Oil Coolers and Over cooling

NYBladeZ

For those of us with oil coolers, I hope you know what I'm talking about. I know the simple solution is to build some sort of shroud. However, all these thermostatic plates state that they only open at 180+ but clearly that isn't the case. Is there any way to adjust the plates so that it doesn't slowly trickle oil to the cooler causing overcooling? I'm doing an oil change soon and the plate will be readily accessible, building a shroud just seems like another headache albeit a simple one.

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m4a1mustang

The plates are never 100% closed for a reason. They only close to about 90% to prevent thermal shock by introducing cold oil kept in the lines/cooler to the engine once the engine oil temps reach a certain temperature.

The only real way to prevent over-cooling is to block a portion of the airflow to the cooler.

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NYBladeZ

I figured...

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2009 Carbon Fiber/Red 370z aka Trish: Sports Package, Meisterschaft full catback, Fast Intentions Longtube Headers, Injen Long Tube Intakes, UpRev Tune: Sold
2008 Lotus Exige S Club Racer aka Bella, always leaves me smiling

m4a1mustang

The shroud is the simplest and most effective way anyways. Hard for a properly secured sheet of aluminum, cardboard, plastic, etc. to fail.

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cdoxp800

You guys do realize that the oil Temp you see on your gauge is the Oil Temp of the oil temp returning to the Pan correct. This is the Temp coming from the return of the Oil cooler and not the Temp of the oil in the engine.

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adampetrasek

I'm pretty sure this is an impossible question to answer... but i'll put it out there anyways

Any idea what the temp of the oil entering the engine is based off what the gauge is reading.

ie: gauge reads 160, but b/c of some educated guesses, the oil entering the engine would be ...?

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MattP725

Not true... oil coolers (at least in the US) are aftermarket and there is no temp sensor anywhere inline on our cars (unless someone added one).

This should be the temp at the bottom of the block or oil rail and has nothing to do with the returning oil.

cdoxp800

I never said it was "on" the return line from the oil cooler. I said

The FACTORY (OEM) sensor reads this Temp on the block on the return path to the oil pan. As seen in the attached Pic. Any more questions?

Attached Images

temp.jpg (114.9 KB, 139 views)

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Jordo!

So what's a likely temp differential then?

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Rooskey

Yea. Do you have an oil flow chart of the previous pick you posted. I already have a way to override the limp mode with the computer. The reason I ask is cause I have never heard of such a major problem on a car, and also have never heard of someone trashing a motor because of this situation. Unless someone proves otherwise I think this oil temp thing is nothing more than having a stupid guage on the dash. IF anyone has trashed an engine due to this please chime in. Thanks... (I know there are alot of debates on this subject and im not trying to start crap. Im just looking for facts on the situation)

ImportConvert

You do realize the limp mode serves a purpose, yes? It took time to program, and time means money, and no corporation spends money without profit in mind, and what profit is there to be made with a limp mode unless warranty work were avoided by having it...

phunk

The oil temperature sensor is in the pressure channels just off the oil filter. It is measuring oil temp of the oil that is entering the pressurized lubrication passages in the engine.

The only thing I cannot answer on the VHR specifically is if it is before or after the oil filter, because I have not taken the upper pan off and followed the oil passages in the upper pan casting. If it is before the oil filter, meaning just inline after the pump, then we are not able to see the immediate effects of the oil after leaving our aftermarket coolers. If it is after the oil filter, then we are seeing the immediate effects of our added coolers. I have an extra VHR engine sitting in my garage to use for my built engine project, sometime in the next few weeks when I take it apart to begin the build I can report back the answer to this.

But regardless of all that, the oil temperature sensor is definitely in the pressure channels after the pump.

Also, engines do not really have much of a return path for oil. The only passages for it are positioned near the cylinder head studs so that the oil can leave the cylinder heads and just drip back into the open crankcase down the sides. The upper oil pan itself, does not have any oil return passages.

Refer to service manual page LU-7. There you will read it instructing you to test engine oil pressure by removing the oil temp sensor and installing the nissan oil pressure test gauge hose. This is the only evidence I have at the moment of what I am saying... but it is clear evidence.

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MattP725

I think your wording is off... this isn't oil coming back to the pan, it is oil leaving the pan to the block.

All in all I wouldn't see this being a major issue anyhow... once the oil is at operating temperature, the oil in the pan/block/cooler are eventually going to meet some sort of equilibrium. Even without a cooler you have to beat on it pretty heavily to get an immediate and sharp climb in oil temperature and that is generally only 10-20 degrees.

cdoxp800

Opps, correct. Been a little sick.

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wstar

Actually, with the standard Mocal thermo plate most people are using, the lines to the oil cooler are never closed even slightly. The thermostatic valve operates on the bypass flow that skips the cooler. When you're under 175-ish, the bypass is open and most of the flow bypasses the cooler because it's the shortest path (but the lines to the cooler are wide open and some flow goes through them, gradually warming up the cooler itself). From 175-185-ish, the valve gradually closes off the bypass passageway, forcing all flow through the cooler at 185+.

I only recently found out about this myself, but the general idea is that yes, the oil temp gauge is reading the coldest point in the cycle if you have an external cooler. The oil that's about to enter the cooler is probably significantly hotter. Still, the value on the gauge is the one you care about for overcooling. If it's too cold at the coldest point, that's right before it gets pushed to the top of your engine to lubricate the very critical stuff (your VVEL heads). Assuming it's even true, which I haven't seen any direct evidence of. But either way it's unimportant for the purpose of discussing overcooling.

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