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Thread: M73 Engines, What's the Newest we can fit?

  1. #1
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    M73 Engines, What's the Newest we can fit?

    What's the Newest M73 usable in our cars, I've found a couple 2001 M73's in great shape and was wondering if they will work by swapping the usual parts, Thanks!

  2. #2
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    found my answer, There the same, Thanks!-)

    https://en.wikipedia.org/wiki/BMW_M73#Models

  3. #3
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    Later M73 engines have water cooled alternator. The latest you can use is 1997 M73.

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    Thank you!

  5. #5
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    If you use the complete engine, it shouldn't matter that the alternator is water cooled. I personally do not like those, but they do work.
    '93 850Ci - Mineralweiss Metallic
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    ...the price of cool ain't cheap!

  6. #6
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    Re: Water cooled alt, and dejavu my '97-> '02 V8 swap, so speaking in general terms, not necessarily V12 specific.

    On the V8, same circa, the issue was not water vs air cooled per se, but generic ancillary issues.

    * The upper hose gained a branch going to the new water alt. Couldn't grab the newer hose because it was for the other/newer app, therefore the new hose had a different shape/routing, therefore incompatible with the e31.
    * Compounding that incompatibility BMW had migrated to a fancy clip-on end style (all three ends) whereas we are stuck with our radiators with old-style squared ends. My solution: Cut/splice a new clip-on hose with our old-style radiator end.
    * The alternator was physically larger, due to the water jacket and increased output (?). In the V8 the new housing did not bump into anything but, general speaking, there could have been a application packaging problem.
    * If the max output of the alternator increases substantially, then proper engineering requires us to review the cable gauge.
    * The stud on the alt had migrated slightly in style and position. I had to remake the alt cable end, borrowing the eyelet from the later/other app. Fortunately (iirc), it did not in involve lengthening the cable, otherwise start over from that point.

    Next topic (because it comes up in the wiki page): The MAP thermostat technology on the V8 could be reverted back to our circa although I elected to have my adaption computer drive this properly. There was a difference in thermostat port styles, and therefore again the issue of hose route and ends just mentioned. On the V8 it was not an option to retain the older housing and port style (because the new housing angles around the alien vanos heads), but my understanding is that it would accept the older uncontrolled thermostat.

    Next topic (not mentioned on the V12 wiki page, but it's in play V8): Auxillary air injection might (?) wander into the picture, unless they have it covered by that "electric cat". If air injection is present, you'll want to either cap it inconspicuously or retrofit a pump say behind the sheetmetal ahead of the right side wheel, then drive it with you own adaption computer while you are blipping a slightly rich mix. No harm to standard ops if you don't manage to support it.


  7. #7
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    Quote Originally Posted by dragon850 View Post
    Later M73 engines have water cooled alternator. The latest you can use is 1997 M73.
    My 98 M73 E38 is still air cooled, dont know if that helps
    "Understeer is when you hit the wall with the front of the car, Oversteer is when you hit the wall with the rear of the car, Horsepower is how fast you hit the wall, Torque is how far you take the wall with you."

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