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    n54 Twin Turbo vs n55 Turbo - 135i

    On the 135i can you tell that the n55 only has a single turbo while driving it? The n54 has two turbos so there is a bit more of an even flow of power but with the single is it the same?

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    1 out of 1 members liked this post. Reputation: Yes | No
    I read this:

    you’ll have to wash your brain of the preconceived notion that more is better, because in place of two smaller turbochargers working alongside one another, BMW’s new turbo six goes to work with one single, albeit twin-scroll, turbocharger pumping in air. One thing that does carry over from the outgoing twin-turbo engine, though, is BMW’s attention to detail and the engineering team’s fight against turbo lag. As such, this new engine uses a very clever exhaust manifold and turbocharger design that is essentially a concentrated twin-turbo design. Inside the manifold, the front three cylinders are completely divided from the rear three, so while from the outside it appears that gas from all six cylinders is routed through one exit to the turbocharger, there’s actually a wall inside splitting the air in half. That splitting of air is continued right into the twin-scroll turbocharger housing.

    The idea of this system is to split the pulses of exhaust gas so that regardless of where the engine is in its firing order, there’s always good pressure and as such, reduced lag. Additionally, the design allows for a lower exhaust gas counter-pressure buildup at low engine speeds, again reducing lag. It’s like having two turbochargers but without the complexity and like having one, only without the drawbacks of having to use one large, lagging turbo in place of two smaller ones. The best of both worlds.
    This makes the n55 single turbo sound not as bad but the question remains, is there any lag?

    Reference: http://www.mwerks.com/artman2/publis...Cylinder.shtml

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    Click here to enlarge Originally Posted by dh58 Click here to enlarge
    I read this:



    This makes the n55 single turbo sound not as bad but the question remains, is there any lag?

    Reference: http://www.mwerks.com/artman2/publis...Cylinder.shtml
    There is lag, and this debate will go on and on. Ultimately the cfm airflow will determine your max power level, and turbo size, bearing type, compressor and turbine design, exhaust manifold and a bunch of other things will affect how the turbo spools and the torque curve of your engine.

    Does anyone know the cfm or lbs/min of the N55 single scroll vs the two N54 turbos combined?

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    I've yet to drive an n55 car back to back with an n54 in the same chassis - that will be the ultimate comparison where you would be able to clearly see any variances between the two engines.

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    Have you seen dynos for both engines stock? They are practically identical. You would probably not tell the difference except for the DCT. Tuned, is another story.
    Some people live long, meaningful lives.

    Other people eat shit and die.

    I'm not racist, I hate everybody equally; especially fat people.


    Click here to enlarge

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Have you seen dynos for both engines stock? They are practically identical. You would probably not tell the difference except for the DCT. Tuned, is another story.
    This is why I'm thinking the N55 turbo has a lower lb/min capacity than the N54 turbos combined. The N55 looks like it drops torque harder near redline when you up the boost.

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    If you look at the dynos both are pleasant to drive. The turbos BMW uses are very, very small and the compression is high with a turbo motor in both applications so response is good.

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    If there is a Upgraded turbo out for the N55 within a 18 months im getting one, if not ill im gonna probably opt for a s/c s65 and turn the 335 into an all out race car

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Have you seen dynos for both engines stock? They are practically identical. You would probably not tell the difference except for the DCT. Tuned, is another story.
    No I haven't. Do you have a link to the dynos for both? What do you mean you won't be able to tell the difference except for DCT? Do you mean that it is a good thing?

    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    If you look at the dynos both are pleasant to drive. The turbos BMW uses are very, very small and the compression is high with a turbo motor in both applications so response is good.
    Again do you have a link to the dynos?

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    N54tech should have the dynos overlayed, both for the N54 and N55. They are so similar its hard to tell which is which.

    I didnt mean you would notice the DCT in a bad way, its just you would notice the transmission shift style being very different alltogether going from the steptronic to the DCT.
    Some people live long, meaningful lives.

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    Click here to enlarge

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    Click here to enlarge Originally Posted by dh58 Click here to enlarge

    Again do you have a link to the dynos?
    Yes: http://www.bimmerboost.com/showthrea...6261#post16261

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    N54tech should have the dynos overlayed, both for the N54 and N55. They are so similar its hard to tell which is which.
    We had em first Click here to enlarge Thanks to Terry actually.

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    I didnt mean you would notice the DCT in a bad way, its just you would notice the transmission shift style being very different alltogether going from the steptronic to the DCT.
    Ahhh ok I understand now Click here to enlarge

    Thank you for that.

    I am new to reading these dyno graphs. Why does the n55 start at the 2.5rpm line where as the n54 start at the 2rpm line? Is that related to my original question?

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    Click here to enlarge Originally Posted by dh58 Click here to enlarge
    I am new to reading these dyno graphs. Why does the n55 start at the 2.5rpm line where as the n54 start at the 2rpm line? Is that related to my original question?
    That is just where the signal rpm signal was picked up, not related at all.

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    Ahh, Thank you Sticky!! You answered everything for me Click here to enlarge

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    Click here to enlarge Originally Posted by dh58 Click here to enlarge
    Ahh, Thank you Sticky!! You answered everything for me Click here to enlarge
    My pleasure, here to help all the members.

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