I posted before about not getting the oil to drain properly in my T76/2v 4.6 build. I now have 350 miles on the new motor, there was no oil burning until I started regularily getting into boost. At first it was only when I was IN boost, then it started passing oil when I was just leaning on it a little (moderate load), and ultimately it'll now blow a puff occasionally at cruise, and when I get into boost ya can't even see behind the car it's so bad!

I did a compression test and everything was great (6 of 8 cyl were at 148-151, with 2 cyl @ 144), every plug is bone dry and looks good, no sign of oil. The crossover pipe/inlet flange is dry, and the downpipe is very oily, so it's definatley coming out of the turbine.

I'm using an MMR pan which MMR claims is being used by dozens of turbo modulars without problems, but the inlet size is only 3/8"!!??

What I ended up with was a -10 45* elbow right on the drain flange, a 5/8" i.d. drain hose with -10 fittings on both ends, a -10 x 1/2" adapter fitting into a 1/2" x 3/8" reducing fitting, and a 1-1/2" long nipple into the 3/8" fitting into the pan. There's no droop in the drain hose, and there's about a 10" drop from the bottom of the turbo to the fitting on the pan.

I'm running about 42psi of oil pressure at hot idle, and it hits 90psi by 3,000rpm's, this is the pressure AT the turbo oil inlet. I metered the oil flow and it's moving 1/2 gpm at idle, probably closer to 1gpm or more anything over 3,000 rpm's.

Any ideas? I think 1/2-1 gpm is A LOT to drain via gravity, Tilton's oil pump used in low/remote mount turbo applications are moving 1-2 gpm depending on pump speed, so expecting a 5/8" hose to drain that quantity via gravity through a 3/8" nipple seem sot be a stretch?

Thanks

 

Oh yeah, another concern is the turbo is pitched "up" slightly. If I put a level on the face of the compressor it's pitched about 1/4-1/2 of a bubble. My concern is this is "pitched" so the oil would drain back towards the turbine....possibly making matters worse???

 

sounds like too much oil.since you have a way to meter your oil try this.plumb a ball valve in your system,just ahead of your turbo.meter the valve so that you get the 1/2 gpm that you said you were getting.this will be your starting point.keep closing off the valve until you stop getting smoke.be carefull not to cut off the oil supply.it would also be nice to know the oil psi at the turbo

 

or just buy a oil restrictor i am not to fond of the ball valve one, as you could eaisly close off the oil supply.

 

I agree with the others about a restrictor, but I've never had a 5/8" drain line be large enough, seems every time I try to get away with it I end up with your symptoms. Once I swap it for 3/4" line the smoke disappears.

 

Definately put a restrictor in , and 3/8 seem awful small to me the smallest I've ever used was 1/2" with a t-25 on an import, I would definately put a bigger drain fitting in the pan , It can't hurt anything .
I've also never been a fan of pitched turbo's I've talked to many shops who say a little is ok , but I just don't like it .

 

thats alot of pressure!

 

Is the 3/8" fitting you're speaking of pipe thread? If it is, it will have ~5/8" id, so no smaller than your hose. I think the problem is too much pressure. As was said before, put a restrictor in your inlet line.

 

Thanks for the reply guys. I forgot to mention I'm already running a .065" restrictor at the end of the oil feed line, but the i.d. of the fittings at both ends of the feed line itself are not anymore than .100", so it's not much of a flow restriction.

Well I did put a breather on the valve cover to relieve crankcase pressure while under boost (PCV line has a check valve in-line, and the other valve cover opening has a 3/8" hose running to an oil seperator then to the inlet of the turbo) thinking that whatever crankcase pressure that's building while under boost is the difference between the drain working and it not working, and that was the ticket!

I'm still going to replace the fitting on the pan with a 1/2" or 3/4" opening. The 3/8" fitting takes a 3/8" pipe nipple, which measures .427" ID, considerably smaller than the 5/8" hose and can only flow half as much.

 

the part that concerns me is the progression. You first had no issues, then it smoked at idle, then it smoked on boost, then it spit out misquito-killing clouds etc.

This doesn't sound like an oiling issue, unless something is progressively getting worse in the oiling system, which I find very unlikely.

I'd check your turbo shaft for slop. See if the compressor has been hitting the housing

 

Hmm, all I can think of is that the motor is brand new, so the first several drives it didn't even see boost. I made a 100 mile trip and once there my gilfriends father (who's an old school car guy) beat the LIVING PISS out of the car!!! The oil burning during the beating and the trip back was the concern.

After the trip I pulled the plugs which were bone dry and did a compression test, 148-151 on all cylinders. The only thing I can think of it was passing so MUCH oil that it was continually burning it out of the rest of the exhaust (y-pipe, mufflers, etc.). I know when I cracked piston ring lands in another car it took a while with the new motor to burn all the oil out.

The turbo is a brand new Turbonetics.

 

the motor is brand new. The turbo is brand new. Everything is routed and plumbed as it should be.

Well then, we've illiminated everything. Apperently there's nothing wrong 8)