Oil Catch Can Questions - How much should be drained?

Cire · 10-15-2007, 02:05 PM

How much oil should you be getting in your catch can? Is it a 1/8th of a quart a week or is it a quart? I see there are lots of different types of results. Some people have large catch cans that they dont drain often (years??) and then some people that drain them on a regular basis...

I would have never expected that any would need to be drained. I would think you would get in your car and drive it for years and wouldnt encounter an issue. My other car, my other truck and my camper dont have catch cans that need to be drained. Dont get me wrong, they dont provide me nearly the amount of fun my Porsche type car brings me but it is an interesting question to say the least.

I am at the point where I route my vented oil tank fumes back into the air cleaner or buy a catch can. I dont like the mess that oil creates in my air cleaner so I have been working (like a fool) to fix the issue. I didnt realize there isnt a fix, its just expected to have an oil catch can that needs to be empted on a regular basis.

= )

Eric

JMatta · 10-15-2007, 02:36 PM

Is this a street car? Catch cans are normal for a track car where you run consistently at high RPM. If you have the need for a street car, I would worry about other problems (bad rings) before fitting a catch container.

Cire · 10-15-2007, 02:42 PM

But what I dont understand is why high RPMs would require a catch can? Street, track or off road use shouldnt (unless I am missing something) need it?.?. I agree with you, the only time I see an issue is when I am running along the freeway or desert (off road car) at over 6,000 RPMs for prolonged times. So your are right when it happens, I just dont know that I fully understand why. Once I understand why it happens I can start to formulate a way around it. Could it be that we need bigger oil tanks (30 quarts?) so there is more than enough room to separate air from oil? Is it that we need better oil pumps in the engine to ensure no oil is in the engine ever to be swirld around (vaporized) by the crank and rods?

Just interesting. If you had a race car, how would you solve the issue so it never needed a catch can? = )

Thanks for your views.

Eric

dad911 · 10-15-2007, 05:53 PM

Extra RPM creates more crankcase pressure. Also race engines are typically 'looser' with more blowby. However, you should not collect alot of oil if it is set up properly.

When I had new engine fill the catch every run group, I spent many track days trying to debug the oil system, when the real answer was revealed by doing a leak-down test. Cracked rings and scored cylinders in my case.

Stock engine? Stock oil tank? Have you done a leak-down test?

dad911 · 10-15-2007, 06:32 PM

Thinking about it, I have seen vent lines run along interior roof of the car/rollcage that terminate in a front oil tank (which had a vent)

So in this case, the oil tank collected drains back into the tank.

My mechanic also had a turbo motor where he tapped the valve cover with a small fitting and attached the drain line from the catch can (mounted high) to the valve cover. Leaving the valve on the can open, the catch can always drained back into the engine.