Oil pressure drop on fillters...
06-03-2007, 10:31 AM
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Ken
06-03-2007, 11:23 AM
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06-04-2007, 09:30 AM
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Althought a 20w50 and a SAE 50 are to be equal at 210F, that is the only temp that they are equal. Anthing over 210F a multi vis 20w50 will thin less than a SAE 50. So if you are running oil temps of sat 240F a 20w50 will offer more film strength (less thin ) a SAE 50.
Ken
Ken
06-04-2007, 09:32 AM
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razor 1115:
I understand your question and both those oils are good product. I am surprised though you are using straight 50wt in the motor, that seems a bit to much viscosity as a single grade? If its a single 50wt grade when your motor is cold you might not be getting the best oil flow and protection you need. I feel that multi-grades of the 20-50w, 20-40w and such do an overall better protection as the motor goes through its temperature cycles. What pressures do you see at idle and what pressure at lets say 5000 rpms? Also obviously helpful to know a little spec on the motors, type, size, power levels, etc.
Thanks,
Ray @ Raylar
I understand your question and both those oils are good product. I am surprised though you are using straight 50wt in the motor, that seems a bit to much viscosity as a single grade? If its a single 50wt grade when your motor is cold you might not be getting the best oil flow and protection you need. I feel that multi-grades of the 20-50w, 20-40w and such do an overall better protection as the motor goes through its temperature cycles. What pressures do you see at idle and what pressure at lets say 5000 rpms? Also obviously helpful to know a little spec on the motors, type, size, power levels, etc.
Thanks,
Ray @ Raylar
Pressures are ~60psi when first started. After allowing oil temp to stabilze, ~35-40 psi at idle and 45ish when running. These are slightly warmed 500hp's. (carbed)
06-04-2007, 09:56 AM
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oil pump and break in
wow you guys are loaded with great knowledge, if i may side step here a bit and ask about my 502 that needs bearings badly after the last owner ran it with gas in the oil do to a bad carb, now i have poor oil pres. my plan is to redue the bottom end. how do i pick the right bearings and is it a must to replace the oil pump now. i plan to run R. purple also 20-50!! what clearaces should i be shooting for ,and do i need to break in with something else. Thanks Paul
06-04-2007, 11:26 AM
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JB Marshall
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I have 500 EFI's and seem to have the same oil pressure readings as you do. I was concerned that 45 was low at 3800-4500 RPM's.
06-04-2007, 11:44 AM
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Exactly...but I have the dyno sheets that shows 60+ psi throughout on both engines. So, I am wondering how accurate the sending unit or gauge is. Anyone have any comments relating to this?
06-04-2007, 04:16 PM
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the oil pressure is a direct function of viscosity and the internal clearances . the viscosity is a direct function of the temp. as noted elsewhere, different oils will have different viscosities at the same temp... so... where to start ?
simple....
you KNOW you want oil temps in the 220 - 240 range. this is where the oil works best for a lot of reasons that everyone already knows. so thats a given
you KNOW what you need for oil pressure because that is a function of the mechanical characteristics of the motor... low compression, low reving motors with typical ( and correct) clearances need less oil pressure than blower motors running hi boost. it comes down to unit loading on the bearings and the shear strength of the oil film on the bearings and maintaining that film integrity under max load....
so... if you are like 90 % of the guys here, you are running pump gas, motors w/ comp ratios in the 8 to 10:1 range at revs less than 6000. that being the assumption there is no reason to reinvent the wheel. those motors need between 45 and 55 psi at 3500 and above and 20 psi at hot idle if they were cl;earanced properly when they were built..
ANY good grade of 20 50 or 15 40 will do that for you until the cows come home as long as you maintain the temps.
the blower motor guys need more pressure because the unit loadings are so much higher and the fuel/oil contamination issues are always there.
you don't do yourself any favors on a typical motor by jacking the oil pressures higher or running the oil too thick or too cold. all you are doing is costing yourself power, and keeping the oil from getting clean and lubricating properly. you REALLY don't do yourself any favors by running the motors cold in either a water or oil sense and you absolutely are shooting yourself in the head by running them rich thinking more fuel means more power. all that extra fuel just ends up in the oil and makes it... well ... not oil anymore.
all this is why it is so important to get the clearances, and cooling equilibrium correct when these motors get built... too big and you create a situation where you have to run massive oil pressure to maintain film integrity... too small and the film is not adequate to protect the bearings and overheats...
and the rest is just how much it costs to fix
simple....
you KNOW you want oil temps in the 220 - 240 range. this is where the oil works best for a lot of reasons that everyone already knows. so thats a given
you KNOW what you need for oil pressure because that is a function of the mechanical characteristics of the motor... low compression, low reving motors with typical ( and correct) clearances need less oil pressure than blower motors running hi boost. it comes down to unit loading on the bearings and the shear strength of the oil film on the bearings and maintaining that film integrity under max load....
so... if you are like 90 % of the guys here, you are running pump gas, motors w/ comp ratios in the 8 to 10:1 range at revs less than 6000. that being the assumption there is no reason to reinvent the wheel. those motors need between 45 and 55 psi at 3500 and above and 20 psi at hot idle if they were cl;earanced properly when they were built..
ANY good grade of 20 50 or 15 40 will do that for you until the cows come home as long as you maintain the temps.
the blower motor guys need more pressure because the unit loadings are so much higher and the fuel/oil contamination issues are always there.
you don't do yourself any favors on a typical motor by jacking the oil pressures higher or running the oil too thick or too cold. all you are doing is costing yourself power, and keeping the oil from getting clean and lubricating properly. you REALLY don't do yourself any favors by running the motors cold in either a water or oil sense and you absolutely are shooting yourself in the head by running them rich thinking more fuel means more power. all that extra fuel just ends up in the oil and makes it... well ... not oil anymore.
all this is why it is so important to get the clearances, and cooling equilibrium correct when these motors get built... too big and you create a situation where you have to run massive oil pressure to maintain film integrity... too small and the film is not adequate to protect the bearings and overheats...
and the rest is just how much it costs to fix
