Cold Oil into Hot Engine from Oil Cooler

[pigsear]

Hi All,

A couple of questions:
1) I will be installing a 427 All Alloy Engine (351Z Ford block) into my car and was contemplating if it was necessary to install an oil cooler (Probably a Mocal 235x 19 Row or what fits and it the largest). Hence the questions is it prudent and if so, what size are people installing, and
2) I am interested to know if cold oil suddenly circulates in a hot and high revving engine would this cause much of an issue. I ask this as I figure if I had an oil cooler on thermostat control, the first time the thermostat opens up it would allow "cold" oil that has sat inside in the oil cooler to hit the bearings.

Initial thoughts are:
I would re-route the oil using a sandwich plate at the oil filter (I would be using a solenoid pressure actuated Accumulator teed in the circuit near the sandwich plate oil inlet with a one way check valve just upstream) with a separate in line thermostat.

Oil will likely be 20W50 as I live in Brisbane, Queensland if that is relevant.

[Modena]

I am using an "ImprovedRacing" thermostat that avoids this, here is an excerpt of their explanaion of how the unit operates;

https://www.improvedracing.com/

The way it works is there is a bypass valve in the center, that connects the two sides together. This valve is normally open when the oil is cold. Because there is more resistance for the oil to flow through the cooler and lines, over 90% of the oil simply flows through this bypass and goes back to the engine.

We do it this way instead of cutting flow off to the cooler completely because:
1. It prevents the system from being "shocked" by a sudden flow of cold oil in the cooler
2. It prevents air bubbles from accumulating in the lines or cooler
3. It allows oil in the cooler to be drained more easily.

When the oil reaches operating temperature, the valve closes the bypass, and all of the oil is now forced through the cooler.

[pigsear]

Thanks Modena, read the information on the website and the product is reasonably priced. Also they stick with an aluminium theme, compliments the PACE build and motor! Cheers, Pigsear.

[bobcowan]

Oil is heated primarily by rpm's. If you're road racing and ppushing the rpm's hard, the oil will get hot enough to be a small problem. On the street, drag strip, and autocross course, the oil generally stays within 10-15* of the water temp.

The bottom line is, unless you're road racing, skip the cooler. It will only add weight, complexity, cost, and failure points.

Some people like to install the cooler in the lower opening just for looks. If that's the case, don't connect the lines to the engine.

[Gav]

Unless you are planning to drive your car in sub zero temps your oil won't get cold enough in the cooler to cause issues.
Here in Oz we don't get the extremes that they do elsewhere.

A cobra looks a bit funny IMHO without an oil cooler up front though!

[AL427SBF]

Originally Posted by Modena

...
1. It prevents the system from being "shocked" by a sudden flow of cold oil in the cooler ...

Is this correct? I think they mean prevents the system from being "shocked" by a sudden flow of cold oil in the engine.

[bobcowan]

Originally Posted by Gav

Unless you are planning to drive your car in sub zero temps your oil won't get cold enough in the cooler to cause issues.
Here in Oz we don't get the extremes that they do elsewhere.

A cobra looks a bit funny IMHO without an oil cooler up front though!

Not true. Doesn't need to be sub-zero to create a problem. It's common for me to leave the house in the morning with temps in the 40's. On a highway cruise, there's a lot of air flow and not many rpm's. Even with the thermostat "closed", the oil would not get to operating temp. Tried covering with duct tape, plastic, and cardboard. Those things helped, but the oil never really got up to temp.

Originally Posted by AL427SBF

Is this correct? I think they mean prevents the system from being "shocked" by a sudden flow of cold oil in the engine.

Both, actually.

If the oil is cold, and you get on the throttle a bit, the oil pressure rapidly rises with rpm's. If the oil is too cold and too thick (a lot of people use 20W-50 oil), you can actually burst the oil cooler from the pressure spike.

If the oil in the cooler and lines are cold and the thermostat suddenly opens on a warm engine, then a thick and cold slug of oil will hit the bearings, rotating assembly, and valve train. If you're at speed, bad things will happen.

Using something like a 5W-30 or 0W-30 oil will help prevent all those problems.

[Gav]

I agree that for you guys in the colder parts of the world it may cause an issue, but I don't think there is an Aussie cobra owner that has ever had to deal with a cobra that doesn't get up to temp.

For your application, perhaps you need to get rid of the oil cooler? Sounds like it is capable of doing more harm than good.

[Tonus72]

Fake sidepipes, fake oil cooler, fake Ford engine (in my plan anyway...) - anyone would think we are building fake Cobras!!?


(edit: sorry - replica sidepipes, replica oil cooler, replica Ford engine (?) = replica Cobra)

[Towmaster]

So who is going to go flogging their cobra around a race track in Australia before the oil has got up to temp?? Unless of course you are in goulburn.... The other thing would be to get rid of the thermostat. For most Australian Cobras the cooler is for 'the look'. Unless you are going to race it then it is not necessary. I raced mine for years without a cooler. 8 laps at Queensland Raceway sent the temps a little too high for my liking so I installed an oil cooler. Have been racing mine (now retired from racing it) for years and no issues with cold slugs of oil. If you are that concerned then I would get a heat exchanger instead of an oil cooler. A lot more efficient at getting the oil up to temp quicker and keeping it within 5 degrees of water temp. V8 Supercars only use heat exchangers if anything.

[bobcowan]

Originally Posted by Gav

For your application, perhaps you need to get rid of the oil cooler? Sounds like it is capable of doing more harm than good.

It was. So I did.

Originally Posted by Towmaster

If you are that concerned then I would get a heat exchanger instead of an oil cooler.

A much better choice. If you're going to insist on putting some kind of oil cooler on your street car, this would be it. That's what Ford does. The down side is that you're putting the thermal load into the cooling system. Might be a good thing, and might not be.

The bottom line is, though, for a street car you just don't need anything extra.

[pigsear]

Thanks for the replies everyone. I shall forego an oil cooler (air con cooler may go there yet!). I shall see if my needs require it later down the track. Also found out 10W40 is the oil I supposed to use...