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General E46 Forum
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Old 10-29-2014, 11:12 PM   #1
Novaskotia
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Question Downgrade 330ci to 2.5L?????

I have a blown m54b30 in my 330ci Vert. I found a M54b25 to buy. Can i just swap it in there?

I have searched far and wide for a thread like this, didn't find anything..

Everyone wants to go from 2.5L to 3.0L , but i never saw anything about going the opposite direction.

Any thoughts?
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Old 10-29-2014, 11:44 PM   #2
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No way man, be patient I'm sure you can find a used m54b30 out there, SEARCH. No reason to go backward, and the swap would be plug and play if you go with the correct motor.
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Old 10-29-2014, 11:59 PM   #3
JapanRot325ci
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loool no.


just go back to a 3.0l or a s54 swap

you're gonna regret it big time if u go to a 2.5l...lesss power harder to swap because youll need to hard code etc
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Old 10-30-2014, 12:03 AM   #4
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Quote:
Originally Posted by Novaskotia View Post
I have a blown m54b30 in my 330ci Vert. I found a M54b25 to buy. Can i just swap it in there?
Yes you can. I actually did that. Customer wanted better gas mileage after his 3L blew up. He ordered complete 2.5L from same year, I did the swap. It all fits and bolts right up, then you will need to flash your engine computer for the 2.5L engine.
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Old 10-30-2014, 06:03 AM   #5
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:Facepalm: very dumb move.. Who moves backwards?!
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Old 10-30-2014, 08:23 AM   #6
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Yes you can. I actually did that. Customer wanted better gas mileage after his 3L blew up. He ordered complete 2.5L from same year, I did the swap. It all fits and bolts right up, then you will need to flash your engine computer for the 2.5L engine.
The 3.0 actually gets better gas mileage than the 2.5 .
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Old 10-30-2014, 08:23 AM   #7
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Yes you can, but don't. You will trash the resale value of the car, and the convertibles are too heavy for you to give them any more of a speed handicap.
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Old 10-30-2014, 09:28 AM   #8
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The 3.0 actually gets better gas mileage than the 2.5 .
Definitely not with my experience, and I own both. The 2.5L easily yields 2-3 more mpg (calculated).
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The E46s are the Knights of the chessboard. They can outmaneuver the other, more powerful pieces on the board. They aren't the King or Queen of the garage, but they are the first piece that you want to move.
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Old 10-30-2014, 09:37 AM   #9
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EPA rates both engines the exact same as far as economy. My experience owning both is my 330i got slightly better economy than my 325ci by 1-2mpg (while both totally stock and both 5-speed manuals).
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Old 10-30-2014, 10:01 AM   #10
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I'm running both automatics, though the 325i has 100k more miles. I think I'll need to run a little Seafoam through mine to clean out the mess from the PO.

But OP, most people go the other way. I would hold out for one (if you can), or search for one outside of the area you are searching. Don't give up so easily!
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The E46s are the Knights of the chessboard. They can outmaneuver the other, more powerful pieces on the board. They aren't the King or Queen of the garage, but they are the first piece that you want to move.

Last edited by TRITONAL; 10-30-2014 at 10:01 AM.
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Old 10-30-2014, 11:52 AM   #11
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Thanks for all your reply's

(fangirling about Mango responding)

I have took what most of you said into consideration. I think I will wait it out now. I was considering throwing that 2.5 in there and just selling it right away, as a 3.0 - but that is dishonest. I will keep you posted.
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Old 10-30-2014, 04:07 PM   #12
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More likely the differences in mpg may be related to differential gearing ..

http://www.bokchoys.com/differential/GearRatios.htm
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