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The mkiv Supra Owners Club

Are twin auto coolers overkill on BPU?


gordy.r

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Got myself a new radiator to go onto the TT, and I've been looking at a few aftermarket auto box oil cooler kits.

Now, whilst I know one cooler should be sufficient for BPU mods, there's always the chance of going single, hybrids or bigger twins in the future, and to future proof the box I was looking at installing two coolers but will this have any negative effects on the gearbox temps whilst only running BPU power figures?

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The only issue is that it will take a little longer for the atf to get up to temperature, the cooler in the rad serves as a heater from cold as well as a cooler when hot. During this time from cold its possible you may notice harsh changes, but I never have and I run two separate coolers. The proper way to do it is to use a thermostatic valve that bypasses the coolers when cold and opens up and let's the atf pass through them when it gets up to temperature. Mocal make them and DacidP has one on his car and it can be seen in his build thread I think. But two is good IMO.

 

http://www.ebay.co.uk/itm/Mitsubishi-Pajero-Shogun-mk2-94-99-3-5-V6-6g74-OIL-COOLER-DENSO-024100-8112-/120952778255?pt=UK_CarsParts_Vehicles_CarParts_SM&fits=Car+Make%3AMitsubishi&hash=item1c2958ee0fThese fit perfectly either side behind the vent.

 

And these are good too and from a reputable dealer.http://www.ebay.co.uk/itm/Flex-a-lite-4120-Translife-Transmission-Oil-Cooler-Kit-/380970446654?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item58b39baf3e

 

I have one of each fitted to mine.

Edited by Shane (see edit history)
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That's the exact same as the one I've bought for mine, although I got the 3/8 version.

 

I'm planning to fit it where the stock smic would be, and also keep the stock cooler in the rad.

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On the road the fluid may stay too cold. Too cold is bad for engine and gear oils, as the moisture is not driven out. You may find you need to blank one or both off on the road in winter. Whether you can get a thermostat for auto box coolers I don't know, but if you can it would address any issues.

 

We have never found this issue on the gearbox as its runs fairly warm even with the coolers

 

I completely agree with engine oil though, needs a thermostatic sandwich plate on the cooler.

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Searching the web for "ideal automatic transmission temperature" returns a lot of info, mostly for American gearboxes, as you might expect.

 

For example: http://www.hotrod.com/techarticles/general/hrdp_1110_technical_questions_and_answers/

 

The consensus seems to be that ATF should be 175 to 200 F or about 80 to 95 C, and that above 225F/107C is bad.

 

There is nothing to stop you using a bypass thermostat for the transmission cooler(s). Think Automotive (Mocal) sell 80 and 92 degree thermostats with 3/8 or 1/2 inch (c. 10mm/13mm) tails.

Edited by garethr (see edit history)
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Many thanks for all the info guys, seems there's a little more to consider than I first thought!

 

We have never found this issue on the gearbox as its runs fairly warm even with the coolers

 

I completely agree with engine oil though, needs a thermostatic sandwich plate on the cooler.

 

Lee, is the thermostatic sandwich plate something you guys could sort out / make / source for me if I were to order some oil cooler kits from yourselves?

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I have to say i am no expert on auto boxes, although they are my choice for a road car. I have never really probed one to see just how hot they run to be honest.

 

With the facelift models you can plug in to the OBD connection, i use a Blitz iVit on mine to monitor gearbox and water temperatures.

 

The consensus seems to be that ATF should be 175 to 200 F or about 80 to 95 C, and that above 225F/107c is bad.

 

Seems about right, mine is generally 85-90 when pushing hard and i think i've seen 92 as the highest. It would be interesting to test it on track though.

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