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  1. #1
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    External transmission fluid cooler

    So as I add performance upgrades to my car, I知 sure the transmission is going to generate more heat. The other reason I chose to go with the CR-Racing intercooler versus one that goes back in the stock location is that I wanted to add an additional transmission oil cooler behind the intercooler in that area.

    After doing a lot of research I found that keeping the transmission fluid temperature lower can also increase its lifespan. The recommended way to do this is by running the hot fluid coming out of the transmission to the external oil cooler, to the stock heat exchanger and then back to the transmission. The external oil cooler lowers the temperature so the heat exchanger does not have to work as hard. This also allows the radiator to work less, allowing the engine to run cooler in hot weather. The reason for having the heat exchange being last in the system is so that it can bring the fluid up to operating temperature in cold weather and maintain a more stable temperature for the fluid.
    The diagram below is for the 335d

    1. Heat exchanger
    2. Outlet line
    3. Inlet line


    Click here to enlarge


    After looking at the lines going into the heat exchanger, it seems like you can cut the one time use clamps off like the intercooler hoses and slide a hose over the fitting. What I may do is to tap into line #2 from the diagram above and use a coupler to tie to the line coming from the transmission and run it to the external cooler. I値l run a new line from the outlet of the external cooler to the inlet of the heat exchanger.

    I値l post the DIY later on when I get to that project

  2. #2
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    Well, it seems it's better to run the external cooler after the radiator according to B&M. So i may also go that route.

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    On american cars, I was always of the belief that cooler is better ... period. The BMW engineers believe that a cold transmission is as bad as an overheated one, they want the temps around 200 degrees. To meet their beliefs, your original idea seems better.

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    Bravo Zulu @TurboEddie

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    Click here to enlarge Originally Posted by Velocity26 Click here to enlarge
    On american cars, I was always of the belief that cooler is better ... period. The BMW engineers believe that a cold transmission is as bad as an overheated one, they want the temps around 200 degrees. To meet their beliefs, your original idea seems better.

    I agree that "cold" transmission fuid is bad but with the heat exchanges in the loop, i don't think it'll ever get too cold. We have to remember that the radiator will also climb in temperature with more power. I'll have to do more research before i decide.

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    Ed, are those lines and exchanger your post for the transmission fluid or the engine oil? Here's the drawing from realoem, and the lines/exchanger are labeled as "oil":

    Click here to enlarge
    I guess BMW means transmission "oil" with their part names, but just wanted to be sure. I've been trying to understand what these particular parts do for some time, and you've broken the code very quickly! Well done! Thanks for sharing what you are doing, and keeping us all in the loop.

  7. #7
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    Click here to enlarge Originally Posted by TurboEddie Click here to enlarge
    I’ll post the DIY later on when I get to that project……
    I have to say you are doing some absolutely great stuff with this platform.

  8. #8
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    I noticed that too so i'm looking into it more. i could not see anything for the transmission other than that. I may just follow the lines too.

  9. #9
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    Still looking into this guys, just working on tuning first. I'll get back on this once i start turning up the power.

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