We are currently running on the new domain and server: www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

Oil pressure vs volume

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Steve.k
HotPass
HotPass
Posts: 1344
Joined: Sat May 28, 2016 10:41 am
Location:

Re: Oil pressure vs volume

Post by Steve.k » Mon May 18, 2020 5:35 pm

Thanks Randy. Its coming.

piston guy
Expert
Expert
Posts: 897
Joined: Mon Sep 10, 2012 1:55 pm
Location: Anaheim, CA

Re: Oil pressure vs volume

Post by piston guy » Tue May 19, 2020 11:49 am

David Redszus wrote:
Thu May 14, 2020 5:10 pm
Oil volume is much more important than pressure. Oil pressure is merely a surrogate for estimated volume through the bearings.

Given bearing dimensions, clearances, oil viscosity at operating temperature, and engine rpm, it is possible to calculate
oil flow volume. Given oil specific gravity, the oil mass flow can be determined which is necessary to calculate the heat
transfer from the bearings into the oil. The oil temperature will also determine the minimum oil film thickness.

An alternative method is to measure the bearing cap temperatures directly.
Dave ,
Do you think of "oil pressure" as "excess volume"? In other words if the "supply" or volume exactly matched the "need" , wouldn't oil pressure be "zero"? And if the volume was sufficient to cause pressure , why would more volume be advantageous? Oil pressure "alone" does not prevent metal to metal contact. To "accept" more volume , wouldn't the oil passages need to be increased in size ? We know bearing clearance will cause the pressure to drop because of less restriction , but the same amount of oil is flowing from the positive displacement oil pump.

Steve.k
HotPass
HotPass
Posts: 1344
Joined: Sat May 28, 2016 10:41 am
Location:

Re: Oil pressure vs volume

Post by Steve.k » Tue May 19, 2020 3:18 pm

As you may know this new block has 3 galleries instead of two. That may contribute to a little lower than im used to seeing in oil pressure. Last runs we seen even lower pressure but used a standard volume pump. Last dyno session even seen in mid 40’s. When we tore down for inspection bearings looked new. For some reason im just gun shy when guage drops below 55.

tuffxf
HotPass
HotPass
Posts: 247
Joined: Wed Dec 20, 2006 7:34 am
Location: Central Qld Australia

Re: Oil pressure vs volume

Post by tuffxf » Tue May 19, 2020 5:52 pm

Gday Steve,
The added gallery won’t make any difference , your results from going to a std volume pump and seeing lower pressure is telling the story imo that you are losing oil volume through a clearance issue , Mains, cam or through the lifter bore clearance and or pin oiling
It may not be an issue at all! Your dyno pulls are short compared to engine in the car but.
If it was a sbc, I could live with it.
Ford, standard clevo crank - definently no way, your crank will or should be better designed
If it was my engine with 20/50 oil which I think is a good choice considering what you have or maybe a /60 i would want to see 60 psi min through a pull or pass
Again only my deranged opinion!😀
Be good to see one of these things with some real use on it, big plug to you guys and Tim
Cheers

Kevin Johnson
HotPass
HotPass
Posts: 8664
Joined: Tue Nov 22, 2005 5:41 am
Location:

Re: Oil pressure vs volume

Post by Kevin Johnson » Tue May 19, 2020 7:23 pm

Idea: use a bifurcated fitting at the oil pressure sensor gauge location. At an rpm of interest draw a small sample of oil into a burette or graduated cylinder and read the number of CC. Let the oil rest and cool for at least 10 minutes. Check and see if the volume changes due to air release. You might need to lightly tap the container to dislodge any visible air bubbles and allow them to break at the surface.

This should help falsify/reject the hypothesis that the lower oil pressure is an artifact of the pan/windage flow.

Use an orifice of known area so that when the sample is drawn it does not cause a precipitous drop in and of itself. Maybe a remotely operated valve can be employed so that safety is maintained in the dyno cell.

Steve.k
HotPass
HotPass
Posts: 1344
Joined: Sat May 28, 2016 10:41 am
Location:

Re: Oil pressure vs volume

Post by Steve.k » Tue May 19, 2020 7:35 pm

Tuff you like more pressure for standard size Cleveland journals is what your saying. I could shim releif up also i guess. Never thought about putting a valve in Kevin but thats a good idea. We used to get air leaks on cat trans all the time cause of all the oring couplings would get hard and leak! Overheating and lube problems till u pull tube out of tranny and reseal.

tuffxf
HotPass
HotPass
Posts: 247
Joined: Wed Dec 20, 2006 7:34 am
Location: Central Qld Australia

Re: Oil pressure vs volume

Post by tuffxf » Tue May 19, 2020 10:09 pm

G,day Steve,
yes what i mean is with a stock ford clevo crank it has its own issues with how the rod bearings oil due to oil timing, your crank rod oil timing should be different to that.
As well as other things the stock design doesn't have going for it including journal size,
Shimming the relief valve up in your current set up won't change a thing as your not on the relief valve when your warmed up by your current oil pressure readings, may show an initial higher reading on cold start up until the oil starts to warm up.
if your readings were in the 40's with a stock pump then that relief valve is shut.
Even in the mid 50's on the dyno sheet you posted, warmed up as it was i'd say it was shut tight too.
I like the idea that throughout the time when we are flogging the engine, dyno pull or 1/4 mile pass that the relief valve is shut, engine oil pressure is dictated not by the relief valve but by oil pump size, oil viscosity at operating temp we desire and engine clearances.
The relief valve should only comes into play on cold starts and until the oil is up to the temp we want to race it at.
That's how i see it
Cheers

smeg
Pro
Pro
Posts: 486
Joined: Fri Feb 09, 2007 12:43 am
Location: melbourne, Australia

Re: Oil pressure vs volume

Post by smeg » Tue May 19, 2020 10:48 pm

bob460 wrote:
Sat May 16, 2020 10:08 pm
Steve would love to see a set of Aussie HIGGINS heads and intake on this new track boss block...... 900hp+ easy.
SCM new race head would be killer on one as well.

Mark O'Neal
Guru
Guru
Posts: 1449
Joined: Tue Mar 06, 2007 7:23 pm
Location: Torrance, CA
Contact:

Re: Oil pressure vs volume

Post by Mark O'Neal » Wed May 20, 2020 12:07 am

Pressure is what blew the filter off the car.

Volume is what determined how long it took to clean it up.

David Redszus
Guru
Guru
Posts: 7848
Joined: Tue Nov 27, 2007 9:27 am
Location: Chicago
Contact:

Re: Oil pressure vs volume

Post by David Redszus » Wed May 20, 2020 12:52 am

piston guy wrote:
Tue May 19, 2020 11:49 am
David Redszus wrote:
Thu May 14, 2020 5:10 pm
Oil volume is much more important than pressure. Oil pressure is merely a surrogate for estimated volume through the bearings.

Given bearing dimensions, clearances, oil viscosity at operating temperature, and engine rpm, it is possible to calculate
oil flow volume. Given oil specific gravity, the oil mass flow can be determined which is necessary to calculate the heat
transfer from the bearings into the oil. The oil temperature will also determine the minimum oil film thickness.

An alternative method is to measure the bearing cap temperatures directly.
Dave ,
Do you think of "oil pressure" as "excess volume"? In other words if the "supply" or volume exactly matched the "need" , wouldn't oil pressure be "zero"? And if the volume was sufficient to cause pressure , why would more volume be advantageous? Oil pressure "alone" does not prevent metal to metal contact. To "accept" more volume , wouldn't the oil passages need to be increased in size ? We know bearing clearance will cause the pressure to drop because of less restriction , but the same amount of oil is flowing from the positive displacement oil pump.
Engine oil serves two purposes; to keep metal surfaces from touching and to carry heat away from the bearings.

The first is a function of oil film thickness which varies with viscosity and therefore with temperature.

The second is a function of oil mass flow. Mass flow is governed by: bearing journal diameter, sum of bearing clearance flow areas * Cd including oil viscosity * square root of (oil density * oil pressure)

Increased bearing flow area will allow a greater oil mass flow provided that viscosity, oil density and pressure remain the same. But oil pressure does not remain the same under all operating conditions, so oil mass flow will change with pressure. How much you ask?

press. flow
psi ... rate
10... 3.16
20... 4.47
40... 6.32
60... 7.75
80... 8.94
Note that oil flow increases with the square root of oil pressure. An increase in pressure from 20 psi to 80 psi
will double oil mass flow.

The oil mass flow required by the engine is determined by the heat generated in the bearing/journal interface.
At lower speeds and loads, the engine requires less oil mass flow.

So far...easy. But oil mass flow is not a constant, static flow; it pulsates much like a fuel injector nozzle.
And is subject to density and viscosity changes due to aeration.

The best way to come to slippery grips with it all, is to measure and log oil pressure (hopefully in the oil galley)
against engine rpm. The oil pressure should increase with rpm up until the pressure relief valve opens at which time the pressure curve will flatten. Logging oil temperature the same way is very useful.

Kevin Johnson
HotPass
HotPass
Posts: 8664
Joined: Tue Nov 22, 2005 5:41 am
Location:

Re: Oil pressure vs volume

Post by Kevin Johnson » Wed May 20, 2020 4:34 am

David Redszus wrote:
Wed May 20, 2020 12:52 am
...
The best way to come to slippery grips with it all, is to measure and log oil pressure (hopefully in the oil galley)
against engine rpm. The oil pressure should increase with rpm up until the pressure relief valve opens at which time the pressure curve will flatten. Logging oil temperature the same way is very useful.
Jay mentioned that his AVL measured real time density.

There are a number of SAE papers on this topic.

bob460
Member
Member
Posts: 116
Joined: Thu Sep 26, 2019 6:19 am
Location:

Re: Oil pressure vs volume

Post by bob460 » Wed May 20, 2020 5:59 am

smeg wrote:
Tue May 19, 2020 10:48 pm
bob460 wrote:
Sat May 16, 2020 10:08 pm
Steve would love to see a set of Aussie HIGGINS heads and intake on this new track boss block...... 900hp+ easy.
SCM new race head would be killer on one as well.
The new CID/MBE head would be the ticket i think for max hp.

tenxal
Expert
Expert
Posts: 671
Joined: Sun Nov 17, 2013 8:48 pm
Location:

Re: Oil pressure vs volume

Post by tenxal » Wed May 20, 2020 7:38 am

How is the bypassed oil being handled?

Coloradoracer
Expert
Expert
Posts: 663
Joined: Sun Mar 21, 2010 9:48 pm
Location: Lehigh Acres, FL.
Contact:

Re: Oil pressure vs volume

Post by Coloradoracer » Wed May 20, 2020 9:12 am

tenxal wrote:
Wed May 20, 2020 7:38 am
How is the bypassed oil being handled?
That depends on the pump. Some pumps will dump the bypassed oil back to pan, others will redirect it back to the inlet....
Mark Goulette
Owner/Driver of the Livin' The Dream rear engine dragster
Speed kills but it's better than going slow!
http://www.livinthedreamracing.com
Authorized Amsoil Retailer

Steve.k
HotPass
HotPass
Posts: 1344
Joined: Sat May 28, 2016 10:41 am
Location:

Re: Oil pressure vs volume

Post by Steve.k » Wed May 20, 2020 9:57 am

This being that mustang 2 pan is a bit of a challenge cause it can dump two quarts in there where it will stay.

Post Reply