pushed' against the thrust bearing causing wear and then eventually a slight oil leak at the worn thrust bearing area (not nearly enough for a run away). ive replaced the thrust bearing on the HX-40 3 times now. each time it shows heavy wear. im using 360* thrust bearings.

so tonight what i did was put a factory style waste gate actuator on the hx-40 set to open at 30psi. i was planing to run the vacuum line to it from the PRIMARY turbo so as the primary begins to boost, the gate on the HX will open and take some stress off of it.

i havent taken the car for a drive yet (this is in a hot rod), but im assuming already that to gate it for 30psi off the primary, its a bit too late. im thinking that by the time the primary is making 30psi, the over spinning is already in full swing.

so for the questions....
should i lengthen the actuator arm to open off the primary at say 15psi,
or should i leave it gated at 30psi and have it actuated off the manifold pressure at 30psi?

from what i see, the HT3B seems to begin waking up when the manifold pressure is between 10-15psi.

with the actuator set to open at 30 as it now sits, my thinking leads me to lean toward using the manifold pressure to open it, not the primary.

would i be wise in this? or should i lengthen the arm and use the primary pressure at say 15psi?

would using the primary to actuate the gate cause fluttering or overly rapid responses??

or should i use the the actuators vacuum port at all? and just let the exhaust pressure push the gate open and regulate itself?

im not so much trying to lower boost as i am just trying to keep thrust bearings alive.


ignore the oil drip/stain just below the HT3B feed pipe. that was from greasing the flange when putting things back together

 

[12vriviera]

I would run overall boost into it and see what it does, then pull hose off and see what it does.
And see if it needs to be anywhere in between.. Then make you rod length changes, boost controller changes etc.... And not break input any more. LOL

 

[Scooter's Roofing]

bad ass car!

boost is not everything... I'd put the thing on a dyno and play with wastegate settings. If you can make the same power at 65psi as you can at 94psi, guess which setup lasts longer?

 

[bgreen776]

Forgive me if I'm stating the obvious...

How much drive pressure are you running at 90+ pounds of boost? I'm just making an educated guess that its probably nearly double. With high drive to boost ratio, say 1.5:1, you are putting high thrust load on your turbo.

 

[jasonc]

Advancing the timing will lower boost.

 

[Drothgeb]

While lowering your drive pressure is always a good thing, using steel thrust bearings will last many times longer than the standard bronze ones. I use to go through bronze 360s in less than a month, the current steel ones have lasted over a year and they're still fine.

 

[bgreen776]

The current ones are Steel? Or do they just look like steel, with their fancy coating.

 

[Drothgeb]

Check them with a magnet. If they are steel and you're wearing them out that fast, you have serious drive pressure issues.

 

[bgreen776]

Did you check yours with a magnet? I just installed a new 360 thrust bearing in my s366, it wasn't bronze or brass colored, kinda a steel grey but I assumed that was a coating, not the actual base material. Never thought to check if it was ferrous.

 

[JQmile]

My 95 made more power at 57psi with the gate open, than it did at 65psi with the gate shut. I bet your drive pressure is like 150psi or something insane. Try it with the gate open and see how you like it. It'll probably make the same or more power with less boost.

Edit: Oh, and nice rod!

 

[turbominivan]

My thrust bearings are bronze. Ive never seen a steel one.
Ill try it with the gate open and see what kind of manifold pressure i get before the primary wakes up

 

[nwpadmax]

I would venture a guess that it's not steel....but an iron-based powder metal sintered bearing with some % porosity to hold oil. Like an Oilite bronze bearing but based on iron.

 

[Mechanical 96]

Where are you guys buying the "Brass" 360* thrust bearings at?

 

[biggy238]

Or the ferrous one for that matter?

Squeaky Wheel

 

[turbominivan]

the ones im using are just off ebay

 

[bgreen776]

Where are you guys buying the "Brass" 360* thrust bearings at?

I bought my "brass" 360 kit on ebay, from mbwracing_6. It measured in all dimensions the same as what came in my two box S300's, within a few .0001". I put some hard test runs on it in my S366/483 setup, and a few hundred hard street miles on it. Not so much as a mark on any of the bearings when I pulled them out a couple days ago. The thrust pads are flat.

I bought my "Steel" looking genuine Borg Warner from Stainless Diesel. This bearing has oil wedges milled into the the thrust pads like a high quality thrust bearing should have, but I haven't run it yet. It also cost 3 times as much as the brass thrust bearing, and roughly the same price as the entire used S366 it went into.

The 363 came with a stock Borg Warner 270 bearing in it, I ran it as a single, and it barked badly. Within 500 miles the thrust bearing was completely wasted. When I installed the 360 bearing in this turbo, I installed the turbo above an S483 so I can't really say if the cheap 360 is any better than the good 270, but I'd bet on it, oil wedges or not.

You can see in the pictures below, the wedge shaped thrust pads, even though the tops of them have been wiped off from the high thrust loads due too high of DP across the turbo.

 

[bgreen776]

This thread makes me want to take my turbo back apart and have it PMI'd just so I know what it is. Or at least mag test it and take a cut on it with a small endmill to get a feel for it. LOL. It also makes me want to pull down my BD R700 turbos and see what kind of thrust bearings are in them, as they have endured extremely high (by most peoples standards) drive to boost ratios.

 

[bluthndr]

I just redid my 362 that I found a worn thrust bearing in by accident. I could feel some in and out play in the shaft when I expected none. Radial play felt on the high side of "normal", and was close to allowing the compressor wheel to make contact with the housing. After reassembly things feel normal again with no perceptible in and out movement and the normal radial "up and down" movement. I work with turbos most everyday, so I didn't actually measure the play with an indicator.

I did however, measure the thrust surface on the new and old thrust bearings, and the difference was approximately .008" - even with them next to each other you really couldn't notice it until you measured it. Turbo did not have more than probably 20k miles on it, so it proves that I have some drive pressure issues I am still trying to work out.

Hope this is useful info for someone.

It is totally dumb luck I caught it while I was working on other issues. I was probably less than 1,000 miles from blowing up that turbo and all that goes with it.