Yep, when tuning twin 1050 Holley Doms at the track, go rich until the car slows, then lean them one jet size to prevent the engine oil from becoming fuel diluted.
Interpreting oil pressure vs engine RPM
- Thread starter Emperors6
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My point in the above post; is it is wrong to paint all fuel systems with the same brush.
Fuel in DI systems can be injected at anytime after the exhaust valve is closed, even late into the compression stroke.
Another blanket statement that has gained traction on BITOG; DI means fuel diluted engine oil.
Poking around, I found this link on GM Authority.
www.d3cadillac.com
Fuel in DI systems can be injected at anytime after the exhaust valve is closed, even late into the compression stroke.
Another blanket statement that has gained traction on BITOG; DI means fuel diluted engine oil.
Poking around, I found this link on GM Authority.
www.d3cadillac.com
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Originally Posted By: Shannow
Your OEM provides a minimum oil pressure recommendation as a maintenance intervention point for a worn engine on the recommended oil viscosity...others on BITOG who have literally zero understanding of hydrodynamic lubrication (flow equals lubrication in their world) have taken that minimum oil pressure as a target for viscosity choice...the fact that they get away with it does not make it optimum.
I see you're still trotting out that same old nonsense to anyone who asks a question about oil pressure. If you had any track or other high performance engine experience you might know how wrong you are but you don't.
The test OP spec's provided in a service manual are a guide to an engines overall condition when measured at the LOW RANGE OF NORMAL OIL TEMP'S. But at very high oil temp's and/or with significant fuel dilution it's entirely possible to test these spec's even in a new engine in perfect condition on the specified oil.
In high performance applications other OP spec's are given such as a minimum and maximum operating OP range at a certain specified high rpm. The maximum OP is invariably below the relief valve setting of the oil pump itself. This info is often only available from racing departments or engine tuners. Therefore in lieu of this more relevant info, the OP test spec's are a conservative guide to maintain a minimum safe operational viscosity. The reading on an OP gauge is the best proxy for operational viscosity that I know of.
Your OEM provides a minimum oil pressure recommendation as a maintenance intervention point for a worn engine on the recommended oil viscosity...others on BITOG who have literally zero understanding of hydrodynamic lubrication (flow equals lubrication in their world) have taken that minimum oil pressure as a target for viscosity choice...the fact that they get away with it does not make it optimum.
I see you're still trotting out that same old nonsense to anyone who asks a question about oil pressure. If you had any track or other high performance engine experience you might know how wrong you are but you don't.
The test OP spec's provided in a service manual are a guide to an engines overall condition when measured at the LOW RANGE OF NORMAL OIL TEMP'S. But at very high oil temp's and/or with significant fuel dilution it's entirely possible to test these spec's even in a new engine in perfect condition on the specified oil.
In high performance applications other OP spec's are given such as a minimum and maximum operating OP range at a certain specified high rpm. The maximum OP is invariably below the relief valve setting of the oil pump itself. This info is often only available from racing departments or engine tuners. Therefore in lieu of this more relevant info, the OP test spec's are a conservative guide to maintain a minimum safe operational viscosity. The reading on an OP gauge is the best proxy for operational viscosity that I know of.
Caterham;
I'm going to have to read though your post a few more times to fully understand what you are saying.
Your 1st sentence should be deleted, as it does not add credibility to your position.
I somewhat agree with your last sentence, as sump oil viscosity is what the oil pump sees.
But depending where the oil pressure gage sender is located, it may be reading post relief valve setting pressure.
The rake to step on in late model engines, is the variable displacement and oil pressure on demand programmed pumps.
An attempt to adjust oil pressure on these engines by experimenting with engine oil viscosity will not work.
GM publishes specifications on several 3.6L engines, right up to the race model with 600 hp.
The oil delivery system on that engine should be the starting point in this thread, especially now that you have jumped in to the discussion.
I'm going to have to read though your post a few more times to fully understand what you are saying.
Your 1st sentence should be deleted, as it does not add credibility to your position.
I somewhat agree with your last sentence, as sump oil viscosity is what the oil pump sees.
But depending where the oil pressure gage sender is located, it may be reading post relief valve setting pressure.
The rake to step on in late model engines, is the variable displacement and oil pressure on demand programmed pumps.
An attempt to adjust oil pressure on these engines by experimenting with engine oil viscosity will not work.
GM publishes specifications on several 3.6L engines, right up to the race model with 600 hp.
The oil delivery system on that engine should be the starting point in this thread, especially now that you have jumped in to the discussion.
Originally Posted By: Emperors6
According to the engine spec , the minimum hot pressure are 6 psig @ 1000 RPM, 18 psig @ 2000 RPM, 24 psig @ 4000 RPM. Is the gauge giving me psig or psi so I can do a direct comparison?
PSIG is PSI plus the atmospheric pressure wherever you are.
So 24 psig in our area would be 24 + 14.4 = 38.4 psi.
At 4,000 rpm your lowest oil pressure was about 47 psi at I believe 212F oil temp's from your other thread on the subject:
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4108313#Post4108313
So your oil pressure and maximum track oil temp's of only 223F are fine with plenty of viscosity reserve.
At you next oil change prior to the winter I'd dump the unnecessarily heavy RL and go back to the spec' M1 5W-30 or something with a similar HTHS viscosity.
According to the engine spec , the minimum hot pressure are 6 psig @ 1000 RPM, 18 psig @ 2000 RPM, 24 psig @ 4000 RPM. Is the gauge giving me psig or psi so I can do a direct comparison?
PSIG is PSI plus the atmospheric pressure wherever you are.
So 24 psig in our area would be 24 + 14.4 = 38.4 psi.
At 4,000 rpm your lowest oil pressure was about 47 psi at I believe 212F oil temp's from your other thread on the subject:
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4108313#Post4108313
So your oil pressure and maximum track oil temp's of only 223F are fine with plenty of viscosity reserve.
At you next oil change prior to the winter I'd dump the unnecessarily heavy RL and go back to the spec' M1 5W-30 or something with a similar HTHS viscosity.
I see that you're absolute lack of any understanding of hydrodynamic lubrication, or any engineering training is still outshadowed by your ego...
You refuse to even acknowledge that there's a temperature rise across the bearing, which demonstrates that you you simply don't get it...you do not even understand the fundamentals.
Tell me again what the OEM's minimum oil pressure for mechanical intervention tells the user what's happening in the big end ?
"Invariably" they set a maximum OP lower than relief...present some data. to that effect.
Present one piece of data that an OEM has provided stating that their oil pressure recommendations are for viscosity selection at the lower end rather than maintenance intervention.
You've failed to respond to my discussions re piston cooling spray volume versus oil pressure.
And you've NEVER come back with the list of blown up engines that you keep spouting you have witnessed at the track.
On the other hand, I have designed bearings, been trained in bearing design and hydrodynamics and fluid mechanics...
CATERHAM, again, please put SOMETHING on the table rather than your condescending posits (and the occasional advertising puff piece).
You refuse to even acknowledge that there's a temperature rise across the bearing, which demonstrates that you you simply don't get it...you do not even understand the fundamentals.
Tell me again what the OEM's minimum oil pressure for mechanical intervention tells the user what's happening in the big end ?
"Invariably" they set a maximum OP lower than relief...present some data. to that effect.
Present one piece of data that an OEM has provided stating that their oil pressure recommendations are for viscosity selection at the lower end rather than maintenance intervention.
You've failed to respond to my discussions re piston cooling spray volume versus oil pressure.
And you've NEVER come back with the list of blown up engines that you keep spouting you have witnessed at the track.
On the other hand, I have designed bearings, been trained in bearing design and hydrodynamics and fluid mechanics...
CATERHAM, again, please put SOMETHING on the table rather than your condescending posits (and the occasional advertising puff piece).
Originally Posted By: CATERHAM
PSIG is PSI plus the atmospheric pressure wherever you are.
So 24 psig in our area would be 24 + 14.4 = 38.4 psi.
At 4,000 rpm your lowest oil pressure was about 47 psi at I believe 212F oil temp's from your other thread on the subject:
You obviously meant using absolute oil pressure as a joke didn't you....it's a good one.
It's gauge that moves the oil around, and gauge that reliefs operate at.
To introduce absolute pressure is remotely relevant to the discussion is either intentional obfuscation (look over there, a bunny), an absolute demonstration that you don't get it, or humour.
If it's not humour, then....
PSIG is PSI plus the atmospheric pressure wherever you are.
So 24 psig in our area would be 24 + 14.4 = 38.4 psi.
At 4,000 rpm your lowest oil pressure was about 47 psi at I believe 212F oil temp's from your other thread on the subject:
You obviously meant using absolute oil pressure as a joke didn't you....it's a good one.
It's gauge that moves the oil around, and gauge that reliefs operate at.
To introduce absolute pressure is remotely relevant to the discussion is either intentional obfuscation (look over there, a bunny), an absolute demonstration that you don't get it, or humour.
If it's not humour, then....
ROFL
Does this engine use a turbo? Does this engine safely rev to 6,000 or higher? Does the oil pressure sensor take the signal just after the filter, or somewhere along one of the service galleries? Can you find taps for gauge feeds at the end of the service galleries furthest from the pump and filter?
When you set a motor up fro race conditions, you have to monitor critical flows, not initial flows and not know what's happening down stream ...
Are you going to install an oil temp gauge independent of the ECM?
The oil selection can be a wide spread synthetic that will have decent cold viscosity and still maintain high temp viscosity.
the way I'd look at it is to look at nominal viscosity at highway speeds (oil temp plotted against oil spec) and them look at viscosity at the track say 30 laps in (oil temp plotted against oil specs - various). In the end, I'd try to get my track oil to be about the same viscosity as owners manual oils on a cool day cruising down the highway...
You might indeed end up with 10W-60 to get that result. But you'd know exactly what the oil was doing as far as viscosity and therefor the systems that depend on it to be equivelent to "normal" driving
When you set a motor up fro race conditions, you have to monitor critical flows, not initial flows and not know what's happening down stream ...
Are you going to install an oil temp gauge independent of the ECM?
The oil selection can be a wide spread synthetic that will have decent cold viscosity and still maintain high temp viscosity.
the way I'd look at it is to look at nominal viscosity at highway speeds (oil temp plotted against oil spec) and them look at viscosity at the track say 30 laps in (oil temp plotted against oil specs - various). In the end, I'd try to get my track oil to be about the same viscosity as owners manual oils on a cool day cruising down the highway...
You might indeed end up with 10W-60 to get that result. But you'd know exactly what the oil was doing as far as viscosity and therefor the systems that depend on it to be equivelent to "normal" driving
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Emperors6;
I had a look at your UOAs.
Would an engine oil costing $4.00 a liter with the following profile work for your summer program?
40C 100
100C 12.4
HTHS 3.8
P %/wt. .1000
Z %/wt. .1100
SA %/wt. 1.0
TBN 7.9
I had a look at your UOAs.
Would an engine oil costing $4.00 a liter with the following profile work for your summer program?
40C 100
100C 12.4
HTHS 3.8
P %/wt. .1000
Z %/wt. .1100
SA %/wt. 1.0
TBN 7.9
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Originally Posted By: Shannow
Originally Posted By: CATERHAM
PSIG is PSI plus the atmospheric pressure wherever you are.
So 24 psig in our area would be 24 + 14.4 = 38.4 psi.
At 4,000 rpm your lowest oil pressure was about 47 psi at I believe 212F oil temp's from your other thread on the subject:
You obviously meant using absolute oil pressure as a joke didn't you....it's a good one.
It's gauge that moves the oil around, and gauge that reliefs operate at.
To introduce absolute pressure is remotely relevant to the discussion is either intentional obfuscation (look over there, a bunny), an absolute demonstration that you don't get it, or humour.
If it's not humour, then....
LoL, +1 ... if he was talking about turbo boost pressure, then yeah.
PSIG (or just PSI) is gauge oil pressure in this case. 0 means zero oil pressure, and 30 means 30 PSI of oil pressure. No need to complicate it.
Originally Posted By: CATERHAM
PSIG is PSI plus the atmospheric pressure wherever you are.
So 24 psig in our area would be 24 + 14.4 = 38.4 psi.
At 4,000 rpm your lowest oil pressure was about 47 psi at I believe 212F oil temp's from your other thread on the subject:
You obviously meant using absolute oil pressure as a joke didn't you....it's a good one.
It's gauge that moves the oil around, and gauge that reliefs operate at.
To introduce absolute pressure is remotely relevant to the discussion is either intentional obfuscation (look over there, a bunny), an absolute demonstration that you don't get it, or humour.
If it's not humour, then....
LoL, +1 ... if he was talking about turbo boost pressure, then yeah.
PSIG (or just PSI) is gauge oil pressure in this case. 0 means zero oil pressure, and 30 means 30 PSI of oil pressure. No need to complicate it.
Originally Posted By: Shannow
Originally Posted By: CATERHAM
PSIG is PSI plus the atmospheric pressure wherever you are.
So 24 psig in our area would be 24 + 14.4 = 38.4 psi.
At 4,000 rpm your lowest oil pressure was about 47 psi at I believe 212F oil temp's from your other thread on the subject:
You obviously meant using absolute oil pressure as a joke didn't you....it's a good one.
It's gauge that moves the oil around, and gauge that reliefs operate at.
To introduce absolute pressure is remotely relevant to the discussion is either intentional obfuscation (look over there, a bunny), an absolute demonstration that you don't get it, or humour.
If it's not humour, then....
+1 ......
not sure if there are engine valve covers and oil sump chambers that operates at absolute vacuum , where oil oxidation could be reduced/eliminated.
Originally Posted By: CATERHAM
PSIG is PSI plus the atmospheric pressure wherever you are.
So 24 psig in our area would be 24 + 14.4 = 38.4 psi.
At 4,000 rpm your lowest oil pressure was about 47 psi at I believe 212F oil temp's from your other thread on the subject:
You obviously meant using absolute oil pressure as a joke didn't you....it's a good one.
It's gauge that moves the oil around, and gauge that reliefs operate at.
To introduce absolute pressure is remotely relevant to the discussion is either intentional obfuscation (look over there, a bunny), an absolute demonstration that you don't get it, or humour.
If it's not humour, then....
+1 ......
not sure if there are engine valve covers and oil sump chambers that operates at absolute vacuum , where oil oxidation could be reduced/eliminated.
In the high dollar race engine world, we do have vacuum pumps to work with dry sump scavenge pumps to keep the windage as low as possible (crankcase in vacuum). But it is not a good trade-off unless you are spinning well north of 7,000 RPM ...
BrocLuno,
could you post some pics of some donks that you've done ?
If you were to evacuate a chev V8 sump, the psi across the pump would stay the same, gauge pressure would drop.
What does the relief on a dry sump reference to ?
The inlet side or ambient ?
could you post some pics of some donks that you've done ?
If you were to evacuate a chev V8 sump, the psi across the pump would stay the same, gauge pressure would drop.
What does the relief on a dry sump reference to ?
The inlet side or ambient ?
Imagine if 10psi of oil pressure was actually referring to absolute.
Good one. Lol
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Originally Posted By: Shannow
BrocLuno,
could you post some pics of some donks that you've done ?
If you were to evacuate a chev V8 sump, the psi across the pump would stay the same, gauge pressure would drop.
What does the relief on a dry sump reference to ?
The inlet side or ambient ?
Never been able to post pics here. Do not have external picture service and will not likely set one up. Other sites allow direct uploads if the picture is appropriate size. I understand BITOG not wanting to host pictures as it hits the servers pretty hard. But it becomes an unreliable reference on external links, so no pics unless on the host site for me . Just my personal policy...
Most gauges reference ambient as they are dash mounted. The oil pressure reading range is set in the dyno room as plotted against RPM. We will install oil pressure sensors at key location and use them to trigger dash lights and feed data loggers. Most drivers never look at pressure gauges. Same with coolant temps. The two gauges they will look at are fuel pressure and Tach/Light(s).
The evac pumps and vacuum pumps are stages in a belt driven assembly off the front of the engine (usually). Two stages for oil evac with two pick-up points in the pan and two stages of vacuum pump with pick-ups at the back head/valve cover. Some small blocks have old casting bosses that used to serve road draft behind the intake manifold. If they do, we'll us that as the vacuum pick-up point. Either way, they are baffled.
Crankcase vacuum is usually effective down to about 3 psi relative to atmospheric. The vacuum pumps feed an oil overflow tank that may have liquid separator plates and allow a final stage in the pump assembly to return liquids to the main oil tank.
But for short races (drags and 25 lap heats say), the vacuum pumps go to waste tanks. If you loose a ring pack, you have added so much fuel/blow-by to the "atmosphere" in the crankcase that your main oil tank is going down (with a level alarm) and your waste tank is going up fast (with a 3/4 full alarm). So you are headed for the pits.
These are full roller cam'd, full roller rocker systems running "rev-kits" which are divided valve spring systems where some of the system inertia is handled by springs under the head pushing down on the lifters and the upper springs just trying to return the valves to their seats. These systems are somewhat reliable up to just shy of 9,900 RPM.
The springs have a useful lifespan of about 40~80 hours total run time. You can gauge them for useful tension, but stress risers will have formed and they will break destroying an engine. Better to just replace on time in service. Usually Isky Tool Room spring wire...
We DO NOT allow by-passed oil filter systems. All factory by-pass's are blocks and we run 100% filtered oil. On the nitro motors that have to have 50 to 70 wt oil, the oil is pre-heated before it goes into the car. We do not have "cold start" issues. We have oil at, or near Op Temp so the filters are not dealing with molasses.
Most of the engines I have crewed for have 2 2-qt filters on a Racor frame. We do not log pressure drop across the filters because if we have any question about oil pressure, the first thing that gets changed are the filters. We'll cut the old ones open and see what's inside. If no shiny bits, we know we have an incipient mechanical failure in the motor...
BrocLuno,
could you post some pics of some donks that you've done ?
If you were to evacuate a chev V8 sump, the psi across the pump would stay the same, gauge pressure would drop.
What does the relief on a dry sump reference to ?
The inlet side or ambient ?
Never been able to post pics here. Do not have external picture service and will not likely set one up. Other sites allow direct uploads if the picture is appropriate size. I understand BITOG not wanting to host pictures as it hits the servers pretty hard. But it becomes an unreliable reference on external links, so no pics unless on the host site for me . Just my personal policy...
Most gauges reference ambient as they are dash mounted. The oil pressure reading range is set in the dyno room as plotted against RPM. We will install oil pressure sensors at key location and use them to trigger dash lights and feed data loggers. Most drivers never look at pressure gauges. Same with coolant temps. The two gauges they will look at are fuel pressure and Tach/Light(s).
The evac pumps and vacuum pumps are stages in a belt driven assembly off the front of the engine (usually). Two stages for oil evac with two pick-up points in the pan and two stages of vacuum pump with pick-ups at the back head/valve cover. Some small blocks have old casting bosses that used to serve road draft behind the intake manifold. If they do, we'll us that as the vacuum pick-up point. Either way, they are baffled.
Crankcase vacuum is usually effective down to about 3 psi relative to atmospheric. The vacuum pumps feed an oil overflow tank that may have liquid separator plates and allow a final stage in the pump assembly to return liquids to the main oil tank.
But for short races (drags and 25 lap heats say), the vacuum pumps go to waste tanks. If you loose a ring pack, you have added so much fuel/blow-by to the "atmosphere" in the crankcase that your main oil tank is going down (with a level alarm) and your waste tank is going up fast (with a 3/4 full alarm). So you are headed for the pits.
These are full roller cam'd, full roller rocker systems running "rev-kits" which are divided valve spring systems where some of the system inertia is handled by springs under the head pushing down on the lifters and the upper springs just trying to return the valves to their seats. These systems are somewhat reliable up to just shy of 9,900 RPM.
The springs have a useful lifespan of about 40~80 hours total run time. You can gauge them for useful tension, but stress risers will have formed and they will break destroying an engine. Better to just replace on time in service. Usually Isky Tool Room spring wire...
We DO NOT allow by-passed oil filter systems. All factory by-pass's are blocks and we run 100% filtered oil. On the nitro motors that have to have 50 to 70 wt oil, the oil is pre-heated before it goes into the car. We do not have "cold start" issues. We have oil at, or near Op Temp so the filters are not dealing with molasses.
Most of the engines I have crewed for have 2 2-qt filters on a Racor frame. We do not log pressure drop across the filters because if we have any question about oil pressure, the first thing that gets changed are the filters. We'll cut the old ones open and see what's inside. If no shiny bits, we know we have an incipient mechanical failure in the motor...
Oh, and just in case you want to know, we generally do not run over 50 PSI for usable oil pressure. On a SBC, that is measured at the front of the engine at the combined lifter galley drilling above and behind the cam timing gear. That is deemed to be the most distant pressurized point.
50 PSI hot at that point is entirely adequate at 9,000+. I have been involved with two motors where that pressure was 25 PSI as the owner did not want to waste power driving a feed pump against head needlessly.
For sump oil systems, anything you can do to lower the stress on the cam/distributor drive is a good thing. They are the smallest and most vulnerable gears in any Chevy - SBC or BBC. They are either mellonized or bronze gears running on a steel cam core, so they can go away very fast. Maybe 200 hours if driving higher oil pressures.
If the motor is not using an internal pump and only relying on external pumping, all bets are off. But why would anyone want to drive a pump against static head ...
On BBC's we will read pump pressures at just above the filter boss and at the front main. Like I said earlier. If > 15 PSI difference, you have lost something and your bottom end is coming apart. 6~8 PSI differential is normal along the lenght of this gallery.
50 PSI hot at that point is entirely adequate at 9,000+. I have been involved with two motors where that pressure was 25 PSI as the owner did not want to waste power driving a feed pump against head needlessly.
For sump oil systems, anything you can do to lower the stress on the cam/distributor drive is a good thing. They are the smallest and most vulnerable gears in any Chevy - SBC or BBC. They are either mellonized or bronze gears running on a steel cam core, so they can go away very fast. Maybe 200 hours if driving higher oil pressures.
If the motor is not using an internal pump and only relying on external pumping, all bets are off. But why would anyone want to drive a pump against static head ...
On BBC's we will read pump pressures at just above the filter boss and at the front main. Like I said earlier. If > 15 PSI difference, you have lost something and your bottom end is coming apart. 6~8 PSI differential is normal along the lenght of this gallery.
I agree, pumping against a head just so the gauge looks good is silly.
If the 9,000 RPM SBC was moving (say) 10gpm at those speeds, dropping from your 50 psi to 25 pse is going to save about 1/4 of a horsepower, a few hundred watts. Yes that's a few hundred watts going into heating the oil, but the heat generated by viscous drag is going to be 10s of KW.
Some of the posters in this thread claim that pumps operating in relief waste massive power and cause huge oil temperature increases, it's not the case...in a street (or race) engine, it's nothing like it...
Broc, I would imagine that as a builder, you are choosing a viscosity that keeps big ends in good condition, then tuning the lube system to get your desired pressure, rather than dropping viscosity to your pressure target.
If the 9,000 RPM SBC was moving (say) 10gpm at those speeds, dropping from your 50 psi to 25 pse is going to save about 1/4 of a horsepower, a few hundred watts. Yes that's a few hundred watts going into heating the oil, but the heat generated by viscous drag is going to be 10s of KW.
Some of the posters in this thread claim that pumps operating in relief waste massive power and cause huge oil temperature increases, it's not the case...in a street (or race) engine, it's nothing like it...
Broc, I would imagine that as a builder, you are choosing a viscosity that keeps big ends in good condition, then tuning the lube system to get your desired pressure, rather than dropping viscosity to your pressure target.
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