Oil collecting in TB coupler

[serkan]

05 Legacy gt, 5EAT, VF46 and everything else is stock.

 

I did compression test all cylinders were 120-125 psi (cold engine)

 

Car doesn't smoke at start up. If I do some spirited driving and take the intercooler off I see oil collecting in the TB coupler.

 

I put a catch can (w/o routing back to intake), I didn't see oil collecting there.

 

No trace of oil in the downpipe.

 

Could it be turbo seals ? If so wouldn't there be oil in the exhaust side as well ? I bought the VF46 from a guy here and it has considerable shaft play (in and out and side to side). Doesn't make noise at boost or anything.

 

Any suggestions to figure out the culprit ?

[ehsnils]

It can be the crankcase ventilation that spews out some oil when driving inspired. Check for oil residue also in the air box after the filter and in the ventilation hoses to confirm.

 

If it's the ventilation that's the culprit you shall see oil even before the turbo.

[chato]

where did you put the catch can?

catch can won't likely catch anything if there is no vacuum pulling air/oil out of the engine into the can.

 

there are two systems (besides turbo seals) that could be causing oil to get in the intake tract--pcv and VC breathers.

 

my pcv valve was stuck which was causing a fair amount of oil residue and consumption. also i get a small amount of blowby oil through the VC breathers. As I understand it, these cars should have a proper air/oil separator or a dual catch can setup (breather and pcv) if you want to take all the oil out.

[serkan]

I changed the pcv valve with a working one, so it is not that.

 

When I tried the catch can, I didn't hook it up to the inlet. And I only did the VC breathers.

 

I will try it on the crank case breather before pcv and route it to the inlet. And see what happens.

 

Problem is I have a crappy Greddy catch can. It is basically an empty aluminum can. There isn't even a separator between the ports So I doubt it will catch anything.

[chato]

yeah, IIRC that breather is a two way, so air should travel both ways.

 

the answer on proper catch can routing is in here somewhere:

 

http://www.iwsti.com/forums/2-5-liter-litre-factory-motor/146699-official-sti-engine-venting-o-separators-catch-cans-thread.html

[rob-2]

if it's not pcv you have bad comp.

[serkan]

I did compression test and I got same numbers for all four (120-125 psi) on a cold engine.

 

No smoke out of oil fill cap or dip stick.

 

I can do leakdown test too.

[rob-2]

I did compression test and I got same numbers for all four (120-125 psi) on a cold engine.

 

No smoke out of oil fill cap or dip stick.

 

I can do leakdown test too.

 

Well that's good. There aren't a lot of ways to get oil there.

 

A leak down test might be needed. Someone with a cracked ringland might chime in but I think you'll still make reasonable compression.

[ehsnils]

Be aware that the oil from the engine vents may be in the form of a mist and might not be caught well by the catch can while it sticks well to the intercooler which has a large surface.

 

An empty canister makes a lousy oil catch can, try something like the following. Also locate it in front of the radiator in order to keep it cool.

 

 

http://www.bedug.com/pics/oil_catch_can.jpg

 

Here's a DIY version:

http://www.team-bhp.com/forum/modifications-accessories/117722-diy-cheapo-oil-catch-can.html

[dga]

...

If it's the ventilation that's the culprit you shall see oil even before the turbo.

 

Wouldn't this be normal operation, oil in the turbo inlet especially since the PCV valve is made to go into both the inlet and the intake manifold?

[serkan]

I plugged the PCV valve hose and hose going to the inlet. Ran the crank case breather directly to a plastic bottle (Not T-ed to PCV or inlet)

 

Went out and did some pulls. Nothing collected in the bottle. There was traces of oil at the turbo compressor outlet. But no puddles in the TB.

 

Maybe oil vapor didn't condense in the plastic bottle and just vented to atmosphere.

 

I will try hooking up the catch can tomorrow and see it catches anything.

[chato]

one thought is that by just venting into a can, you removed the vacuum source present in the normal system, might impact the amount of oil collected. as I understand it, the vacuum is also highest when out of boost, because the pcv pulls from the manifold and not the inlet in those situations.

[ehsnils]

Wouldn't this be normal operation, oil in the turbo inlet especially since the PCV valve is made to go into both the inlet and the intake manifold?

 

You don't really want the oil to end up in the inlet, it shall remain in the engine. But you want to get the blow-by gases back into the engine to be burned.

 

Under normal conditions the PCV shall open and let some of the blow-by gases into the manifold and at the same time pull fresh air from the air box into the engine. This to avoid accumulation of water vapor in the engine.

 

During boost the manifold is pressurized and therefore a temporary alternative is to vent into the intake before the turbo. When driving hard the ventilation goes "backward" also in the vents from each cylinder head into the intake, and when cornering the oil may not be evacuated from the cylinder heads in a timely manner and it ends up in the intake instead.

 

So doing straight pulls may not yield much "spill". A proper oil catch canister that takes all hoses (both cylinder heads and the alternate PCV route) and then vents into the intake before the turbo is the way to go when doing track exercises or driving inspired. Also be aware that the oil temperature plays a role.

[dga]

^^^Thanks. That was my understanding of the system without a catch can installed.