P928s2

This is a most interesting thread!!

I do have a question.. in one of the first posts it is mentioned that it is the 32V engines that suffer this problem. Is the 16V equitted from it or is it just less?


Grtz

Stefan

Ducman82

just a little less is my guess. but the set up on the first posts is on a 16v

Alan

Jake's is a 16V - not sure how bad the breathing was before the install...

As I understand it the breather set up has never been excellent but it became less effective over time due to displacement (esp. stroke) changes - and some of the evolutions of the breather system ultimately seem to have been counter productive.

Alan

Lizard928

The 16V are less prone to high oil consumption as they breathe from the center of the crankcase and not the cam housings.
However the reduced stroke of the 4.7/4.5 also has a huge effect on why they got away with it.

ptuomov

Don't all pre-GTS engines have 78.9mm stroke, the same as the 32v 5.0's?

17prospective buyer

Has anyone explored making separators/baffles in the cam covers like a lot of other manufacturers have done? If you take a look at cam covers for the majority of OHC car motors with a simple PCV system there are screens and baffles around where the vent is to try to separate as much liquid oil as possible. Is the problem with the stock design inadequate flow/volume as well as oil throwing from the cams? Where the stock system scavenges oil from the covers, could you not just put in a series of screens and baffles to get most of the liquid out of the vapors?

Lizard928

I don't believe so. But if I'm wrong it won't be the first or last time.

Lizard928

Venting from the valve covers is the worst place to vent from, so no.

Rob Edwards

I find that marriage is the best way to keep track of how often you're wrong.


78-91: 78..9 mm stroke

92:95: 85.9 mm stroke

dr bob

Matt-

The issue gets critical when the drains from the head to the crankcase get flooded. Blowby gasses push the liquid back into the heads and the problem snowballs until the heads and intake are full of oil, and the crankcase isn't. Possible solutions include Greg B's oil scavenging system for the heads, and/or a pump and separator that scavenge blowby gasses and separate the oil out before passing the scrubbed air back to the intake.

Newer Ford V-8 engines have dedicated external drains for oil from heads to sump. The bottom end is below oil surface so no gasses flow through and therefore no oil flow choking on reversed gas flow.

The screens and baffles method has been popular in the past as a method of separating the droplets of oil from a gas flow, can be effective so long as velocity is low and there's a clear drain path for the oil back to the sump. Tuomo's picture of JK's oil filler baffle is a good example. Oil droplets get caught on the scrubby pad used as a 'filter', and drain back by gravity. At high vapor flows, there's always the risk of carryover into the vent above, with the gas velocity keeping oil from falling back into the sump again. The Provent pieces are centrifugal separators that depend on having a certain velocity to vapor to be efficient. They also depend on gravity separation at low velocities, but in the end it's gravity drain to the sump or maybe a pumped system that returns the liquid to the main oil sump.

In large industrial systems, there are some separator systems that one would think would be very sophisticated. They are generally just larger versions of the woven mesh separators, with a fan/blower moving the vapors. The blower sucks from the vapor space in the sump, creating a slightly lower pressure, then pushes the vapors up through the separator mesh. The oil that falls out is at a slightly higher pressure than the sump, so liquid flow back to the sump is by that little pressure difference plus gravity.

AO

So, my 1985 Euro (need to come up with a better name for it...) had a crazy breather setup that was "powered" by angled ports into the exhaust just downstream of the collectors, but before the Y. It attempted to draw crankcase vapors from the oil filler neck, through two separators, with the return air flow through the heads. Remember this is a 16v head. There was a catch can in the system, so no oil was returning to the heads.

This was a total disaster for a number of reasons. The hoses used to for the venting were too small and made from heater hose which tend to soften and collapse when in contact with oil. I've not measured the vacuum created by the ports in the exhaust yet, but may in the spring when things thaw out. It should have provided plenty of draw to drive the system, I think. But where I think things went wrong is that the heads quickly were able to over power the draw on the system and force oil down the "return flow" ports. They were filled with oil.

This is probably less of a problem in a 32v engine where you have "baffles" and such making it difficult for oil to flow out the ports. But on a 16v head, I think it's inevitable. This is what prompted my assumption that there must be a check valve on Ducman's line running back to the head(s).

Personally, I'm venting to atmosphere through the Provent and running the return flow to the "oil tube" that ties into the front of the oil pan next to the oil level sender (32v cars don't have it, but it can be easily added). The bottom of the oil tube is below the oil level which acts like a check valve to make sure any crankcase pressure is directed out the oil fill port in the V below the water bridge. As return oil flows back to the Oil Tube, the level automatically adjusts itself. It's pretty slick, and not too different from how the stock system on the OBs worked.

I'm not sure if this would work on a 32v, but in theory it should. The biggest difference between the motors is the volume of the heads (and displacement) and stroke in the GTSs. I believe the 16v head has less volume. (Does anyone know for sure?)

I know Greg Brown has postulated a theory that states the 32v heads "pack with oil" thus starving the sump for oil. His solution is similar to the one offered here in this thread. Except here, the return flow for the vacuum pump is directed to the heads thus aiding flow to the sump. This is not a cheap solution, and I'm not sure it is entirely needed.

If the crankcase is allowed to breathe, there shouldn't be any need to vent the heads. If the heads are packing with oil, there is air trapped in the heads. If the drains are filling up - essentially blocking the return path back to the sump - there is air also trapped in the heads. As the heads continue to fill with oil, this air will become pressurized due to the decreasing volume and will want to force oil presumably down the drain passages down into the sump. Of course, if the crank case is pressurized, that can overcome this effect. But if the crankcase is free to breathe such that there is no higher than atmosphere, there shouldn't be any need for a return flow to go through the heads - as far as I can see.

This is how my Euro is today, and so far (1,500 miles) it's working great.

I'll be pulling the GT motor soon and I'm thinking about redesigning the breather system to incorporate this design of returning the oil through the oil tube like in the OBs and close off the ports in the heads.

Thoughts? Pitfalls?

Ducman82

Ah yes, exhaust scavenge valves hooked to the valve covers. They use that angled adapter to create a vacuum using the exhaust gases flowing by. Think of it as you would blowing a whistle. I had tried that approach with my stock 4.5, and hooked to the fill port lid. Worked well actually, but u need oil rated hose. Work great on drag cars!!!

AO

No. it wasn't hooked up to the valve covers. It was very much like what you have, but they used the scavenge in place of the vacuum pump, and then "caught" the oil instead of returning it to the system.

And it didn't work... at least when I got the car with a blown motor.

Ducman82

gotch ya. :-(

Alan

Andrew it isn't a cheap or easy solution for sure. .. but I've been down the path of all of those that seemed reasonable and - like the stock setup - they don't work very well either.

Pros:
The vacuum pump system can be guaranteed to eliminate intake oil ingestion depending on how its configured and it can have some engine performance benefits.

Now oil consumption could still be due other things than just intake ingestion... so VMMV

Cons:
Expense, difficulty of installation*, long term reliability & effectiveness (unknown), current lack of a kit version. Making a closed loop (emissons compliant - ex. CA) system is harder and may risk MAF degradation, a Provent 200 (alone) probably isn't an adequate volume AOS for this for all configs & uses.

Edit:
*assuming air-pump delete, vac pump install, crank baffle & oil filler mods and in my case full cam cover porting & clocking.

Now I should have noted that soon Colin and Roger will have a kit that will significantly ease the parts sourcing, AOS design, and most of the other configuration decisions.

Alan