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In reality, brittle or ductile is a state of the material, and a mode of failure. Allow me to quote a page from the book:
"Unfortunetely, there is no clear boundary between yielding (ductile type material) failure and fracture-dominant (brittle type material) failures. Indeed, classification of many materials as ductile or brittle is meaningless unless physical factors such as temperature, state of stress, rate of loading, and chemical environment are specified. For example, many materials can be made to behave in a ductile manner for given set of conditions, and in a brittle manner for another set of conditions. To be mmore precise, one should speak of a material being in a brittle or ductile state. "
-page 547 Advanced mechanics of materials
I am suggesting an aluminum oil return tube will behave as brittle in this example because it is exposed to a wide range of conditions which typically cause Aluminum to behave in a brittle manner. For example, the chemical environment both internally and externally (oil, acids, atmospheric content), effects of temperature over time (heating/cooling), modes of vibration. The Aluminum oxide superficial is also classified as "brittle" and crack forming with very little ductile strain, meaning a crack in the oxide will create a stress concentration, snowballing quickly to complete failure in a brittle mode (a sudden break, with very little bending or 'ductile behavior' evident)
Finally, an important distinction between ductile steel and ductile aluminum is the fatigue limit,
e.g. quote,
"Aluminun has no fatigue limit, constant exposure of aluminum to repeated loading will ultimately lead to failure, no matter how low the actual stress magnitude experienced for all practical purposes"
file:///C:/Users/TaliNg/AppData/Local/Temp/ProBoat-June-July-2012-Aluminum-Welds.pdf
An oil return is subjected to several types of stress, nearly all of them. It's loaded physically, vibrated, chemically attacked, etc... just a poor choice of alloy for the location IMO, given how easily a hose could be fitted.
I think it is safe to say that the OEM manufacturers are typically using steel with rubber oil return for these reasons. And that failure is going to be experienced eventually no matter what you do in this application.
It might also last a long time, who knows. Its just my super-cautious nature when trying to build a reliable car, if you start putting 'maybes' all over the place, one or two of them could turn into 'oops'. And an oil return drain is not a place to have an 'oops' when a $14 hose could have prevented it. $.02
Sounds like you're fresh out of school.
In theory, practice and theory are the same. In practice they are not.
I did all the fabrication for this twin turbo ZR1 Corvette (93 model) back in the 2004 time frame and as of 2-3 years ago I was told it is still going strong with no issues. The oil drains are 100% aluminum that I welded as custom one off pieces. The passenger side scavenge tank is connected to the driver's side scavenge tank via AN line and it is then pumped back to the pan by the scavenge pump since the turbo's sat so low.
I cleaned up the lower radiator hose and then black wrinkled coated it. I also notched the compressor heat shield because it was interfering with the radiator fan and then coated it with a high temp black paint.
I next fabricated a heat shield for the radiator as well as the upper radiator hose. I will also clean this up and coat it with a black high temp paint.
A sad part of my story. I took my manifold to a machine shop last week to have them flatten the flange, which I did at the same shop for the previous two manifolds. The shop has a very nice table sander and they did a very nice job previously. However, when I went to pick up my manifold Friday they had done a number on me. Only the very ends of the flange were slightly bowed, which is expected and I had done some leveling on my own sander, but it is too small.
They ended up sanding an angle in the flange so the top of the flange was ground more than the bottom of the flange. Needless to say I felt sick to my stomach and dropped about 5 F-bombs trying to understand how such incompetence could happen. You would literally have to try to put an angle on the flange so i just don't understand the level of stupidity displayed by this shop. They guy kept saying the flange is now straight, but since the mating side is stepped he could see he ground an angle into the flange. I took it home and sure enough the angle caused the runner to touch the valve cover.
I took it back and told the guy I was going to fix it myself. I spent about 1 hour patiently getting the flange back straight, but in the process the flange is ~0.100" thinner and the room I had for the heat shield to go between the runner and the valve cover is just about gone. I am going to have two flanges CNC waterjet cut tomorrow, one from 0.125" 304 SS so I will put on a gasket...SS spacer....gasket and then manifold. I will also have him cut a 3/16" mild steel flange as a backup plan in case the 1st approach doesn't work. In this approach I will tack weld the spacer to my manifold and then weld the ID of each runner basically fusing with little to now filler rod. We will see what happens and I probably should have given myself more room, but I didn't think this shop would jack up a simple process of sanding the flange flat.
I sent the .DXF file to a buddy of mine and he is going to water jet cut the flange for me tomorrow and send back via priority mail. I am traveling M-W so it should be hear when I get home. Once I verify the flange is accurate I will post the file since it is different than a normal 4G63 (non EVO) bolt pattern.
Last edited by 240Z TwinTurbo; May 5, 2019 at 04:58 PM.
Crap. Good luck. That flange file would be invaluable as a resource!
Thanks and I know it is not that big of a deal, but I felt sick to my stomach on Friday. After flattening the flange and seeing that it no longer hit the valve cover made me feel better, but I now have to spend time and money to resolve the issue. I can also have a 1/8" solid copper gasket made for ~$100 so I have plenty of options to address the issue. I've got over 40hrs in this setup so I take it personal when stuff like this happens. I'm sure I won't even think about his issue once it is running.
Well my buddy still hasn't sent me the cnc stainless flange so I purchased a piece of 1/8" T7075 and traced the bolt holes for the exhaust manifold gasket. I am just using this as a spacer so I can finish the heat shield and downpipe this weekend. With the 1/8" spacer I have plenty of room for the heat shield with it gapped off the valve cover and gapped off the manifold. I'm using stainless, which is a PIA because it moves around a lot.
Last edited by 240Z TwinTurbo; May 9, 2019 at 04:32 PM.
@240Z TwinTurbo Why dont you switch to white lighting by swaintech?
And are you water cooling your waste gates ?? I'd be interested in your plumbing route.
Switch from what? I don't use coatings. No, I don't water cool the gates because I don't see a need to do so. I've been running these gates for almost 5 years without the water cooling.
I would if only especially for the gate near the compressor.
The compressor cover of my S364 initially ran 350*F during normal driving. I emailed BW engineer and he said that was normal.
I made a little shield to go between the compressor and turbine, and added water cooling to the gate nearby, and now it runs about 180*F.
Lower temperature means longer component life, and a cooler compressor potentially, and it doesn't cost much. And its completely reversible if you hate it for some reason.
I would if only especially for the gate near the compressor.
The compressor cover of my S364 initially ran 350*F during normal driving. I emailed BW engineer and he said that was normal.
I made a little shield to go between the compressor and turbine, and added water cooling to the gate nearby, and now it runs about 180*F.
Lower temperature means longer component life, and a cooler compressor potentially, and it doesn't cost much. And its completely reversible if you hate it for some reason.
I made the shield already between the gate and compressor housing as shown above. I can cool the gate, but I still have convection from the manifold, which is hotter and has substantially more surface area vs the gate. I will likely be adding a turbine blanket.
Even though I can now get the downpipe off the car with the radiator in place I decided to add a 3.5" vband to the downpipe. It is located on the 90deg bend before going below the oil pan. Not an ideal location, but it is still a seamless transition. It will also make it much easier to tie in the new downpipe to the current exhaust if I don't have to pull it from the turbo and wastegates every time I fit a pipe.
The downpipe put up a good fight, but he finally surrendered with this hands in the air.
Now that I have the downpipe in the car I locked down the vband clamps on the turbo and wastegates. I can now just fab the short piece to tie into the old downpipe.
Don't mind the dent, this was a recycled piece from my downpipe when I ran the top mount setup.
Downpipe is finally done, but I am going to weld an O2 bung before the oil pan because I want to position the wideband closer to the turbo. Other than waiting for the 1/8" stainless spacer plate and trimming the heat shield for the hood the setup is ready to go.
May 4, 2019, 07:06 PM
