Oil pressure low- Not a basic problem

[IJ.]

LOL'd @ the aircleaner "mod"

In the past I've found Oil temps to follow coolant temps, I run a coolant T-Stat around 180ish so the 215 doesn't really make much sense to me.

 

[FloTex]

As we know, we need to flash water and solvents out of the oil. If glycol is mixed with the water it is a whole different dynamic.

In the system with increased pressure things change. The ideal gas law equation is PV=nrT with n and r being constants in this case so PV~T and as pressure goes up so does flash temperature (if volume stays the same). Looking at a phase diagram of water (http://www.physics.ubc.ca/~outreach/phys420/p420_00/zachary/webpg420/images/trip_pt1.jpg) illustrates this and that as pressure goes up the water would not flash until way above 212F.

So ... Canton's approach seems to be considering water intrusion from condensation only (no glycol). This is just water and it won't mix with the oil. So it should flash independently at 212 degrees F, 100C, since it is still at atmospheric pressure. The flashing would have to be in the oil pan or valve train not the pressurized flow stream. The 212F is well within the safe operating range of the engine so Canton went with 215F for their thermostat.

Gasoline and solvents can go into solution with the oil and would flash at different temperatures. Water-glycol in the oil would flash at a much higher temperature than the water itself.

I understand why Canton chose 215, but I'm interested in everybody's experience with the 160F and 180F thermostats.

 

[FloTex]

I was thinking of that also. I like the 180F engine thermostats. If the oil is hotter the engine will be a heat sink for the oil also. I haven't run an oil temperature gauge, so I'm wondering how hot everyone's oils may be running. I will measure mine to see when I start up. I will use my IR gun if my wife doesn't let me use her turkey basting thermometer :icon_razz

 

[jdub]

Keep a couple things in mind in mind:
- There's not that much water from condensation in the oil...if you have enough in the oil to "flash" you have much bigger problems.
- Oil viscosity drops rapidly above 100 deg C...running a thicker oil is not the answer.

 

[FloTex]

This is directly from Canton's website:
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Why Use An Oil Cooler Thermostat?
An oil cooler thermostat helps your engine's oil come up to temperature quickly and holds it at the right temperature. Cold oil does not flow and does not lubricate correctly. Plus, moving cold oil robs power. Our thermostat is designed to bypass the cooler until the oil reaches 215 degrees. At 215 degrees water condensation in the oil will evaporate and the oil will be warm enough to flow and lubricate properly.
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The articles jdub has from Dr AE Haas are excellent; they state (Article 101) that engines are designed to operate at 212F. I am always trying to get into the head of the designing engineers (maybe more dangerous than an exploding pressure plate) to understand why they design things the way they do. Sometimes it is correct, sometimes not. It is the real world results that tell the story.

So my thought is that Canton (along with what they stated above) is trying to keep oil at equilibrium with the engine operating temperature so that it isn't used for cooling or heating, just lubrication and is somewhat stable in it's passes through the engine. (The water temperature thermostat is lower to move the heat out through the coolant and keep the engine at ~212F.)

There is an (IMO) interesting story about engineers at GM discussing the performance impact of changing various engine parameters. Charles Kettering (inventor of the spark plug, powered generators, the first ignition system, leaded gas, lots of others ...) overheard them and asked "Why don't you ask the engine?". So the real results are hard to predetermine, but are best measured.

So, my thanks- keep the real Supra engine results info coming.

 

[FloTex]

From the Dr AE Haas Lesson 201:
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Cold engine showing very high pressures because of the thickened oil at startup:

For a 40 wt oil at 75 F at startup:
The oil is thicker, has more internal resistance and therefore requires more pressure to get the same flow.
RPM....Pressure..Flow
1,000......60 PSI....1
2,000....120 PSI....2 The maximum flow because of the oil pop off valve at 90 PSI will be 1.5
4,000....240 PSI....4
8,000....480 PSI....8

At 1,500 RPM you reach the maximum oil flow rate and if you run to 8,000 RPM it is the same rate. The flow cannot increase and it is insufficient. This is why we must wait until our oil temperature comes up to 212 F or higher. The maximum flow rate in this case will then double, up to 3.
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These articles are great and detailed, so everybody interested should read them in their entirety (thanks again Dr H and jdub). Taking one cut & paste out doesn't do them justice, but the quoted excerpt above seems to explain the possible school of thought of the Canton designers. Pressure doesn't help if it is high from cooler oil with low flow and there is inadequate lubrication. We want warmer oil for top flow (therefore lubrication). So we want to get to maximum flow ASAP and this appears to be about 212F in testing.

I want to be confident in the 215F thermostat before I install it. I think I'm feeling OK about it so far. Dr AE Haas did state that his temperature runs 180F in normal operation but didn't state what thermostat he uses. It could open at 215F and cool the oil to 180F through the lube cycle. It depends on where it is measured and where the cooler is placed for a given engine (ie his Ferrari).

Keep any thoughts coming.

 

[jdub]

You want to use a 180 deg stat. That will allow oil flow to the cooler a bit sooner so it can do it's job. Depending on the size of the cooler, the oil will achieve temps above 180 degs easily...especially under hard driving conditions.

Your logic is flawed...a higher temp stat is for drag motors to get the oil to ops temp in the shortest time. It takes time for the cooler to do it's job...the 180 deg stat allows it to get ahead of the desired temp and is more suited to a street car. You do not want oil temps to hit in the 240-250 deg range due to the decrease in viscosity...a 215 deg stat is risking temp overshoot.

 

[adampecush]

also remember that the tstat is located at a point before the oil makes its trip through the engine. as a result, it is going to get quite a bit hotter before it gets to the pan, giving ample time to flash off volatiles/vapors

 

[FloTex]

Makes sense.

Good chart reference also:

http://fordfuelinjection.com/files/engine_trans_temps.gif

MoCal 180F thermostat it is- will order it and return the Canton 215F.

 

[FloTex]

All is in an working great. Pressure is up just from changing out the stock system and adding the remote filter and cooler. I feel great about the 180 degree t'stat. THANKS FOR THE HELP.

If I get a chance to post pics later I will. It would be good to add a post on making up the hydraulic fittings/braided steel lines also since these can be tricky. When making them up I thought of the extra steps I take to prevent leaks and contamination that would be worth posting.

First I have to get it on the road ... loose harmonic balancer (and then the new ATI was marked 120 degrees out), had low fuel pressure problem, and now MAP ECU communication problems.