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Thread: BMW 745Li n62b44 - engine swap for n62b48

  1. #1
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    BMW 745Li n62b44 - engine swap for n62b48

    I've got a 2003 745li with a bad engine (n62b44). Anyone know if it would be a straight swap with an n62b48 engine from a 2006 750li?

  2. #2
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    It might physically be a straight swap (and I'm not even sure of that). But it's not going to work. Everything is different. Wiring harnesses, DME, sensors, etc.
    ASE and BMW Master Certified Technician

  3. #3
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    I finished the swap this weekend...glad to report it IS possible and the extra 30hp and torque is very noticeable from the newer engine.


    I used the upper oil pan and alternator bracket from the 2003 engine because they form the bracket for the steering pump. I also swapped 2 sensors on the cylinder covers that had different electric plugs. And drilled a hole in the water pump for the alternator line.



    From the b44:
    - wiring harness
    - intake manifold and fuel injectors
    - upper oil pan
    - alternator / compressor / steering pump
    - alternator coolant line
    - 4 sensors (cylinder head cover)


    From the b48:
    - block
    - cylinder heads
    - cylinder head covers
    - lower oil pan


    .
    Last edited by Bavarain; 05-29-2018 at 02:31 PM. Reason: formatting

  4. #4
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    Hi Dave,
    I am planning to do very similar swap but instead of 7 series I want to swap N62B48 into 2004 545i.
    Did you need to do any software modifications to ECU for the engine to work properly?
    Do you have any side effects or OBD error codes as a result of increased displacement that might be causing them?
    The newer N62B48 does not have secondary air pump at all, so it will cause Check Engine and I will not be able to pass SMOG check. How did you solve the secondary air pump problem?
    Just looking for an advice from someone who has done it.

    Thanks!
    Last edited by flashcoder; 09-10-2018 at 05:13 AM.

  5. #5
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    I did not do any software modifications except reset the transmission adaptations.


    Yes, I have the check engine light on with OBD codes for the secondary airpump. I haven't had time to figure out how to override that but I've got a few months b4 my smog is due.


    The other differences I saw were in the upper oil pan. In my case, the bracket for the water-cooled alternator is not the same. Also, there were oil baffles inside the pan that i had to cut out so that it would fit. Looks like you may not have that problem though. In the end it was really no more difficult than a straight swap.

  6. #6
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    Dave

    since Secondary Air Pump could be an issue I am thinking of swapping heads from N62B44 to the N62B48 block, that way I am keeping the secondary air pump.
    If I keep the N62B48 heads then it requires software modification, I asked some guys on chip tuning forums they say its doable to code out the Secondary Air Pump from DME but as a consequence it can impact the longevity of the catalytic converters, they need this secondary air pump to heat them up quickly. Also what might happen is that if they are not heated then DME could detect that the cats are not working efficiently and could set some more codes related to catalytic converter especially in the mornings.

    The reason why the newer N62B48 does not have secondary air pump is because they used next generation catalytic converters that do not need to be heated up by extra air.
    And even if there isnt any problem to run the old cats with Secondary Air Pump coded out of DME and there would be no check engine codes there is still a chance that SMOG check will require you to have the secondary air pump just because this year car is expected to have it by the specifications which they technically can determine with their computer system.

    So the proper method would be to do massive coding and transplant newer DME in place of the old one and also get those next gen catalytic converters but these next gen catalytic converters from N62B48 cost ridiculous money.. Add the cost of new DME and the coding that probably can be done only by very skilled indy.
    Or just go cheap with the old heads that have the secondary air pump exhaust passage in them and then stuff should just bolt together with no check engine codes and no software modification at all. And maybe swap the cams in there from the newer N62B48 though I am not sure if they are any different from N62B44.

    So this is a bit of a dilemma here how to do it correctly and not pay a fortune.
    Last edited by flashcoder; 09-10-2018 at 06:31 PM.

  7. #7
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    I just checked again and there are no other OBD codes besides the secondary air. That's after three months of driving.

    If I was smart like you I would have realized this problem up-front and probably not even installed the engine. Swapping the heads seems like crazy amount of work. Used b44 engines are only around one grand. I think I'll just get the right engine and put the b48 in another project.

    Good luck with your swap~

  8. #8
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    This is great news! If you have only the secondary air pump codes and no other emissions codes then it could be possible to build a Secondary Air Pump simulator similar to what I found on this forum:
    http://www.318ti.org/forum/showthread.php?t=24726
    I still have the old engine in my car so I will try to build something like this and run in place of the secondary air pump and see if this does the job.

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