Oil Venting for Front Mount Oil Tank with Turbo Scavenge

[buster1015]

In the process of swapping out the turbochargers I decided to relocate the oil tank because it was in the way. The schematic below shows the setup I came up with along with a photo.





This requires three oil lines running between the engine and front compartment, all of which are routed along the rocker panel. While the oil line to and from the engine function fine, the line connecting the 'breather' to the oil tank doesn't work so well since it contains both oil and air. It must dip down to the rocker panel and then back up to the oil tank inlet allowing oil to pool at the low spot. In my previous setup (with the stock oil tank location) this path had no low spots and I also had virtually no oil ever in the stock breather hose. I get a gurgling sound at the oil tank as air travels through the low portion of the oil line (must have oil pooling) on its way to the tank. That Peterson tank is pretty well designed for de-aeration and has several baffles so this may not be an issue. I tried a simple catch-can (one inlet, one outlet, with air cleaner vent) near the engine and it seemed to work but oil would build up too fast so not sustainable.

I've read that racers often run the breather hose up high in the passenger compartment on the way to the front oil tank to avoid this oil pooling and gurgling issue. Any oil that gets in that line would either drain back to the engine or to the oil tank. I would really prefer to find an alternative solution, don't want to hack up the interior, let alone have an oil line at head level.

It seems like, under stock conditions, the breather hose should primarily allow air with oil vapor through but a minimal volume oil. I know if the oil tank is overfilled oil can travel back through the system to the breather but under hard driving does the breather normally cough up a significant amount of oil?

Not included in the schematic is the oil scavenge system, photo below. Concept is pretty simple, scavenge tank mounted below each turbo (~200-300 ml capacity), a turbowerx nano scavenge pumps connected to each turbo outlet scavenge tank to lift the oil and push it back into the lower valve covers. This does create additional air flow into the lower valve covers that I believe will go out the breather.


So, two different but overlapping issues:
1) Would the positive pressure created in the lower valve covers from the scavenge pumps create any problems in the oil system? Maybe the pressure doesn't actually increase because it gets vented out the breather faster than it can build and there is no issue. Solutions:

• Add a small high mounted collection tank after the turbo pump that could drain by gravity to the lower valve cover with a vent at the top to allow extra air to escape. Basically a crude oil/air separator. I think this could also reduce the amount of oil and air going out the breather to help the second issue.
• Or, use the scavenge pumps to push the oil all the way back to the front oil tank directly. According to the manufacturer, this is within it's capability.

2) Deal with oil coming out the breather so it doesn't pool in a low section. I'm not convinced this is a problem that must be eliminated completely but seems like it should at least be minimized. Possible solutions include:

• Adding a pump at the low section of the breather hose in the rocker panel area to push oil up to the tank. Additional cost and weight
• Add an oil/air separator in the breather hose line near engine to vent majority of air. If mounted high enough in engine compartment most of the extra oil might drain back to engine. Some oil might still get past and pool in the rocker panel area but if the total flow (air and oil) is decreased significantly this might not matter.

I suspect addressing the first issue might partially mitigate the second issue. Just wanted to find out if anyone else had run across these obstacles and how they dealt with them. Maybe someone can explain whether I should even be concerned with the additional air flow into the valve covers from the pumps.

-Patrick

[BoxsterGT]

Its been my experience that the breather/vent must run up & along the roll bar.

Nothing else works as well.

Len

[BoxsterGT]

Wondering what your ultimate solution was?

Len