Hi I have a Audi 5 cylinder engine and build a turbo on it using manifold from s2 and hoses. Bought new turbo and fitted. After some minutes the oil is coming out of the exhaust side. Send the turbo back I was thinking it’s a bad manufacture but new turbo the same problem . What do I wrong? Oil feed have around 5 bar and return hose is bigger than feed line

 

What kind of turbo ball or journal bearing? Journal is full flow, ball needs a restrictor. Is the return straight down? Knock on wood mine doesn't smoke, some say if the drain is too flat they will smoke. You said bigger? I think the minimum recommendation for drain size is -10.

 

There is a sized restrictor for for journal bearing and a different sized restrictor for ball bearing. If your turbo is good you are dealing with to much oil pressure/inability for oil to leave turbo efficiently/points of too high crankcase pressure/inability to allow the crankcase to breathe effectively in order to release needed crankcase pressure. You can buy an automatic 40psi oil pressure regulator from turbosmart for turbo. Welcome to the game!

 

The turbo have a 1/4 turbo Feed and 3/8 return line it’s very tight under the turbo so there is a 90 degrees fitting under it. Is this size to small? It’s a journal bearing turbo

 

Turbo needs at least a -10 drain hose with good routing.

 

So the turbo is dead ? Or if I put bigger hose on it the problem solved

 

If you do a search you will find that there are a lot of issues when the drains are too small and you will also find solutions that fixed peoples issues.


ks

 

Needs a bigger return as was said. 10an or 3/4 barb.
Also pay attention to the adapter that bolts to the drain at the turbo. It needs to be as large or larger than the drain opening of the turbo itself.
Some peeps use an adapter with 3/8 npt opening at put a 5/8 or 3/4 drain fitting in it. Some times the 3/8 npt side is the restriction.

And the hose needs to be on a downward drain on its travels back to the pan. Any upward or horizontal runs will kill or reduce the oil flow back to the pan.

 

Did you say 5 bar of oil pressure? Like 75psi of oil pressure?

 

Yes I don’t know how much pressure is going to the turbo but the oil pressure gauge go to 5 bar oilpressure on the block

 

Thats probably your issue right there if you're not running a scavenge pump. A 90 degree right under the turbo is going to impede oil return so it'll back up in the turbo and cause it to end up going into the exhaust or intake.

You need a good long slope back to the oil pan to drain correctly, otherwise you can't gravity drain. If you can't pull that off, a scavenge pump to pump it back to the pan works too.

 

Is this a problem if the oil feed is a little out of the center ? Otherwise the return can not be straight please let me know

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No, the feed direction is not critical since it's under pressure.

The issue on drains is that the oil can be a bit frothy and doesn't drain easily on its own so the drains needs to be large and as straight as possible otherwise the oil can slow/puddle at a bend causing the oil to backup into the housing then the oil pressure from the feed line will push oil past the seals.

A slight angle on the drain can be acceptable IF the drain is really large.
My drains are 7/8" ID for each turbo but are fairly straight down to the pan.

ks

 

I believe the rule of thumb is that the drain can be clocked up to 15 degrees from vertical. With 70+ psi of oil pressure your drain needs to be large, constantly down hill, without many bends, and no 90 degree fittings unless its a long radius hose end. Also avoid restrictors until you've addressed the drain issue. Crank case pressure also needs to be addressed if you haven't already.

 

The worm clamp on a high pressure oil line would be an issue for me. Now on to your turbo leaking issue.

99% of all turbos smoking oil out the exhaust is due to a poor drain, albeit an undersized or restricted drain line, or crankcase pressure building up which is still a drain back issue, but by different means.

Feed a journal bearing turbo all the oil you can, never restrict the oil feed, not only does restricting the feed lower the volume of lubrication, but more importantly it reduces the volume of cooling that the oil provides. This is IMPORTANT, every journal bearing turbo that I've rebuilt where someone added a restrictor to, burned itself up due to heat, not lack of lubrication.

Ball bearing turbos are a bit of a different animal. They require less oil volume for lubrication, but many units are water cooled to aid in heat extraction.

 

When you say “Feed the turbo all the oil you can” do you ever stop and think that maybe the engine would rather have that oil pressure and oil volume? This is something I think about and I feel that a pressurized oil feed to a turbo should always be restricted somehow as without you are slowly killing your motor throughout time due to added wear from points of unsatisfactory oil supply and less engine oil cooling due to now limited oil volume supply. So yea there has to be a restriction based on pure mechanical logic, who cares about your stupid turbos feelings haha.

 

It's a -4 feed line. Your engine will be fine.

 

The journal bearings in your turbo are essentially like rod, or main bearings.. they're only going to use so much volume at a given oil pressure. You could feed it with a -8, and as long as the clearances are right it's still gonna pass the same volume of oil. The bearings are the restriction. If you wanted to reduce the volume/pressure, it should be done with a oil pressure regulator.

 

Just as

Exactly. This is what I did. I setup a regulator so the oil system for the turbos is just like a fuel system with a return line. I feed the turbos with 25psi and return what doesn't get used.
The oil pump pumps enough volume that whatever is returned has no affect on what the rest of the motor is seeing.

ks

 

Problem with this thinking, is that as the turbo rpm goes up, so does the centrifugal forces around the shaft and bearings trying to push the oil away.

So much so, that's why new bearings have grooves around them to help reduce the pumping affect the oil holes create.

It also takes oil pressure to keep the shafts centered. Oil comes in from the top and ~1/4 of the way clockwise. This means there's less pressure to the bottom and left, with high shaft rpms and gyroscope action, the shaft will move up and to the left. With low oil pressure its more exaggerated, and can even hit the housings.

main point is, feed the damn turbos as much oil as you can.

Journal bearings need all the oil they can get.