Water to oil cooler

[lrov90]

Hi guys,

I just though I would add this to the forum for peoples future reference.

When we first had our twincam Europa on out on the race track I found that when it came into the pits it was struggling to hold oil pressure at idle. After 15 minutes of cooling with then engine off, idle pressure was good again.

I noticed that Pfreen had a post about his water to oil cooler, so I contacted him and he kindly provided some photos of how he did it.

I have attached some photos of how I went about it, although I used a slightly shorter cooler than Pfreen.

Today we had the car out on the same track again in about the same ambient temperature and the idle oil pressure was normal when the car came back in. I will take that as success!

The car also a new, but Chinese aluminum radiator.   

Cheers

Gav

[jbcollier]

Very interested!

Did you have an traditional air/oil cooler before?  If so, what size and location?

[Grumblebuns]

That cooler is tiny, how can something so small be so efficient.

Joji Tokumoto
Fallbrook, Ca

[EuropaTC]

Agreed, it is a tiny thing but we don't know what the internal construction is like. I remember seeing a spiral plate heat exchanger which had a small footprint but apparently high efficiency, so this might be something along the same lines.

When I first read the post my initial thoughts were "why not a conventional air/oil unit" but perhaps you don't need such a massive drop in oil temperature to drop the oil back into it's working range and hence don't need the cooling medium to be as low as 20-30C from ambient air (or <20C as is more likely over here !)

Brian

[BDA]

I had always thought water/oil heat exchangers didn't make any sense especially in a car with such a marginal cooling system. Also cooling hot oil with 180°F water seemed silly compared with 80°F air. It certainly appears I had been vastly underestimated the efficiency of the water/oil heat exchangers. They are apparently much more efficient compared to air/oil heat exchangers than I expected. It would be interesting to see actual temperature data.

[4129R]

IMHO, if the cooling ability of the water radiator is questionable, adding oil temperature to the water is increasing the risk of the engine overheating, and the head gasket failing.

I am a doubter.

[lrov90]

To answer a few questions....

No the car never had an air to oil cooler before. The engine is however just a stock stromberg TC, so in is not producing any extra power to cool.

I too was a bit sceptical about water to oil cooling. I did a fair bit of research before hand. Mocal/laminova quote that even this small cooler has the equivalent cooling capacity of a 10 row air to oil cooler. Also the Lotus Elise / Exige guys have been using them on their cars with success.

I looked at installing an air to oil cooler but if it was placed at the rear of the car and shrouded I wasn't confident in the actual airflow for cooling it would get. Running oil lines all the way to the front of the car didn't grab me. Apart from the plumbing and aesthetic issues it would have added complexity to oil changes. I suppose I was taken too by the neatness of the water to oil cooler being unseen under the car.

Some manufacturers like Toyota and VW have used water to oil cooling in the past.

At this stage there has been no apparent rise in coolant temp. With the new / clean aluminium radiator that is properly shrouded, is the Europas water cooling really that marginal? Just speculating, but the engine is producing X amount of heat, so by removing some of the heat from the oil, would that not lower the amount of cooling required from the coolant flowing through the head / block?

Unfortunately I never did have an oil temp reading before hand so I can't make a justified comparison. Also the outside air temp has been less than 25*C so far.

No saying that this is the ultimate solution, just that it has worked for me so far.

[jbcollier]

Oil/water coolers are much more efficient than oil/air coolers so they don’t need to be that large.  Added bonus is that they also warm up the oil quicker.  However, they do add a heat load to the cooling system.  You can only find out by experimentation if it is going to be a problem.

 A significant bonus is that the oil system is also much simpler and less restrictive than a traditional front mounted oil/air cooler with an oil thermostat.

Please also note that while an alloy radiator is significantly lighter than the stock copper rad, alloy rads are not as efficient at transferring the heat to the passing air.

[EuropaTC]

(Edited Quote)
I too was a bit sceptical about water to oil cooling. I did a fair bit of research before hand. Mocal/laminova quote that even this small cooler has the equivalent cooling capacity of a 10 row air to oil cooler. Also the Lotus Elise / Exige guys have been using them on their cars with success.

Some manufacturers like Toyota and VW have used water to oil cooling in the past.

With the new / clean aluminium radiator that is properly shrouded, is the Europas water cooling really that marginal? Just speculating, but the engine is producing X amount of heat, so by removing some of the heat from the oil, would that not lower the amount of cooling required from the coolant flowing through the head / block?

Thanks for coming back with some more detail, the more I think about what you've done the more I like the concept for cars such as ours.  Back in the 80s we had a Hillman Imp which I tuned (badly) and fitted an oil cooler to. The engine was rear mounted and both radiator and oil cooler were also at the back. In hindsight I'm not sure how much good it was actually doing there, but as you say moving a cooler to the front is a lot of complication. So what you've done is a neat idea.

Looking at the Laminova website I can see why they claim such efficiency, that's an interesting core design they have there. I didn't expect it to be a simple tube exchanger and it's not !

On the second point of marginal cooling, we know the Stromberg engines used to run hotter than weber/dellorto engines from new but as Lotus didn't increase the coolant capacity I guess they didn't have problems with claims. And of course you have a gauge to monitor what's happening to the engine temperature so you've got the important bits covered.

Thanks for posting.

[4129R]

Just speculating, but the engine is producing X amount of heat, so by removing some of the heat from the oil, would that not lower the amount of cooling required from the coolant flowing through the head / block?

Newton's Law of Cooling. The rate of cooling is proportional to the temperature difference, so very hot oil or exhaust manifold, or sump, loses heat far quicker that 90'C water in the cooling system.

So cooling oil at say 110'C in an air cooler with say 20'C air temp, will lose heat far quicker than running 110'C oil next to 85'C water.

Physics from 1969. I hope I remember it correctly. 

[BDA]

You're right. That's part of it but there's efficiency of the heat exchangers, coefficients of heat transfer (and probably several other coefficients I don't remember), air and water flow rates and probably still more factors to consider. Alas, since I gave up being a mechanical engineer thirty years ago, I just remember enough to know I've forgotten A LOT.

[jbcollier]

Yes and no.  You are comparing apples and oranges.  The higher the temp difference the greater heat transfer in an otherwise unchanged system.  A better way to compare oil/air and oil/water is by comparing standing naked in 32F (0C) air with doing the same in 32F salt water.  No change in temperature difference but an enormous change in the rate of heat transfer.  The rate of heat transfer is so much greater in a oil/ water system that small temp differences still result in high heat transferance.

[EuropaTC]

I'd agree with the basic principles of temperature differences but as John says, the total heat content removal isn't purely dependent on the differential temperatures, other things come into play such as the density of the media, the arrangement and type of heat transfer surfaces, etc. (I chuckled at the "stand naked" idea but don't think I'll try it myself)

I also suspect the dT is greater than 85C:110C if the 85C is coming from the temp gauge in the cabin. That's recording the water temperature at the thermostat where it leaves the head whereas by the time the coolant has travelled up to the front it's lost some temperature via the steel transfer pipes before entering the radiator. Then it loses even more before heading back to the engine bay. If the cooler is plugged in the water return immediately prior to the engine it wouldn't surprise me to hear that we're looking at 40/50C by then. 

Add in the more effective heat transfer of water than air and yep, I can see how such a small thing could work. And when you look at the cores that Laminova show on their website, it's an impressive heat transfer surface they've managed to achieve in such a small package.

http://www.laminova.se/technology/the-core