How To Plumb In A Dry Sump Oil Pump?

[manta22]

Whether talking about a dry sump oil pump or a fuel pump, the idea is to not restrict its inlet enough to cause it to cavitate. This is aggrivated by high temperature and high altitude. Pressure drop across filters can vary widely and it does no good to ask the supplier for flow data-- you'll get a blank stare at best unless you are talking to the right person at the factory (who is almost impossible to contact). Setting up a test yourself is probably the only way to get any pressure drop vs flow rate data.

Regards, Neil  Tucson, AZ

[Glen]

The suction,inlet side of any pump should be of greater size. When I worked at Vickers Inc.( a hydraulic pump & valve Mfg. ) The design engineers always made sure of this on all test stands for pumps. Never starve inlet side. Rule of thumb was suction was usually twice the out put tube size.

[Rex Schimmer]

Neil is somewhat correct regarding automotive filters, not much info on pressure drop vs. flow but on industrial filters , such as the Pall HH7400 filter that Buddy is planning to use you can find extensive information on pressure drop vs. flow rate and how it is affected by such things as oil specific gravity. Yes, having a filter between the high pressure pump and the engine does protect the engine and is the recommended setup by many dry sump pump manufactures, in the industrial and aerospace hydraulic world, were we are talking about real pumps at high pressures with exotic fluids, the preferred position for the finest filter is in the line that is returning oil to the system reservoir, the scavenger sections in our case, because this is were all of the crud from the system (engine) is returned to the reservoir. Why have this junk be pumped by the most important section of the scavenger pump package, the engine pressure pump, before it is filtered into the engine. Every time a piece of contamination runs through the high pressure pump and causes damage it makes literally hundreds of additional contamination particles that accelerate wear of both the pump and the engine.  Doesn't make much sense to me no matter what the scavenger pump manufactures say.

Rex

[Bob Drury]

  Rex, maybe it is more a question of viscosity of the fluids used than the pressure drop seen thru the filter.
  I don't claim to have much knowlege of fluid dynamics but common sense tells me that a pump used for hydraulics or any light viscosity fluid (such as a Enderle or Kinsler fuel pump) certainly has tighter tolerances than a automotive oil pump.
  A lot of racers have found out the hard way that mechanical fuel pumps wear especially when using alcohol or Nitromethane fuels which provide no lubrication.
  A fuel pump that puts out say 10.2 gpm when new may only put out 8.5 or 9 after a mere handful of runs.
  The results are that if you don't stay on top of your tune up you may be buying pistons before long even though you havn't changed a thing.  This is especially true in Drag Racing where you are usually running the engine on the lean edge anyway.  
  In my mind a pump is no different than a piston in a cylinder, where alcohol and nitro leech past the rings much faster than petroleum based fuels like gas or deisel.  
  I just can't see or should I say have never seen any apparent wear in any wet or dry sump oil pump in a race motor that came from normal use.  This may not be true in a Indy motor that runs for several hundred miles but for our use I still feel the best bet are the inline filters which catch most actual visable debris.
  Because of the heavier viscosity of engine oils, the pumps are not built to the high tolerences needed in many industrial aplications. Thus  the fine particulants that might hurt a Enderle fuel pump shoudn't do much harm to a oil pump.
  Given that most race cars have a minimal amount of room to accomodate filters, I would be hesitant to run too fine of a filter on the scavenge side. unless I was using a light weight synthetic oil which doesn't fare well with non petroleum based fuels.
  Just my two bits worth....... Bob

[Jack Gifford]

Umm... just a comment from a disinterested party-
The last half dozen comments appear to ignore that Flattie said he's planning two filters in series on the output side of the scavenge pump.

[Bob Drury]

  Jack, if you reread the posts you will notice the concern is not about pressure side filters rather scavenge side filters.............  Bob

[38flattie]

The plan I've settled on is a Wix filter on the pressure side, with an oil pressure sending unit, and an Oberg with 60 micron screens on the scavenge side. I'll have the Pall 7400 on the return line, as I really believe on keeping the oil reservoir clean, and not running contaminated oil through the pump.

To be honest, I'm only adding the Wix in case I shell the dry sump-it will keep those parts out of the engine!

Guys, I realize that it's not a 'traditional' style setup. Luckily, we all do things different, and have different ideas, otherwise we would all be running identical cars!

I do appreciate all of the ideas and advise, even if I sometimes stray from conventional wisdom!

[manta22]

Rex;

Kinematic viscosity is a key spec that is hard to find, that's why I recommended setting up your own test. That way you are getting data on the filter with the fluid that it will actually be used with. Don't forget that it is temperature dependent.

Regards, Neil  Tucson, AZ

[Jack Gifford]

... reread the posts...

I did read them. Can't YOU read?

[Rex Schimmer]

Neil,
Pressure drop through a filter is proportional to the specific gravity and the viscosity of the oil. If you know the pressure drop per gpm of flow that the filter is rated and what the viscosity and specific gravity of the fluid that the filter is rated at you can then calculate the new pressure drop with a different oil that has a different viscosity and/or specific gravity. The Pall Corporation, and therefore almost all filter manufactures, rate their filters and housing using 150 SUS viscostiy oil that has a specific gravity of .9. So if you have an oil that has a viscosity of say 200 SUS and a spec. gravity of .85 you take the rated pressure drop and multiply it by 200/150 x .85/.9. Several things certainly need to be considered, most important of which is oil temperature as it has really controls the oil viscosity. Standard 50 wt oil at say 80 deg F has a viscosity of about 2000 SUS! so the pressure drop is increased by 2000/150= 13.3 times! This is a great reason to have an oil tank heater because at 150 deg F the viscosity is down to around 290 SUS and at 200 deg F it is around 100 SUS. So if you don't preheat your oil you should really have a bypass style filter or a 15 to 20 psi check valve around the filter to allow the cold oil to bypass the filter until it is at operating temp. Also if you are putting a low micron filter on the return oil from the scavenger pumps this oil is typically at the highest temp the oil will see as it is just out of the engine, so it is at its minimum viscosity. This is also probably a good reason to consider some of the multi viscosity oils such as a 20-50 wt, which should provide a lower viscosity at low temps. If you do not have an oil reservoir heater then I would think that using multi viscosity oil is a must.

Rex

[38flattie]

Neil, Rex- you both offer up great info!

For the record, Exon-Mobile is sponsoring all our lubrication needs, so we will be running Mobile 1 Racing 0W-50 oil.

The dry sump oil tank that I bought from Tony has a heater that we will be utilizing, so I think this setup will work well.