Thoughts on using a "header" evap system over an AOS?

Tippy · 07:45 PM

Some of you mentioned I needed to run an AOS like the 930 has (I'm a 3.2 Carrera).

I'm not a fan of clutter and lots of hoses in the already cramped engine compartment, and thought a header evacuation system might work.

For those who don't know what it is, on a naturally aspirated engine, it is simply a small pipe you weld onto a header collector (in my case, on the tailpipe) that provides a vacuum as the exhaust passes by. This is then connected to a hose from the oil tank, that for my car was connected to the airbox.

Lookey here:

Any one tried this or know how well it would work?

Ken911 · 03-16-2017, 11:50 AM

I think it would only work with a zork tube and not an actual muffler. but hey it might be worth a try.

Tippy · 03-16-2017, 01:31 PM

Not in the muffler, rather the taipipe

RarlyL8 · RarlyL8's Garage

What is AOS?
Some mufflers create back pressure. Scavenge systems are typically used on high powered N/A engines that create excess internal pressure. Doesn't work well with a muffler due to back pressure. Turbos also create back pressure.

Tippy · 03-16-2017, 07:52 PM

Air-Oil Separator

jsveb · jsveb's Garage

You need to find "the" spot where the speed of the exhaust gas is high. High speed results in a low static pressure, creating a scavenging effect.

boosted79 · 04:20 AM

Used that on diesel trucks running straight thru mufflers, works well tied into the downpipe. The old Cummins just have a "draft tube" that is daylighted. On these you could put it between the turbo and muffler if using a straight thru or in the tailpipe, pressure delta between pre and post muffler on a straight thru is essentially zero.

edit - keep it downstream of the WBO2.

RarlyL8 · RarlyL8's Garage

AOS were not present on all 930s. I didn't have one on the Red Rocket and there was no need. The oil tank vent hose attached to the OEM air filter mail box. I canned that box and ran a small filter sitting on top the air meter assembly. Ran both stock breather hoses (one from the oil tank and one from the turbo) to that air filter. Never saw the first hint of oil from either one of them.
The Gray Slant has one of these separators but I pulled that hose and did the same thing. No issues.

Porsche 935 · Porsche 935's Garage

I ran the header evac on my engine for awhile but it would pull oil with it and drip out the exhaust pipe. So I ran vent to tank and vented the tank. Some engines I don't think you can vent the tank.

Tippy · 03-17-2017, 11:37 AM

Worst I have to lose is diconnecting and capping if it sucks oil out.

TurboKraft · 03-17-2017, 11:40 AM

Tippy -- what's the problem you're trying to solve?
I've built many 3.2-based setups without an AOS, no issues.

Tippy · 03-17-2017, 12:38 PM

Quote:

Originally Posted by TurboKraft

Tippy -- what's the problem you're trying to solve?
I've built many 3.2-based setups without an AOS, no issues.

'Member I had the lifting heads and massive black gunk on my piston tops?

Some of you thought an AOS would help.

T77911S · 03-20-2017, 05:08 AM

bad oil rings, valve guides?

lifting heads?

Tippy · 03-20-2017, 05:34 AM

Quote:

Originally Posted by T77911S

bad oil rings, valve guides?

lifting heads?

New TotalSeal rings when I rebuilt it and new guides.

TurboKraft · 03-20-2017, 09:33 AM

A 930 AOS wouldn't hurt. You'd have to add the AOS drain port to your factory oil tank.

A 3.2L setup with a restrictor cone in the tank vent out also works, and route the tank breather high to assist in oil vapor condensation and run back. From there it can go down to a catch can, breathe out below the car, etc.

Q: are your Total Seal rings gapless?

Tippy · 03-20-2017, 10:07 AM

Not gapless, standard