heretic

Re-read the notes about aeration for one clue.



As for the rest, pump cavitation would be my best educated guess. At some point, with ANY kind of pump, it takes less energy to create a vacuum on the backside of the rotors/blades/whathaveyou than it does to draw the fluid being pumped. Enhance the passages to require less energy to get the fluid into the pump, and you will reduce cavitation at a given pump speed, netting more flow.



And of course, if the fluid is aerated in the first place, the cavitation process is greatly facilitated, since air is compressible and expandible, and it's far easier to expand a gas than it is to create a vacuum. Vacuum being used here in its truest sense, a space with no or next to no matter in it.

Lynn E. Hanover

Not enough data, and it is a kind of personal thing. If you have the experience and the facilities to ****** an engine out every now and then just to look inside, I think you should take it off and mod the end of the pickup. Because, the above would indicate that you use the engine well above the 6,000 RPM where this problem starts to restrict flow and add foam to the oil.



If you don't spend much time above 6,000 RPM, I wouldn't do it. Just no point to it.

In the airplane engine they will be very close to a 100% duty cycle. You jump in and go to WOT, and sit on it for three hours. So wide open right in the RPM range where this problem lives.



On the street you pass through this for just a second or two with each gear change. So it just is not going to hurt you unless another set of factors is in play.

Using a straight weight oil will get rid of most of it. Just leave out the plastic. If the book says 5W40 or 10W30, the small number is the actual weight of the oil (a scale of flow resistance) and the big number is the weight it acts like when it is hot (operating temperature). So you have a very light oil for good start up lubrication and cold starts where that is a problem, and a 30 or 40 weight at temp. But you get there by adding plastic strings that link up when heated(polymers) that by themselves don't lubricate worth a damn. Also, if the metering pump is still in use you won't be feeding the apex seals that gummy plastic crap. Good old straight weight dino oil burns better than polymers.





This my opinion. Your results may vary. This information came to me after a nasty in line skating head strike.





Lynn E. Hanover



The picture is the inlet end of my Weber. Vena contracta? I don't think so!

Lynn E. Hanover

Nobody bites on the "vena contracta" or a 12A bolted to a Chevy S-10 bellhousing,



but the group answers almost all of the pump questions on their own. You gotta like that.



A big centrifugal fire pump on an aircraft carrier can put out 5,000 GPM at 100 PSI.



The suction piping may be in the 24 inch area. This pump is kept full of sea water 100% of its life. It must be primed with water or it won't work when you need it.



There are 4 smaller pumps in front of this pump to provide the required "feed" so that the suction side of the big pump never drops below 50 PSI. These pumps are called booster pumps. The big pump will not start until there is 50 PSI in the inlet.

If it did start up Several 400 HP electric motors 440 volts 400 cycle three phase AC, The big pump would cavitated (instantly boil the inlet water) and damage itself.



As has been offered, the suction side of any pump can be pulled down well below sea level pressure. One bar (barometric) or 14.7 PSI at sea level. So if our pump spins up and pulls a perfect vacuum in the inlet, there will never be more than 14.7 pounds available to push oil into the pump. So, since Murphy lives, there will never be a suction side design that will deliver the full 14.7 pounds to the pump interior. So a predicted pump output must include the losses of available fluid in the suction side caused by design faults. The pumps are rated in their ability to pull close to a perfect vacuum as suction lift. You can see the pump struggling to lift a column of oil some 8 feet, or in our case 7 inches. In any case the farther away from perfect we get on the suction side, the poorer the pump performance as output speed increases.



A poorly designed pump and suction side piping may work very well at low RPM, and be a complete disaster at a higher RPM. Like the Mazda. In the Mazda case that point is high enough that in simple street use there is no problem.



The many ways to improve the suction side:



Add a pair of booster pumps. Very good outcome but too complex.



Remove bug screen. Cheap, works well. Must keep crap out of sump.



Mod pickup tube to look like a trumpet bell. Very big improvement. Easy for some folks. A good change.



Use a small ball bit in a die grinder, to streamline the junctions of drilled passages and cast in place kidney shaped ports below the stock pump land area. Very big improvement. Should practice on junk iron before ruining your good engine.



Bolt on a three stage dry sump pump, and forget most of your oiling problems.

Expensive but the most effective fix.



Lynn E. Hanover

cach22

Hey Lynn,



ok im going to bite please explain to us about the 'vena contracta' and the chev bellhousing some great knowlegde in this thread



cheers



Lance

Lynn E. Hanover

Vena Contracta in our case is the apparent restriction caused by a dynamic in hydraulic flow caused by container shape or inlet or outlet shape in a system.



When you see a air horn on a carburetter instead of just the flat top of the carb, it seems natural to think that the carb with the air horn will work better, but why?



We live in a pressurized bubble. One bar, or 14.7 PSI at sea level. We can cause air or fluids to move to locations where we want them by lowering that local pressure in a device like a pump, a rotor housing or a cylinder. By enlarging a sealed chamber from a near zero volume to some larger volume, From TDC to BDC, in a rotary or a piston engine. One side of the piston or rotor has added a small amount of pressure to our world. So a slight pressure increase is apparent in the crank case. The pressure inside the sealed volume will go way below the local pressure (14.7 at sea level). If you then open a port that leads from the outside world to the inside of the low pressure in the test volume, the local pressure will flow into the volume and equalize the pressure.



Use your mouth to suck some air out of a pop bottle, then while holding that low pressure in the test volume (the inside of the bottle) stick your tongue over the hole to hold the vacuum in the bottle. Now quickly think about what is going on. Don't take too long or your tongue will hurt for a week. You are on the outside of the bottle in our world and the pressure in our world is trying to equalize the pressure inside the bottle and your tongue is in the way, so the 14.7 PSI in your tongue is being forced into the bottle. Now get you tongue out of there, your mother is going to see you doing that stupid stuff.



You cannot suck oil up a tube. You cannot suck a Slurpie up a straw. You cannot suck the air out of a pop bottle.



Don't feel bad. Nobody can do it. It just seems like we can. You can lower the pressure inside the straw and inside your mouth by spreading your jaw and pulling your tongue to the rear of your mouth. Increasing the volume in your mouth, and thus lowering the pressure in your mouth to a point lower than that in our world. So our 14.7 pounds becomes slightly higher than the pressure in your mouth and forces the oil, or better yet the slurpie up the straw. Or the air from the pop bottle flows into your mouth to equalize the pressure.



So, if our oil pump is a system of mechanical low pressure generators on one side

(the suction side) I know, it shouldn't be called that. It should be called the low pressure generating side.



At any rate the fluid or gas is forced by local air pressure up the pickup tube because of the differential pressure. The tube is submerged in the oil and the oil is forced to the low pressure at the end of the tube in a uniform manor and at a uniform speed inverse to the distance from the tube end.



The fluid moving into the tube from a location directly in line with the tube need not change direction in order to enter the tube. But there will be a large percentage of the liquid that is moving from areas that will require a 180 degree turn or less to enter the tube. The fluid is moving at high velocity, and has mass, so there at the very edge of the pickup tube, the oil making the 180 degree turn will tend to interfere with oil entering from any angle less than 180 degrees. The same for oil from 170 degrees, 160 degrees and so on. It will be as though the end of the tube has crontracted because this reduces the flow to what would be typical of a smaller tube. "Vena contracta" (the vein has contracted)



If there is no room for a long horn shape, you will see a horn that has the outer rim turned clear back to 180 degrees from the centerline of the tube. The larger the horn shape the lower the flow velocity of the fluid before it gets the the tube entrance and the less it can interfere with all of the other fluid entering the tube.



On the flow bench, the difference can be over three times better flow through the tube by adding the air horn, or trumpet bell shape to the end of the tube.



The more dense the fluid the better the effect. So in hot oil it works like magic.





When we say that the pump is a "positive displacement" design, never believe that. There is just no such thing. On the low pressure side, if there is not enough flow to completely fill the working chambers of the pump, what will be the effect on pump output? Say that the pumps calculated displacement is one cubic inch. But we have time to fill the working chamber only half full on each revolution. Remember we have only 14.7 pounds to work with in the attempt to fill that exposed volume, and only a very small part of one second, several thousandths of a second to do it.



The "Positive displacement pump" has become a variable displacement pump has it not?



The Chevy bell housing was used because the only transmission we could afford that had a good choice of ratios was the Richmond Gear road racing 5 speed. And it bolts up to any chevy bell housing.



To adapt the Mazda bell housing you just about have to have access to a vertical mill. The Mazda has the bearing retainer cast in place. That must be removed and a pilot hole that fits the Chevy bearing retainer must be installed. I don't have a mill, so I made a 1/4" steel plate adapter to fit between the S-10 bell housing and the rotary.



Lynn E. Hanover

TYSON

[quote name='Lynn E. Hanover' date='Jun 26 2004, 02:07 PM']IO....110 degrees BTDC



IC.....85 degrees ABDC



EO.....80 degrees BBDC



EC.....75 degrees ATDC

Lynn E. Hanover


[/quote]











Lynn, what runner length are you using for your exhaust, and have you done a lot of testing? I've got almost exactly the same exhaust duration as you, and maybe the same RPM target. My exhaust port timing is about 10 degrees earlier though.

Lynn E. Hanover

[quote name='TYSON' date='May 15 2005, 03:58 PM']

Lynn, what runner length are you using for your exhaust, and have you done a lot of testing? I've got almost exactly the same exhaust duration as you, and maybe the same RPM target. My exhaust port timing is about 10 degrees earlier though.






[/quote]





I have 1 7/8" ID tubes 22" to the collector. A 6" long collector to a megaphone 24" long with a 2 1/2" start diameter and 4" end diameter. The most important feature of a rotary header, is that both tubes be exactly the same length. If you get nothing else right, get that right.



You cannot make a big HP change with headers alone, but you can kill off a ton of HP with a bad design. Find a flex hose that will be a slip fit inside of your header tubes. As you build the system keep inserting the hose and marking the depth with tape. Both tubes should get to the collector with the same length of hose showing.



Lynn E. Hanover

TYSON

I already drew them in AutoCAD At 20" they're less than a millimeter different in length. From looking around it looks like about 24" is what I was expecting. thanks!

crispeed

Actualy the RX-8 pump took the design a little further. There's now an extra cavity/notch in the pump to allow the rear section of the pump to feed the pressure section of the front housing. The pump rotors are the same dimensions as the FD's one though.

drewrey2004

mr hanover im not very sure exactly wat u guys are talking about with the oil pump and pickup tubes can you show where exactly to make these modifications on the pump and tube.