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N55 Motor is it Forged like its N54 brother?
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07-19-2015, 10:11 AM | #45 |
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07-19-2015, 10:26 AM | #46 |
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Yes. Look under forged vs cast tab.https://en.m.wikipedia.org/wiki/Hypereutectic_piston
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07-19-2015, 02:03 PM | #47 | |
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07-19-2015, 06:40 PM | #49 |
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Actually, it has more to do with the ratios of the elements in the alloy. The process gives a better handle on how the material reacts to heat. But, it's still cast - poured hot into a mold and machine finished. Whereas forged items use extreme pressures to produce the items before machine finishing, and of course billet is machined from a solid forged "block".
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07-19-2015, 07:01 PM | #50 | |
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That being said, I'm pretty sure we haven't heard the last of this. Someone's is going to insist 54s have forged internals. Not sure when..... But it will happen. Last edited by Wingnut335; 07-19-2015 at 07:09 PM.. |
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07-19-2015, 07:43 PM | #51 | |
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I will say one thing...the rods pictured in that article certainly LOOK like forgings to me. Don't see many cast rods with a parting line like those have. |
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07-20-2015, 12:08 AM | #52 | |
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It's well documented how well the N54 can perform and take a beating. Logic dictates that the N55 is just as capable for such power gains as the N54. So I highly doubt our problem is inherent solely to engine component constraints. How well can our transmissions hold up when pushing 500whp/wtq consistently? Most people, from what I've read, report transmission slipping just slightly north of that mark. The engine is more than capable.. our transmissions.. as expected is a valid weak point in terms of longevity. |
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07-24-2015, 11:10 PM | #53 | |
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07-27-2015, 12:22 PM | #54 |
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I love all the speculation here from people who barely understand what they are talking about.
Hypereutectic pistons are chosen for the minimal thermal expansion property of the aluminum alloy. The important part is WHY? would you chose this material for a piston? This allows you to run tighter piston/bore clearances, yielding higher MPG, lower blow by, cleaner emissions, and increased efficiency. These are the primary design goals for any OEM. The fact that they are also cheaper helps too. They aren't chosen based on just cost is my point. If forged pistons provided the above benefits, all engines would probably have OEM forged pistons. Forged pistons are indeed stronger (in similar design), but come with a higher thermal expansion coefficient. This means you must run larger cylinder/bore clearances which is moving away from all the goals listed above plus also exposing you to piston slap during warm up. It takes time for the pistons to heat up to operating temp and therefore "dimensions". Your strong pistons have more room to move and impact around inside the bores until they heat up. Forged pistons also wear surfaces at a higher rate vs HypE pistons over time. That is not helping you in the long run for a 150K mile engine. Forged pistons are much louder on the knock sensor and can trigger false knock on certain engines with sensitive knock feedback loops (like ours ). Remember that there are multiple variables in determining if something will fail or not. Strength of material is obviously one of them, but do not forget the design geometry. Despite being HypE, these OEM pistons have proven capable of withstanding severe boost pressures (30+psi) for extended periods of time. We can probably assume that BMW executed well on the design of these pistons....despite them being made of a less resilient material This is why the people who flat out claim that Forged > HypE don't really understand things. They both have their pros/cons and you must choose what your goals are while also conceding the cons of a certain type of piston. |
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07-27-2015, 12:50 PM | #55 | |
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Don't mean to hijack the thread, but I have a theory. I wonder if someone would swap over the n55 heads from the f series cars even the new m4 and see what power gains can be had from there. Assuming the head will bolt up and the chains line up for the vanos. THAT would be interesting seeing as though the new n55 have more power with just basic tunes and better turbos.
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07-28-2015, 01:04 AM | #56 | |
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07-28-2015, 02:13 AM | #57 | |
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07-28-2015, 08:41 AM | #58 | |
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Holding to redline is clearly an electronic issue and not a turbo issue. PSI is just a build up of pressure and turbo can endlessly provide this pressure unless there is an release i the system. Whether or not the boost is efficient, that is a whole other story. But that is slightly off topic.
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07-28-2015, 10:41 PM | #59 | ||
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It is a completely different engine block (closed vs open deck), head and nearly everything else that bolts onto it. Quote:
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07-29-2015, 02:48 PM | #60 |
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Correction I believe it was Burger who figured out what exactly causes the diverter valve to open and cause the boost to taper off as you get to redline.
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