You have a drain issue if you need a restrictor on a journal bearing turbo to stop if from spewing oil.

 

No way I would do both

 

I don't like using tiny holes to restrict oil flow either b/c they also restrict it at low oil pressures, like at idle, so I use a pressure regulator on mine that operates exactly like a fuel return regulator. I regulate the oil psi down to what I want then the excess oil is returned to the pan.

http://www.petersonfluidsys.com/pump_remotereg.html


ks

 

Just to be clear, when my turbos wheep oil into the hot side turbine it only blows smoke after the turbo has been ran through hell and I rev the engine sitting still or when it is cold ran on a dyno. I believe this issue is from crankcase pressure getting to high from cylinder blow by, me running a high pressure oil pump, and having two tiny breathers on each valve cover that became clogged. I have since put the correct size breathers and will install the regulator also, then I will do some testing to make a determination.


Now it’s time for @F4K to take the cake!

 

Depending what bb turbo you bought you might not need a restrictor. The newer bb turbos have the restrictors built-in to the bb cartridge/ outer race.

 

Yeah, that’s what they swore.

 

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You want me to say something
The breathers allow pressure of the crankcase to go over atmospheric. This increase gas density and reduce organization of flow within the crankcase as pressure is a scalar with no direction and there is no primary vector component flow for turbulence within the crankcase (turbulence in a pipe with a specific flow direction), which leads to reduced mean path between random fluid molecule motions (more frequent collisions between fluid molecules with no specific direction as opposed to more frequent collisions with fluid molecules that have a specific direction, i.e. more pressure in stagnant flow vs more pressure in turbulent flow within a volume), larger oil droplets, and high resistance to droplets which formed in gravitational field of crankcase gas which would normally return them to the pan is instead keeping them suspended allowing them to be pushed out of the crankcase or pushing into regions where they do not belong such as oil seals (oil leaking) and piston rings (Oil seals) and engine oil (contamination and circulated deposits forming) and turbo oil drain (blockage).

What this all leads up for a turbo is a difficulty in the turbo oil drain line. Higher crankcase pressure causes oil to back up in the drain line because of the additional crankcase pressure over atmospheric. I advice measuring the crankcase pressure and modifying the pcv system to provide a vacuum to the crankcase at wide open throttle as I have shown in my videos.

As to the oil feeds. The 4an with no restrictor is classic feed for journal bearing, however the line length adds friction and I was told by Borg Warner engineer not to exceed some length I believe around 3 or 4 feet of -4an otherwise they told me switch to -6an. So keep this in mind your -4an might become a restriction > some length. Also the seal between compressor and bearing housing on some turbos even brand new is terrible, particularly precision and copies of precision turbos, I've noticed they fail pressure testing right out of the box pretty consistently.

The ball bearing restrictors usually you can see them looking down into the turbo feed, built in as cast.

 

You should have an inline oil filter b4 the turbo anyway to keep trash out if there ever is any, restrictor would be best for you. Dont run both.

 

I was advised never to use inline filter by Full Race Geoff (full race motorsports) because the filter just clogs and takes out the turbo anyways which I guess guarantees metal shrapnel into your engine oil

 

I ordered the turbosmart auto 40psi regulator. I agree with what you are saying F4K however the regulator has a filter built into it. I also ordered the restrictor but will just put the regulator first to see if it solves the problem by limiting some oil amount entering the turbo despite me knowing that crankcase pressure also applies pressure to the oil in the turbo through the turbo drain line. I just got to wait to get the parts so I can decide how I will place it and if I can alter the regulator because I don’t use 4an. If the things I haven’t done so far cannot resolve the issue I will install the restrictor also.

 

Crankcase pressure doesn't add pressure, it takes it away. If there's 10psi of cc pressure, it takes 10psi of oil pressure to overcome it.

Also I just want to add, you should not be restricting oil to a journal bearing turbo. When shaft speed increases, so does the g forces acting on the oil trying to push it away from the shaft. Pressure is needed to keep the shaft centered.

If your turbo leaks oil, it has a seal/ drain/ crankcase pressure problem, not oil pressure problem.

 

When an engine have a vacuum pump to suction on the crankcase, oil pressure goes down, I think flow increases. I guess the vacuum pulls oil out of the bearings and because the oil pump is a volume/rotation the vacuum doesn't have much affect on oil entering the oil pump besides cavitation related to viscosity and pressure drop. In other words, pressure pushing down on the liquid oil does not improve oil flow because pressure does not change the density of oil much and the pump can only move so much per revolution.

For example, this is quite common to hear
https://inthegaragemedia.com/horsepower-from-nothing/

It kind of makes sense to me. Despite not being a published engineering source I think the logic is there.

But looking at the turbo feed and drain is not the same as a crankcase bearing system. The feed is a orifice and higher pressure means higher flow through the orifice, like a fuel injector flows more fuel at higher pressure. The fuel pump on the other hand suffers at higher pressure and pumps less fuel. So like you are saying increase the crankcase pressure now we may have a reduced oil pump flow rate just like with vacuum we have increased flow rate. But the oil pressure rises with the crankcase pressure like fuel pressure as oil pump/fuel pump flow rate diminishes. We have to be careful because the orifice of the turbo feed works inversely- I think it will flow more oil with increased oil pressure despite the oil pump flowing less oil throughput to the engine. Just like when we have a vacuum pump and oil pressure drops the oil flows faster through the engine but slower through the turbo oil feed orifice, like a fuel injector would do with reduced fuel pressure, even though the fuel pump is pumping more fuel.

In any case. I wasn't concerned with the oil feed anyways. Its the oil drain I am looking at.
No matter how fast or how much oil we push into the oil feed orifice, if it can drain out quickly enough, there is no problem. This is probably why we put turbos on all kinds of engines, chevy nissan toyota whatever, some have 90psi oil pressure some have 30 or 50 etc... and they all do fine with a nice return line the correctly sized and free flowing. And this is where crankcase pressure prevents drainage no matter what your oil pressure or feed orifice size is, if the drain can't drain there is a backup in the drain which causes oil to force from the turbo seals and it starts to smoke and leak out from the center. The drain is gravity based- we have gravitational field which applies vector acceleration components to fluid molecules and mass contained within the drain line. The opposing force is friction, which is based on line diameter and orientation, gas density, fluid viscosity (temperature related), windage/hurricane (sloshing, foaming, and obfuscated drain exits).

Of those drain friction issues, the gas density is related to pressure. High gas density causes molecules to collide more frequently forming larger oil droplets and maintains more oil as a suspension. It prevents oil from returning to the pan in the drain line and inside the engine crankcase everywhere. This is the main reason high crankcase pressure causes oil drain issues.

 

Your correct when you said the turbo oil ports are an orifice. And that flow increases/ decreased in relation to crankcase pressure, but it does not alter the supply pressure because it is after the orifice.

Although flow rate changes, pressure is what gets the oil past the floating bearings (that act like centrifugal pumps themselves) and to the shaft. Any additional case pressure cancels out its equal amount on the pressure side.

So if you have 40psi of oil pressure, 10psi of case pressure, you now only have 30psi of effective oil pressure to the turbo.

I dealt with this in the amateur turbine world with the fuel nozzles. Guys would try to use 100psi fuel nozzles, then try to make 40psi of boost and wonder why they couldn't. Fuel pressure had to rise to overcome the boost pressure so that the flow rate could stay the same. Which agrees with what you said, but flow rate doesn't matter in turbos. For instance, feed one turbo with 20w50, another 0w20. At the same pressure, the 0w20 would have higher flow rate.
At the same flow rate, the 0w20 would have less pressure, which turbo would last longer? The one with greater oil flow rate, or pressure?

 

@bbi_turbos like I had said in the prior posts it is a ball bearing turbo not a journal bearing turbo.

 

Yes of course just like with fuel injectors. However the return rate of oil to the pan does not increase with increasing oil pressure feed, so the analogy although it works for the bearing lubrication has no bearing (pun intended) on the oil return rate to the pan which is based largely on gravity, oil droplet state (foaming, radius size, droplet density in suspension) and friction. Pressure working against the flow rate into the bearing will also work against it getting out. High crankcase pressure causes all of the symptoms of smoking turbo and oil drain blockage- despite the decreased oil flow into the bearing. Its bad on both accounts.

In my vague effort I would point out that oil film thickness, viscosity, shear force applied by rotating speed of some components, roughness of said components, and other factors influence the longevity of the spinning object which requires lubrication. There isn't enough information in your question and I will easily spot and tell you why this is. First we do not know the required film shear strength or thickness. The higher viscosity oil would be beneficial in a situation where higher shear and thickness is required such as large bearing clearances provided flow rate adequate. The low viscosity oil will flow more easily and if the clearance is tight this would be a requirement. The ability of the oil to resist shear and remove required heat and debris is the other factor- if the light oil can do it then the lighter oil the better for flow rate. But if the light weight oil cannot maintain it's oil film due to applied forces then it doesn't matter how fast it will flow, damage will occur.

 

@TurboSnake281 yep, your good, ball bearing turbos are affected by case pressure, but its not nearly as critical as it is with journal bearing turbos.

Just trying to get some info out there, never know who might be searching for it in the future!

 

I will post the final outcome.

 

I hurt my journal bearing turbo in only a couple hours of runtime with the restrictor.

I took it out with the advice given here and it's been great ever since. Still a little loose but hasn't got worse.
If you have to run a restrictor on a journal bearing turbo to keep it from leaking past the seals, then you didn't spend enough on your turbo.

 

Or the drain plumbing sucks.