300 + Degree Oil Temp HELP !!!!!!

[Infomaniac]

This is a marine engine. Thought I would put a thread here due to the larger volume of people.

OK have a custom built 522 Big block Chevy. Twin Turbo intercooled. Oil temp measured in the oil pan. Water temp stays just above 100 degrees. Jet boat, but oil temp climbs to over 300 degrees during high power runs and never goes below 250 degrees. It has one of the largest oil coolers available. 12 qt oil pan, well designed with windage tray. Oil pressure stays OK.

I'm curious: What design features of the engine will effect oil temp? Assuming that plumbing, oil cooler size, oil quantity etc are correct.

Royal Purple oil being used.

The major concern is oil breaking down. The oil is cooled before entering the engine. Do not know what the temp of the oil is there. Temp is measured in the pan. Even though the temp of the oil going into the engine is probably acceptable, the really hign temp in the pan is the concern of oil breaking down due to temp.

One final note, the turbochargers drain directly into the pan. The turbo housings are water cooled.

 

[Ken2]

Oil is damaged by both the temperature and by the time at that temperature. Synthetic oil handles higher temperature without damage. You need a racing oil of suitable viscosity (20W-50? SAE 50?) and follow used oil analyses to see what the life will be of that oil.

250 to 300 seems OK for a short time. To find out the facts, contact both Terry Dyson and the oil maker. Terry will also help you pick the best oil for that engine.
http://www.dysonanalysis.com/pages/1/index.htm

Oil get heated from the friction in the bearings and the heat picked up from conduction...oil draining across a hot head gets part of that heat. There is liquid friction of the oil itself in the bearings that causes the heating. Thicker oil has more of this, but sometimes is necessary to supply adequate viscosity at operating temperature. A higher rate of oil flow will move the oil faster so it has less time to pick up heat, but the total heat load is still there and must be passed to the cooler. Your engine builder knows the right oil pump, hose sizes, etc. Work with him and a lube expert like Terry to find the lubrication that will let your engine live longest.


Ken

 

[Curious Kid]

Another concern about running high oil temps, is the decrease in strength of lead-containing bearing overlay.

Sounds like quite the high-strung beast!

Good luck and keep us posted.

 

[Mitch Alsup]

How is air routed to the oil coolers (and away from the coolers)? Is there a fan in the outlet duct? Is it running? What is the temperature of air leaving the exhaust duct? How many CFM is moving?

What temperature is the oil when entering the engine? {300dF may not be all that bad for oil fresh out of the bearings; if the oil inlet temps are in the 260dF range (or lower)}

Since you say you are already using the biggest oil coolers, you could always run 2 more and have them pulmbed in series with the existing two (but do supply more air).

 

[Eddie]

My old air-cooled porsches often saw 300-350 F oil temps during jimkanas racing. Never had a problems with std 40 wt oil. We did change oil at about 50-75 hours of operation though. Might be interesting to contact a NASCAR gp to ask some questions. JMO

 

[MolaKule]

quote:

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Oil temp measured in the oil pan. Water temp stays just above 100 degrees. Jet boat, but oil temp climbs to over 300 degrees during high power runs and never goes below 250 degrees. It has one of the largest oil coolers available. 12 qt oil pan, well designed with windage tray. Oil pressure stays OK.

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What oil are you using, and what viscosity?

Is engine oil cooler cooled (heat exchanger) with an electric fan?

Is oil temp sensor measuring oil temp or is heat being conducted to it directly from engine?

Does water temp peak as well? If not, I suspect you do not have enough water flow through heads.

 

[Infomaniac]

Thanks everyone.

It has a water/oil heat exchanger. Total loss water system in a boat. Unlimited 70ish degree water to work with.

Oil temp sensor is under the oil level of the oil pan. Royal purple oil. I'll have to check on exactly which viscosity.

 

[WDP]

With all the cooling media you have it doesn't seem possible that oil temps could be that high. What about your temp gauge setup? Maybe the probe is incorrect causing the high readings. My suggestion is to check the probe and gauge with boiling water, guaranteed 212* at sea level.

WDP

 

[Curious Kid]

That does seem strange that with running 70'ish degree water through the exchangers, it still appears so high. Water/liquid is suppose to be a better cooling medium, yes? I haven't had any hands-on experiences with anything turbo charged, let alone running two...dang.

I second the conformation of tempurature guage accuracy, as well as to double check that the oil-water heat exchangers have good flow - just how is it plumbed in relation to the overall oil system anyhow (sorry if I missed this detail).

 

[Infomaniac]

The system is plumbed pan -- pump -- external filter -- external cooler -- engine -- parallel "T" to turbos -- pan.

The cooler water inlet and outlet is straight up to prevent air bubbles. Water flow is opposite oil flow internally.

May need to check the temp sensing system for accuracy.

 

[Brons2]

Time to break out the SAE 60wt racing oil ;-)

 

[GoldenRod]

What I don't understand is this: if the water temp is only slightly above 100F, how can it be that the oil temp is all the way up past 300F? I have always thought [although I don't remember the info source] is that the oil temp and water temp should be within 50F of each other. Am I right with this assessment?

 

[Steve S]

Infomaniac,do a check on the temps for sure, but that engine will put out some heat at wot. If the oil pressure is ok maybe the temp gauge is off.I would guess the plumbing is ok because of the serious engine. My advice would be get a V- Drive flat bottom so then you won't be able to stay on it long enough to heat up the oil.

Keep us informed. P.S. 1000+ horsepower easy ?

 

[Steve S]

Golden rod,all the stuff you read is not necessary the actual fact. Marine engines are run under a load that in a passenger car or unloaded pickup truck will never see. Look up some of the uoas on marine engines [want to see big wear numbers compared to cars]

 

[va3ux]

quote:

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GoldenRod
Member # 11140 - posted February 06, 2006 09:51 PM What I don't understand is this: if the water temp is only slightly above 100F, how can it be that the oil temp is all the way up past 300F? I have always thought [although I don't remember the info source] is that the oil temp and water temp should be within 50F of each other. Am I right with this assessment?

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Because the oil temp is measured *before* it is cooled.

 

[GoldenRod]

Steve S, va3ux, Thanks Guys.

 

[olympic]

I bet it's those big turbos heating up the oil. 300F doesn't sound all that bad considering the application. But if your looking for lower temps then the only thing to do is add more cooling, adding a cooler after the turbos would probably make the biggest difference in pan temps.

 

[Malaclypse]

I'm no engine expert and I'm no oil expert but working in the business and designing a few aftermarket parts this is what I see.

The main oil line is traveling directly through the oil gallies (Mains, then cam and lifters on a SBC). On this trip the oil picks up heat from the block. Theeeennn it heads directly out to the turbos which add exponentially more heat.

I believe if you T-off mainline oil pressure immedeatly after the pump or cooler with a pressure restrictor in the oil feed lines for the turbos you can reduce the overall oil temp by spreading it across three different paths of flow while possibly adding a full quart to your sump by increasing the amount of exposed line involved.

 

[427Z06]

quote:

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Because the oil temp is measured *before* it is cooled.

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I believe va3ux nailed it. High temps in the heads from boost and the turbos are overheating the oil.

quote:

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The main oil line is traveling directly through the oil gallies (Mains, then cam and lifters on a SBC).

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I don't understand the above.

A stock Chevrolet V-8 engine uses a wet-sump system (oil reservoir located directly below the crankshaft) with internal passages within the cylinder block, crankshaft, and openings in the cylinder heads. A 1/2-inch diameter oil pump inlet on small-blocks (5/8-inch diameter on big-blocks) with an ample suction screen submerged in engine oil provides free-flowing oil to the pump, which is driven by the camshaft. The oil that is supplied to the pump travels through a full-flow oil filter into a 1/2-inch main gallery on a small-block (9/16-inch on a big-block) that is located above the camshaft. From there, the lube travels through a hole to a groove near the rear side of the rear cam bearing ('57-and-later V-8s) and is where the lifters and rear main are oiled. Additionally, all four front cam bearings have grooves that pass to each particular main bearing. Through small holes in the upper main bearings, oil passes down into the crankshafts main journals where it travels to the rod journals.

While all of this is occurring, the crankshaft is spinning and each connecting rod is throwing oil onto the respective cylinders to lube the moving pistons and rings and help seal combustion. At the top of the engine, oil has traveled from each lifter and up through the hollow pushrods, over the rocker arms, and down onto the springs and valve stems where it helps to lube the valve stems as they move in the valve guides. To keep the pressure from getting too high at the oil pump, a relief valve circulates the oil back to the inlet side of the pump when pressure surpasses the relief spring's limit.

One thing I would check for is for sufficent and properly balanced oil flow through your oil circuit. For example, too much restriction on the plumping for the coolers and filter will have you hitting the pump bypass and limiting flow.

A quality synthetic is certainly called for considering the temps.

 

[Steve S]

va3ux,427Z06 ,you are right on, I wasn't thinking.The temps should be taken after the cooler. also ,the sump temps may be too high at a constant 250/300 .Running that engine heats the oil .