A brief discussion of oil pressure, etc.
#31
. . . . . . . . . OEM's are going for the combination of thinner oils but very tight clearances, so much so that in spite of the thin oil, many of the newer vehicles I drive show quite a high gauge pressure. I am sure they have tried to optimize low frictional and parasitic losses with the goal of longevity.
10psi/1,000rpm is still a valid rule of thumb for street performance and sportsman level racing with typical oils and bearing clearances.
Rich
10psi/1,000rpm is still a valid rule of thumb for street performance and sportsman level racing with typical oils and bearing clearances.
Rich
Karl
#32
What happens to hydrolic lifters as pressure is increased/decreased? I know that the intention of the hydrolic lifter is to allow lower valve lift at low RPM's to promote better intake air charge(which increases fuel economy). But at what "pressure" does the lifter appear solid?
I just replaced my 60V6 pump with the HV pump a couple of years ago. The stock gauge indicates 60+ psi at 3k+. Seems to be a little high, so maybe I'll try a thinner oil (5W-30 stock).
I just replaced my 60V6 pump with the HV pump a couple of years ago. The stock gauge indicates 60+ psi at 3k+. Seems to be a little high, so maybe I'll try a thinner oil (5W-30 stock).
#33
What hydraulic lifters have you been using? They don't allow lower valve lift, they allow for adjustments in valve lash so there is none. You can be limited by valve lift, but they don't adjusted to allow lower lift. The only ones I can think of are those special hydraulic lifters that do that, but I didn't think they made those anymore.
#34
I've never quite understood how they work. To adjust them, valve is closed, lifter down off lobe, and then tighten to 0-lash and go 1.5 turns past. This compresses the spring in the lifter. So do the lifters not have enough pressure to "pump up" and stop the valve from seating?
#37
#38
What happens to hydrolic lifters as pressure is increased/decreased? I know that the intention of the hydrolic lifter is to allow lower valve lift at low RPM's to promote better intake air charge(which increases fuel economy). But at what "pressure" does the lifter appear solid?
I just replaced my 60V6 pump with the HV pump a couple of years ago. The stock gauge indicates 60+ psi at 3k+. Seems to be a little high, so maybe I'll try a thinner oil (5W-30 stock).
I just replaced my 60V6 pump with the HV pump a couple of years ago. The stock gauge indicates 60+ psi at 3k+. Seems to be a little high, so maybe I'll try a thinner oil (5W-30 stock).
#39
damn, I'd think that a tenth of those numbers would be closer...
Somewhere I was told 1.5 to 2 thousandths per inch of shaft size. Or at least that is what is stuck in my mind?
Somewhere I was told 1.5 to 2 thousandths per inch of shaft size. Or at least that is what is stuck in my mind?
Last edited by AdioSS; 03-24-2007 at 12:27 PM.
#40
#41
I think "film strength" is the property of the oil that allows the bearings to operate without melting down. The oil flow helps pull the heat out of the area too so you don't overheat the oil film and crap out on film strength. By definition film strength is the amount of pressure needed to cause metal to metal contact by displacing the oil film. Bad when that happens in your engine. Knock knock knock........
The synthetics totally kick *** on the dinosaur oils in this area, 2 to 3 times higher film strength ratings if I remember right. Get some main bearing bores out of wack just enough or lose oil pressure for a split second and if you're lucky the film strength of the synthetics might keep you from melting it down. On an engine I'm beating I wouldn't run anything else after break in. You can easily double the oil change interval to cut the cost difference. Running good quality filters like the Purolator Pure One or a synthetic media filter changed every 3K is cheap insurance on keeping the oil clean. I have a buddy that ran Mobil1 synthetic in his Honda Accord from day one when new. Changed it every 10K miles and filter about every 5K. Engine was clean as a pin inside with great compression when he crashed it at about 200,000 miles. Good stuff, just won't sludge up on you.
On the higher pressure part, I work on hydraulics a lot. Our positive displacement pumps draw more amperage when you crank the regulator up for higher system pressure. You can hear the pitch of the pump change as the output pressure is dialed up too. I believe they are doing more work as more energy is being expended to drive the pump ( higher measured amperage). I'm thinking that a high pressure relief spring is a good idea but it does increase HP loss through the oil pump. Very reasonable trade off if true.
Good thread, Michael
The synthetics totally kick *** on the dinosaur oils in this area, 2 to 3 times higher film strength ratings if I remember right. Get some main bearing bores out of wack just enough or lose oil pressure for a split second and if you're lucky the film strength of the synthetics might keep you from melting it down. On an engine I'm beating I wouldn't run anything else after break in. You can easily double the oil change interval to cut the cost difference. Running good quality filters like the Purolator Pure One or a synthetic media filter changed every 3K is cheap insurance on keeping the oil clean. I have a buddy that ran Mobil1 synthetic in his Honda Accord from day one when new. Changed it every 10K miles and filter about every 5K. Engine was clean as a pin inside with great compression when he crashed it at about 200,000 miles. Good stuff, just won't sludge up on you.
On the higher pressure part, I work on hydraulics a lot. Our positive displacement pumps draw more amperage when you crank the regulator up for higher system pressure. You can hear the pitch of the pump change as the output pressure is dialed up too. I believe they are doing more work as more energy is being expended to drive the pump ( higher measured amperage). I'm thinking that a high pressure relief spring is a good idea but it does increase HP loss through the oil pump. Very reasonable trade off if true.
Good thread, Michael
#42
, , , , , , On the higher pressure part, I work on hydraulics a lot. Our positive displacement pumps draw more amperage when you crank the regulator up for higher system pressure. You can hear the pitch of the pump change as the output pressure is dialed up too. I believe they are doing more work as more energy is being expended to drive the pump ( higher measured amperage). I'm thinking that a high pressure relief spring is a good idea but it does increase HP loss through the oil pump. Very reasonable trade off if true.
Good thread, Michael
Good thread, Michael
very very true.
You also mentioned oil flow for cooling and that's worth talking about. The only way to increase flow in the engine oil circuit is to have the oil pump make more pressure, (or increase the bearing clearance). And a HV pump won't flow more oil than a Standard Volume pump when on the relief circuit. A HV pump at 40psig relief is going to flow, (through the engine oil gallies) exactly the same oil as a SV pump at 40psig relief. Pressure is the only way to increase system flow at that point. Thus the importance of oil pressure.
HV pumps give a bit more low rpm (idle) flow and pressure, though, than SV pumps because of the taller gears. That's why they are so popular. Race cars don't need HV pumps because they don't idle at low rpm (650 to 850rpm). Keep that in mind when comparing what a race car uses to what a street/strip car uses.
So that is why the 70 psig high pressure relief oil pump is so popular, (SV or HV). If the motor turns to 7000rpm then you'd think the oil system should peak at 70 psig to give more flow to the bearings. I agree.
Yea I've heard that NASCAR dry sump (gerotor) engines run 45psig and that may be true. If it is true then how do they get away with it running 9000rpm? Very interesting.
Karl Ellwein
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