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Gray Smoke & Oil on plugs


RedFive

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I've been reading topics on this for the last week. I keep uncovering one more little bit of evidence at a time, but I'm really not sure what to pin this problem on.

 

Setup:

-Freshly rebuilt L28ET (approx 500 miles)

-Stock turbo

-Intercooler

-Oil cooler

-Ignition and fuel running on SMS (side note: if anyone has maps I can look at for similar setups, I'd love to see them!)

-PCV on the valve cover is open to atmosphere, crank vent is connected to stock vacuum port on intake manifold

-3AN oil pressure line to turbo (thus I've ruled out a restrictor issue). Stock drain tube from turbo to pan.

-Stock injectors

 

Problem:

I'm getting lots of gray smoke out of the exhaust. Smoke is minimal to non-existant while everything is cool. After it warms up, the smoke is constant. It does not change with acceleration or deceleration.

 

-No oil in the coolant

-No oil in the intercooler pipes

-Turbo appears to have minimal play, though I understand that is a subjective test.

-There IS oil on the plugs.

-All of the gaskets, rings, etc are brand new due to the rebuild.

-There is no blue tint to the smoke, it's just gray

-I tried applying vacuum to the valve cover pcv, but nothing changed...

 

 

Ideas? Thanks guys!!!

Edited by RedFive
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Do you have an oil restrictor fitted in the turbocharger? Your post makes it sound like you don't.

 

You want no restriction at all on the oil drain...most turbochargers use a 0.060" or so restrictor on the oil supply line to them, depending on oil pressure. They do not require very much oil to live a long, smoke-free life...but you can not allow oil to back up the drain tube into the turbo or it will cause coking and scoring of the bearings.

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Ok, sorry, but you guys are both wrong. AN stands for Army Navy. The line number is represented in 16ths of an inch of the inner diameter. In other words, the inner diameter of a 3AN line is 3/16ths = 0.1875 inches.

 

Bottom line, do I need to be using 0.06 inch inner diameter line with the stock turbo? That would be roughly 1AN...

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Setup:

-PCV on the valve cover is open to atmosphere, crank vent is connected to stock vacuum port on intake manifold

Problem:

I'm getting lots of gray smoke out of the exhaust. Smoke is minimal to non-existant while everything is cool. After it warms up, the smoke is constant. It does not change with acceleration or deceleration.

 

 

-I tried applying vacuum to the valve cover pcv, but nothing changed...

 

Ideas? Thanks guys!!!

One possibility is that you're sucking oil vapor in to the intake system through the crank vent.  The PCV system is designed to move air and exhaust byproducts at a variable rate, usually low volume, through a pressure imbalance between the PCV valve and the fresh air supply in the valve cover.  If the rings seat well and the valve seals are good there's not much aitr movement at all.  You had it set up to pull air down through the valve cover through the crankcase, through the crankcase vent and in to the intake system at full intake manifold vacuum.  That's a lot of air.  You said that you applied vacuum through the through the valve cover, but it's hard to tell what that means.  Might be worth studying the Emissions chapter in the FSM, or blocking the crankcase vent from the intake manifold to see if it gets better.  Even if it's not the problem, I don't think that your crankcase venting system is right.  It's a giant intake manifold vacuum leak, the way you've described it.

Edited by NewZed
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You do NOT want a smaller line, you want a 0.060" restrict or.

 

The piping losses through a -1 A/N line would result in LESS flow than a restricted larger line.

 

Usually the turbo lines are -3 or -4 A/N and incorporate a restrict or right at the turbo ol feed, thus minimising losses in the line downstream of the restriction.

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Ok, sorry, but you guys are both wrong. AN stands for Army Navy. The line number is represented in 16ths of an inch of the inner diameter. In other words, the inner diameter of a 3AN line is 3/16ths = 0.1875 inches.

 

Bottom line, do I need to be using 0.06 inch inner diameter line with the stock turbo? That would be roughly 1AN...

 

Ok...  :rolleyes:

 

First off, I don't think anyone was debating what AN stands for.

 

Here is how the AN scheme actually works: the dash number represents the outside diameter of the tubing, not the inside diameter. A -3AN line will have an OD of 3/16". Therefore, the ID will clearly be smaller.

Edited by Leon
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