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    • Technical comparison of the BMW B58 3.0 turbo I6 in the 2016 F30 340i to the N55 engine it replaces - Stock and Stage I Alpha tuned dyno figures

      The new B-Series engines from BMW are going to be with us for a while. BMW created a modular set of engine that all share the same bore and stroke in three, four, and six cylinder configurations. All that really changes is the cylinder count between the motors.


      Last year around this time BimmerBoost took a look at the B48 2.0 liter inline four-cylinder motor. The B58 is basically the same thing except longer due to offering two more cylinders.

      The B48 replaced the N20 2.0 four-cylinder engine. The B58 will replace the N55 3.0 liter inline-6 throughout the lineup. The B58 differs from the N55 in a few ways the most important which is the new bore and stroke of 82mm x 94.6 respectively and the higher compression ratio. Here is a quick overview of the N55 and B58 replacing it:

      N55 I6:

      Displacement: 2979cc
      Bore x Stroke: 84mm x 89.6mm
      Compression Ratio: 10.2:1
      Horsepower: 302-335
      Torque: 332 lb-ft
      Redline: 7000 rpm

      B58 I6:

      Displacement: 2998cc
      Bore x Stroke: 82mm x 94.6mm
      Compression Ratio: 11.1:1
      Horsepower: 320
      Torque: 330 lb-ft
      Redline: 7000 rpm

      The difference in architecture between the B48 and N55 is greater than the N54 and N55. It has a new cylinder head design to lower carbon buildup, new intercooler, new thermostat, lighter Valvetronic, and new pumps.

      While the N55 did go to a single turbo instead of the twins the N54 had it maintained the same basic geometry sharing the same bore and stroke as well as the same compression ratio. The N55 could be essentially boiled down to an N54 with one turbo and Valvetronic added in.

      The B58 changes the architecture a bit going to an even more undersquare design. Less bore, more stroke. They also raised the compression ratio. 11.1:1 is definitely getting up there for a modern turbo motor even one that is direct injected. The B58 is slightly larger although this is a minor point. BMW seems to want more stroke and higher compression for low end performance and spool. The N55 is not a high revver by any means but the B58 is geared even more toward low end torque and spool. The higher compression will help with fuel efficiency as well.

      The B-Series is going to make nice gains in the aftermarket as all the BMW factory turbo inline-6 motors do. BMS (Burger Tuning) is already at work at this. Let's take a look at their stock and Alpha Stage I tuned figures:


      The stock motor through the automatic transmission puts down 331 horsepower to the wheels and 339 lb-ft of torque to the wheels. As is the BMW trend now with the turbo powerplants their crank output ratings tend to be closer to wheel output ratings. 331 to the wheels exceeds the 320 crank rating meaning this motor is closer to 400 horsepower than 320.

      This is not all that different from the N54 and N55 era although the N54 started in the 275 wheel horsepower range with a crank rating of 302. BMW actually is moving more towards being conservative in their ratings.

      Comparing the B58 F30 340i automatic to the N55 F30 335i automatic at the wheels shows a definite factory advantage for the B58:


      298 wheel horsepower and 306 lb-ft of torque for the stock N55 automatic. It is underrated as well just not quite to the same degree as the B58 F30 340i.

      Comparing the tuned numbers is tricky. For one, the above graph shows a flash tune. The B58 tuned numbers are from a BMS JB4 piggyback. You will see B58 tuning evolve just like the N55 and N54. Piggybacks will dominate early on and flash tuning will be more prevalent over time. Eventually, both approaches will likely be used as history shows us.

      For now, the B58 is at 379 wheel horsepower and 378 lb-ft of torque on the early BMS JB4 Alpha Stage I setup. The horsepower numbers stands out in particular. BMS believes the B58 turbocharger is larger and therefore it holds its torque better toward redline which results in the better horsepower curve toward redline. It comfortably exceeds a flash tuned N55 which drops off much harder toward redline. However, the N55 shows much more peak torque down low. It is almost a 100 lb-ft of torque advantage.

      The N55 should not have that large of a torque advantage down low but this is early B58 tuning once again. Look at the BMS N55 JB4 figures:


      Also much larger torque figures down low than the B58 and again a sharper torque drop off toward redline. Based on the figures on paper one would almost expect this to be reversed.

      With further testing beyond this Alpha stage tune from BMS we expect the B58 to show well over 400 lb-ft of torque at the wheels on pump gas just like the N55 except with a better top end. That should mean in theory more average horsepower throughout the entire curve.

      Here are some thoughts from BMS regarding their B58 F30 340i testing:

      Quote Originally Posted by Terry@BMS
      Random thoughts:
      1) The factory B58 turbo seems larger than the factory N55 turbo as evident by how much better it holds boost/power at higher RPM. It's almost a flat power curve from 5200rpm to redline even tuned.
      2) Peak power stock is an impressive 330whp. I'll overlay with some stock N55 dyno charts for a visual comparison.
      3) There is pretty good tuning potential for the platform. I've been burning the midnight candle the last few days to get the B58 JB4 ALPHA up and running. Some interesting changes were needed but nothing we couldn't easily handle. The B58 JB4 ALPHA has the in dash boost gauge, map switching, logging, boost by gear, and other features found in our other JB4 applications. Results of our current map1 below. I think this is about as far as we will want to push a stock car on pump gas although I did push it harder on the dyno for internal data collection purposes.
      4) I'm not yet sure how the platform will take to E85. I plan to work on that next week. I'm hoping it responds well.
      5) I've also included a JB4 log of the stock and tuned run in the dyno to add some context to the results
      Will the B58 become another N54? Will it be better? Who knows at this point. It will definitely make power and things look good early for its tune only power figures as well as the top end horsepower curve which has not exactly been a strong point in the direct injected inline-6 turbo era for BMW.

      We will see what happens but the B58 responds well to tuning and will no doubt hit numbers that open eyes just like the N54 and N55 before it.

      This article was originally published in forum thread: Technical comparison of the BMW B58 3.0 turbo I6 in the 2016 F30 340i to the N55 engine it replaces - Stock and Stage I Alpha tuned dyno figures started by Sticky View original post
      Comments 46 Comments
      1. ms335i's Avatar
        ms335i -
        Good article. Thanks for summing it all up.
      1. sahyoun's Avatar
        sahyoun -
        Those timing chains look like they'll be fun to get to....

        Does anyone know what the stock boost on the B58 is?
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by sahyoun Click here to enlarge
        Does anyone know what the stock boost on the B58 is?
        @Terry@BMS should.
      1. subaru335i's Avatar
        subaru335i -
        Nice article!
      1. ezec63's Avatar
        ezec63 -
        BMW did a great job on the exhaust manifold I'm kind of surprised how they included that in a mass production motor its a much better design than the typical log style manifold the n55 has
      1. DavidV's Avatar
        DavidV -
        [edit]
        Click here to enlarge Never mind. Wrong table [footinmouth]
      1. sighting's Avatar
        sighting -
        Click here to enlarge Originally Posted by sahyoun Click here to enlarge
        Those timing chains look like they'll be fun to get to....

        Does anyone know what the stock boost on the B58 is?
        Think I heard its 8-11Psi up form the 7-10psi before.
        But it should average lower than the n55's 7.4.

        I will try and find a reference to it.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by sighting Click here to enlarge
        Think I heard its 8-11Psi up form the 7-10psi before.
        But it should average lower than the n55's 7.4.

        I will try and find a reference to it.
        Do the BMS logs not show the stock boost?
      1. sighting's Avatar
        sighting -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Do the BMS logs not show the stock boost?
        yes they are capable of logging it.
        Would also be interested in seeing what it is.
      1. sahyoun's Avatar
        sahyoun -
        Click here to enlarge Originally Posted by sighting Click here to enlarge
        yes they are capable of logging it.
        Would also be interested in seeing what it is.
        Wasnt the 335i w/ the n54 around 8.8 psi or am I mistaken? Im guess it might be a little lower since its slightly higher compression. That turbo is pretty decently sized though
      1. sighting's Avatar
        sighting -
        Click here to enlarge Originally Posted by sahyoun Click here to enlarge
        Wasnt the 335i w/ the n54 around 8.8 psi or am I mistaken? Im guess it might be a little lower since its slightly higher compression. That turbo is pretty decently sized though
        Think the N54 335is was around 11 and the 335 around 8.x

        The N55 had a range from 7-10 and it set it on a range of factors, some would log 7.4 and some close to 10.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by sighting Click here to enlarge
        yes they are capable of logging it.
        Would also be interested in seeing what it is.
        I'm not sure if he posted the stock log here: http://www.boostaddict.com/showthrea...8-dyno-testing
      1. sighting's Avatar
        sighting -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        I'm not sure if he posted the stock log here: http://www.boostaddict.com/showthrea...8-dyno-testing

        Wow so it looks like its 17?!
      1. maxnix's Avatar
        maxnix -
        "The N55 could be essentially boiled down to an N54 with one turbo and Valvetronic added in. "

        Well, the author needs to read the official BMW publication detailing the differences between the N55 and N544. The block, the lubrication scheme and oil pump control, oil vapor control, among other things are different. The intake valve is 1mm greater in diameter.

        All of these changes are in the S55 also.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by maxnix Click here to enlarge
        Well, the author needs to read the official BMW publication detailing the differences between the N55 and N544. The block, the lubrication scheme and oil pump control, oil vapor control, among other things are different. The intake valve is 1mm greater in diameter.

        All of these changes are in the S55 also.
        The S55 and N55 block are not the same thing.

        The N55 has minor changes, sure, but not to the degree the S55 has versus the N55.

        Regardless, the B58 architecture is a more significant departure as stated in the article which you clearly need to read again.
      1. RobNyc's Avatar
        RobNyc -
        What does everyone thinks?
        The N55/35i engine, M40i/M2 engine and the B58/340 engine
      1. sahyoun's Avatar
        sahyoun -
        Yeah in general thats true but the new "N55" block in the m2 is a lot closer to the s55's block since theyre both LDS blocks that are closed deck whereas that old n55 in the 35's have cast in iron sleeves and are open deck.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by sahyoun Click here to enlarge
        Yeah in general thats true but the new "N55" block in the m2 is a lot closer to the s55's block since theyre both LDS blocks that are closed deck whereas that old n55 in the 35's have cast in iron sleeves and are open deck.
        I was referring to the classic N55. I don't know why they call the closed deck motor an N55. It should be an S55 variant.
      1. RobNyc's Avatar
        RobNyc -
        Click here to enlarge Originally Posted by sahyoun Click here to enlarge
        Yeah in general thats true but the new "N55" block in the m2 is a lot closer to the s55's block since theyre both LDS blocks that are closed deck whereas that old n55 in the 35's have cast in iron sleeves and are open deck.
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        I was referring to the classic N55. I don't know why they call the closed deck motor an N55. It should be an S55 variant.
        Looks like a B58/S55 hybrid
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by RobNyc Click here to enlarge
        Looks like a B58/S55 hybrid
        Based on what? It's more of an N55/S55 hybrid.