stepped oil passages
stepped oil passages
(OP)
Howdy all,
I understand that if you were to take pressure readings along the main bearings of an engine, each main would have less and less pressure coming from the oil pump.
In an effort to remedy this, has anybody ever tried a stepped oiling system?
In the HVAC systems and Foundry gating systems that I'm familiar with it is important to have one large runner w/ several gates coming off it. The runner starts out relatively large and gets smaller by the CSA of ea gate. This keeps the pressure the same at each gate.
These are relatively low pressure systems.
In an engine you must make sure the lowest pressure bearing never gets too low, you must make sure you're making enough at the front. This usually means way more pressure than you'd otherwise run.
Would a stepped oil galley allow the use of a smaller (less power to drive) oil pump?
Am I totally out in left field here?
Jason.
I understand that if you were to take pressure readings along the main bearings of an engine, each main would have less and less pressure coming from the oil pump.
In an effort to remedy this, has anybody ever tried a stepped oiling system?
In the HVAC systems and Foundry gating systems that I'm familiar with it is important to have one large runner w/ several gates coming off it. The runner starts out relatively large and gets smaller by the CSA of ea gate. This keeps the pressure the same at each gate.
These are relatively low pressure systems.
In an engine you must make sure the lowest pressure bearing never gets too low, you must make sure you're making enough at the front. This usually means way more pressure than you'd otherwise run.
Would a stepped oil galley allow the use of a smaller (less power to drive) oil pump?
Am I totally out in left field here?
Jason.





RE: stepped oil passages
RE: stepped oil passages
The other thing to consider is that it would be impossible to design a perfect stepped oiling system. The step sizes necessary would depend on the oil pressure and viscosity, but both of these vary dramatically during an engine's operating cycle.
ISZ
RE: stepped oil passages
wrt hvac, it is definitely a constant pressure deal.
This foundry paper puts it in better perspective.
ht
see pg. 14.
The fluid flow in the first gate of the non-stepped runner is actually reversed! the runner is taking metal in thru the gate instead of feeding it out.
Also ice-I said the main galley would reduce in CSA by the same CSA as each main feeder. E.g. 11/16"dia galley would be reduced to about 5/8 after the first main, and then reduced to 9/16 then 7/16 then finally 5/16.
JM
RE: stepped oil passages
RE: stepped oil passages
A stepped main gallery would have some merit if the starting size were somewhat larger than a typical constant diameter oil rifle, and stepped down from there as described in the OP.
I see a potential manufacturing cost issue here though, as well as a potential space/weight issue. Is there a known problem with oil pressure distribution that needs to be solved?
Another way to reduce inequality of pressure to the mains would be to supply oil from the pump to both ends of the main gallery. This, just possibly, is something you could rig up on your own, depending on the engine, as well as the level of engineering and effort you are willing to undertake, of course.
RE: stepped oil passages
RE: stepped oil passages
Regards
Pat
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RE: stepped oil passages
A furnace duct is stepped down because as each outlet is tapped off the required airflow in the duct is reduced by the amount of flow that outlet requires. Once you reach the point where you don't need the huge duct to support the airflow requirements of the remaining outlets you might as well reduce the size of the duct. The ducts are sized to maintain the pressure throughout the length of the duct considering the number of outlets in use - each reducer do not re-booste the pressure. The flow is controlled by the round pipe runners to the outlets. Reducing the size is a simple case of economics and space reductions.
RE: stepped oil passages
I bring it up because it is a problem that something so simple can't be addressed. It just winds my engineering propeller really tight. In a race motor where every horsepower counts, running a slightly smaller oil pump or slightly smaller bearings could be the difference between 1st winner and 1st loser.
In an economy box, 1% economy or 1% more power could be the deciding factor to thousands of people in choosing a new car or meeting emissions standards for another 5 years w/o a complete redesign.
Mostly, it just winds my propeller.
RE: stepped oil passages
this idea that the downstream pressure is increased somehow by the step reductions in diameter is bogus... might want to review your fluids textbook.
h
RE: stepped oil passages
YES
RE: stepped oil passages
Whether it's worth doing or not or causes some other problem are different questions.
RE: stepped oil passages
RE: stepped oil passages
It could be argued that the rear main bearing load capacity was greater than the front or the middle ones
RE: stepped oil passages
JM
RE: stepped oil passages
When the Porsche 928 came out, they were noted for having a much larger than normal main oil gallery, which functioned more or less as a plenum.
Modern designs like the Ford Mod V8 or GM LS1 have a single modest diameter all the way through.
Most engines use somewhere around 3/8", with 1/2" cup plugs or 1/4 NPT pipe plugs to seal the ends. These sizes are common across most 4, 6, and 8 cylinder engines I've encountered. I suspect 3/8" is used more because the deep hole drills and equipment being common and (relatively) inexpensive than because of design considerations.
RE: stepped oil passages
Velocity pressure of the oil inside the gallery = maybe 1 psi if that?
It just isn't going to matter much.
RE: stepped oil passages