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

[VaccaRabite]

My 2056 is getting elevated oil temps on the freeway. I am using a high volume pump, and seeing about 40 pounds of pressure on the freeway when my oil is up to temp.

What I think is happening is that there is too much pressure, and the oil is not being pumped through the oil cooler due to the check valve closing the passage. However, this is just a guess, as I don't have any way to test it. All I know is that when I am driving at revs, oil temp goes up and if I keep driving at higher revs the oil temps stay up). if I drop revs, oil temps fall back into place, but I can't do that on the freeway without building a lot of head heat.

Before I go through the trouble and expense of adding an oil cooler, I want to make sure that I have checked out the simple fixes first.

What do I do to make sure oil if going through the oil cooler? What is the point where pressure cuts off passage through the cooler?

All tin is in place, and fan housing flaps divert air over the oil cooler 100% of the time (no thermostat in place, so the flaps are always set to cool).

Zach

[HAM Inc]

You need to keep in mind that all of the oil does run through the cooler before it hits the bypass valve.
Tight piston clearances will cause high oil temps.

[tradisrad]

I'm curious how high oil pressure makes the oil temp rise?
My car does not run too hot, between 180 and 220, and my oil pressure is 60 psi on the freeway and over 80psi (pegged gauge) on cold starts.
Also, Zach mentioned that there is a check valve to bypass the oil cooler how and at what pressure does this work?

[VaccaRabite]

You need to keep in mind that all of the oil does run through the cooler before it hits the bypass valve.
Tight piston clearances will cause high oil temps.

Interesting. Is the bypass valve just for the oil filter? I thought it was for the oil cooler. So adding a more powerful spring would have zero effect in this case, as it makes no difference if the valve is open or closed?

When you say tight piston clearances, do you mean the piston on the spring that works the valve, or the 4 biggies that move the car?

Learning every day.

Zach

[DanT]

When I built my 2056 I did away with the thermostat for the motor and permanently put the flaps to the position to always direct air over the stock oil cooler...I also ran a very large cooler and fan up front...
Car never had an issue with temps...but I also ran stock oil pump and did not change any of the bypass springs...also ran a Tuna Can.
I had good oil pressures at all operating RPMS and temps....

[HAM Inc]

Zach the pressure bypass drops the pressure in the entire circuit from the pump to the bearings. It doesn't matter which end of the circuit the relief occurs. That is the cool thing about the circuit design. Bypassed oil has already been through the cooler before it is dumped back into the case. And since a certain amount of oil is always being bypassed (if the system is working properly) you have a % of oil that routes through the cooler more than once before it sees the bearings.
By tight piston clerances I meant the piston to cylinder clearance of the 4 pistons.

[VaccaRabite]

Okay. Bear with me, as I am just thinking through my fingers right now.

If a percentage of the oil is always going through the cooler, would adding a stiffer spring to the relief valve increase or decrease the percentage of oil going through the cooler? Or would it give no change to the oil going through the cooler?

I don't think that my pistons are too tight. before I put the rings on, you could put them in and out of the cylinders w/o issue.

Zach

[mightyohm]

What oil temps are you actually seeing?

[jhadler]

...Tight piston clearances will cause high oil temps.

Thanks! I guess I kinda knew that in the back of my head, but seeing it written but one who knows has reminded me again to look at everything on my few hours old rebuild that was running way too hot.

Haven't had the time to finish the full tear down as work and family obligations have priority. But I've now got a clean bench in the garage, and will start going over it in detail.

Just to ask the question... What is the mechanism for the high oil temps with tight pistons. Is it just ring-wall friction wear that causes it? Or something else?

I found out later on that the builder claimed to have needed to "hammer" the pistons into the cylinders... Might be my culprit...

Sorry for the hijack....

-Josh2

[VaccaRabite]

What oil temps are you actually seeing?

235-245 when on the freeway, before I get off the freeway and hit the side roads so my car cools down. Right now I am just not on the freeway that much.

Zach

[Spoke]

I could try blocking the vents at the bottom of the car.

These are the tubes that used to go to the heat exchangers, correct?

If you think about it, with all the HE stuff in place, blowing air in the HE would cause some backpressure and limit some of the volume of air flowing.

Now you have removed the HE and all the tubing so the little stub of the tube on the fan assembly has no backpressure and would allow more air to escape to the atmosphere instead of being forced across the cylinders and oil cooler.

Kinda like if you put a big hole in the top of the fan shroud. The air will blow out through the hole where there is no backpressure instead of going across the cylinders and oil cooler where there is some resistance to air flow.

You don't want any air escaping from the fan shroud that could be going to the cylinders and oil cooler.

[jhadler]

I forgot who originally mentioned the cavitation issue with block off the HE ports (Jake probably?). But I do see how it's possible if you're not venting enough pressure that you can decrease the efficiency of the fan by retaining too much pressure downstream of the fan blades.

Perhaps a small hole in the block-off plate to allow some of that excess pressure to bleed off?

-Josh2

I could try blocking the vents at the bottom of the car.

These are the tubes that used to go to the heat exchangers, correct?

If you think about it, with all the HE stuff in place, blowing air in the HE would cause some backpressure and limit some of the volume of air flowing.

Now you have removed the HE and all the tubing so the little stub of the tube on the fan assembly has no backpressure and would allow more air to escape to the atmosphere instead of being forced across the cylinders and oil cooler.

Kinda like if you put a big hole in the top of the fan shroud. The air will blow out through the hole where there is no backpressure instead of going across the cylinders and oil cooler where there is some resistance to air flow.

You don't want any air escaping from the fan shroud that could be going to the cylinders and oil cooler.

[Spoke]

I thought cavitation was in respect to closing off the HE at the output of the HE or just leaving the HE on with no air flowing through them. Then you have a cavity. I'm not sure how the little (about 6 inch) part of the tube on the fan shroud could cause the fan to be less efficient.

One could block off the entrance of the tube inside the fan shroud to allow air to flow more efficiently to the cylinders and oil cooler.

[underthetire]

Wouldn't blocking them off be the same as if you had a nice tight heat exchanger system and simply closed off the flapper valves with the heat lever ? I don't see how blocking off the shroud ports would be any different than that. I guess it could make a difference at a constant 8K rpm, but I will never see that kind of RPM.

[HAM Inc]

If a percentage of the oil is always going through the cooler, would adding a stiffer spring to the relief valve increase or decrease the percentage of oil going through the cooler? Or would it give no change to the oil going through the cooler?

The stiffer the spring the higher the oil pressure and therefore the less bypass oil. Zach what is your oil pressure at the highest temps, 235-240?

Just to ask the question... What is the mechanism for the high oil temps with tight pistons. Is it just ring-wall friction wear that causes it? Or something else?

The friction is from the pistons dragging down the bores. Piston friction also increase if the jugs aren't square to the crank center line. That also leads to poor head sealing too. The head sealing issues are not as easy to pickup on as you might think. Jake is damn good at detecting it, but he has had some practice!

[AndrewP]

Do you know if your oil temp gauge is accurate?

Andrew

[r_towle]

Do you think your header might be adding heat to the motor?
How about some header wrap?

I dont remember how its designed but is there a tube or two that run under the motor and could create some additional thermal heating to the motor?

Did you have the case machined square prior to the build?

Rich

[VaccaRabite]

[quote name='HAM Inc' date='May 17 2010, 05:37 PM' post='1319705']
[quote]If a percentage of the oil is always going through the cooler, would adding a stiffer spring to the relief valve increase or decrease the percentage of oil going through the cooler? Or would it give no change to the oil going through the cooler?[/quote]
The stiffer the spring the higher the oil pressure and therefore the less bypass oil. Zach what is your oil pressure at the highest temps, 235-240?

35 psi when it gets hot cruising on the highway. I have only let it get there twice though. By the time the oil gets that thin I am looking for an exit.

At idle it will be about 10psi.

Rich, I might consider some header wrap for the pipes thatgo under the case. The headers are ceramic coated coated so they should not rust.

[r_towle]

I had a decent idea for your header leak issue.

Cut a star that would fit into the middle of the pipes but it will only fit if the middle is higher than the points.
This would raise up the middle so you CAN get to it with the mig gun.
The sides and outer areas you can already get to...
Try it with posterboard....you will see what I mean.

Rich

[HAM Inc]

35 psi when it gets hot cruising on the highway. I have only let it get there twice though. By the time the oil gets that thin I am looking for an exit.

At idle it will be about 10psi.

Zach that is propbably in the 10lbs/1000rpm's range. You sure don't want a softer bypass spring. I would be inclined to leave that alone and look elsewhere for your heating issue.

What is the history of your O.E. cooler?

[VaccaRabite]

What is the history of your O.E. cooler?

Came with the motor. I flushed the inside with oil and made sure the outside had no obstructions that would block air passage when I rebuilt the motor. I did not have it ultrasonicly cleaned.

I am using a EuroRace header, and the drivers side pipes do pass right under the oil pan, so that can't be helpful.

So, right now, these are the actions I am going to take:
1) Cap the stubby vents that are supposed to go to the heaters that currently just vent to open air, and see if that puts more air into the tins.

2) Try to add a little more advance to the timing (go from 28* to 30* and see what happens).

3) add a little header wrap or header blanket to the pipes that cross under the engine case.

Do the experts here see any issues with this plan?
Zach