Lokasil 1, 2 and Gen 2 9A1 engines
11-10-2017, 09:03 AM
#76
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Thread Starter
I would say that is spot on Silk - well done - but I have to factor in owners who are too impatient or have too short a journey time to resist driving faster sooner - and I think better that they can restrain themselves for 15 minutes of gradually increasing throttle than not at all (being diplomatic here) but you keep up your regime - it is ideal.
The heat is generated by combustion and so it is directly impacted onto the piston and through the rings and piston face to the cylinders and underneath the piston crown (and inside the cylinder head) to the oil.
The coolant flows into the block, the cylinder head and the oil cooler, but then back into the radiator in a circuit. When not up to running temperature - the thermostat restricts the flow so the coolant is almost static in the engine to start with and some parts of it are hotter than others until it is flowing more and touches more hot surfaces.
To start with the coolant heats up and this turns the oil cooler into an oil heater until the oil gets hotter than the coolant at which point it becomes an oil cooler again.
To enable the Gen 2 cylinder block to expand fully will take the temperature to reach all the internal areas and feed into thick sections - and does usually TAKE AROUND HALF AN HOUR OF NORMAL DRIVING. However 15 minutes should make a big difference and is better than nothing.
Because the thermostat is initially closed the coolant in the block heats up and eventually finds its way to the radiator but because the flow is so slow - it stays a long time passing through the radiator and time influences the amount of cooling (the longer it is in there the cooler it becomes) - so it is quite cool on its return to the engines where the thermostat - sensing it is cool - restricts the flow once more.
It takes a long time for the temperature to rise enough to open the thermostat enough to make the coolant pass through the radiator fast enough to help it warm up quicker.
The whole system is actually extremely crude. The better scenario would be both individual thermostats on each radiator and either blinds or air flow flaps that are operated automatically to restrict radiator coolant and/or air flow that are initially closed and only open as temperatures rise higher - but that would cost too much and would be unnecessary if owners followed the handbook guidelines.
The oil is always hotter than the coolant (once it is at operating temperature) because it goes through an oil cooler that is fed with coolant and whenever there is a heat exchanger across a barrier the temperature drop is always lower as the material in between never conducts heat fully across its thickness.
The rate of oil flow into the heat exchanger is proportional to the revs whereas the rate of coolant flow is more proportional to the ambient conditions influencing the cooling rate at the time and therefore the amount the thermostat is open.
Centrifugal pumps (as in the coolant pump) have odd characteristics. At slow speed they hardly pump (displace) anything at all but then there is always a critical speed after which they are capable of huge flow. However if the pump speed is high but the thermostat is restricting flow the mechanical losses driving the pump are low as it basically just free wheels in the coolant (or if not designed properly may cavitate).
Our race 996 had a 3rd radiator but we split the coolant output from each cylinder block separately and each side had its own thermostat on the outlet side of the engine (so controlling the hottest temperature the engine can reach not the temperature it can enter then engine) and our third radiator had another thermostat set at a slightly higher temperature (so it only came into use when needed and helped quicker warm ups).
Despite this we still had heat soak problems when the races ended and considered fitting an electric coolant pump - before we decided just to support the sport by supplying engines and not to race with our own cars.
We are building another race car this winter and are presently discussion how we are going to protect the engine cooling and what systems to adopt and use.
Baz
The heat is generated by combustion and so it is directly impacted onto the piston and through the rings and piston face to the cylinders and underneath the piston crown (and inside the cylinder head) to the oil.
The coolant flows into the block, the cylinder head and the oil cooler, but then back into the radiator in a circuit. When not up to running temperature - the thermostat restricts the flow so the coolant is almost static in the engine to start with and some parts of it are hotter than others until it is flowing more and touches more hot surfaces.
To start with the coolant heats up and this turns the oil cooler into an oil heater until the oil gets hotter than the coolant at which point it becomes an oil cooler again.
To enable the Gen 2 cylinder block to expand fully will take the temperature to reach all the internal areas and feed into thick sections - and does usually TAKE AROUND HALF AN HOUR OF NORMAL DRIVING. However 15 minutes should make a big difference and is better than nothing.
Because the thermostat is initially closed the coolant in the block heats up and eventually finds its way to the radiator but because the flow is so slow - it stays a long time passing through the radiator and time influences the amount of cooling (the longer it is in there the cooler it becomes) - so it is quite cool on its return to the engines where the thermostat - sensing it is cool - restricts the flow once more.
It takes a long time for the temperature to rise enough to open the thermostat enough to make the coolant pass through the radiator fast enough to help it warm up quicker.
The whole system is actually extremely crude. The better scenario would be both individual thermostats on each radiator and either blinds or air flow flaps that are operated automatically to restrict radiator coolant and/or air flow that are initially closed and only open as temperatures rise higher - but that would cost too much and would be unnecessary if owners followed the handbook guidelines.
The oil is always hotter than the coolant (once it is at operating temperature) because it goes through an oil cooler that is fed with coolant and whenever there is a heat exchanger across a barrier the temperature drop is always lower as the material in between never conducts heat fully across its thickness.
The rate of oil flow into the heat exchanger is proportional to the revs whereas the rate of coolant flow is more proportional to the ambient conditions influencing the cooling rate at the time and therefore the amount the thermostat is open.
Centrifugal pumps (as in the coolant pump) have odd characteristics. At slow speed they hardly pump (displace) anything at all but then there is always a critical speed after which they are capable of huge flow. However if the pump speed is high but the thermostat is restricting flow the mechanical losses driving the pump are low as it basically just free wheels in the coolant (or if not designed properly may cavitate).
Our race 996 had a 3rd radiator but we split the coolant output from each cylinder block separately and each side had its own thermostat on the outlet side of the engine (so controlling the hottest temperature the engine can reach not the temperature it can enter then engine) and our third radiator had another thermostat set at a slightly higher temperature (so it only came into use when needed and helped quicker warm ups).
Despite this we still had heat soak problems when the races ended and considered fitting an electric coolant pump - before we decided just to support the sport by supplying engines and not to race with our own cars.
We are building another race car this winter and are presently discussion how we are going to protect the engine cooling and what systems to adopt and use.
Baz
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Presto (03-17-2021)
11-10-2017, 11:05 AM
#77
RL Community Team
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In old days I had a Saab 900 turbo that was fitted with a pump called a Turbo Saver. It was part of the oiling system and after the car was shut off, would actually cycle oil through the turbo for an additional 30 seconds to prevent coking. That original turbo is still in the car that my dad now owns at 250,000 miles.
Seems like something similar to this for the cooling system would be a really good idea to allow the coolant to continue to cycle through the motor when the car was parked hot. My 997.1 is actually supercharged by RUF and part of their kit is the additional of a 3rd center radiator with a coolant pump that moves the coolant through the system. In my case, I wonder if I could just hook up a key-off time delay relay to that pump to allow it to run for some period of time after engine shut-down.
You think there's any merit to this idea? That car sees oil temps in the 225 to 235 F range during the summer when being pushed hard due to the extra power it's producing with forced induction. I run Driven DT40 oil which they say can handle temps up to 300 degrees F and it has a 2L baffled deep sump with windage tray. The engine setup looks like this (from RUF's promotion material upon it's release).
11-10-2017, 02:24 PM
#79
RL Community Team
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Thermostat location makes no sense to me.
Why is the thermostat located where fluid is going into the engine and not out of the engine?
Where it is now (going in), it is measuring the temp of already cooled fluid. I would think it cares more about the temp of what is coming out to better temper the flow... measuring the temp coming out of the block tells the thermostat how effective the flow rate is.
Peace
Bruce in Philly
Why is the thermostat located where fluid is going into the engine and not out of the engine?
Where it is now (going in), it is measuring the temp of already cooled fluid. I would think it cares more about the temp of what is coming out to better temper the flow... measuring the temp coming out of the block tells the thermostat how effective the flow rate is.
Peace
Bruce in Philly
11-10-2017, 02:51 PM
#80
Burning Brakes
Baz, what is your opinion regarding engine friction reduction additives such as Liqui Moly Ceratec?
Do those provide any pros? Cons? Don’t do anything?
Thanks
Do those provide any pros? Cons? Don’t do anything?
Thanks
11-10-2017, 03:38 PM
#81
Thermostat location makes no sense to me.
Why is the thermostat located where fluid is going into the engine and not out of the engine?
Where it is now (going in), it is measuring the temp of already cooled fluid. I would think it cares more about the temp of what is coming out to better temper the flow... measuring the temp coming out of the block tells the thermostat how effective the flow rate is.
Peace
Bruce in Philly
Why is the thermostat located where fluid is going into the engine and not out of the engine?
Where it is now (going in), it is measuring the temp of already cooled fluid. I would think it cares more about the temp of what is coming out to better temper the flow... measuring the temp coming out of the block tells the thermostat how effective the flow rate is.
Peace
Bruce in Philly
11-13-2017, 11:03 PM
#82
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Bruce,
You are one dedicated P car fan! If I was unfortunate enough to have TWO engines blow on me, I'd be done with that brand. The ole screw me twice rule..
I've been out of Pcars since my 964 I owned 18 years ago. Now I'm looking at either a 997.2 or a 987.2...and we know why.
You are one dedicated P car fan! If I was unfortunate enough to have TWO engines blow on me, I'd be done with that brand. The ole screw me twice rule..
I've been out of Pcars since my 964 I owned 18 years ago. Now I'm looking at either a 997.2 or a 987.2...and we know why.
11-13-2017, 11:10 PM
#83
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Here's what I do to prevent scoring. It also works for irritable bowel syndrome.
I only drive on Mondays between 1127 am and 248 pm and Thursdays from 558 am to 730 am. To warm it up, I shift at 2250 in first, 2100 in second, 3300 in third, I skip 4th, 3200 in 5th, and 2400 in 6th. Unless it's colder than 56 degrees. Then I reduce RPMs in all gears by 21%.
Once warm, I only drive in reverse and only make left turns.
When I get home, I change the oil. I use 5.7W34 oil from Quebec. Leave the cap open for an hour to let it breath before filling.
Finally, on the off days I roll the windows half down.
Hope that helps.
I only drive on Mondays between 1127 am and 248 pm and Thursdays from 558 am to 730 am. To warm it up, I shift at 2250 in first, 2100 in second, 3300 in third, I skip 4th, 3200 in 5th, and 2400 in 6th. Unless it's colder than 56 degrees. Then I reduce RPMs in all gears by 21%.
Once warm, I only drive in reverse and only make left turns.
When I get home, I change the oil. I use 5.7W34 oil from Quebec. Leave the cap open for an hour to let it breath before filling.
Finally, on the off days I roll the windows half down.
Hope that helps.
Good thing these damn cars cost so much and are so well engineered.
11-14-2017, 06:06 AM
#84
User
Thread Starter
Yes that Saab turbo saver was typical of their advanced thinking, like the manual radiator blind on the Saab 96 and the variable compression engine they developed with such outstanding results.
The thermostat position puzzles me too. It means you control the temperature entering the engine but not leaving it – so the top of the cylinder block and the hottest part of the engine will vary in temperature and the colder the ambient conditions (and especially with a 3rd radiator fitted) the slower the coolant passes through the engine and hence the hotter the hottest part of the engine will be and the thinner the oil in that vicinity.
If you imagine a std car set up driving though a hot desert into a cold valley - as the temperature of the air drops the radiators cool the coolant more so the thermostat closes up more to try and raise the temperature back to its set point and hence the coolant flow is reduced - it then picks up more heat passing through the engine - so leaves at a higher temperature - which the radiator deals with well because it is in there longer with the reduced flow rate.
On our 996 race car (with 3rd radiator) we removed the standard thermostat all together, split the outlet from each bank and fed each through thermostat housings with different temperature settings until the temperatures balanced. They then joined together on their way to the radiators with a thermostat housing set at a slightly higher temperature before the 3rd radiator so it only opened when needed.
ATSR I am sorry I am not familiar with Liquid Moly Ceratec – but I think the most important feature an oil needs to avoid scoring is to be thick when hot to maintain as thick as possible oil film between the piston and bore on the power stroke and to resist squeezing out under the thrust loads present during the time of one power stroke cycle.
Special additives may help crankshaft shell life but I don’t know if they make any difference to the body of the oil when hot under pressure.
This post started in response to a question about the difference between Lokasil 1 and 2 and Alusil – which I think we have pretty well covered now and perhaps some other issues that have arisen would be better asked under a new topic heading now?
Baz
The thermostat position puzzles me too. It means you control the temperature entering the engine but not leaving it – so the top of the cylinder block and the hottest part of the engine will vary in temperature and the colder the ambient conditions (and especially with a 3rd radiator fitted) the slower the coolant passes through the engine and hence the hotter the hottest part of the engine will be and the thinner the oil in that vicinity.
If you imagine a std car set up driving though a hot desert into a cold valley - as the temperature of the air drops the radiators cool the coolant more so the thermostat closes up more to try and raise the temperature back to its set point and hence the coolant flow is reduced - it then picks up more heat passing through the engine - so leaves at a higher temperature - which the radiator deals with well because it is in there longer with the reduced flow rate.
On our 996 race car (with 3rd radiator) we removed the standard thermostat all together, split the outlet from each bank and fed each through thermostat housings with different temperature settings until the temperatures balanced. They then joined together on their way to the radiators with a thermostat housing set at a slightly higher temperature before the 3rd radiator so it only opened when needed.
ATSR I am sorry I am not familiar with Liquid Moly Ceratec – but I think the most important feature an oil needs to avoid scoring is to be thick when hot to maintain as thick as possible oil film between the piston and bore on the power stroke and to resist squeezing out under the thrust loads present during the time of one power stroke cycle.
Special additives may help crankshaft shell life but I don’t know if they make any difference to the body of the oil when hot under pressure.
This post started in response to a question about the difference between Lokasil 1 and 2 and Alusil – which I think we have pretty well covered now and perhaps some other issues that have arisen would be better asked under a new topic heading now?
Baz
11-14-2017, 11:48 AM
#85
RL Community Team
Rennlist Member
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Bruce,
You are one dedicated P car fan! If I was unfortunate enough to have TWO engines blow on me, I'd be done with that brand. The ole screw me twice rule..
I've been out of Pcars since my 964 I owned 18 years ago. Now I'm looking at either a 997.2 or a 987.2...and we know why.
You are one dedicated P car fan! If I was unfortunate enough to have TWO engines blow on me, I'd be done with that brand. The ole screw me twice rule..
I've been out of Pcars since my 964 I owned 18 years ago. Now I'm looking at either a 997.2 or a 987.2...and we know why.
1 - No other that appealed to me. I wanted a sports car that i could drive in the winter and as my only driver. Not many out there that do this and still qualify as a sports car (defined as track-ready off of the showroom floor). Some old Porsche ad of a 911 blasting up a snowy road with a ski rack on the roof still resonates with me. Further, I loved that 2000 Boxster S.... just a great car to drive.
2 - Low weight, short wheel base, wide (at least relative to alternatives).
3 - Not a 'vette. I admit I actually admire these things... and I loathe them for all the same reason: I grew up in a dirty steel town. Vette's were the car to own.... and everyone who did had a gold chain and a mustache. Sorry, I am permanently scarred.
4. Not a BMW.. my brother in law drives new M3s and I have driven each iteration... I am shocked that folks call these sports cars... powerful as heck, but like driving a big brick... I don;t get it at all... side by side to a Porsche, the wheel base is way longer than a Porsche's base... making the BMW a nice highway cruiser. (Long wheel base makes for slower turn snap but smoother on bumps due to increased leverage.)
4 - I had a belief/faith/hope that Porsche would address reliability since they became way profitable... they apparently did with the 9A1.. that "leaked" vid of the 9A1 on a test bed really did have an affect on me. Also, there were virtually no engine failures being reported on these forums... In '97 when the then-new platform was released... these things were blowing up for years on end. Yikes!
Peace
Bruce in Philly
11-16-2017, 10:21 PM
#86
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04-30-2018, 10:45 AM
#87
04-30-2018, 10:52 AM
#88
The most depressing statistic I've ever heard when trying to justify spending $50,000 for a car that can go 180mph.