too much oil pressure?, high OT on the freeway Options

[70_914]

Sorry to hijack the thread discussing basic thermodynamics but I will make a couple real world examples- since now I have agreement that fluid speed is the only variable in a closed system with a fixed cooler.

Example A: You are a college student. You are going to WWU taking plastics engineering with a double minor in physics and chemistry. You want to throw a killer party, and decide that running copper coils throgh a bucket of ice water is a good way to cool your beer as it exits a keg. The ice water is a constant temperature, the keg beer is also a constant temperature. You have a pressure valve to control flow through the copper coils. Your beer won't be the same cold temperature if you crank the pressure up to 50 psi and blast it through the coils, it will be colder if it goes through the coils a little slower and allows the ice water to remove more of the heat from the beer.

Example B: You are a fry cook and want to leave work early. You have a large griddle that needs to be cold before you can go home. You also have a piece of ice that is the exact width of this griddle. You can take the ice and rush it across the surface of the griddle at 2 inches per second and have over half the ice cube left at the other end- inefficient because the ice was not able to remove all the heat from the griddle and did not do as much work as it could of, or you could move the ice across the griddle at 1 inch per second and at the very last moment the ice is completely melted- very efficient because the ice was able to do all the work possible.

Both examples are abstract, neither example shows specifically a type IV engine with a pass through cooler, both examples show thermodynamics. Laws of physics don't change on a whim.

The overall heat transfer coefficient for a wall or heat exchanger can be calculated as:

1 / U A = 1 / h1 A1 + dxw / k A + 1 / h2 A2 (1)

where

U = the overall heat transfer coefficient (W/m2K)

A = the contact area for each fluid side (m2)

k = the thermal conductivity of the material (W/mK)

h = the individual convection heat transfer coefficient for each fluid (W/m2K)

dxw = the wall thickness (m)

The thermal conductivity - k - for some typical materials:

•Polypropylene PP - 0.12 W/mK
•Stainless steel - 21 W/mK
•Aluminum - 221 W/mK

The convection heat transfer coefficient - h - depends on

•the type of fluid - gas or liquid
the flow properties such as velocity
•other flow and temperature dependent properties

Heat transfer coefficient for some common fluids:

•Air - 10 to 100 W/m2K
•Water - 500 to 10 000 W/m2K

[realred914]

Too much oil pressure could cause excess heat because the oil would be flowing too quickly through the cooler for it to take enough heat out of the oil.

too much pressure causes the oil to flow more quikly???? seems that is the passage was blocked (ie no flow ) the pressure would really get high, the opposite of what your saying. if the oil flow had no resistance and no restiction, the pressure would be low and the flow rate very high.

flow rate and pressure are not always corrolated this way.

I high flow rate may give better cooling than a low flow rate. if the flow rate is too slow, the heat flux is too low and less cooling is done. remeber the heat exchanger is most efficinet when there is a big temperature delta.

I say there maybe an optimal flow verses heat rejection. but it will not be the highest flow nor the lowest flow rate

[70_914]

Too much oil pressure could cause excess heat because the oil would be flowing too quickly through the cooler for it to take enough heat out of the oil.

too much pressure causes the oil to flow more quikly???? seems that is the passage was blocked (ie no flow ) the pressure would really get high, the opposite of what your saying. if the oil flow had no resistance and no restiction, the pressure would be low and the flow rate very high.

flow rate and pressure are not always corrolated this way.

I high flow rate may give better cooling than a low flow rate. if the flow rate is too slow, the heat flux is too low and less cooling is done. remeber the heat exchanger is most efficinet when there is a big temperature delta.

I say there maybe an optimal flow verses heat rejection. but it will not be the highest flow nor the lowest flow rate

Exactly... If the fluid is not moving no work is being done. If the fluid is flowing too quickly, inefficient work is being done.

I only answered the question of the post- would too much oil pressure cause high engine oil temps. Yes, in theory. There are a lot of variables in fluid systems, though...

[70_914]

GO VIKINGS! WWU is in Bellingham and has an outstanding engineering program... didn't figure everybody would get that reference.

[realred914]

Sorry to hijack the thread discussing basic thermodynamics but I will make a couple real world examples- since now I have agreement that fluid speed is the only variable in a closed system with a fixed cooler.

Example A: You are a college student. You are going to WWU taking plastics engineering with a double minor in physics and chemistry. You want to throw a killer party, and decide that running copper coils throgh a bucket of ice water is a good way to cool your beer as it exits a keg. The ice water is a constant temperature, the keg beer is also a constant temperature. You have a pressure valve to control flow through the copper coils. Your beer won't be the same cold temperature if you crank the pressure up to 50 psi and blast it through the coils, it will be colder if it goes through the coils a little slower and allows the ice water to remove more of the heat from the beer.

Example B: You are a fry cook and want to leave work early. You have a large griddle that needs to be cold before you can go home. You also have a piece of ice that is the exact width of this griddle. You can take the ice and rush it across the surface of the griddle at 2 inches per second and have over half the ice cube left at the other end- inefficient because the ice was not able to remove all the heat from the griddle and did not do as much work as it could of, or you could move the ice across the griddle at 1 inch per second and at the very last moment the ice is completely melted- very efficient because the ice was able to do all the work possible.

Both examples are abstract, neither example shows specifically a type IV engine with a pass through cooler, both examples show thermodynamics. Laws of physics don't change on a whim.

The overall heat transfer coefficient for a wall or heat exchanger can be calculated as:

1 / U A = 1 / h1 A1 + dxw / k A + 1 / h2 A2 (1)

where

U = the overall heat transfer coefficient (W/m2K)

A = the contact area for each fluid side (m2)

k = the thermal conductivity of the material (W/mK)

h = the individual convection heat transfer coefficient for each fluid (W/m2K)

dxw = the wall thickness (m)

The thermal conductivity - k - for some typical materials:

•Polypropylene PP - 0.12 W/mK
•Stainless steel - 21 W/mK
•Aluminum - 221 W/mK

The convection heat transfer coefficient - h - depends on

•the type of fluid - gas or liquid
the flow properties such as velocity
•other flow and temperature dependent properties

Heat transfer coefficient for some common fluids:

•Air - 10 to 100 W/m2K
•Water - 500 to 10 000 W/m2K

if you run the beer slow enough, it will some get to near the temp of the ice water. however your party friends may get a little upset that teh flow rate is just a trickle. they want their mugs filled fast. the engine has a requierment for pressure to keep up lubrication. you drop the oil presusre to slow up the time in the cooler and you lose the important pressure needed to keep up luibrication of the bearings.

also keep in mind the oil is in a closed loop system. the faster it gets thru the cooler, the sooner it can make the return trip and be cooled again. Lets look at flow rate not speed or time in the cooler on any single pass of a molecule of oil. the faster any molecule of oil makes it thru the cooler, the faster it will be back for a second round thru the cooler.

the argument about speed thru the cooler is not taking this into account. The oil will return, it is not a one pass system like the hypothetical beer keg.

[Chris Hamilton]

If you wanted Example A to apply to this situation you would try to determine how much ice you could melt with the beer, not how much beer you could cool with the ice.

You seem to have the concepts in your mind but you are misapplying them pretty badly here.

realred914 is correct here in pointing out that this is a closed system and we are dealing with an energy transfer problem. We are trying to transfer the most energy from the motor to the oil cooler in the smallest time possible.


The Bottom Line: More flow through his cooler is going to cool the motor more. You can try to bring up as much misapplied theory here as you want, but the bottom line is that oil pressure is not going to overheat his 914.

[ChrisFoley]

Higher pressure from a high volume pump isn't necessarily going to increase the flow rate through the cooler.
At a certain point, the primary pressure relief valve will open and allow some oil to bypass the cooler. The flow rate through the cooler is therefore regulated to a large degree by the pressure relief valve.
The viscosity of the oil changes with temperature. When the oil is very hot it won't develop as much pressure and will flow more quickly through narrow passages such as in the cooler and between the bearings and crank.
Even though it is flowing faster and has less time to dump heat, the delta T is greater thereby increasing the rate of thermal transfer.

[ChrisFoley]

but the bottom line is that oil pressure is not going to overheat his 914.

(IMG:style_emoticons/default/agree.gif)
unless the pressure could be so high that added friction causes the oil to heat up more. (IMG:style_emoticons/default/biggrin.gif)

[70_914]

but the bottom line is that oil pressure is not going to overheat his 914.

(IMG:style_emoticons/default/agree.gif)
unless the pressure could be so high that added friction causes the oil to heat up more. (IMG:style_emoticons/default/biggrin.gif)

Or unless the cooler is not able to remove enough heat from the oil as it passes through...

Or unless there is a bypass somewhere in his oiling system (oil thermostat, bypass spring, pressure causing the oil filter case to flex and bypass internally...)

Or unless.... I don't care anymore.

My engines don't overheat. I am done with this thread- it is turning into an "I am right, you are an idiot and you can't prove otherwise" thread.

[VaccaRabite]

So, coming back down from high science to backyard engineering...

For those of you that added oil coolers, how did you route the oil from the case to the cooler?

Did you use a spin on type adapter and relocate the oil filter? Or did you pull the motor and tap the galley plugs? If I use a cooler, I'd like to use a spin on type adapter, but don't know if thats a good or bad idea.

Zach

[jhadler]

So, coming back down from high science to backyard engineering...

For those of you that added oil coolers, how did you route the oil from the case to the cooler?

Did you use a spin on type adapter and relocate the oil filter? Or did you pull the motor and tap the galley plugs? If I use a cooler, I'd like to use a spin on type adapter, but don't know if thats a good or bad idea.

Zach

The first iteration of aux cooling I did used a spin on adapter with a built in thermostat. While it was easy, and convenient to install. Service was a bit of a PITA, as the filter then came very close to a bunch of other things under the car, so it added effort to every oil change. It worked, I guess... But the oil cooler was not optimally installed, hanging on the engine lid. Now the motor is out and getting re-done, I'll be tapping the plugs, relocating the filter, and hopefully (if time and money permit) installing a cooler up in front.

-Josh2

[type11969]

Spin on type, drops the filter about an inch, no clearance problems. If anything it makes the filter a bit easier to remove when changing the oil.

-Chris

[realred914]

Spin on type, drops the filter about an inch, no clearance problems. If anything it makes the filter a bit easier to remove when changing the oil.

-Chris

You can buy a shorter filter also, that will help.

[sean_v8_914]

did you check, make sure your fan did not eat something?

[yeahmag]

I had that happen on my 2276 Type I once... Good point! Took me quite a while to figure it out.

[realred914]

hence you put on a fan screen taken from a late model VW bus. fits right on the 914 fan housing