Oil Drain Plug Return Line

[Edub1]

Ok, I know this is going to sound totally ghetto but it's worth considering.

I'm wondering why the oil drain plug couldn't be used for the return line. Obviously some care would have to be taken when changing the oild but other than that I don't see why this would be a problem.

Also, where do most of you take the feed from?

[BillKlineVT]

would never work.

Oil return line is gravity fed, and wrapping it all the way around to the drain hole would not only be ugly, but it'd be at the bottom of the oil in the pan, wouldn't flow well at all.

This has been brought up a million times, just to let you know.

[TheOne]

i think its cause the oil would stay in the line and go back up to the turbo and mess up the turbo.(because the oil around the pan is allready in there makin weight and well the oil comin out of turbo can't move all of that oil so that the turbo oil goes in, thats why people put it up on the pan so that the oil flows down to the pan without restrictions), as for the feed line people use a sandwich adapter where the oil sendin unit or whatever goes.

[Edub1]

No kidding, I've never seen it mentioned.

Anyway, being at the bottom wouldn't matter as the oil would seek it's own level.

[DammitBobby]

Good luck with that one! TheOne is correct if you put your drain at the bottom of the pan then oil will back up to the turbo and blow your seal. That is why everybody tries to put the bung as high as possible on the oil pan. Some people even run with a quart low on oil to prevent oil from backing up into the turbo.

[eddiec]

there would have to some sort of force to "push" the oil up into the pan. gravity only works one way and any rock climber will tell you that is str8 down.

in addition what would happen if you bottom out on the pan?

[:: orion ::]

Some people even run with a quart low on oil to prevent oil from backing up into the turbo.

I would like to point out that that is the WORST idea EVER on your KA.

The oiling is barely adequate as is when running at sustained high RPMs...and half a quart low is enough to spin bearings.

Seen it over and over and over and over and over....seriously.

(Just a heads up[ for the newbs that may read this and think it an OK idea. It's not.)

...

I run mine half a quart OVER for track days!

- Brian

[pr240sx]

What would happen if I pressurize the crank. For ex, if I accidentaly connect the valve breather to a pressure line?Does the turbo seals will suffer in any way.Also, can I damage anything if I use a hose too big?

Just for curiosity, my KAT is safe and sound.

[Edub1]

You guys ever play with a siphon at all?

The oil in the line is being pushed down by gravity untill it is at the same level as the oil in the pan. Are you guys thinking that the oil in the line has to push against the oil in the pan?

Try this:

Get a bucket and fill it to the top with water. Submerge one end of a 1" pipe in the bucket so it runs straight up & down. Now have your friend hold the pipe while you pour a second bucket of water into the top of the pipe. Feel free to do this on your mothers new carpet as the water in the bucket should prevent the water in the pipe from comeing down. Let me know how it turns out.

[BillKlineVT]

Assuming you're trying to be saracstic on that on there edub1...

Since oil has a higher viscosity than water, that's not really an accurate comparison for starters... Not to mention that "siphon" theory does not take into account that the oil needs to flow at an acceptable rate to avoid backing up in the line. That would never happen by gravity feed, especially because it has to go "uphill" to get back into the bottom of the pan from the drain plug.

Also, oil backing up into the center section doesnt necessarily blow the seals, it just lets oil blow past the seals... those seals arent that easy to blow, from what I gather.

[Edub1]

I'm all for guys using some good old mechanical intuition but the fact is the line being blow the oil line will not casue any resistance to the line. I know it seems like it would, but if you look at the physics involved (from a book) you'll see that this is true. In fact, the drain line pressure will exceed the pan pressure by the oil density * column height * -9.8m/s^2 . This shows that column height is the only relavent factor and the height of the turbo is way higher than the level in the pan. If you don't believe me, look it up.

It sure does seem like there would be some back pressure, but there isn't.

Can anybody think of any other reasons?

[guyaverage]

Edub1, your thinking is right on track for the most part as far as flow, gravity, siphoning, etc are concerned, but there are things that come into play here because of the way turbos are lubricated.

Since oil has a higher viscosity than water, that's not really an accurate comparison for starters...

True. A large drain tube could make up for that though.

That would never happen by gravity feed, especially because it has to go "uphill" to get back into the bottom of the pan from the drain plug.[/

The oil going "uphill" is irrelevant. The oil going "downhill" has the same weight as the oil going uphill. As long as there are no air gaps, leaks, or breaks in the hose and the oil (or any fluid) fills the entire void inside the hose, the amount of "rise" is irrelevant as long as the outlet is ultimately lower than the inlet. However, as you point out.............

Not to mention that "siphon" theory does not take into account that the oil needs to flow at an acceptable rate to avoid backing up in the line. QUOTE]

THATS the problem. The oil flowing through a drain line that drains above the oil level has no restriction and will flow the fastest. If the line terminates below the oil level (at the drain plug for example) even though the oil will flow, and will EVENTUALLY seek the same level as the oil pan level, it wont do it FAST enough to prevent excess pressure at the seal. Its too thick, and wont flow quick enough against its own weight or its internal resistance to flow (viscosity) to do this.

The problem with turbos is that they rely more on oil FLOW, not oil PRESSURE. The pressure of the oil, even the little extra bit caused by the oil flowing (by gravity) through a less than 100% restriction-free oil drain, can push it past the seals. If you look at the size of oil drain lines compared to the oil supply line, you'll see that the manufactures are clearly trying to get oil OUT of the turbo as easy and quickly as possible.

The turbine shaft needs to float on a cushion of oil to spin at the rediculous speeds they spin at (100,000+ rpms) and when combined with the incredible heat inside a turbo, a good flow of oil is necessary to keep things cool enough to prevent oil coking. High oil pressure isnt necessary because the load on the shaft is a spinning load, not a force-transfering load. High pressure isnt necessary, and the design of the seal accounts for that.

If you research it more (outside of this forum) you will see EVERY single sight (at least all that I found) that talks about oil drain lines, emphasizes (some emphatically) to drain the oil ABOVE the oil pan level. I have been researching turbo installations for months in preparation for my KAT project. Edub1, I would have typed your exact words not a few months ago, until I really dug into this. Take the advice of masses on this one, dont plumb into the drain plug. Some may have done it, and may be "getting away" with it, but dont take the risk. The extra couple hours removing the pan is not a good place to take a shortcut in this case.

[fiznat]

I'm all for guys using some good old mechanical intuition but the fact is the line being blow the oil line will not casue any resistance to the line. I know it seems like it would, but if you look at the physics involved (from a book) you'll see that this is true. In fact, the drain line pressure will exceed the pan pressure by the oil density * column height * -9.8m/s^2 . This shows that column height is the only relavent factor and the height of the turbo is way higher than the level in the pan. If you don't believe me, look it up.

It sure does seem like there would be some back pressure, but there isn't.

Can anybody think of any other reasons?

This assumes that you have a constant column of oil standing in the return line. It may be feasable if thats what happens, but the fact that you have oil backing up in the line like that is reason enough not to use this setup. 1, the KA cant spare the oil sitting idle in the return line (not being used on bearing surfaces), and 2, the higher that column gets, the closer you get to to the turbo and resulting oil back-up- choking bearings and leaking through seals. Youd have to be pretty damn confident in the system to risk the possability of the return line filling and choking off the turbo like that.

The idea MAY work, but it flirts just a little bit too close to disaster for my taste.

[4felix20]

plus it's kind of foamy on the exit from the turbo. doesn't really flow well..

[Edub1]

Intuition & popular opinion tells us that having the line below the oil level will cause an opposing force. I'm fairly well versed in physics and I'm 99.9% sure that despite this seeming intuitive to most people, there is in fact no opposing force.

Consider a wave runner with the jet relocated to above the water line. Most people would say that it won't go because the jet would not have the water to push against. In fact, the craft would operate exactely the same because it is the mass & volocity of the fluid being ejected that pushes the craft. So, it should also follow that the force working against the oil flow comes from the mass, velocity and viscosity of the oil exiting the tube & not from "pushing" against the pan oil.

I'm not saying this is exactely the same but it has similar principles.

But I'm not here to win an argument, so if someone can explain via formula I'm all ears. But I'm 99.9% sure that if you open a physics book you will find that the only way the oil would see resistance is if the turbo it self was below the level in the pan. As long as this isn't the case, you have pump pressure and gravity on your side.

[WDRacing]

THIS DOES NOT WORK....PERIOD. I HAD A RETURN LINE INSTALLED LOWER THEN I WANTED ON MY PAN AND THE OIL BACKED UP AND CAUSED MY SEALS TO LEAK. SO EVEN LOWER WILL BE WORSE.

THIS THREAD IS DONE, I DON'T WANT ANY NOOBS TRYING THIS.

[fiznat]

hahahaha.

Hes right though. Dont do it.