Custom water/oil heat exchanger

[af300e]

Sam, is the 5s one so bad for your application that it's worth making one? I'd not be too worried about it unless there is a specific reason for your apprehension. Generally, I'd say the 5s one would be about as effective as a 3sgte one (I have both at home).

That TRD jobbie really looks just like a gen 2 3sgte version. I wonder if there is any difference?

[Sam_Q]

its a good question, lets go from the start then why I want this:

I like the idea of the oil warming up quicker on first startup and also having an oil cooler without any extenal oil lines/thermostat/cooler core. The 5S one fits like it was made for it, its just I have some serious doubts on how much it does considering it has crap all surface area for the oil to transfer the heat, the total oppersite can be said for the water though. So in my pig headedness I think I know of a better design. I just want it to equalise my oil and water temps without any real delays. With enough instruction and abuse of TAFE reasources I think I might be able to pull off making this.

That trd one looks nice, I would want straight outlets though. At this stage I am leaning towards milling one doing roughly the following steps:

getting two blocks of aluminium, machine them true and making them face each other

drilling, taping and counter-boring to make them bolt together possibly with locating dowels

drill and tap a water inlet and outlet unless I use another method to fix the steel pipes in there.

mill a cavity either side of the water pipes on the inside and from there using a dividing head and just one of the two plates cut a zig-zag slot all the way around. Repeated again for the oppersite side.

for one quarter of the section I would have it seperated for the oil, in this part I would machine a small accumulation cavity beween the two plates and then have a matrix of holes of a small diameter going to the top and bottom which the oil would work its way through. To make sure I dont strave my engine I would work out what the cross sectional area of the original oil return is and then work out how many holes I need to have the same amount as a minimum. Repeated the same for the top plate.

Finally with both sides bolted together I would put it on a rotating table and with a large end-mill I would make the outside mostly rounded shape except for around the fittings.


I really need to do a drawing.

[af300e]

I haven't had a good look at these exchangers, so I'll take your word for it that the oil surface is far smaller than the water surface. Edit: just had a squiz, the oil surface area looks pretty good, maybe you require more efficiency than my application does?

If that is the case, then since the idea is to keep the oil closer to the water temp (rather than the water at oil temp), wouldn't it make sense that there is more water surface area/volume than oil?

What I mean is, if there was more oil surface/volume than water, the water would tend to be heated/cooled to the oil temp.

Air cooled ones work like that, the oil is required to be cooled, so a small amount of oil at a time is spread thinly into a large volume of air and is thus cooled. If the reverse was true, the oil would heat up the air without losing much heat itself.

I could also present this analogy. If you put a litre of cold oil in an oven at say 100 deg, it will heat up at a certain rate. If you put 5L of oil in the same oven in the same conditions, won't it take much longer for it to reach over temperature? (The same would apply if the oil was hotter than the oven)

As far as I can see, the water jacket in the 3s type heat exchanger is larger than that of the 5s. This would make it a little more effective i suppose.

[Sam_Q]

thats a very interesting point, I will have to think about that, thanks for the tip

[oldcorollas]

i reckon if you have a water to oil cooler, it will take longer for the oil to heat up.

reason being is that oil is heated by the engine block itself when it is pumped around.. including the head (above the water), the bearings, the cylinder walls...

the water heats slower thru the block and the head galleries...

if you run oil thru water, perhaps for the first part the oil is heating the water, taking the oil longer to warm up?

i suppose ideally, you would have an oil thermostat to stop cold oil going to the cooler if the water temp is lower....



and the surface area of the 3SGTE one that horse posted doesn't look that bad...
it's not like air, where you need large surface areas... with liquids, you have excellent thermal contact, and high rates of heat transfer.... ie, if you put 100deg oil in a metal cup, then try hold the cup.... uh uh...

what AF is saying may depend on rates of flow...
in this case, the oil flow rate is known, and you can work out from the oil temp, what flow of water is needed to go for a given temp change etc..


have you measured temp of oil vs temp of water durign warmup phase without a cooler? (water temp being that which passes out of the block, not circulating inside)

if you really want to maximise heat transfer, you need to not only have more surface area, but also have more residence time....


edit: i reckon ideally you would have oil pump -> thermostat -> external oil cooler -> water to oil heat exchanger -> engine....

if you only have water to oilo, the water has to shed all the heat.
if you have external oil cooler, then you lose heat directly, and then the oil temp going back in is stabilised by the water.. either by being heated by water (adn removing more demand from radiator), or by being cooled by the water (with less demand than with no external cooler)
ie effectively having a second thermostat..... sicne the water temp is easy to control with radiator and fan etc and has a high heat loss capacity

[Pube]

I know my BF XR6 Turbo has an separate water to oil heat exchanger for the auto 6 speed gearbox. It is separate from the engine and apparently it works quite well. Worth checking out.

[oldcorollas]

KE10 corolla also have a water to oil heat exchanger for the 2 speed auto gearbox (bottom of radiator)

maybe not as purdy as the falcoon one tho

[af300e]

I just edited my post to include volume along with the suface area as the efficiency is related to both.

I had a look at the 3s exchanger I have, and it looks about right. It appears as though a small volume of oil is spread between plates in a sandwich around which flows a larger volume of water.

I like the residence time point OC. If you could slow the oil flow through the exchanger, it would make a marked difference.

I suppose another point is, do you really have a problem with your oil temp? I mean, too cold is likely worse than slightly too hot. I'd check this before adding an air/oil cooler.

I used to have a car with the required guages to show that, during warmup, the water definately warms more quickly than the oil.............unless you pull the thermostat

Anyway, on closer inspection, I'm happy that the 5s one will suit my application, however, I don't for a minute discard the fact that your situation Sam, may require a more efficient cooler/heater.

[Billzilla]

FWIW the Setrab heat exchanger used in my racing car ...

[Sam_Q]

corollas: as always you have given me heaps to think about, thanks for the tips

bill: as always I am impressed

af300e: I have thought about what you said about the temp differences and I agree with you now. I decided if I end up making my own I will modify the design to have the oil flow disproportionate to the water flow. i would do this with modification to the channels.

guys I dont know if i need this i was too busy last time to weld a boss in the sump for my electronic temp sendor last time i changed my engine. I like to have things a bit more than what I need just incase and I also like to do my research before i pick up a spanner. I will check my gauge and I will if I can get it go somewhat high give the 5S one a go, if it works well I keep it, or from what I have been told I might just straight out give a 3sge one a go.

[Bananaman]

So i'm reviving this thread as i'm looking at oil cooler options for my ke20, because i don't think i'll have space to run a conventional cooler i thought i'd look at water > oil ones (also keeping in mind my rad is about 50x bigger than it needs to be).

Looked up the xr6 ones, they seem to be lemons so abort on that, this is one of a few google results saying the same thing

http://www.motorsm.com/complaints/up...y.asp?aid=3015

That setrab unit looks good but freakin expensive:

http://www.mmsport.com.au/productvie...ab_Oil_Coolers

Are any of the standard units worthwhile or a waste of time? WRX ? that TRD one? S3 RX7?

Rx7 unit


The above having the benefit of being an oil filter relocation kit as well it seems

Any ideas if they work reasonably?

[Sam_Q]

and where is that normally fitted in the engine bay of the said RX7?

[Billzilla]

The WRX ones look pretty good.



I might be trying one on one of my racing cars.

[YLD-16L]

JZ series engines run an oil/water heat exchanger similar to that WRX one pictured above.

Not sure the JZ ones offer much in the way of cooling though under track conditions from what I've seen. More in place to heat the oil quicker from cold start.

[trdee]

adm aw11's came with a passthrough type oil/water cooler as well.