davidc1

So...is there a difference between oil blow by and real oil combustion and burning?

Meaning, lots of us "burn" oil and use catch can's and such for it. It usually results in some noticeable blue smoke under WOT, but not much. I'm referring to the oil use a lot of us experience and have to add oil occasionally to top up the car.

Then, there's the infamous S2000 smoke screen that some of us experience at the track. This is the huge billowing clouds of blue/white smoke that is less common than above.

I hypothesize that the clouds of smoke in the latter are essentially complete combustion of the oil that gets in the cylinder, hence the huge cloud of smoke, while the former may be oil getting into the combustion chamber, but not completely combusted or burned as it goes out the exhaust, hence only much smaller amounts of blue smoke.

Would people agree? Any other ideas?

robrob

"Oil blow by" isn't really the correct term. "Blow by" occurs when combustion gasses get by the piston rings and pressurize the crankcase. Excessive pressure in the crankcase can cause oil to squirt out of pretty much any orifice, including the PCV valve. It can also kick your dipstick out.


This is not normal but when it does happen it usually is due to a bad ring to cylinder wall seal.

Oil smoke during straight line deceleration is usually caused by oil being sucked down the valve guides.

The standard S2000 big blue/white oil cloud in long sweeping turns is usually caused by oil pooling on top of the valve cover baffle near the PCV valve. When the throttle is closed at high rpm (such as during a track shift) a great deal of vacuum is created in the manifold and the oil near the PCV valve is sucked into the intake and burned. This is the only normal oil smoke you should ever see coming from an S2000. This can be fixed by adding a catch can to the PCV line, drilling holes in the valve cover baffle near the PCV valve or switching to an AP2 valve cover (helps but not a complete fix).

davidc1

Thanks for the good explanation.

Interestingly, the only billowing clouds I've had have been when under WOT after LEFT hand sweepers at high rpms...go figure. And only certain tracks with certain turns.

Otherwise I don't burn a drop with my new engine. And even though I get these huge billowing clouds, it apparently doesn't happen enough to affect my oil level.

robrob

Are you sure you're getting the smoke in the left turns at WOT and not when you actually shift gears?
I forgot to mention, everything above pertains to normally aspirated engines. Forced induction changes the troubleshooting routine.

davidc1

It occurs after the left hand turns as I go down the straight and accelerate at WOT. Only occurs if the turn was taken at high rpms, and even then, not all the time.

At a track where there is a left hand sweeper that it did it twice at a few months ago, it didn't do it at all last weekend. At that track a couple months ago, it did it three times taking that turn in second at 6-7000rpm, and then not a all in 3rd. Then, at that same track last weekend, it didn't do it at all on that turn, even in second.

At that track this last weekend, on another turn, a 90 left taken in second at about 5000rpm, a bid dip had developed at the apex. It did it this weekend there, but not a couple months ago. I hypothesized it did it because when I hit the dip it would splash oil above the valve cover baffle.

dsddcd

Here is a vid of mine, I disconneted the PCV and am going to modify the interal baffle on valve cover and see if that helps.


http://www.youtube.com/watch?v=bbkc0reNj6I