Educate me on breather lines

[Kroggers]

I am installing an oil catch can along with the 3.6 transplant. The car is mainly for track use, and I have been told that it is recommended to install one, and that it is required for track cars...

But I have a small question regarding the installation.

I understand that the can should go into the line that sits between the oil tank and the intake (the crank case breather is left as is from the factory).

What I am trying to understand is if it is better to have the line go from oil tank to can and then to atmosphere via a small filter and block off the existing hole on the 3.6 intake - or -

keep the line at the intake as well and connect that to the catch can as well, so you basically keep the factory configuration, but just install a can in the middle of the line?

Hope this question makes sense

[burgundyben]

I thought we'd already been round this and decided we didnt need it?

I have fitted the crankcase breather to the oil tank as per factory.

I've fitted the oil tank vent back to the inlet, just like factory on an SC, I think on a 993 install its a bit more complex but that is mostly due to emission regs.

On the subject of venting to atmosphere, when you have a car idling and you take of the oil filler cap the idle dips, I sometimes read reports of 3.2's stalling when folks do this to check the oil level, in which case, I wonder if venting the catch tank with a little KN style filter will adversly affect idle? I have seen a couple of cars with catch tanks and little filters venting, I dont know why.

[Kroggers]

I have been back and forward on this one Ben. The catch can is there to stop oil and condensation (water) from the oil tank and crank breather ending up back in the intake during heavy driving i.e. during track time. I also believe that the line from the oil tank to the inlet is more for keeping emissions down rather than for performance reasons - but I could be wrong.

All I have read is that it is not mandatory, but will not hurt on a car that spends most of it's time on track. And I like to make things complicated from time to time

I have had some pm discussions with Jevvy who installed the Tuthill catch can, and whilst he did not experience any issues before installing it, he still decided it was good insurance to have it.

[psalt]

Paul

The crankcase breather connects to the oil tank. The oil tank vent connects to the catch can, not the intake. Two reasons to do this, HP goes down (1% per 10F) and octane requirement goes up ( 1 RON per 20F) with increasing intake air temp. Diluting the intake air with oil vapor also increases octane requirement and increases the possibility of detonation. Getting the hot oily crank vapor out of the intake is a good thing martha.

[Kroggers]

Cool, thank you Paul...

So to clarify.

.- Crankcase breather stays as is.
.- breather from oil tank to intake is removed.
.- oil tank gets connected to the catch can.
.- Catch can has a filter to vent to atmosphere.
.- Old breather on intake gets blocked-off.

Is this correct?

[psalt]

Paul,

Yes. The best set up has the breather hose going uphill with two 90 degree bends, so the oil laden, high velocity air drops some of the oil on the way out. The oil can then drain back into the tank. Many factory road draft breathers used this design in the 50's and 60's. On road 911's, I use a short hose , two pipe elbows and a foam sock over a perforated pipe. If your rings are good and the blowby is normal, you do not need a catch tank on a road car.

A Norwegian lost in NYC

[Kroggers]

Cool. Then I will install the catch can on the breather line and block off the breather line on the intake.

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