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Thread: M54B25 to 2.8 or 3.0. Or don't bother at all?

  1. #1
    Join Date
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    M54B25 to 2.8 or 3.0. Or don't bother at all?

    Its been too long since I swapped out a perfectly good engine. My recently purchased e46 325i MT seems like a good candidate, but the gains are not necessarily clear cut. Looks like a healthy stock M54B25 put out mid 170's at the wheels. I am also finding modified M52TUB28 dynos in the mid 170's. For the 3.0's I'm seeing a lot of dynos in the 190-200rwhp range. Not an earth shaking power increase.

    Last time I went down this path I pulled an M60B40 and swapped the OBD1 trimmings onto an M62 4.4 block. That transformed the car. I would like to see some significant gains for the work and cost and I am not seeing a whole lot of gains on the table between the 2.5/2.8/3.0 variants.

    What I am considering is an M52TUB28 engine with the M54B25 intake and throttle body. The 2.8 has the same cams as the 2.5 and with the M54B25 intake swapped over it should have a similar character as the existing 2.5 with more power everywhere. Mathematically speaking, it should be good for a 20rwhp bump. I don't know if this is realistic though. That would be right in the middle of M54B30 territory, which seems optimistic.

    The 3.0 seems like an obvious choice but it would quite likely be choked off with the stock 325i exhaust system. I would also have to do something about the throttle body/intake duct/MAF since the B30 uses larger diameter parts. This would also likely require some sort of tune or programming which adds more complication.

    Anybody done it? Would you do it again? The stock M54B25 produces just enough power to get around, but its just about the minimum amount. Just enough power for highway driving and passing without downshifting, but only just enough.

  2. #2
    Join Date
    Feb 2017
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    Metairie, LA
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    2001 325i; 2006 325i
    I have an E46 325i that I got for my son to drive and an E90 325i. The E90 325i has a 3.0 in it and is very close to the E46 330i in terms of power. The difference between the E46 and E90 325i is noticeable. My E90 definitely has more "zip" to it, but it isn't night and day. Personally, I don't think it's worth it. You might do better to dump the 325 and find yourself a 330, if that's what you want.

  3. #3
    Join Date
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    Looks like its going to be a 2.8. Got one for $600 shipped. Cheaper than trying to find a viable 330i. The used car market out here is a wasteland.

    Time for a build thread I guess.

  4. #4
    Join Date
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    EXOTICS
    S54!
    What other option can satisfy your needs?

  5. #5
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    I don't require too much from the car these days. Used to drive a 468rwhp e28. Sold that. Then it was an M60B44 540i/6. Selling that. I think the e46 will do just fine. Looking more for comfort, reliability and economy these days. If I want to go fast I have some two wheeled machines for that. I actually daily drive my Yamaha 600. This will be the car I keep in the garage and never use.

  6. #6
    Join Date
    Mar 2015
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    01 E46 330i 5sp man spor
    A built S54 maybe drop the c.r. a bit, add a big turbo and fill the tank with e85. Would easily make 4x the power of the build currently in the works. Then go embarrass the shit out of super car owners who think their $200k car is the best thing on the planet. The look on their faces when a 15 year old bmw wagon leaves them in the dust would make it all worth it.

    Sent from my SAMSUNG-SM-G870A using Tapatalk

  7. #7
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    Not really interested in dropping 20 grand on another turbo build. I've had my fun.

    I expect to pick up about 20rwhp from the M54B28. Should be just fine.

  8. #8
    Join Date
    Jun 2009
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    2004 330 vert 2004 X5
    Looking forward to the build and the Dyno numbers. I've owned almost every year e36 made including a m3 I eventually put a supercharger then a turbo on. I love my 330 but like you said it would require new exhaust etc. I've always been a fan of supercharger. They are pretty cheap if you find a nice used one. I like the linear power band. They don't require very much maintenance. The only modifications you'd really need would be slightly bigger exhaust. They're so much simpler than a turbo system. Just putting it out there. If you're looking for a real power boost without the cost of a turbo it's worth considering. After all it's going to be a weekend toy. Make it fun.
    Last edited by flyfishvt; 06-23-2017 at 09:11 PM.

  9. #9
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    01 E46 330i 5sp man spor
    Quote Originally Posted by nonturbodan View Post
    Not really interested in dropping 20 grand on another turbo build. I've had my fun.

    I expect to pick up about 20rwhp from the M54B28. Should be just fine.
    Lol yeah 20k would probably go quickly on that kind of build. Then you would need another 20k for bail, tickets, lawyers, court fines, ect. Why not go with m54b30? The longer stroke gives a noticeable torque increase. Even over m52tub28. There should be plenty available. Bmw put it in every model sold here except the 7's. People seem to just buy another engine when something goes wrong (head gasket, ect) you should be able pick up a bad one for very little or even free if someone wants it out of the garage. You seem like you would not have a problem repairing it. A used engine should come with intake, throttle body and injectors but probably not the maf. Worst case you buy a maf and get the dme flashed to m54b30 spec.

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  10. #10
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    I was looking at B30's. Could have gone either way. I just lowballed an offer at a B28 and I got it.

    Supercharging is an option. I'm just at a point in my life where I'd rather put that money toward my mortgage than car parts. I wonder some times how much money I sunk into my turbo e28. Tens of thousands over the years, no doubt. Not to mention the time spent turning wrenches and tuning.

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