Carl Fausett

I have expressed my experience with Mann-Hummel ProVent on several threads. On one occasion, the small coil spring in the cap that is meant to hold the pressure-releif valve in fell out of the cap, opening the oil separator to atmosphere and spilling oil all over my headers. On another occasion, during a spirited downshift into a corner, that little valve in the cap blew out entirely (and spilled oil all over my headers).

I diasbled the troublesome valve completely and thought that would be the end of it. Mid-race, with everything nice and hot, the platic top softened sufficiently for the cap to flex past the locking tabs and blow off (and spilled oil all over my headers).

That's it for me.

The design is strange. Commonly accepted oil separation engineering dictates that the oil/air mixture enter at the side, condensed oil goes out the bottom, and the vent/exit for the "dry" air is supposed to be as high as you can get it for maximum separation and effectiveness of the separator. The Mann-Hummel is backwards of those generally accepted design principals, and the air/oil enters at the side, and the exit is LOWER rather than HIGHER of that port.

Still, I believe it may function adequately in non-boosted and/or non-racing applications. It could be that I ran it past its temperature limits, or pressure limits.

Other 928 racers reported that when the membrane/separation material became oil soaked, it became restrictive to air flow. Somehting to think about.

BTW: it has almost no capacity. It is not designed to be used as a catch tank. It is a flow-thru oil separator only.

SwayBar

I have used it at Road America and it works perfectly in my GT racecar.

From here you stated: https://rennlist.com/forums/showpost...2&postcount=98

I read where Tony did a leakdown on his 150k mile engine, and several cylinders were 0%, and the rest were less than 5%. Needless to say, that engine is virtually perfect even after 150k miles, and is quite a bit less than the 20% you reported on a brand-new engine.

For whatever reason, your rings did not seal, and 20% leakdown is typically considered the threshold for a worn-out motor. Under those circumstances, there is not a device on earth, including the Pro Vent, that can accomodate all of that blow-by.

So to say the Pro Vent failed is unfair, when the root-cause is the ailing motor.

I did remove the oil-soaked material and stuffed a plastic 'scrubby' down into the center; the end-result is virtually no restriction.

Yes; I have it plumbed through an aircraft-quality one-way valve, which then enters the oil-pan through it's drain-hole.

smiffypr

re: The design is strange. Commonly accepted oil separation engineering dictates that the oil/air mixture enter at the side, condensed oil goes out the bottom, and the vent/exit for the "dry" air is supposed to be as high as you can get it for maximum separation and effectiveness of the separator. The Mann-Hummel is backwards of those generally accepted design principals, and the air/oil enters at the side, and the exit is LOWER rather than HIGHER of that port.

I've been looking at the possibilities, and in doing so, looked at industrial solutions for separating liquid from gas. The centrifugal, baffles, gauze, approaches all appear, and the most effective systems use more than one technique. A multi-chamber approach might be the most effective, but isn't ideal with the space limitations we have. I have found that large "tanks", (6 litres) work well by allowing the gass speed to drop, and gives time for gravity to pull the liquid down. In this case, yes the outlet needs to be high, and well away from the inlet, which is easy on a rectangular box shape.
Trying to make something smaller, I am experimenting with a cylindrical shape (about 3 litres) to allow for some centrifugal action. Because gravity is still there, the flow of oil and hence the gas/liquid mix at first, has to be a downwards spiral. taking the outlet from the top would cause the gas flow to short circuit the cyclone , and go straight out the outlet, and fail completely. So with this design, the outlet can't be taken from the top (even if the pipe emerges from the top of the container), and it can't be at the bottom because that's where the liquid is collecting. It also can't just come straight out from the middle because the gas speed will pull the settling oil with it, so some sort of "diffuser" is needed. I think the pro vent looks like a sensible design, but maybe not big enough.

re: Still, I believe it may function adequately in non-boosted and/or non-racing applications. It could be that I ran it past its temperature limits, or pressure limits.

If you had to by-pass the pressure relief valve, it certainly looks that way. Mine (on an '80 S) is always running slight vacuum as the outlet goes into the throttle body upstream of the throttle, but downstream of the K-jetronic air-flow plate. I know that it never sees positive pressure because the pipes aren't clamped, and don't blow off.

re: BTW: it has almost no capacity. It is not designed to be used as a catch tank. It is a flow-thru oil separator only.

I meant capacity in CFM, and in that respect, it sounds like your 20% leakdown is going to test the flow capacity of any separator system small enough to fit under a 928 bonnet.

Have you checked the postage to NZ?

Smiffy

smiffypr

That's the idea of the tangential entry on the standard S oil seperator, and things like the ProVent.
You don't need anything moving other than the gas/oil mist. My experiments have used transparent or translucent materials wherever possible so that I can see what is happenning.

Smiffy

Carl Fausett

You pulled up an old post - and if you had read further you would have seen that I reported 20% leak-down on a motor with new rings and 450 miles on it. Not yet bedded in, and standard rings with standard end-gaps.

I do agree with you - 20% cold leakdown is a large number that would task the outer limits of any air/oil separator.

Since that post, I have taken those rings out and installed gapless Total-Seal rings. I have 650 miles on these rings and will be leak-down testing the motor this weekend.

Just ran it hard and long at the Autobahn racetrack yesterday for our Performance Driver's School.

When I assembled the engine, I had four P928 dipsticks to choose to use, each with different full/low lines on them. See my post earlier in this thread where I show photos of the variables in dipsticks alone.

I started with the dipstick that held the most oil, and decided I'd work it backwards from there. Because of the Ishihara-Johnson crank scrapers and tray, I am a little less concerned with missive air in the oil than I would be otherwise, so I felt I could safely experiment with the "top" of the oil level.

Results at the racetrack: although my catch-tank remained empty all day, I puffed blue in the morning, but as we practiced, I blew less and less blue until the oil level went down to just below the "add" mark. At that oil level, it really blew very little if any. Running 6-8 psi of boost if anyone wonders, I had de-tuned it a tad for this event because the motor is so young.

If I engine-braked at all, it made it much worse on the next acceleration.

Anyway, I added about a pint before the last practice session just to bring her up a tad, and fogged for mosquitoes all over again.

Trial and error - that dipstick is coming out now, and the next longer dipstick is going in for next time.

Here is the "blue" out the tailpipe....

Carl Fausett

Yes, tangental entry is correct, especially at the outermost edge of the cylinder to set up the swirling action. But, IMHO, the exit for the de-oiled vapors should be at the top, ABOVE the entrance.

Smiffy - I can get you a shipping quote but I need your complete shipping address to do it. A partial address is not enough. You can email it to me at carl@928motorsports.com

smiffypr

I have come a bit further with my "spaghetti jar" oil separator. It now works reasonably when tested with water mist. (better than 95% recovered). The swirl has to be a downwards spiral other wise the oil will be draining down against the air flow. This means that the air exit from the cyclone section has to be lower than the inlet. In my case, I have the outlet at the top of the jar, but I have tube and an inverted funnel to separate the downward and upward flows. At the edge of the funnel there is only a 5mm gap, so that the gas speed downwards pulls any drips of oil downwards, and the low gas speed upwards at the entrance to the funnel means that oil drops don't get pulled up into the outlet tube. So my outlet is effectively from below the inlet, it just looks odd when it actually comes out the side half way down.

I intend to try to get my design fabricated in ss or ally, but would still like to try the Mann-Hummel thing, and it would also be useful as a standby, or could be used on the road car.

The postal address would be:
Paul Smith c/o eServGlobal
Unit 3, Ngauranga Estate,
Hurring Place,
Newlands,
Wellington 6037,
New Zealand

smiffypr

RE: Results at the racetrack: although my catch-tank remained empty all day, I puffed blue in the morning, but as we practiced, I blew less and less blue until the oil level went down to just below the "add" mark. At that oil level, it really blew very little if any. Running 6-8 psi of boost if anyone wonders, I had de-tuned it a tad for this event because the motor is so young.

That sounds like what I would expect with the standard S breathing set-up. Sounds like your catch tank was doing nothing at all.

Keep an eye on your oil pressure as you drop the level, there will come a point where the wrong combination of revs, time, G's will make it drop.

Smiffy

Carl Fausett

Smiffy - to ship the used Mann-ProVent to you 4-10 days through US Mail, the cost would be $21.60.

*Note, the customer is responsible for all import taxes and duties. Also, the 4-10 days does not account for customs delays.

Just let me know if you still want it.

GlenL

On a separate but related note...

I'm considering making a deeper sump. This would have a deeper pick-up to make use of it. Anyone tried this?

I've recently acquired an S4 pick-up. It has the same basic dimensions as a 16V pick-up including the depth it extends into the pan. Drat! Was hoping for an extra cm or two. At least it has a screen over the hole.

Louie928

Glen,
I made a 3/8" aluminum spacer to space the oil sump down mainly to give more distance between the crank throws and bottom of the pan. I also wanted to eliminate the pan gasket so I could bolt the pan directly to the block for added stiffness. I used a sealer similar to Yamabond 4 on the surfaces. So far, it's remained sealed. The lowered oil pan prevented use of the stock starter. I used one of the small "high torque" models, but rotated it so it didn't hang down like they normally do. I still have about 1/4" clearance between the pan bottom and cross member. I have the Anchor "solid rubber" mounts. I made an aluminum spacer where the oil pickup bolts to the block to space down the stock pickup tube. The pickup end of the tube has the same clearance to the bottom of the pan as normal.

You could cut off the sump part of the pan and weld aluminum around to space the sump down by maybe an inch. It is pretty low already so you can't go too far down. Add a skid plate.

GlenL

Thanks, Louie. It'd be low. I am worried about un-even pavement.

I was admiring your spacer. Didn't know it required a change to the starter.

BC

Louie - did you make those two spacers by hand? Or in solidworks? I am designing one, but I am concerned about which kind of metal to use. It would have to be somewhat eleastic in nature right? Or dead soft?

Louie928

Glen,
The original starter was too big in diameter. I didn't like the angle the Hi Torque starter fit either. It was either hanging down too low or was too close to the headers. I had to change the location of the +12 post so I'd have clearance between it and the pan. I also changed the location of the drain tube because I rotated the motor by about 180 degrees. Here are some pics. The dark color of teh oil pan is a heat shedding ceramic coating.
https://rennlist.com/forums/attachme...d=142951&stc=1
Starter fit 4 640x480.jpg
https://rennlist.com/forums/attachme...d=142952&stc=1
Starter solenoid contact mods 640x480.jpg

Louie928

Hi Brendan,
I do not have Solidworks drawings for the spacers. I just made them, and didn't have time for fussing with Solidworks. I believe Tom Cloutier has SW drawings of the sump outline. Actually, the entire dry sump system he's making. One should be done by now. I used 6061 -T651 precision plate for the pan spacer. I picked up the plate at scrap so it wasn't too costly. I wanted something hard and flat that wouldn't deform and maybe leak. I used the pan itself as a pattern and rough cut the outside on the bandsaw. I cut the inside out on the mill and also finish cut the outside on the mill and die grinder. I used a transfer punch to locate the holes. The spacer is a simple 3/8" thick piece that locates the oil pickup tube 3/8" lower. It has a proper sized hole that the oil sump big O ring type seal fits into. I'm trying to think of how I sealed the spacer to the block and I can't quite remember now. I'm thinking that I may have cut a circular groove in the bottom of the spacer to hold an O ring. Tightening the spacer between the oil pump pickup flange and block with the O ring between would seal. I can't remember and I can't find pictures, but I probably took some. The outside of the spacer is shaped like the pickup tube flange and all held to the block by the same bolt, but longer of course, and secured with Loktite. Spacers had to be made for under the pickup tube bracket that bolts to the main bearing girdle. Just simple aluminum round stock 3/8" thick for those. It seems to work fine as I don't have any unusual oil pressure problems, but the proof won't really be known until it gets on the track. I had to space down the oil pan because with the longer stroke crank, I didn't have room between the pan and crank throws for an oil catching screen. The extra 3/8" gave me the room. Otherwise, extending the depth of the sump section would have been a lot easier.