3.6 breathing quarts of oil

Heeltoe914 · 09-22-2009, 07:08 PM

I have a 993 motor with Varioram in a racecar that is having a problem that most would love to have on a older P-cars.
From the time I start the car the Duck pressure jumps to 5 + bars I had figured it was a gauge problem and had planed on looking at it after a track event. But as the day went on the car was literally breathing oil out the crankcase breather. Started with a pint after about 15 mins around Willow springs but by the afternoon within 12 minutes of running at high RPM it filled up about 3 quarts of oil into the breather catch can. I shut it down and called it a day.
After hooking up a Snap-on mechanical gauge it was still running high oil pressure but after checking the oil pressure relief valves at the bottom of the case and the one on the side of the case it still seems to be running very high oil pressure even when very hot like oil temp 230 its still at 5+ bars.
My system is running a Peterson oil filter housing with a Fram P4 filter and the stock 993 oil filter on the case. All lines run up to a MoCal thermostat & a 16 quart oil tank in the front of the car as well as to the oil cooler. All seems to be getting hot so I feel oil is circulating But I am at a lost at why the pressure is so high and what to do next to correct the problem.

Also there is no oil coming out the exhaust or any smoking until oil drips from the catch can onto the headers.

stownsen914 · 09-23-2009, 07:03 AM

A couple things ... I'm not as familiar with the later 911 motors, but 5 bar (~ 75 psi) seems like good war oil pressure. Personally I'd be fine with that in my earlier 911 motor.

As for your oil breather issue, a couple points and questions:
1. Excess oil in your spit tank shouldn't be related to oil pressure. Crankcase or oil tank pressure wouldn't be related to oil pressure.
2. Where is the spit tank connected? Directly to the engine crankcase breather? Or to the oil tank breather? If you're connecting directly to the engine, it could be too much oil, but SOME oil coming out of your engine breather is normal (not 3 quarts in 15 minutes though). You can try connecting your engine breather to your tank so the oil goes there (in that case make sure your tank is vented of course), but you would still need to figure out why the 3 quarts, if indeed that's coming straight from the engine. Excessive piston blow-by is a common reason, I understand.
3. If the spit tank is coming from your oil tank already, then the problem is probably not engine blow-by, but oil sloshing in your tank, or maybe it's the tank is just overfilled. A couple things to try: fill the tank about 2/3 filled only, and make sure the baffles are installed correctly in the tank. You might also look at the placement of the breather hose to the tank, in case you have an option to move it to a spot that doesn't get as much oil sloshing (for example maybe it would be bad to attach the breather hose at the front in case hard braking causes oil to slosh forward and go out the breather hose). Or maybe make an additional baffle inside the tank to keep oil from sloshing so easily into the vent line. I would think Peterson would have figured this out though ...

For what it's worth, I have a similar setup on my 914 track car that has a 2.7L race engine. I run my engine breather to the tank, and have a spit tank connected to the oil tank as a vent. I get hardly any oil in my spit tank at all, just vapor.

Good luck troubleshooting!

Scott

Heeltoe914 · 09-23-2009, 11:44 AM

Thanks Scott for some great things to look at. Yes the slit tank is hooked as it would be for a 9146 about 20" of the motor breather.
and the fill tank in the front of the car has its on tank vent.

How did you run your breather from the motor to the front of the car? Thats seem like a long way for that oil to travel?

OK how do you check the oil level with the front mounted tank? Maybe I did add to much oil. Eng running and motor warm I checked it and filled untill the oil tank was about half full, Just below the grid?

stownsen914 · 09-23-2009, 04:50 PM

Quote:

Originally Posted by Heeltoe914

How did you run your breather from the motor to the front of the car? Thats seem like a long way for that oil to travel?

It does make for a pretty long breather line, but it's common practice on race cars with front mounted tanks. You will often see the hose attached to the upper roll cage tube on the passenger side of the cockpit.

Quote:

Originally Posted by Heeltoe914

OK how do you check the oil level with the front mounted tank? Maybe I did add to much oil. Eng running and motor warm I checked it and filled untill the oil tank was about half full, Just below the grid?

I have a Patterson tank, which I think is similar to the Peterson ones. I fill mine about 2/3 of the way up, so it sounds like you're in the ball park.

Let's see if anyone else can chime in as to whether 3 quarts of oil out of the crankcase breather is a lot for 15 minutes of track time for a 3.6. Seems like it to me, but I don't know.

Scott