Hey guys -

I've been thinking about this, and one of the local guys here has had some woes with stock twins that barf oil into the exhaust.

Basically, the turbos are used, and it's pot luck if they're in good shape or not. Of course, it just takes one turbo to be bad and you've got smoke, but you don't know which one is bad. Sometimes it's obvious when you remove them from the car and one is dripping oil and one is dry, but it would be nice to know beforehand.

Anyhow, there's GOT TO be a way to positively bench test a turbo before installation to verify that it doesn't have oil leaks into the exhaust or intake side. I'm guessing to do so you'd probably need to go full-bore - an oil pump of some kind that can run 30-40psi of oil pressure into the turbos then return to a tank to be pumped around again.

Anyone have any ideas? Tried anything before? Have some secret handshake to know if they're good or not?

This is going to be more critical going forward as more stock twins wear out. And, if you have 2 sets of bad twins and each has one bad turbo, you can make one good set of twins without having to track down another set and pay more money.

Any ideas? Let's work out a solution for this problem.

Dale

 

Pressurizing the oiling galleries is the easy part but they will leak unless you can simulTe the pressure differential in the turbine and compressor housings which is what keeps you oil 'sealed' it's essentially half an air seal and half piston ring style seal. That's why turbos that don't pressurize every so often like just idleing can start to smoke as the oil gets past the seal.

Z

 

I wonder if there would be a way to use air over oil. Just throwing this out there but take some oil and cap the drain, buy a cheap pressure regulator and a Y manifold for your compressor. Run the cheap regulator to the oil galleries and pressurize to your desired oil press (30-40 like you said) then run the other line out of the compressor to the turbo (of course use some silicone couplers and a plug like the fighters intake pressure tester) to pressurize the turbo to your desired boost level say 10.
First thing that came to mind I could be completely out of my mind though( long winters up here )

Mike

 

I found a pic of a turbo and made some lines and letters near it LOL. It might work if I had my turbos off I would mock something up.

 

Most turbos will smoke at idle if they're bad, and at idle you should have little exhaust pressure if any.

Also, the pressure on the oil side will have to be higher than the exhaust side - that's how the oil gets out. If exhaust pressure was higher, the exhaust would push into the oiling system.

This is a tricky one... There's GOTTA be a way.

Dale

 

I still don't think that would work as even though pressurized oil is feed to the CHRA it is essentially non pressurized once it hits the bearings basically just bathing them. So any pressure greater than the pressure on the turbine and compressor would leak. You'd have to have the drain to simulate real world operation.

Z

 

Hmm this is going to be a tough one. i will stew on it lol

Mike

 

I have pondered this one for some time now. The most basic test I could come up with was applying 30 psi (idle oil pressure). Beyond that, it gets way way to complicated between pressurizing the compressor/turbine and spinning them. (Since just pressurizing the compressor/hotside would not spin the shaft, which creates the seal. Its not just the pressure involved here.)

 

Read this:

https://www.rx7club.com/single-turbo-rx-7s-23/turbocharger-oil-seal-leakage-explained-727476/

Point 1:

"1. Large turbos on small displacement engines means that turbo speeds are lower than properly matched turbos, therefore, the dynamic seals are not as effective. Furthermore, the air pressures at idle are likely lower on the turbine side with a large turbo."

The ring seals are dynamic seals and need pressure + turbo SPEED to work, hence your test will not be sufficient.

 

This is probably more than you were looking for but it seems to me a electric over hydraulic power unit would do it. They are commonly used on liftgates and small
dump bodies (I am the parts & service manager for a heavy truck equip. co.). I have used these to operate port-a-powers and other manual pumping hydraulic tools. You can turn the output pressure down to say 100psi or whatever you want. If you have a demand for such a unit I could try to put you a used one together free w/free UPS to you. Fill w/ motor oil and just run the out port on turbos back to top of oil tank on unit.

 

Generally, no, I would not expect that type of seal to perform similarly with air vs. oil. Oil has a much higher viscosity that helps create the seal.

As far as applying air pressure on both sides of the turbo, that may not be necessary. You simply apply less pressure with the oil.

Regardless of the test setup, you're trying to detect qualitatively if the turbo seals are good. Quantitative differences (leak rates) don't matter if you can predict a bad seal.

 

i ran into several used sets that were junk.... all blowing oil into exhaust... what i started doing to test them faster was id hook up the bare minimum, bolt turbos on, hook up oil lines, hook up exhaust, but no intake piping,no intercooler no water lines , then drive it around a few blocks does it smoke or not?
this will test if oil is going out the hot side, u could shine a flash light into the cold side and look for evidence of fresh oil to see if its blowing by there also,

 

^ just mow a few more lawns, save up for some bnrs