Oil Cooler?

John and Sue wrote:

Sergi Bmw wrote: I had this very doubt when I was about to purchase my oil cooler (In my case not a 20quid part)
What is actually better? Water to Oil or Air to oil...
Bearing in mind the TF 160 has already a water to oil cooler but it's not the perfect system... I asked Mr. Blackoctagon about this very same question and here you have his aswer :broon:

I think it is enlighting for non engineers drivers:

PS: I am relocating to Spain and intention of doing many track days over there. :yesnod:


Mr Sergi,
If heat removal in a hot climate with a high duty is the only consideration then I would choose the crossflow heat exchanger type (Air to oil) as it will give the best temperature differential and the reduced fluid-to-fluid heat transfer coefficient that results from air-to-oil will be more than compensated by the extended surface area.


I'll assume you have no engineering background -

The transfer of heat between two fluids is dependant on
1. The surface area between the two fluids (the meniscus),
2. the thermophysical properties of the fluids,
3. the thermophysical properties of the meniscus,
4. the difference in fluid temperatures.

You then have to overlay that with the flow rates and thus the velocity of the fluids - this impacts how the fluid flows over the surface (turbulent or laminar)

You can safely assume that the flow rates of the air, water and oil will be such that the flows will all be turbulent.

A air-to-oil cooler has a poor fluid thermophysical behaviour, a good material one, and a good surface area. It also has a good big temperature differential - Lets say 110oC oil and 30oC air.

The water-to-oil cooler has a smaller surface area, good fluid thermophysical properties and a good material one. It has a smaller temperature differential - Let's say 110oC oil and 95oC water.

On that balance the air-to-oil is the better unit.


The advantage to the water-to-oil unit is that it creates less pressure drop in you oil system, so the delivery pressure of oil to the bearings and cam is higher and so it supports more load and prevents wear better.

BUT hotter oil supports less load.

This means that although the air-to-oil will give less delivery pressure it will give cooler oil that supports load betterl.

In competition and OEM engine design for high performance vehicles we would do experiments, and perhaps choose the air-to-oil, but flow/modify the oil pump to try to get back some of the pressure.


On the basis of the above, and assuming you really will be driving hard, for a good distance, in high heat i'd have to recommend the air-to-oil unit.
For me here in Scotland where it is rarely warm, and who does not race I would choose the water-to-oil unit.

I hope that all explains the reasons for my answer.



PS2: I am upgrading the oil pump as he suggested :beer:

...I could argue against some of these conclusions with regard to the specific heat capacity of air and laminar flow.....but I wont! All I will say is that I would go for oil/water....

Why not? We are here to learn and any discussion is welcome, remember it is not what I am saying! (I don't have this knowledge in the field) is what a member from .org has adviced me. I did follow his advice, maybe he is wrong? Could be but certainly my system would be better than a stock one and is a messure of prevention against the HGF.

Ozzy wrote:
that is only true for a certain window of oil temp, ie greater than (lets say picking a random number) 120C, this number will vary on the grade of oil used in the engine, and if it is a mineral of synthetic type...


but yes i agree with the rest you said

oil -> air with a thermostat in racing may give a marginal advantage, but lotus's 24Hr Evora endurance racer GT2, GT3 and GT4 cars all use twin Laminova OIl -> Water coolers as it provides a better thermal working temp for the whole system without random high and low points at lower and faster velocities, thus creating a more consistant working temp, and a lower delta between the oil and water, thus prolonging the life of the engines....

they run this set up on their 280bhp GT4 and 440bhp GT2... both with great results...

personally i would go for oil -> water every time and if my temps were getting too high invest in a higher flow radiator and water and oil pumps...

again my 2p's worth.

Oz

Thanks Oz! Well I could be wrong but the system I got was tested by Jon Norris, so I trust him as well. At the end of the day as I said the point was to improve the whole system and that will happen no matter what oil cooler you choose. I will have a mild twisted engine with just around 180HP. So hopefully will do the job.

Jack of Hearts wrote: When I mentioned 20quid part I was refering to the thermostat not the whole system :coat:

Sorry then! :oops:

I thought it was the whole oil cooler :bang: