A/C on induces more load on the engine(requiring more air/fuel), and may be diluting the oily smoke exhaust by producing more general exhaust energy/burn/flow...
might be 'redneck' but might be worth trying an oil additive for a couple hours/on-off cycles, such as Lucas Oil Stabilizer, might reveal more; less smoke would likely indicate a 'rubber' seal issue, while same/very near same oil smoke level would indicate a metallic seal or breather system issue...
Also, try adding oil to the top 'bar' level, if smoking gets worse it could also indicate the breather system is to blame.

 

I had a similar issue, smoke at startup sometimes 50% lets say. Other times no smoke at start, but then starts smoking after engine warm up and sitting in idle traffic conditions. Similar M.O. just one big blast of smoke on take off then no more for the rest of day.

I was daily driving the car to work with very short commute each way, less than 15 minutes door to door with about 2 miles on freeway and plenty of opportunities for spirited blast of throttle.
I realized it was more prevalent during the cool months, and I would also sometimes get a buildup of yellow oil/water vapor "jelly" in the oil fill cap. This freaked me out(thinking head lifting, coolant getting oil), so I had the oil checked by Blackstone and found nothing wrong.

Short story being car was not getting hot enough to burn off water/oil vapors out of crank case and intake track. So sometimes it would condense and drip down intake manifold for cold start smoke, sometimes it would drip down during warm-up, or hot re-start after short warm-up & runtime.

A couple of longer highway trips with less boosting, especially in hot weather seemed to clear this up quickly. It also melted and re-absorb "jelly" build up under fill cap and cooked out the water vapor that caused it.

Might not apply here, but just another scenario that I experienced.

 

This sounds interesting...! My car still has the stock valves in it and my mechanic did mention that they were a common problem item...perhaps I should change them....

@mikes996t....Do you still run the stock valves?? Sorry if it was mentioned before...

 

I had almost the same problem. Both of my turbos were rebuilt by Tial. After installing 65% on cold start they would smoke and 25% after warm up. Changed brand and weight of oil and no more smoke. Maybe here or there but I only drive my car on the weekends. If the oil is to thin it always gets by. Not saying you don't have turbo or other problems but its worth changing the oil weight. Not sure what weight but will let you know when I get home.

 

mine smoke 50%chance on startup!and i dont stress with it!but i will change oil brand soon just to see if it get better!

 

born2boost - my engine is totally stock

silverfox - interesting, I think I also noticed a small reduction when I changed to mobil 20w/50, btwmy turbos are brand new tials A28's

 

993gt - your point on the oil level, yes that happens when I add oil to the top level she smoke much more....

 

I'm wondering if either oil is rapidly draining down into the crankcase from the tank(flooding the rings/cylinders) , or breather system is hurting bad...

 

Hi Sam, yes running very strong, these A28s just love to spin up at the slightest chance
rgds
mike

 

993GT I really think its the breather system, but problem is I have not been able to find a decent description of how it all works and the various hose/gaskets etc to check, I know the oil flow/scavenger paths but not much on the breathers.
rgds
mike

 

Not sure why you need to know how the thing works.

The breather system works like most others. Basically some engine vacuum is directed to the crankcase so the engine crankcase operates under low pressure. This helps lower the boiling point of unburned fuel and water so they boil away and keep the oil dilution to a minimum.

At the same time crankcase fumes are routed to the intake. They follow a path that has them going through some kind chamber (often shaped like a nautilus shell) which is intended for the oil vapor droplets to due to centrifugal force impact the walls of the chamber and form a fluid that then drains back into the crankcase where it is returned to the oil tank.

Under times of no engine vacuum such as is the case under hard acceleration there is a valve that closes to prevent pressurization of the crankcases to avoid pushing oil past seals/gaskets. This valve or another valve also closes in the event of a backfire to prevent a sudden spike of pressure in the crankcase. It is also intended to prevent a backfire from possibly igniting the fumes in the crankcase.

Based on what you have posted it would appear the engine crankcase is being subjected to too much vacuum and this is pulling oil vapor out of the engine into the intake where it gets routed to the engine and burned. Hence the smoking. And running the oil level at near its max level makes this worse reinforces the theory.

Now with my Turbo at idle there is no vacuum or low pressure at the oil tank filler tube. If a valve has failed you might experience low pressure at the oil tank filler tube with the engine idling.

Regardless I think checking the hoses/connections and possibly just replacing -- it depends upon the parts/labor cost -- some or all of the valves in the vapor recovery system might be a good idea.

Or you can take the car in and have this system's performance checked out and a diagnosis made.

I would on no account run the wrong oil in an attempt to cut down smoking. I would hate to think what you would do if the engine had an oil leak...

I would make a serious attempt to find or have someone find the cause of the smoking and address it.

Then at the same time go back to running an approved oil and running as near to the max line as you wanted, but certainly not over.

 

Just some food for thought....

Today I went to my mechanic (ex-porsche mechanic of 15 yrs+ experience)...I took my 996tt in to have the front shock mounts replaced.

I mentioned that occasionally my car would puff out some smoke on start up for a few seconds and then it would disappear. He said that its nothing to worry about as the engine is a boxer engine and depending on where the engine stops when shut down, a little oil might settle on the lower edge of the piston/sleeve....This oil then gets pushed up and burnt out the combustion chamber on start up and this is the smoke you might see occasionally...

I don't know....not sure if I understood it correctly...not sure if it makes sense...

Anyone else have this explanation given to them?

 

what your mechanic is suggesting is correct when sitting for a long time(ie. winter storage) and is related to what I had suggested with the tank draining into the crankcase, but is happening much quicker than proper. If he is suggesting some oil gets flung off the crankshaft, etc. then that could, and does happen the odd time too
Have attached a couple pics of the oil 'sytem'

 

for my understanding the reason are the turbos, but nothing to worry about.

At the turbo exhaust side only at standstill it is possible to have a small oil leak...that should be no problem.(some turbos have that symptom without a failure)

sometimes one of the scavange pumps made problems when metalparticles in your engine/but in this case your oilfilter shows that

if your intake is free of oil than nothing is wrong with your oillevel ore crankase breather system