[grepin]

Hi. I have an 84 EURO 16V motor that I am thinking about adding a catch can. I will probably get a Provent but I have something just to trial first. In theory I was just going to attach it via the oil filler outlet and back into the inlet near the throttle body like factory.. Then I came across the Sharkvent and I like the idea of not returning any oily air back to the inlet at all. I do have a question regards the Sharkvent and that is - why only to one cam cover not both? And I assume the one way valve is open towards the canister to allow the cam cover to breath. But from the pic it sort of looks like a potential collection point for oil coming back against the check valve. Since the originator has passed I cant go to the source. RIP.

Greg

[smiffypr]

I haven't had the cam covers off this car but I assume it was original from the condition of the hoses (I put my finger through one of them), so now the cam cover connections are just blanked off.
I did have the intake off to unseize the ISV and found that the inlet tracts were badly coked up, that prompted me to try plumbing in a separator, but it seems that the change in plumbing is preventing oil getting as far as the separator. Because the hose from the base of the filler neck is sloping upwards to the separator at the top of the radiator, it could be that the oil has a chance to fall out of suspension in that hose, but I wouldn't have expected that as it is only about 20mm. I should have used transparent hose then I would be able to see the oil staining where it did get to.

[smiffypr]

First, I would not vent the cam box. Oil is draining down the passages in the heads and block, to create an upwards flow of "air" is only going to slow that. All the leakage is into the crankcase (past the rings) so just vent from there.
Second, in my experience you need a bigger container to allow space for oil to collect at the bottom with a space above it with little "air" movement, and an area at the top with high speed circular flow to fling the oil to the sides.
I experimented with transparent plastic so I could see what was going on, using a wet vac to generate flow and a spray gun to simulate oil mist.
I can see that it works because the transparent hose to it is heavily oil stained, the hose from it is clean.
A big problem with a provent is that it has a "filter" which can get saturated, then pressure will open the pressure relief valve and oil goes everywhere, but it's not big enough anyway.
Smiffy

[grepin]

OK so thoughts about just venting from the oil filler vent to a catch can (to be determined) and cap the inlet to the original return. I like that idea as it only gets clean air to the throttle body then. Or plumb it back to there to keep things legal. Not sure if I was a fan of the residual returning to the sump. Condensation etc. I do have an oil control baffle plate installed but still get oil in the inlet however last check of my plugs show them quite sooty. I read possibly due to breathing oil.
Also I think I worked out the valve allows oil to return into the cam tower and not the other way around. As you said so it doesn't allow air to breath upwards. And of course hence why there is only one line to the cam tower.

[worf]

D.R. thought long and hard about the SharkVent systems. One constraint he imposed was that the system must be installable without non-trivial effort. That constraint also means that a better system can be devised if you are willing to do non-trivial disassembly.

The check valve from the ProVent is to keep crankcase pressure from pushing oil into the ProVent. Yes, a bit of oil will collect there when you are at WOT. Unless you are doing open road races where you are sustaining WOT for minutes it’s not an issue; once out of WOT the crank case will return to negative pressure.

One thing “we” have learned about the 928 in the last decade is that it needs twice - at least - the breathing that it gets from the factory.

It doesn’t matter where the “holes” originate. A GT - notorious for eating oil - will more-or-less stop oil ingestion if two (rather than one) “cam cover elbow” vents. (There are some under-cam-cover tricks too. But vent volume is key.)

I’ve probably installed more of D.R.’s systems than anyone else. And since D.R. stopped offering then in 2008, Doc Brown’s ProVent system.

[grepin]

Thanks WORF - I think I will follow a similar concept. So correct me if I am wrong but the main offender is the oil getting in past the oil filler breather and back into where it plumbs in under the throttle body.

[worf]

Thanks WORF - I think I will follow a similar concept. So correct me if I am wrong but the main offender is the oil getting in past the oil filler breather and back into where it plumbs in under the throttle body.

First let me address something I missed. You asked about the check valve at the cam cover.

I recall from David Lloyd's 16v racing days that his 5.0 hybrid motor would puke oil out of the oil filler under certain conditions. So, I suspect that the check valve at the cam cover was meant to keep the "puking" in the direction of the ProVent.

As for why only one cam tower, venting one cam cover and the oil filler doubles crank case breathing. (As least on the 32v for sure and, I think, the 16vs.)

Now, to your latest question:

You want to avoid putting liquid oil back into the throttle body. Doubling the volume of breathing will have the most dramatic effect since crank case pressure will not be attempting to force aerated oil out of any available orrifce.

Adding proper air/oil separation is a bonus, or mandatory depending upon if you'd like to obey the spirit of EPA regs. The "standard" SharkVent design was "for off road use only" and vented separated crank case gases to atmosphere. There was "guidance" available from D.R. on how to vent back to the air box or air pump lines for those that required it but he never offered that as a "kit."

Beyond that general description I'm not familiar enough with the 16v architecture to offer specific suggestions.

The ProVent used in the kits can handle twice the volume of the "one hose" breather system as it exists on the 32v engines. So, plumbing two "supply" breather lines into the ProVent is quite possible as long as you use a proper Y-fitting where the output has twice the area of the two inputs. That proper y-fitting was one of the bespoke pieces of the kit. D.R. welded those himself IIRC.

[smiffypr]

The mechanism which transports oil through the standard system to the intake is gas speed, so given that the engine is breathing at a certain rate (litres per second), the speed of the gas is determined by the area of the outlet ("volume of breathing"), so I agree completely that more or bigger outlets is good to reduce gas speed. On the 16 v motors, the gas outlet from the oil filler top has a small drilling which can be drilled out for easier flow.

This theory also applies to the separator, getting the gas speed down so that gravity can do it's thing is important.

On the issue of draining collected oil back to the sump, I decided not to do this initially so I could see how much oil was being collected. What I found was that on a track day, the collected oil was good enough to go back into the sump, but in other situations, most of what was collected was water, which I did not want to dump back into the sump. I think this is partly a result of a large metal cannister which will take a lot to get it warm, so this may not be an issue with a plastic separator.

[grepin]

Only for initial testing I was starting to think about just tapping off the crank case breather before it reaches the filler and sending to a catch can I already have. Then just capping the inlet to the filler swirl pot. Just to see what Oil I do get in there. Less removal of standard hoses in hard places initially until I formulate a better way ahead. Any issues with this idea?

[Gary Knox]

Gregg seems to have developed a new alternative for oil scavenging to reduce the amount drawn through the vacuum system. These are baffles that fit into the 'holes' in the valve covers where the vacuum connections are located. His postings on another site indicate major reduction in the ingestion of oil with these baffles. $50 a piece, not quite 'plug and play', but close to it. NO FURTHER info from him unless you buy the baffles and agree not to photograph/post pictures of them!!!

He indicates that Worf has seen (used?) them. Any comments about them and their success in reducing oil in the system David?

[worf]

Gregg seems to have developed a new alternative for oil scavenging to reduce the amount drawn through the vacuum system. These are baffles that fit into the 'holes' in the valve covers where the vacuum connections are located. His postings on another site indicate major reduction in the ingestion of oil with these baffles. $50 a piece, not quite 'plug and play', but close to it. NO FURTHER info from him unless you buy the baffles and agree not to photograph/post pictures of them!!!

Those apply to the 32v motors. Not applicable directly to the 16v motors.

[potdog]

Susppression of oil vapers have bean done on all vehicles OHC / OHV when theirs an open port to recirculate the vapers from times gone by nothing new about that. 928s had the unfortunate problem made by having the tube that are on the vents going down into the cylinder heads that fill up with oil some thing like this solves that problem.

[worf]

Lol Potdog.

Yes, something “similar” to your picture where “similar” means “missing important details that actually make it work.”

[worf]

Now that I look again at PotDog’s “copy” I see a major flaw that indicates that he is clueless.

Once again Potdog, I bid thee go away and troll some other forum with your shameless and clueless copies of other’s work.

[potdog]

No MAJOR FLAW at all not a copy had an motor sport enginer advice on problem , go and kiss some one ass . this problem has been solved back many years ago by vehicle manufacturers and home mechanics.

[Crumpler]

David, my friend, you have remained silent on Gary's previous question about the efficacy of said technology. Cough up an opinion as we look to thee for advice

[Crumpler]

Greg, my opinion would be that you are probably fine with what you are planning.
I have tried many variations over the years, I never got any appreciable oil off the cam vent lines. Closed system, or to atmosphere. You could argue I never had system "perfect" to achieve proper results but that's my opinion.
I can tell you what made the most difference for my engine was a baffle on oil filler and drilling out the cap. Nuclear option yes, but no weeping from cam seals and crank case breaths well without a mess somehow. This is low boost system (5-7), but forced induction.
Everyone else close your eyes:

[worf]

David, my friend, you have remained silent on Gary's previous question about the efficacy of said technology. Cough up an opinion as we look to thee for advice

Ah. Yes. I apparently blacked-out when I finished Gary's first paragraph and missed his question completely.

I apologize.

He indicates that Worf has seen (used?) them. Any comments about them and their success in reducing oil in the system David?

I must have missed that thread on TOS.

What's below applies to 32v engines and specifically 87+ (although I have no reason to think it doesn't apply to S3 motors too.)

Yes, for about 7-ish years now, whenever cam covers come off I've been installing at least one set of Greg's under-cover parts. In cases where the client is aware of oil ingestion and wants to "do more" then the left-side cover will get attention along with some re-architecture of the breather lines.

Yes, these parts work.

One issue with the 32v engines is the "black can" under the right-rear cam cover which acts as a suction cup once that head fills with oil. That is a major source of oil ingestion on 5-speeds. When you remove that "black can" from the cover you are then left with a hole that will enable aerated oil to be sucked out of the cam cover. So, you need a piece that will actually function, at least a bit, as an air/oil separator and not as an air/oil injection mechanism.

Are they the be-all-end-all for eliminating oil ingestion?

Hmmmm... my jury is out. They absolutely reduce oil ingestion.

I suspect that on Automatic '87-'91 928s the reduction will be dramatic enough that most folks would call it elimination. I have few automatic data points since the vast majority of 928s I touch are 5-speeds. In fact I think I have only one Auto running around with the parts and one more "in the works" right now. 5-speeds? Many more.

But, and this is something that Greg will agree with, further-eliminating oil ingestion requires better crank case ventilation. If the crank case was better ventilated the "black can" would be less-often immersed in oil. There is at least one 928 running around with those pieces on both covers with 2x (might be 3x, I forget) the stock ventilation capacity that the owner reports uses no oil on the track. It's not one of my clients.

There's nothing earth-shatteringly complicated about the parts as long as you have a picture of both sides when you attempt to copy them. And there's a couple of other "items"(*) associated with their installation.

But, that's all 32v stuff and this thread is about 16v.

(*) I offer no judgement on Doc Brown's position of not providing pictures of the parts and not promulgating the instructions that go with them. Those are his conditions. I agreed to them. End of story.

[worf]

this problem has been solved back many years ago by vehicle manufacturers

On Friday, I drained a pint of oil out of the right-side charge hose on my 991 Turbo. This is standard operating procedure for 2014-2019 991 Turbos. It is *directly* a result of Porsche, still, not spending the money to install effective air/oil separation mechanisms in their crank case ventilation systems. Luckily, that charge hose functions exceptionally well as a "catch can."

So.. please tell me again how it's been "solved back many years ago by vehicle manufacturers."

[worf]

The mechanism which transports oil through the standard system to the intake is gas speed, so given that the engine is breathing at a certain rate (litres per second), the speed of the gas is determined by the area of the outlet ("volume of breathing"), so I agree completely that more or bigger outlets is good to reduce gas speed.

This is incompressible fluid flow theory which is generally considered "good" enough up to about Mach 0.5 (if I recall correctly; it's been many decades since that number was useful to me.)

I think perhaps the tricky thing with breather outlet area may be at that point where compression effects begin to throw the numbers off.

This theory also applies to the separator, getting the gas speed down so that gravity can do it's thing is important.

I would argue that while gravity is important what we actually want is to force momentum changes in the mixture such that we get the "energy" our of the oil. Or, in other words, if we make the flowing air/oil mixture take a 90° turn we will force some oil out of suspension. If we make the flow go through many twists and turns we'll "beat" a lot of energy out of the oil and therefor the mixture.

This of course comes with complications. We need a way for the liquid oil to flow away less it simply flow along with the gas. This is where gravity can play a very useful role. And we need to make sure that we're letting the gas flow effectively. Too many twists and turns and we leave the realm of incompressible flow and we have to to do real math.

And, of course we need to do this in spaces that are tight and for a unit cost that will be approved by the accountants. Once we're done, we're done and won't be able to fix anything with this model generation if we don't get it right.

The 5-pot Audi engine in the TT-RS has a remarkable ventilation/separation system. At least it did in the MK IIs. For the MK IIIs the accountants may have won ("tell me again why we need a vacuum pump?")

of what was collected was water, which I did not want to dump back into the sump.

Why? As in why worry about it? Water condensation after cool down which then flows down from almost ever part of the inside of the motor into the sump is just something that happens. Always.

The inside of your exhaust is also coated it in water once it cools.

[worf]

I can tell you what made the most difference for my engine was a baffle on oil filler and drilling out the cap.

Your experience adds data to what I originally wrote: doubling or tripling crank case venting is where the big win is. Your oil cap holes look - by my MK-1 eyeball - to be the equivalent of three "normal" breather hoses. The extra filler baffle acts as a secondary air/oir separator. CARB, would of course, look disapprovingly on your for-off-road-use-only architecture in the hypothetical case of street use in CA or lemming states.

For those that wish to obey the spirit of regulations the breather system must vent back to the intake. Forced induction systems make the plumbing more challenging since you need to vent to a section of the tract that sees vacuum. And good air/oil separation becomes more important in either NA or FI architectures since you have to reburn your crank case ventilation system's output.

[Gary Knox]

For anyone contemplating upgrading with a Provent collector system, I have a brand new Provent 'canister' I did not and will not be using. Selling for half price (whatever that is, I haven't checked recently) plus shipping.

[smiffypr]

On Friday I did a track day in my '91 GT with 140,000 miles on it. A couple of years ago I changed the breathing system to: blocked off cam cover breathers, blocked off vacuum connection to oil filler neck, single hose from oil filler neck to oil separator and outlet from that fed into intake MAF elbow. The result is no oil lost. every up-shift was at the red line, there was no pussy footing on R-spec tyres so plenty of lateral Gs, but there was no oil burnt. I find it hard to believe myself because previously I would be topping up after every 15 minute session. My conclusion is simple, breathing out of the cam covers on a 32 valve 928 motor is a bad idea.

[Benno]

On Friday I did a track day in my '91 GT with 140,000 miles on it. A couple of years ago I changed the breathing system to: blocked off cam cover breathers, blocked off vacuum connection to oil filler neck, single hose from oil filler neck to oil separator and outlet from that fed into intake MAF elbow. The result is no oil lost. every up-shift was at the red line, there was no pussy footing on R-spec tyres so plenty of lateral Gs, but there was no oil burnt. I find it hard to believe myself because previously I would be topping up after every 15 minute session. My conclusion is simple, breathing out of the cam covers on a 32 valve 928 motor is a bad idea.

Can you share some pics of your installation and details on your separator? Are you using as catch can or drain back into oil tank?

[smiffypr]

See pictures of the single breathing outlet and single breather return, all other connections blanked off. I don't have a picture of the separator and I'm away from the car for a couple of weeks, but I can try to describe it. It fits where the air pump filter used to live, and I made a baffle to try to create a bit of centrifugal flow, it has a sight tube and nothing is showing on the sight tube. I was expecting it collect oil and am amazed that it didn't, and amazed that it burnt so little oil I didn't have to top up all day. This is the first dry track day I have done in a 928 when I didn't have to top up the oil after every session.

GTsingleBreatherOutlet.jpg

GTsingleBreatherReturn.jpg

[worf]

My conclusion is simple, breathing out of the cam covers on a 32 valve 928 motor is a bad idea.

Did you remove the “suction can” from underneath the right-side (starboard) cam cover and evaluate that mod?

Or is the “suction can” still installed, but its hole now blocked?

[smiffypr]

I haven't had the cam covers off this car but I assume it was original from the condition of the hoses (I put my finger through one of them), so now the cam cover connections are just blanked off.
I did have the intake off to unseize the ISV and found that the inlet tracts were badly coked up, that prompted me to try plumbing in a separator, but it seems that the change in plumbing is preventing oil getting as far as the separator. Because the hose from the base of the filler neck is sloping upwards to the separator at the top of the radiator, it could be that the oil has a chance to fall out of suspension in that hose, but I wouldn't have expected that as it is only about 20mm. I should have used transparent hose then I would be able to see the oil staining where it did get to.

[worf]

I haven't had the cam covers off this car but I assume it was original from the condition of the hoses

That's what I thought.

It is the "suction can" that really helps oil get into the intake. And why Doc Browns replacements have such a dramatic effect.

On the front side of the starboard cam cover, the elbow has a restrictor but otherwise nothing that prevents oil from moving past it in either direction.

With the "stock" level of crank case breathing, sustained high rpm operation fills the heads (starboard more than port) with oil that can't drain back too well. Eventually the oil level in the right-side head fills to the point where it covers the bottom of the "suction cup" and then ... we know what happens.

but it seems that the change in plumbing is preventing oil getting as far as the separator. Because the hose from the base of the filler neck is sloping upwards to the separator at the top of the radiator, it could be that the oil has a chance to fall out of suspension in that hose, but I wouldn't have expected that as it is only about 20mm. I should have used transparent hose then I would be able to see the oil staining where it did get to.

This is what I see, tell me if I have mis-observed:

- You have the "stock" ~10mm exit from the filler neck plumbed to an elbow
- the elbow is ~10mm ID on the neck side and ~20mm ID on the hose side?
- ~20mm hose from elbow 'up' to separator?

[worf]

A slightly-off-topic pic....

After 30 more years Porsche still hasn't figured-out crank case ventilation and oil separation.

On the 991 Turbo the A/O separator vents to the intake tract just before the 4-6/right-side/starboard-side turbo inlet.

This is what came out of the 4-6/right-side of the charge tube on mine:

[smiffypr]

I think I put a sleeve over the original outlet to bring it up to 18 or 20 mm, then the hose to the separator is all 18 or 20mm with the elbow being a bit smaller to fit in the hose. I need to learn to take more pictures when I'm doing jobs.

Overall this seems a much simpler way of avoiding oil coming from the cam cover vents than fitting devices inside.

[Benno]

On Friday I did a track day in my '91 GT with 140,000 miles on it. A couple of years ago I changed the breathing system to: blocked off cam cover breathers, blocked off vacuum connection to oil filler neck, single hose from oil filler neck to oil separator and outlet from that fed into intake MAF elbow. The result is no oil lost. every up-shift was at the red line, there was no pussy footing on R-spec tyres so plenty of lateral Gs, but there was no oil burnt. I find it hard to believe myself because previously I would be topping up after every 15 minute session. My conclusion is simple, breathing out of the cam covers on a 32 valve 928 motor is a bad idea.

@smiffypr
Thanks so much for the photos and explanation of how your system is plumed. I am thinking of doing something very similar in my GTS.

I have a couple questions for you and anyone who may be have insight:

1. What are the downsides or concerns with capping the breather ports in the valve covers and venting exclusively from the oil filler neck? Is there a concern of excessive condensation in the heads or would that be circulated out? The theory of venting crank case pressure from 'below' the heads make sense for me.

2. what about keeping the GTS style vent hose between the left and right heads to balance head pressure? We know V8 cars have higher pressure on the right side so the theory of having a pressure balance hose makes sense to me.

Here is a diagram of the proposed implementation I am planning. Comments appreciated.


Also, I noted @maddog2020 has done something similar in one of the iterations of his monster. The cam cover vents are all capped and all vending is being done via a vent from the oil filler opening which has a cap on it. Oil return is to the pan. I cannot see where separated air is disposed of though. Hopefully he will chime in as well

[Geza-aka-Zombo]

What I don't know about crankcase ventilation is a lot, but offer the following:

On my Ford GT350 (5.2l DOHC, 32 valve, NA, 8250 rpm V8) the ventilation looks fairly simple. On the left cam cover is a hose that connects to the engine air intake duct after the MAF and before the throttle. This allows a portion of the metered inlet air at ~atmospheric pressure into the crankcase.

On the right cam cover is a hose that connects to the air inlet between the throttle and engine (vacuum side). This sucks the oily crankcase air back into the inlet to meet up with the inlet air that wasn't diverted into the crankcase. This accounts for all the air that passed over the MAF.

Ford Performance makes catch cans for both the left and right hose. The left catch can is useless, as only atmospheric air passes thru it. People that added one report no oil collection. I added the right side catch can on mine which does collect some oil, as the oily crankcase air passes thru. The catch can consists of a horizontal screen between the inlet (from the cam cover) and exit (to the intake hose). This inlet is below the screen and he exit above the screen.

Not my car (no catch can) but this is what it looks like.