Hi,

 

I have replaced my OEM radiator with an aftermarket bigger better unit and fitted a separate MOCOL oil rad unit for the purpose of stopping the Auto Tranny frying itself stupid. (I also have SAW which does not help!)

 

What is the working oil temp for a TT AUTO Tranny and should I fit a (probably high temp) OILSTAT so that it gets up to speed first. I believe auto tranny oil is happy at around 140 degrees, but would like that confirmed by a guru.

Thanks again. :tooth:

> is happy at around 140 degrees

 

that's not really a temperature you want the ATF oil to reach, as you box will start to fry.

ATF oil breaks down very quickly, but also depends on quality of the oil.

 

Best is to keep ATF Tranmission oil temps between 80C and 90C..basically the same as the coolant temperature in our engines.

If you run an automatic there are a couple of things you should be aware of. As stated above, the oil in the box under hard driving can reach 130 to 140 deg C, which is Ok providing everything is working as it should. By this I mean the auto box oil cooler and the engine oil cooler. The auto box cooler on early models I believe is built into the radiator so it also transfers it heat into the cooling system thus raising the temp. On the ones fitted with seperate coolers this does not happen but you need to ensure that the stand alone cooler is clear and not blocked by road debri. (I saw one recently full of bird feathers and a dead bird wedged into one corner) If you can afford to update your autobox cooler I would recommend it. If the autobox is running at high temps for long periods, it transfers that heat via the torque converter to the crankshaft which heats up the engine oil and thins it. This is when there is a chance of a bearing picking up causing permanent damage. So, keep both coolers clear of crap and make sure that both the box and the engine oil levels are kept topped up, = happy motoring.

Thanks Guys - maybe I was not clear. I have replaced the main rad, and I have added a new dedicated rad for the autocooler. Question was really regarding an oilstat for this RAD.

 

I don't want to overcool the oil so that it never reaches it's working temp. So I am asking if I should fit an oilstat, and if so at what temp should the oilstat be set. Standard oilstats work at about 80 degrees. But knowing that auto tranny oil can get up to near 140 degrees, I am looking for confirmation as to what an oilstat should be set at ultimately. If 80 degrees if fine - I will be good to go.

I get an oil temp readout from my SAW (SHIFT AT WILL) and I have seen it at over 120 degrees after some spirited prolonged driving ;-( Maybe it will be a case of fitting a standard 80 degree oilstat and seeing how it goes. Standard wax oilstats will not operate at temps over 110 degrees and will effectively be screwed/require wax replacement module so a high temp oilstat may be required.

I think I have sized the new rad correctly with an 80 degree oilstat so I will suck it and see and let you guys know.

 

Thanks again.

Yeah - I forgot to mention that I am talking about a JAP AUTO here...

dont think an auto gbox cooler needs a stat at all as it flows through the system AFAIK there isnt one on the stock set up is there(?)

you cant overcool the oil as it works from deadcold in any event...unlike your average F1 car :D

You can over cool the oil - by preventing it from reaching its optimum operating temperature (that it is designed to operate at). Of course you can! I have cooked a JAP AUTO tranny before because it's cooling is inefficient for fast road/spirited driving. It's the major reason for failure of these auto boxes. If your car is bog standard fine, it may live on the edge and survive a few more years but if you are asking more of it (JAP AUTO) you should think about a rad upgrade as a matter of course IMHO.

New Oil Rad

 

New Auto Tranny Rad

i think the crux of this is that the size of the cooler will effect the pressure in the box/flow of the fluid, that is more likely to cause a problem not the temp of the oil itself as the range on ATF oils IIRC is @ 30C to over 100C.....overcooking oil very bad but not really seeing a problem with cooling unless as above you go well under 30c...unlikely in my opinion.....but hey i'm no mechanical engineer :D

 

that said maybe a different grade oil will overcome the extra cool oil system...that would work better allowing for that change in viscosity

 

 

btw nice pipe work andy...looks good

Edited March 5, 201015 yr by Uno

Cheers matey - thats the old FMIC - just got a new one - all piping has now changed again lol!

 

Adding an oil cooler correctly should not effect the normal oil pressure AFAIK, it will effect initial cranking pressure, i.e. takes takes a second or two longer to see full cold start-oil pressure. Noticed this in other cars I have modded in this way but otherwise no difference. If you run long lengths of pipe to and from the cooler then it is advisable to go up a size (which I always do) otherwise pressure is same as before - I have not noted any change. The Oilstat will effectively shut out the rad at cold start as well and that helps.

 

I am trying to create a more reliable longer lasting engine by sensibly upgrading everything in line with, and matching, the performance and output gains.

 

This stuff is critical, we change bumpers and add spoilers with no regard to how it effects airflow to the sump/rad. We increase performance (and combustion temperatures) and we forget that for every extra 1000rpm we need to provide a threefold increase in oil cooling!

 

Your right - modern oils will not be damaged by high temps (although some might leave varnish deposits) but my engine is unforgiving and will only suffer me being foolish once. ;-))

New bumper will allow full flow to and through those baby's....