PorKen

After a bit of thought and weekend of Googling...

Crank venting using a marine oil/diesel transfer pump, with offset rotary vanes like factory smog pumps but with oil friendly vanes.

Example: Itt Jabsco "Vane Puppy"

click pic for 'Your American Backyard'

"Self-priming rotary vane pumps are a positive displacement type design w/an off-center eccentric rotor whose vanes slide inward and outward, as they move from the top to the bottom of the bore, this action creates a vacuum to pull liquid into the pump. Designed for diesel fuel and light weight oils. Self-Priming to 3 feet, quiet, low amp-draw 8 amps."

The pumps are ~$160, and the rebuild kits are <$20. It has 1/2" pipe ports.
...

Like the $350+ Moroso engine driven vacuum pump, it requires some oil passing through to lubricate and better seal the vanes, so the air/oil separator would have to be on the output side.

A high throttle angle switch or even a vacuum/pressure switch (manifold or crankcase) could switch on the pump.

There are even higher amperage, higher lift models that might pull some serious vacuum.

Old & New

Porken,

How much vacuum is desirable in the crank before we concern ourselves with water and dirt being sucked in through seals and fissures?

How much HP do you expect to scavenge?

I would go with a vacuum switch, for precise control.

PorKen

Old & New,

Here's a nice article on the subject: The Pros and Cons of Racing Vacuum Pumps.

"How much vacuum is desirable in the crank before we concern ourselves with water and dirt being sucked in through seals and fissures?"
15" mercury is oft quoted to be the max before there's not enough oil mist to lubricate the non-pressure fed engine parts. As for the seals, well, that's a maintenance issue.

I would like to pull upwards of 7-10". BTW: I tested the vacuum of an electric air injection (smog) pump (these have centrifugal impellers), and it only could pull 3".

"How much HP do you expect to scavenge?"
A lot. I would think that there would be big benefit for the supercharged cars.

"I would go with a vacuum switch, for precise control."
Perhaps two speeds, low with a vacuum switch, and high with a WOT switch?

One plus, an electric pump should wear more slowly, if it wasn't running all the time. And cheaper/easier to service. You can buy all the parts seperately for the pump above; motor, pump body, vanes, etc.

PorKen

Boat stores have cool stuff.

Of course, the one I went to today didn't have the vaned pump, though.

GoRideSno

Yeah, The boat stores have a bunch of cool pumps and hoses and such.

I bought a Shurflo Aqua Tiger SS 21 gpm pump from Boater's World for $155.

I hooked it up to a vacuum to see if it would pull a vacuum after reading your post and it will hardly do it. It is a centrifugal type that must have a flooded intake so it is no surprise. It will really move the water though.


ANdy K

GoRideSno

Would you consider a water puppy?


Andy K

PorKen

I figure it has to be an 'eccentric rotary vane' type to pull vacuum.

Here's some better specs on the one I'm looking for:


Jabsco Vane Puppy 12V

Part Number 18680-0920
Amp Voltage 12VDC
Amp Draw 8
Fuse Size 15

Body: Bronze
Rotor: Plastic - Liquid Crystal Polymer
Vanes: Plastic - Polyphenylene Sulfide
Seal: Lip Type, Nitrile
Motor: Permanent Magnet Type, Fully Enclosed, Stainless Steel Shaft Fully Enclosed, Stainless Steel Shaft
Ports: 1/2" Internal Pipe Threads 1" External Hose Barb
Height: 3-3/8" (86mm)
Length: 6-7/8" (175mm)
Width: 4-3/4" (121mm)
Weight: 5-1/2 lb (2.5 kg)
6 gpm (23 lpm) at 10ft (3m) head.
30ft (9m) maximum total head.
Self priming up to 9ft (2.8m) vertical lift.
Duty cycle-35 minutes at 10ft (3 metres) at 860F (300C)
Rugged bronze pump head.
Complies with USCG 183.410 and ISO 8846 MARINE (Ignition Protection).

GoRideSno

The water puppy self primes up to 4 feet above the water so it has to pull vacuum.

I figure the vane puppy to be better since it mentions oils. One deciding factor may be the GPM though.
Andy K

PorKen

Note that they're spec'ing the GPM at 10ft head*...

They did have a water pup at the boat store, along with replacement impellers. The impellers are centrifugal type, but are flexible and touch the walls of the pump for a better seal.

Jabsco also makes an oil change pump which looks to be a water pup with a Nitrile impeller. That might work and it's cheaper than the vane pup.


Jabsco Pump Oil Changer

*The difference in depth of a liquid at two given points
...

My thinking so far (without actually having a pump), is to mount the pump low, with the hoses down to it trapping some oil in/near the pump.

I'm trying to figure out a way to use the 16V separator... The upper crankcase hose would go to the pump, the output of the pump goes to the separator, and the cap hose goes to atmo, or exhaust. There would need to be a (ball) valve on the oil drain hose from the bottom of the separator. It would be slick if the valve was electric, open only when the pump/car is off. I suppose a floating ball in the bottom of the separator would seal the drain under pressure, and dump when there was oil...

SharkSkin

Guys, I've been watching this with interest, as I'm wondering whether there is enough mist to keep those pumps from frying. Cheap experiment I guess, as long as you make damn sure there's no way broken pump guts can get back into the motor. See, most pumps should not be run dry... running dry requires that the pump be designed for such duty, and that's not usually the case. From the page Ken linked to, there is a technical data sheet link to this PDF.

You may have noticed on the second page where they say:

Rotary Vane pumps must NOT be run dry, as the pumped liquid is the lubricant for the rotor and vanes.

What they fail to mention is that the pumped liquid is also the coolant for the pump, and you're talking about a warm area as it is.

So again, I'm really interested to see what you guys come up with and how it pans out long term. Gotta love pioneers, man!

PorKen

I don't think the pump needs to run continuously. This means there'll have to be a bypass so the engine can breathe without it.

The drag-race-engine-driven-vacuum-pumps are basically the same design, using modified smog pumps, with 3 or 4 vanes, whereas this one has 5 (albeit with smaller volume per chamber). In the pro/con link above, they don't recommend running on the street without sufficient oil at low rpms.

So either with an electric or an engine driven pump there are oiling issues.

Some fixes I can think of are: using a hose loop, a bypass oil drip from the separator, or even an external oil reservoir or a small feed from the sump to keep an oil bath in the pump.

If heat is an issue one could add fins (a Pentium-4 cooler?), or a coolant circuit to the rear pump plate.

In regards to keeping pump bits out of the engine, the separator should take care of this. With the 16V separator, the output of the pump should enter through the cap, and the outlet of the separator would now be the hose connection on the body of the separator.
...

Interesting description of operation:

Rotary Vane Pumps: Technical Notes

PorKen

Jeepers! Using an online conversion calculator I converted the 15CFM value from GoRideSno's blowby thread. 112GPM (liquid)!

PorKen

OK, I guess I was a bit, uh, optimistic, with the electric pump idea.

On the up side I found this manufacturer in CA, GZ Motorsports, their entry level 'Sportsman' belt-driven vacuum pump is only $179.

The next thing, then, is to figure out how to mount an electromagnetic clutch to the belt driven vacuum pump.

GoRideSno

Ken,


This dosen't seem correct. If you consider the real world example of a shop vac sucking up water v/s it's exhaust blowing up a garbage bag then it seems the inverse is more likely.

Andy K

SharkSkin

Ken,

I think that you're going to have a real hard time pulling 15" at 15CFM, or even half that... especially in a way that will be as reliable as the rest of the system(meaning your 928). The airpump powered crankvent seemed like a real viable solution for a non-cat configuration. Not a whole lot of vacuum was generated, but SOME is a whole lot better than none. It would be interesting to see how that system would work out on a medium boost application(5-10 lb).

A better solution might be to simply design a venturi that goes in the exhaust pipe, developing more vacuum as you develop more exhaust(and blow-by). You may still not get to 15", but it might give you more than 3". The trick would be to get an adequate venturi effect without leaving power on the table from exhaust restriction. The big payoff would be the lack of moving parts. If you can pull 3" or more with such a setup, leaving the air pump available to keep the cats healthy, then IMHO you will have truly perfected the design... though oil buildup in the muffler packing material may ultimately be an issue for some. Extra weight if nothing else.

Good stuff though... lotsa cool pumps. Have you considered just getting a smog pump core and trying to replace the vanes with a hi-temp plastic that will withstand the oil/fuel mist and just evacuating the crankcase directly? Really that boils it down to a simple improvement on an existing system to make it suitable for a new purpose, and if you just eyeball the entrapped volume in the stock air pump I think you'll find that it's at least an order of magnitude greater than the volume of the pumps you posted links to. Plus, you can put a smaller pulley on it, especially if you have lower-friction vanes.