Oil cooler system?

[lindy 911]

I'm building an oil cooler system for my new 3.0 SC hot rod. I'm using AN 16 lines and fittings to a Mocal 70 row turbolator cooler (RUF) in the front spoiler. My question is; is the thermostat really necessary. If I avoid it, it simplifies my plumbing by being able to go down the drivers side rocker from the engine to the cooler and return to the tank via the passenger side rocker.

The hose offers little cooling as it is Goodridge with a braided jacket with Goodridge fittings; very trick. I could still use this set-up by running the thermo at the cooler but I would rather just skip it all together. Any thoughts?

Lindy

[burgermeister]

I'd use a thermostat and a high pressure bypass. The thermostat so the engine warms up as quick as possible, and the bypass to keep the cooler from seeing too much pressure when the oil is really cold & thick.

[86 911 Targa]

+1 That's the way to do it.

[Steve@Rennsport]

Originally Posted by burgermeister

I'd use a thermostat and a high pressure bypass. The thermostat so the engine warms up as quick as possible, and the bypass to keep the cooler from seeing too much pressure when the oil is really cold & thick.

The factory thermostat contains a high-pressure bypass and thats one of its most valuable attributes.

[boyt911sc]

Originally Posted by lindy 911

I'm building an oil cooler system for my new 3.0 SC hot rod. I'm using AN 16 lines and fittings to a Mocal 70 row turbolator cooler (RUF) in the front spoiler. My question is; is the thermostat really necessary. If I avoid it, it simplifies my plumbing by being able to go down the drivers side rocker from the engine to the cooler and return to the tank via the passenger side rocker.

The hose offers little cooling as it is Goodridge with a braided jacket with Goodridge fittings; very trick. I could still use this set-up by running the thermo at the cooler but I would rather just skip it all together. Any thoughts?

Lindy

Lindy,

Don't do it!!!!! You have to understand how the oil flow in the system works in conjunction with auxiliary thermostat. With this proposed set-up, you'll build up so much pressure and do more harm than good. Why? The circulating engine oil from the engine will have no place to go. The way the system is designed, is for the engine oil to warmed up initially controlled by the engine cooler then go back to the oil tank. The oil keeps circulating via the auxiliary thermostast's by-pass valve and back to the oil tank.

The auxiliary thermostat does not come into play until around 186°F and when it does, it gradually change the oil flow. Instead of directly all (100%) going back to the oil tank containing already the warmed oil, the return line from the auxiliary cooler starts to flow. So a steady flow rate change is achieved. In plain words, the cross-sectional areas (close / open) of the by-passed and return valves are kept the same or equal thus maintaining a steady uniform flow.

You need to use the auxiliary thermostat unless you have a better designed configuration than what Porsche engineers have done. If you have any question/s or concern, bring it up and we could all learn from this forum.

Tony

[lindy 911]

So I guess the biggest problem is the cooler seeing too much pressure. If I use a thermostat at the cooler it would prevent this and I could still use the up and back routing on the left and right rockers. This system would mean warming up about one more quart of oil but in the grand scheme of things that seems pretty insignificant considering the size of the oil tank. You would have to warm all of that oil anyway.

Interesting comments; thanks for the input.

Lindy

[Elombard]

Curious how you are going to route down the drivers side? Are you coming right off the engine case and skipping the hard pipe that goes under the motor?

I cant remember how does the oil from the on engine oil cooler get into the system if you do that?

[JFairman]

[QUOTE=I cant remember how does the oil from the on engine oil cooler get into the system if you do that?[/QUOTE]
It doesn't and never will...
The scavange and main pressure oil circuits are completely seperate, alot of people posting don't know how this dry sump system works.

After oil is hot enough to be routed to the engine oil cooler from the engines onboard oil thermostat it goes directly to the oil galley in the case and then to the crankshaft bearings and rod bearings, and whats left over goes on to the chain tensioners, cam journals, and cam spray bars.

[lindy 911]

The pressure side of the oil pump gets it's supply directly from the oil tank. There is no circulation other than from the tank to the pump and then on to the engine thermostat. The thermostat either sends the oil through the engine mounted cooler or directly to the oiling circuits in the engine depending on temperature.

The oil from the pressure side ends up in the case sump where it is picked up by the scavenge side of the pump and is returned to the tank either directly or via the cooler by way of a second thermostat.

So yes, the hard pipe is eliminated and a fitting from the case where the hard pipe once was adapts the 16 AN line. This line goes up the drivers rocker and connects to the front mounted cooler. This will be done with either a thermostat inline or not; haven't decided. Once it leaves the cooler it travels down the passenger rocker and returns to the tank cooled. Basically, the scavenged oil from the sump is what flows up to the cooler and back to the tank. The scavenged oil has nothing to do with the pressure side of the system other than replenish the tank.

Lindy

[JeremyD]

I am in the middle of planning this - I plan on using the factory hard lines from the engine to the thermostat and use the factory thermostat - Then use Aeroquip -16N into a front mounted cooler.

You want the oil bypass that the factory thermostat provides. Don't skimp on size

[DW SD]

Originally Posted by lindy 911

So I guess the biggest problem is the cooler seeing too much pressure. If I use a thermostat at the cooler it would prevent this and I could still use the up and back routing on the left and right rockers. This system would mean warming up about one more quart of oil but in the grand scheme of things that seems pretty insignificant considering the size of the oil tank. You would have to warm all of that oil anyway.

Interesting comments; thanks for the input.

Lindy

In general, a thermostat is not a pressure relief valve. The Porsche factory unit serves both purposes. Many folks here have blown up coolers due to thick oil from cold nights when they've run without the factory thermostat. Search on popped cooler or something similar.

The factory thermostat / unit is expensive, but not as expensive as replacing a cooler.

Doug

[Grady Clay]

NO,

This is not how the system works.

The front cooler thermostat and pressure relief valve needs to be in the shortest circuit back to the oil tank from the engine.

Having the oil go down the driver’s side and back the passenger side is just fine so long as the thermostat ‘short circuit’ flows cold oil directly from the engine to the oil tank with the shortest possible path. This is critical. Anything other will overpressure the front oil cooler.

The system you propose will cause the front cooler to fail.

It is absolutely essential that the thermostat/pressure relief valve be situated where the cold oil has the shortest path possible from the engine to the oil tank.

Best,
Grady

[86 911 Targa]

Originally Posted by lindy 911

The pressure side of the oil pump gets it's supply directly from the oil tank. There is no circulation other than from the tank to the pump and then on to the engine thermostat. The thermostat either sends the oil through the engine mounted cooler or directly to the oiling circuits in the engine depending on temperature.

The oil from the pressure side ends up in the case sump where it is picked up by the scavenge side of the pump and is returned to the tank either directly or via the cooler by way of a second thermostat.

So yes, the hard pipe is eliminated and a fitting from the case where the hard pipe once was adapts the 16 AN line. This line goes up the drivers rocker and connects to the front mounted cooler. This will be done with either a thermostat inline or not; haven't decided. Once it leaves the cooler it travels down the passenger rocker and returns to the tank cooled. Basically, the scavenged oil from the sump is what flows up to the cooler and back to the tank. The scavenged oil has nothing to do with the pressure side of the system other than replenish the tank.

Lindy

Here you go..........

And,

God luck,

Gerry

[Elombard]

Thats what I was thinking, if you just by pass the cooler with your up front thermostat there will be issues. I am thinking I have never seen an oil line up the drivers side even on a race car.

[arrivederci]

Grady,

Any thoughts on how this works with the thermostat on a '72 oil console? My car has (had) a mocal thermostat, but in my rebuild I'm going to plumb it the way the factory did utilizing the built-in thermostat on the oil console. I'll also have a cooler in each front fender (lines running along the passenger side).

[Grady Clay]

When cold, this (red) is the route of the oil.
Note that it is short.
Note there is no pressure relief in the crankcase.
Note the diagram shows the long path to the front cooler with a broken (long) path.
Note also the ‘trombone’ cooler (high pressure resistant).

In ’73 (only) Porsche did away with the pressure relief valve. That was because they only used the ‘trombone; cooler (even on the Carrera RS). On that ’73 (only) system, if you replace the trombone with a real cooler, it will fail from over-pressure. Ask me how I know X 40+.

Porsche put the thermostat/relief valve just ahead of the RR wheel (’74-’89).
The ’72 911S is unique with the functions in the oil filter console.
The ’69-’71 911S has a separate oil pressure relief valve.
That all seems to work OK.
Better is to shorten the cold oil path.

Never, ever put the thermostat/pressure relief valve in the front of the car.

Also keep in mind that a Mocal is only a thermostat.
It is NOT a pressure relief valve.

Anyone considering a (race) front oil tank, consider the GT2 & GT3 system.
There is a valid engineering reason.

Best,
Grady

[lindy 911]

Grady,

Making sure I have this straight, even with the oil hot the scavenge pump will make too much pressure to run through the cooler without relief from a high pressure by-pass of some sort. Is that right? If so I can understand the problem and that's why I posted here.

I have these really nice 16AN lines and fittings that look a lot better with only one on each side instead of trying to run two together up one side. I think I can still make this work with the thermo-press-relief circuit in the engine bay, just a little more complicated.

I'm running in the motor this weekend without any of this set up yet, just the scavenge going straight back to the tank. It'll keep all the molly and such out of the cooler and lines anyway.

Thanks for your input.

Lindy

[Grady Clay]

Originally Posted by lindy 911

Grady,

Making sure I have this straight, even with the oil hot the scavenge pump will make too much pressure to run through the cooler without relief from a high pressure by-pass of some sort. Is that right? Lindy

Yes.

More severe with cold oil.

EDIT
Here is the issue:
When ‘parked’ with hot oil, the oil will gravitate to the sump (bottom of the engine).
When you first fire up the engine, the sump scavange pump will see only solid oil (no entrained air).
With no pressure relief in the crankcase, the engine relies on the external pressure relief valve to prevent damage to the system.
If there is not an external pressure relief in place, damage will occur.


Best,
Grady