Stock ATF Cooler revealed

[phosty]

Hi, since I replaced my VR4s leaking radiator a couple of months back (replacement courtesy of Mo) I was getting around to chucking out the old one at the weekend.

Now I had my Leggie down at Knockhill Racetrack a month or so ago and it was great fun but......I got the flashing 'N' light on the dashboard after 20 or so spirited laps and brought it into the pits to let the autobox cool down.

I know from reading the forum that the stock VR4 ATF cooler isn't really up to the task for track days but out of curiosity I thought I would see just what it looks like and hacked the old one out of the radiator.

It really isn't much at all - just a hollow tube. So I'm guessing even a relatively small additional cooler in series will give big cooling gains:


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[Wouter]

Thats Tiny!

[bradc]

that couldn't cool the breath of a single ant!

[jpnvr4]

WTF is that!!! that's sooo small ... No wonder I neary messed up my gear box ... geez what were they thinking???

[Kieran]

Good lord, that really is sod all cooling, isn't it!!:speechles

[Physician]

that couldn't cool the breath of a single ant!

Bet it can Brad! What volume are we talking? :scholar:

[bradc]

considering it gets passed through the bottom of the radiator through very hot water, it is likely to heat the breath of a single ant.

[I-S]

Except that the ATF usually runs at higher than boiling point (ie it is hotter than the water in the rad) so the net effect is that the ATF is cooled. Ref the second law of thermodynamics:



Heat cannot of itself pass from one body to a hotter body

However, that really does look pathetic... no wonder ATF coolers have such an effect!

[stuartturbo]

Is that not there to stabilise the temp rather than cool alone
Fluid is over cooled from the fin cooler then brought to close to engine temp via the rad
Heats gearbox up better on cold days and some "limited" /lol cooling on hot days

[phosty]

If I was really interested (and sad - and bored) I could hook up some hoses, a metering pump, a water bath and take some temperature readings so I could calculate a UA value for the exchanger. Then we could compare to the figures for aftermarket models.

But I would have to be really bored and it would only tell us what we already know - it's crap!

Now where can I find a metering pump....

[BuzzPuppy]

Are you serious? That's it? I know what's happening when mine gets delivered then!

[Subaru ETA]

thats all that most std atf coolers are in most cars!

[Davezj]

What were people expecting, it's immersed in very hot water all of it's life. and it can't disrupt the flow of water. I am just surprised it is double skinned, I thought it would be just a tube with end caps. It is quite a clever design, almost doubling it surface area. Keeping a thin stream of hot atf in contact with the cooling water at any one time getting maximum cooling.

For example, it is much more efficient (greater cooling effect with the same amount of puff) to blow on a saucer of tea to cool it down than blowing on the top of a large mug to cool it down. Now imagine a constant stream of tea of the same volume as the mug, but only a saucer thick flowing past you, a constant puff will cool the equivalent volume of the mug so much quicker than blowing on the top of a full mug.

ATF cooler is Simple yet effective, for normal driving.

well that is my opinion.

[White Lightning]

:speechles

[bradc]

but remember the water it is sitting in is at about 90C, maybe more, it isn't going to do a very good job of cooling it!

[colVR4]

Depends on the temperature of the ATF. If the ATF is entering at temperatures well in excess of 90C, is will cool it considerably.

[stuartturbo]

I think that there more to ensure the oil is at operation temp
that is not THE cooler. The cooler is air cooled with no thermostat in colder temps you run a greater risk of over cooling the ATF fluid which would result in a poor change and increased wear.
Odd's on the water is at 90 -110 degC close to oil temp operating range

[Nick Mann]

Oil runs at hotter temperatures than water. I assume you lot are all aware of that? The radiator will cool the oil down to to the water operating temp. Any more and it could be over-cooled. As said above, the cooler is fine for everyday use. In very hot envioronments and extreme use it is a good idea to add extra cooling to help. If I were going to fit an extra cooler, I would fit it before the radiator cooler and leave that system in place. As Stuart said above, the radiator can act as a stabiliser for the ATF as much as a cooler.

[colVR4]

Thats exactly what I have done with my ATF cooler, it is fitted before the standard cooler to make sure that the ATF is not overcooled.

[amsoil]

Good to see that the correct answers and solutions come out in the end. If you are going to push the car on the track just make sure you fit a cooler like Nick says; the harder you push the larger the cooler..... but do be aware that if you do fit a large cooler you may need to include an oil stat as the original heat exchanger (note I'm not calling it a cooler) may not be able to heat up the over cooled oil enough for normal driving especially in cold conditions. I actually believe the auto box is race worthy but do ensure you are using a synthetic ATF, Mitzi's SPII/III is not synthetic.

[Davezj]

I am doing a ATF change at the moment.

Just giving it time to drain out for 20 min and have a brew.

Needless to say i have just bought 12L of AMSoil ATF fluid. I couldn't find a ATF filter on the performance oils web site so i got one from camskill.

I also got the engine flush from AMSoil as well so i am giving that a go. I am going to use some 5W-50 fully syth oil i have found, if it's no good then i can always flush it out again.

I will let you know.

By the way, i found an ODDITY on the ATF Flush article that Kieran did, i am not saying it is wrong for all but it was for my VR4. the drain plug is a 24mm and not 22mm as specified. It does sound a biggy but most socket set only go up to 22mm, Luckily i had to Buy a 24mm socket for another job, so it wasn't a problem for me but for others that try this it could by a massive pain in the arse.

Dave

[Kieran]

Grollox - I thought I'd corrected that. It was a Typo on my part.... /pan

I'll correct it now - They're all 24mm, just like the drain plugs on the transfer box and the rear diff.

Thanks for mentioning that Dave - I'll sort it now.:scholar:

[Davezj]

Just finished my fluid changing day.
As i said before did ATF, but also done Engine oil flush and refil, front plugs check and regap. romove the rocker cover to get to the cam shaft blank end seal which was leaking oil a little bit. So removed cam end cap to get the rubberised end seal out and cleaned the mating surfaces. Bobs your uncle it seals now, no leaks.

Used some power foam in the air intake not sure what difference this made apart from making the engine want to stall, then stop. but that was due to the MAF getting covered in foam. I don't really think it is ment to be used on a car with turbos. as the foam has to be drawn in passed MAF sensor, pipe work, through turbos, more pipe work, intercooler, more pipe work, throttle body, plenum, intake manifold, in to engine.
I could not use any more than 1/4 of a can as the engine would not run after a good squart through the MAF sensor. once foam dispersed car ran fine again.

just a note on the end to say thanks kieran you guide is great well done, oh by the way i used a webbed strap to the racket type of filter remover and i did the filter change in 2 mins no mess at all.

Thanks again Dave

[Nevman]

How about additional cooler AFTER the stock one with thermostate controlled bypass???

[amsoil]

Wouldn't work too well if you think about it. The hot oil would heat the water and be cooled before hitting the cooler . The final temperature would be what the stst was set at.

[Nevman]

But on the track use the stock cooler is not able to cool down the ATF enough to prevent N flashing, ain't it? So the additional radiator would be used on the hot days / track days only. On the regular use the ATF would go through bypass avoiding the cooler.
That's what my logic says... But logic sometimes doesn't work when comes to the cars... /Devil5

[amsoil]

You are right so thats why you should pale the additional cooler before the stock heat exchanger. This will mean that air will strip away the greatest amount of heat rather than exchanging it into the engines water cooling system. If you over cool then then rad water will heat it up and if the cooling is insuffient the heat exchanger will loose further heat to the water. Both ways win.

[Nevman]

Good point, can't agree more.

[Nevman]

BTW, where from to buy easy-to-fit cooler?

[orionn2o]

tHIS TOPIC HAS GOT ME INTERESTED.. With the prospect of track days looming, i'm wondering what to do to avoid the flashing N and cooked fluid!