924Board.org

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Hey folks,
In the quest to really get the "new and improved" 931 as efficient as possible, I'm thinking about removing the line that pulls crankcase air into the intake track. After all, the oily mist from the air/oil separator only serves to muck up the intake (and inside of the new intercooler) and, if the oily air actually reaches the combustion chamber, it lowers the effective octane- bringing detonation on a little earlier.

So what to do? There are aftermarket oil catch-cans, but honestly, they look just like our air/oil separators. I think they still have a line that vents into the intake. Can I just take the intake line off the separator and add a breather filter? That's exactly what this looks like:

http://www.roadraceengineering.com/instructions/catchcaninstructions.htm

The separator should catch almost all the oil, and what little that it doesn't (which would be going into the intake) would get caught by the filter. Any thoughts?

nick

Lizard · Posted: Sat May 28, 2005 3:23 am Post subject:

open the factory 931 air oil seperator, and then fill it with steel wool or equivelent, then reseal it back up, and the line which would normally vent back into the intake just put a small filter on it, the steel wool should prevent you from getting any oil getting throught the filter.
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3 928s,

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Sounds good to me. What's in that separator anyway- anything?

nick

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Lizard has it right. Most cars before 1964 just vented to atmosphere. I was considering the same thing for my setup. Definetly don't want that muck in the intercooler.

Todd

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

I don't have the oil separator so I don't know what is inside of one. I had guessed all along that they had some sort of baffle system, or something to help condense the oil vapor back to liquid. I would recommend against using steel wool though, because it will rust. If the cannister is in fact empty, I'd suggest putting in a couple of those copper "wool" dish pan cleaners (? "Chore-boy" ?). You've probably seen them, they look like a really coarse Brillo-Pad, but made out of copper or some other copper color alloy.
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'79 Eurospec 931

Lizard · Posted: Sat May 28, 2005 8:30 am Post subject:

the air oil seperator has NOTHING in it, just a plastic integrated sleeve.
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3 928s,

simsport · Joined: 06 Nov 2002 Posts: 573 Location: UK Warrington

While doing the cranlcase try fitting a decent breather to the head. I did and the gases that come out are a marvel to behold!
You will need to catch the oil again though.
Cheers
Simon
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Blown is always best!

924RACR · Posted: Mon May 30, 2005 10:45 pm Post subject:

I put a breather into the blockoff plate on the side of the head - bad idea, pissed oil all over the place. But that was on the racecar - 924, not 931. Still fighting to figure out a good plan for breathing.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype