CFM928

Nice to see multiple choices and understanding of the issue. (I remember the first time I saw blue smoke out the tail pipe on hard acceleration, back in the mid-1990's and had a sinking feeling...)

Can anyone comment on the different choices?

https://928motorsports.com/parts/oilcontrol.php

In addition to the baffle, there is an oil recovery system.

vs the GB Baffle pictured in post #12 here - https://rennlist.com/forums/928-foru...il-baffel.html

Michael Benno

Good questions, you may want to post this to a similar active thread: https://rennlist.com/forums/928-foru...il-baffel.html

Ducman82

Months of R&D revealed that the baffles with no sides did stop the "large globs" of oil from being directly thrown in to the filler neck area, but did nothing to stop the suspended oil from blowing around the sides of these baffles and thus get directly to the filler neck.

The key to getting the oil out of suspension is to cause the air/oil stream velocity to decrease and change direction, allowing the oil to fall out of suspension, drop down, and drain out.

In the first picture below of our baffle, you can see how the A/O stream is forced though the openings in the sides and must flow through the internal portion of the baffle. (Picture 1)

This baffle does different things at different flow rates!

At low flow rates, the A/O stream enters the baffle it hits the first angled separator. The air must, at this point, make a significant turn inside the baffle. The angled separator collects a huge amount of oil, which is free to drop down and escape through the drain in the bottom. The relatively oil free air continues on, is forced to make another turn and any oil is further separated from the air by the louvered OE part.

now if you add on the later model stock baffle to the top of ours (designed to fit), you create even more turbulence and areas for the oil to collect. the open sided baffles allow a stronger air flow to go thru the small louvers, but the speed is hight enough the oil can't drop down/collect fast enough and it just tossed back up the filler neck.

in that last picture you can see what path the A/O stream must take.

Red is the walls
green is the oil collection points
blue is the A/O flow

ptuomov

There are too approaches to air-oil separation. One, slow down the air and oil such that gravity separates the two. Two, accelerate the air and oil and then force it to turn, and only lower density air can turn while the higher density oil hits the wall. Both approaches can in my opinion be made to work in the 928 chimney baffle.

Stating the obvious, the inlets to the baffle should be such that they allow the minimum amount of oil spray to make it inside the separator.