Oil pressure at track
03-21-2006, 04:59 PM
#16
Burning Brakes
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just for clarification, the needle drop has nothing to do with throttle on/off - this happens in turn 1 where i am hard on the gas (long sweeper), as well as turn 7 where i might brake a little further into the turn (sharp 2nd gear right hander)
oil change is due soon, i see a majority uses 15-50. may i ask for a technical explaination?
oil change is due soon, i see a majority uses 15-50. may i ask for a technical explaination?
03-21-2006, 05:05 PM
#17
Race Car
For tracking, the biggest advantage is that the 50 weight oil will cling to oiled parts longer, even in case of starvation. The higher shearing strength also better protects hot engines, even in normal street driving. Hydraulic lifters will not bleed oil out of their cylinders during engine shut down, better protecting all associated components.
03-21-2006, 05:30 PM
#18
Nordschleife Master
I don't know if I'd agree with that explanation.
Oil viscosity responds with the temps, and additives chnage that response. 0-40 oil means it will maintain a viscosity of 0 grade oil at cold temps, and the viscosity of 40 grade oil at high temps. The high temp is the operating temp of your engine. So, at operating engine temperature, remarkably steady for me just a hair to the right of 180 on the gauge, the 0-40 oil has the viscosity of 40 grade oil. The engine tolerances are made specifically for that viscosity at that temperature. Going above that viscosity, as in 50 grade oil, may actually be bad for your engine, since the thicker oil won't make it through the tighter passages. Pressures may be higher, but all that means is that there is more resistance due to the thicker oil, not necessarily that there is more lubrication. In fact, maybe there is less lubrication.
Now, if the car were in the Sahara dessert or anywherwhere the engine is expected to run significantly hotter than the normal operating temp, I can see going to a higher grade oil. At the higher temps, the 50 grade oil will have the viscosity of the 40 grade oil at the normal temps, which then would be OK with the tolerances.
Oil viscosity responds with the temps, and additives chnage that response. 0-40 oil means it will maintain a viscosity of 0 grade oil at cold temps, and the viscosity of 40 grade oil at high temps. The high temp is the operating temp of your engine. So, at operating engine temperature, remarkably steady for me just a hair to the right of 180 on the gauge, the 0-40 oil has the viscosity of 40 grade oil. The engine tolerances are made specifically for that viscosity at that temperature. Going above that viscosity, as in 50 grade oil, may actually be bad for your engine, since the thicker oil won't make it through the tighter passages. Pressures may be higher, but all that means is that there is more resistance due to the thicker oil, not necessarily that there is more lubrication. In fact, maybe there is less lubrication.
Now, if the car were in the Sahara dessert or anywherwhere the engine is expected to run significantly hotter than the normal operating temp, I can see going to a higher grade oil. At the higher temps, the 50 grade oil will have the viscosity of the 40 grade oil at the normal temps, which then would be OK with the tolerances.
03-21-2006, 05:43 PM
#19
Burning Brakes
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Palting - perhaps doing track days is somewhat the equivalent of driving a car in the hot desert? esp on a hot july day in georgia, it can get over 100 degrees 
also, it sounds like you're just making an assumption as well. i'm following your logic, but anything else to explain your reasoning?
also, it sounds like you're just making an assumption as well. i'm following your logic, but anything else to explain your reasoning?
03-21-2006, 05:50 PM
#20
Race Car
Originally Posted by Palting
I don't know if I'd agree with that explanation.
Oil viscosity responds with the temps, and additives chnage that response. 0-40 oil means it will maintain a viscosity of 0 grade oil at cold temps, and the viscosity of 40 grade oil at high temps. The high temp is the operating temp of your engine. So, at operating engine temperature, remarkably steady for me just a hair to the right of 180 on the gauge, the 0-40 oil has the viscosity of 40 grade oil. The engine tolerances are made specifically for that viscosity at that temperature. Going above that viscosity, as in 50 grade oil, may actually be bad for your engine, since the thicker oil won't make it through the tighter passages. Pressures may be higher, but all that means is that there is more resistance due to the thicker oil, not necessarily that there is more lubrication. In fact, maybe there is less lubrication.
Now, if the car were in the Sahara dessert or anywherwhere the engine is expected to run significantly hotter than the normal operating temp, I can see going to a higher grade oil. At the higher temps, the 50 grade oil will have the viscosity of the 40 grade oil at the normal temps, which then would be OK with the tolerances.
Oil viscosity responds with the temps, and additives chnage that response. 0-40 oil means it will maintain a viscosity of 0 grade oil at cold temps, and the viscosity of 40 grade oil at high temps. The high temp is the operating temp of your engine. So, at operating engine temperature, remarkably steady for me just a hair to the right of 180 on the gauge, the 0-40 oil has the viscosity of 40 grade oil. The engine tolerances are made specifically for that viscosity at that temperature. Going above that viscosity, as in 50 grade oil, may actually be bad for your engine, since the thicker oil won't make it through the tighter passages. Pressures may be higher, but all that means is that there is more resistance due to the thicker oil, not necessarily that there is more lubrication. In fact, maybe there is less lubrication.
Now, if the car were in the Sahara dessert or anywherwhere the engine is expected to run significantly hotter than the normal operating temp, I can see going to a higher grade oil. At the higher temps, the 50 grade oil will have the viscosity of the 40 grade oil at the normal temps, which then would be OK with the tolerances.
You just stated that your engine temp (coolant) is close to 215F - 220F NORMALLY. What does that make the temperature of your oil....maybe 230 -240F? I sure wouldn't want to drive around in an oil with a viscosity of 40 at those temperatures for very long.
Will you notice a problem in the short run? Probably not other than noisey tappets upon startup and maybe a few seal leaks. But it WILL have an big effect long term on valve guides, tappet life and main bearings.
03-21-2006, 06:18 PM
#21
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so what's the bare minimum oil pressures should be when racing around a track? 1 bar in a long sweeping high G turn still means there's oil getting to the necessary locations right?
03-21-2006, 07:09 PM
#22
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thats what i want to know. theres no question that oil pressure drops in the turns, cause i can see it happen on the gauge (unless the gauge is messed up), the question is whether oil pressure is merely dropping or if there is oil starvation, and whether it is ok to drive when oil pressure drops like that for a couple seconds
03-21-2006, 07:17 PM
#23
Rennlist Member
Maybe of no use to anyone else, but I thought it was interesting (I know nothing about oil other than when to change it). http://www.blackstone-labs.com/oil_viscosity.html
Oil Viscosity
Most of us have only a vague understanding of viscosity. We tend to choose an oil with a viscosity that we believe is correct for our particular engine, but would another viscosity improve or reduce the life of the engine? Can we freely pick and choose a viscosity outside a manufacturer's recommendations?
Technically, viscosity is defined as resistance to flow. Commonly though, we think of it as an oil's thickness. To be more specific, it is the thickness of an oil at a given temperature. The plot thickens (pun intended).
The viscosity of an oil could be reported at any temperature, but to standardize things, most laboratories report either a low temp (100F or 40C) or a high temp (210F or 100C) and stick with either Fahrenheit or Celsius. The standardized temperature reading allows us to compare apples to apples for judging the thickness of the oil. At Blackstone, we report the viscosity at 210F.
An apple is an apple, no matter what language you use to describe it. In the same respect, there are many ways to describe viscosity: SAE Engine, SUS (Seybolt Universal Seconds), cSt (Centistokes), ISO grade, etc. We use SUS. No matter what you call it, the number given simply defines the thickness of the oil at the standard high temperature.
Straight Weight vs. Multi-Grade
Engine oils can be either a straight weight or a multi-grade viscosity. Originally, all oils were straight weights. Relatively few straight weights are manufactured today since most gas- or diesel-engine manufacturers recommend multi-grades. At operating temperature, a straight weight performs just as well as a multi -viscosity oil, and there is nothing wrong with using a straight weight. It's just a simpler form of oil. Some diesel fleets still use straight weights, as do about half the piston aircraft operators.
The difference between multi-grades and straight-weight oils is simply the addition of a viscosity improving (VI) additive. The most common grade of automotive oil in use today is the 5W/30, which is a mineral oil refined to the SAE 5 weight viscosity range containing the usual cleaning and anti-wear additives, then blended with a VI additive that should leave it reading in the SAE 30 weight range when at the higher (210F) temperature. The advantage to the multi-weight is, when starting the engine, the multi-viscosity oil has the thickness of an SAE 5 weight, which allows the engine to spin over more easily.
The most common diesel use oil is 15W/40. It is an SAE 15 weight oil with a VI additive that leaves it the thickness of an SAE 40 weight at operating temperature. What makes an oil a diesel-use oil (rather than automotive-use) is the level of additives used. Diesels require heavier levels of dispersant and anti-wear additives. These heavier additive levels are objectionable for automotive engines since they may interfere with the emission controls mandated by the EPA.
Which Viscosity to Use?
Engine owners often stray from manufacturers' recommendations regarding viscosity of oils. The engine builders dyno-test their engines using a specific viscosity oil, so when you use the viscosity they recommend, you are working with a known result. Going to another viscosity is an experiment, but it's usually a harmless one. For the sake of efficiency you want to run the lightest grade oil in your engine possible, within limits. We are seeing that trend for newer engines, for which the recommended grade is getting progressively lighter. The common 10W/30 has become a 5W/30, and some manufacturers even recommend 5W/20 oil. On the other hand, we can't see (in oil analysis) where it hurts anything to run heavier 10W/30s or even 10W/40s in modern automotive engines. The heavier oils provide more bearing film, and that's important at the lower end. If your oil is too light, the bearing metals can increase. If the oil is too heavy, the upper end metals can increase. The trick is to find the right viscosity for your particular engine, which is why we suggest following the manufacturer's recommendation.
Changes in Viscosity
Adding anything foreign to your oil can change its viscosity. Some types of after-market oil additives cause a quite high viscosity at operating temperature. While an additive might improve bearing wear, it can often cause poorer upper-end wear. We don't recommend any type of after-market additives.
Other changes to viscosity can result from contamination of the oil. Moisture and fuel can both cause the viscosity to increase or decrease, depending on the contaminant and how long it has been present in the oil. Antifreeze often increases an oil's viscosity. Exposure to excessive heat (leaving the oil in use too long, engine overheating) can also increase viscosity. When your oil's viscosity comes back as either lower or higher than the "Should Be" range, something is causing it. The key is to find out what it is and repair your engine or adjust your driving habits accordingly, to correct the viscosity and optimize your engine's efficiency.
If you decide to use a different viscosity oil than what the manufacturer recommends, you might want to use oil analysis while you are experimenting. Your wear data doesn't lie. People selling oils and additives may be sincere, but they don't have to live with the results. They simply smile a lot on the way to the bank.
Oil Viscosity
Most of us have only a vague understanding of viscosity. We tend to choose an oil with a viscosity that we believe is correct for our particular engine, but would another viscosity improve or reduce the life of the engine? Can we freely pick and choose a viscosity outside a manufacturer's recommendations?
Technically, viscosity is defined as resistance to flow. Commonly though, we think of it as an oil's thickness. To be more specific, it is the thickness of an oil at a given temperature. The plot thickens (pun intended).
The viscosity of an oil could be reported at any temperature, but to standardize things, most laboratories report either a low temp (100F or 40C) or a high temp (210F or 100C) and stick with either Fahrenheit or Celsius. The standardized temperature reading allows us to compare apples to apples for judging the thickness of the oil. At Blackstone, we report the viscosity at 210F.
An apple is an apple, no matter what language you use to describe it. In the same respect, there are many ways to describe viscosity: SAE Engine, SUS (Seybolt Universal Seconds), cSt (Centistokes), ISO grade, etc. We use SUS. No matter what you call it, the number given simply defines the thickness of the oil at the standard high temperature.
Straight Weight vs. Multi-Grade
Engine oils can be either a straight weight or a multi-grade viscosity. Originally, all oils were straight weights. Relatively few straight weights are manufactured today since most gas- or diesel-engine manufacturers recommend multi-grades. At operating temperature, a straight weight performs just as well as a multi -viscosity oil, and there is nothing wrong with using a straight weight. It's just a simpler form of oil. Some diesel fleets still use straight weights, as do about half the piston aircraft operators.
The difference between multi-grades and straight-weight oils is simply the addition of a viscosity improving (VI) additive. The most common grade of automotive oil in use today is the 5W/30, which is a mineral oil refined to the SAE 5 weight viscosity range containing the usual cleaning and anti-wear additives, then blended with a VI additive that should leave it reading in the SAE 30 weight range when at the higher (210F) temperature. The advantage to the multi-weight is, when starting the engine, the multi-viscosity oil has the thickness of an SAE 5 weight, which allows the engine to spin over more easily.
The most common diesel use oil is 15W/40. It is an SAE 15 weight oil with a VI additive that leaves it the thickness of an SAE 40 weight at operating temperature. What makes an oil a diesel-use oil (rather than automotive-use) is the level of additives used. Diesels require heavier levels of dispersant and anti-wear additives. These heavier additive levels are objectionable for automotive engines since they may interfere with the emission controls mandated by the EPA.
Which Viscosity to Use?
Engine owners often stray from manufacturers' recommendations regarding viscosity of oils. The engine builders dyno-test their engines using a specific viscosity oil, so when you use the viscosity they recommend, you are working with a known result. Going to another viscosity is an experiment, but it's usually a harmless one. For the sake of efficiency you want to run the lightest grade oil in your engine possible, within limits. We are seeing that trend for newer engines, for which the recommended grade is getting progressively lighter. The common 10W/30 has become a 5W/30, and some manufacturers even recommend 5W/20 oil. On the other hand, we can't see (in oil analysis) where it hurts anything to run heavier 10W/30s or even 10W/40s in modern automotive engines. The heavier oils provide more bearing film, and that's important at the lower end. If your oil is too light, the bearing metals can increase. If the oil is too heavy, the upper end metals can increase. The trick is to find the right viscosity for your particular engine, which is why we suggest following the manufacturer's recommendation.
Changes in Viscosity
Adding anything foreign to your oil can change its viscosity. Some types of after-market oil additives cause a quite high viscosity at operating temperature. While an additive might improve bearing wear, it can often cause poorer upper-end wear. We don't recommend any type of after-market additives.
Other changes to viscosity can result from contamination of the oil. Moisture and fuel can both cause the viscosity to increase or decrease, depending on the contaminant and how long it has been present in the oil. Antifreeze often increases an oil's viscosity. Exposure to excessive heat (leaving the oil in use too long, engine overheating) can also increase viscosity. When your oil's viscosity comes back as either lower or higher than the "Should Be" range, something is causing it. The key is to find out what it is and repair your engine or adjust your driving habits accordingly, to correct the viscosity and optimize your engine's efficiency.
If you decide to use a different viscosity oil than what the manufacturer recommends, you might want to use oil analysis while you are experimenting. Your wear data doesn't lie. People selling oils and additives may be sincere, but they don't have to live with the results. They simply smile a lot on the way to the bank.
03-21-2006, 08:33 PM
#24
If the oil pressure really is dropping in the turns there is a problem. Make sure the oil is full to the max level when you track it. I doubt that the oil viscosity is the issue. It may be the sending unit but I wouldn't run it with low pressure showing. I wonder if the G forces could be kinking an oil line somewhere?
03-21-2006, 09:07 PM
#25
Nordschleife Master
Originally Posted by 1999Porsche911
Cool. So when did Porsche come into my garage and change the tolerances in my engine's oiling system? The car originally coame with 15W50, so they must have had engine damage in all those cars since the passegeways were too small for the oil to get through? This is a common WRONG explaination used by many people who have little to no experience with engines. The tolerneces in this engine are no tighter than any performance engine built 30 years ago.
You just stated that your engine temp (coolant) is close to 215F - 220F NORMALLY. What does that make the temperature of your oil....maybe 230 -240F? I sure wouldn't want to drive around in an oil with a viscosity of 40 at those temperatures for very long.
Will you notice a problem in the short run? Probably not other than noisey tappets upon startup and maybe a few seal leaks. But it WILL have an big effect long term on valve guides, tappet life and main bearings.
You just stated that your engine temp (coolant) is close to 215F - 220F NORMALLY. What does that make the temperature of your oil....maybe 230 -240F? I sure wouldn't want to drive around in an oil with a viscosity of 40 at those temperatures for very long.
Will you notice a problem in the short run? Probably not other than noisey tappets upon startup and maybe a few seal leaks. But it WILL have an big effect long term on valve guides, tappet life and main bearings.
My car came with 0W-40. That is the recommended oil for my temperature range. If your 1999 C2 recommended oil is 15W50, then that's what the tolerances were designed for. If, OTOH, it 's NOT the recommeded oil but just "came with it", then you should check for wear on the valve guides, tappets and main bearings of your car.
The designers of the engines made specific oil recommendations. These are based on the expected operating temps of the cars, and the specifc design of the engine. If your car is operating within the designated range, there is no reason to think you are smarter than the Porsche engineers, and change these recommendation. These people, BTW, DO have long and extensive experience with engines. If you are operating outside of the designated range, then you can make educated guesses. However, I would first question, why are you outside the designated operating range?
The car on the track operating within the temps prescribed is no different than the car driving on the street as far as oil viscosity goes. There will be more cantamination and blow-by due to the harder acceleration/deceleration. Changing to a thicker viscosity does not solve the problem, changing the oil more frequently does. If you put excessive G's for one reason or another, such as putting oversized slicks, you can run the risk of oil starvation. Again, changing oil viscosity does not solve this problem.
I'm not rying to be a know-it-all. Bottom line, I follow the recommendations of the people that designed the car and engine. They may not know it all, but they certainly know a lot more about the Porsche engine than anyone I know.
03-21-2006, 09:45 PM
#26
Race Car
I can write pages and pages of technical data on oil and it's effects on modern engines and never convince some people. The primary reason 0W40 is recommended (by some manaufacturers), is to improve gas mileage rating. It also is pushed big time by Mobil 1 and others and the manufacturers are paid a HUGE sum of money (in the form of free oil) to put this in their cars along with the associated labels and recommendations.
As for difference in tolerences of the journals and crank between my 99 and even the 06's.....there is absolutly none. As a matter of fact, Porsche engine's have historically had greater bearing clearences than many other high performance engines such as Ferrari. So any argument that a 50 weight oil is too thick to properly pass through the various areas on a in the oiling system on a warm engine, is wrong. 240F+ 0W40 oil will not maintain the necessary .0001 (minimum) inch thick oil film between the bearings and the journals as well as a 15W50 oil at the same temperature.
As for difference in tolerences of the journals and crank between my 99 and even the 06's.....there is absolutly none. As a matter of fact, Porsche engine's have historically had greater bearing clearences than many other high performance engines such as Ferrari. So any argument that a 50 weight oil is too thick to properly pass through the various areas on a in the oiling system on a warm engine, is wrong. 240F+ 0W40 oil will not maintain the necessary .0001 (minimum) inch thick oil film between the bearings and the journals as well as a 15W50 oil at the same temperature.
03-21-2006, 09:56 PM
#27
Rennlist Member
the 99 did not come from the factory with 15w50 that is for sure...and there is no benefit to running a heavier oil in the hydraulic top ends of the new 911 engines, in fact it is bad news....porsche recommends 0w40 for good reason, it is unwise to deviate from this...oil pressure does not have to be really high for adeqaute lubrication to occur and a high pressure is actually showing you that there is flow resistance....that is of course unless there is oil starvation....
read this: http://www.wrightune.co.uk/downloads/approved_oils.pdf
they are good oils and recommended with good reason. i have run the cup car very hard with 5w40 synthetics and have verified through used oil testing that my wear rates are better than what i had with 15w50 oil...temps were lower too.
read this: http://www.wrightune.co.uk/downloads/approved_oils.pdf
they are good oils and recommended with good reason. i have run the cup car very hard with 5w40 synthetics and have verified through used oil testing that my wear rates are better than what i had with 15w50 oil...temps were lower too.
03-21-2006, 09:59 PM
#28
Rennlist Member
as a follow up i will post some used oil analysis on 911's running xw40 oils ASAP and i think will agree they are pretty darn stout oils. BTW, the M1 15w50 is on the "low" end of a 50wt oil anyways, it is the "15" rating that will screw up the tappets every morning when you start it. not challenging, just tryin' to help!
03-21-2006, 10:00 PM
#29
Nordschleife Master
Your link is for a "new" TSB that superceded the old TSB that did in fact have 15W-50. The date on your TSB is 1/05 which by my calculations in about 6 years post hoc.
03-21-2006, 10:37 PM
#30
Race Car
Originally Posted by bgiere
the 99 did not come from the factory with 15w50 that is for sure...and there is no benefit to running a heavier oil in the hydraulic top ends of the new 911 engines, in fact it is bad news....porsche recommends 0w40 for good reason, it is unwise to deviate from this...oil pressure does not have to be really high for adeqaute lubrication to occur and a high pressure is actually showing you that there is flow resistance....that is of course unless there is oil starvation....
read this: http://www.wrightune.co.uk/downloads/approved_oils.pdf
they are good oils and recommended with good reason. i have run the cup car very hard with 5w40 synthetics and have verified through used oil testing that my wear rates are better than what i had with 15w50 oil...temps were lower too.
read this: http://www.wrightune.co.uk/downloads/approved_oils.pdf
they are good oils and recommended with good reason. i have run the cup car very hard with 5w40 synthetics and have verified through used oil testing that my wear rates are better than what i had with 15w50 oil...temps were lower too.
Well, hate to tell you that you are wrong, but.....YOU ARE WRONG! The 99's DID come factory filled with 15W50 and this is the recommended oil to use in the manual.
Running 0W40 in hot climates may not provide the solid film required on the journals, and may also allow too much lifter bleed down after engine shut down (valve train noise) which may be followed by irratic idle. Additionally, if there is insufficient journal oil film, this will allow the crank to wander and increases the likelihood of RMS wear and leakage.