N55 vs S55: Technical Differences, Compatibility & Performance Potential

[Boorda]

I do not actually, I guess I should create one.
I've always been the background lurker watching others builds and never really been that public about personal builds.
But I don't mind sharing.

 

[Boorda]

Wow, that scan looks really good too. Do you have/will you have a build thread? Sounds like you've got something cool in the works, if so I'd like to follow along

I do now, and I blame you!
M-Sport 335xi S55 Build

 

[Ali_X]

Hello everyone,

Hope you're all well,

Any news about cooling when using the N55 head with the S55 block and gasket?

Thanks in advance

 

[CalvinNismo]

S55​

• Initial Release
  
  • Forged crankshaft (4-6 lbs. lighter)

---

Just read through this again, having previously looked at this statement. The S55 crank according to parts websites is lighter than the forged N55 crank, but the cast crank is the lightest of the 3.

N55 cast:

RealOEM.com - Part Search

At-crankshaft with bearing shells 2163665 | BMW 11212163665

BMW At-crankshaft with bearing shells 11212163665, 2163665

bmwfans.info

N55 forged:

RealOEM.com - Part Search

At-crankshaft with bearing shells 2334334 | BMW 11212334334

BMW At-crankshaft with bearing shells 11212334334, 2334334

bmwfans.info

S55:

RealOEM.com - Part Search

Crankshaft 7846606 | BMW 11217846606

BMW Crankshaft 11217846606, 7846606

bmwfans.info

The S55 crank does have symmetrical counterweights though, but interesting that (if the parts diagram weights can be trusted) BMW in this instance cherry picked its marketing statement.

 

[wheela]

Just adding some more component cross reference information. The source was realoem, using my 2015 pwg n55 as the base engine for comparison.

 

[wheela]

The exhaust valves are sodium filled for higher heat

Just to clarify, the n55 exhaust valves are also sodium filled to aid heat removal

 

[wheela]

I'm starting this thread to have a centralized location to reference technical deep-dives into the differences between BMW's N55 and S55 engine platforms. My goal is to create a comprehensive resource where we can discuss compatibility between parts and potential performance gains when upgrading or swapping components between these platforms.

Check back regularly as I will do my best to maintain this first post with shortcuts to various posts and resources.

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Technical Documentation​

N55​

• Technical Training

S55 ​

• Technical Training

Other Resources​

N55​

• RealOEM E90 335i
• RealOEM E90 335xi
• RealOEM E92 335i
• RealOEM E92 335xi
• RealOEM F87 M2

S55​

• RealOEM F80 M3
• RealOEM F82 M4
• RealOEM F87 M2

---

Technical Differences​

Below are technical key differences between the N55 and S55 engine platforms.
This section also includes updates and variations within the N55 and S55 engine platforms themselves.
Between engine variations of the same platform, it is assumed that everything in the previous version is identical unless otherwise specified.
Items marked `Unconfirmed` are believed to be true but research is being done to officially confirm the claims.

​

Block & Engine Externals​

N55 ​

• Initial Release
  
  • Cast iron cylinder sleeves
  • Single HPFP
  • Single Oil Pump
  • Pneumatic Wastegate (PWG)
• M2 Variant
  
  • Dual Oil Pump
• Update 1 (2013-2018)
  
  • Upgraded oil cooling - Unconfirmed
  • Electric Wastegate (EWG)

S55​

• Initial Release
  
  • Closed-deck design
  • Stronger cylinder walls
  • Plasma-transferred wire arc sprayed cylinder liners for improved strength and heat dissipation
  • Dual HPFP
  • Dual Oil Pump
• Update 1 (2015-2020)
  
  • Oil Pan Upgrade (Material) - Unconfirmed

Questions:​

• Can you swap an S55 into and E92?

Engine Internals​

N55​

• Initial Release
  
  • Cast Rods
  • Cast Pistons
• Update 1 (20xx-20xx)
  
  • Forged crank - Unconfirmed
  • Forged Rods - Unconfirmed

S55​

• Initial Release
  
  • Forged crankshaft (4-6 lbs. lighter)
  • Forged connecting rods
  • Pistons with Teflon coated side skirts

Questions:​

• Can S55 crank be swapped into an N55?

Cylinder Head​

N55​

• Initial Release
  
  • Working on

S55​

• Initial Release
  
  • Working on

Questions:​

• Are the cylinder heads interchangeable between the platforms?
• Does the S55 head flow better?

Turbocharger Setup​

N55​

• Initial Release
  
  • Single twin-scroll turbocharger (Brand(s)?)

S55​

• Initial Release
  
  • Twin single-scroll turbochargers (Brand(s)?)

Questions:​

• Can N55 owners use S55 turbochargers? What modifications would be required?

Electronics​

N55 ​

• Initial Release
  
  • DME: MEVD172

S55 ​

• Initial Release
  
  • DEM: MEVD172G

Questions:​

• Are N55 and S55 DME's interchangeable?
• N55 DME Plugged with S55?
• What ECU/DME considerations come into play when mixing components?

​

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Question Queue​

1. What's involved in adapting the S55 cooling system to an N55?
   • Not Possible

​

---

@doublespaces Could you please this post from @Boorda to be the first post in this thread as originally intended? It is the introductory post for this thread content, and has lots of useful info that's easily accessed in the first post of the thread. Thanks!

 

[Dumaurier7]

​

Block & Engine Externals​

N55 ​

• Initial Release
  
  • Cast iron cylinder sleeves

S55​

• Initial Release
  
  • Closed-deck design
  • Stronger cylinder walls
  • Plasma-transferred wire arc sprayed cylinder liners for improved strength and heat dissipation

Its hard for me to understand how aluminum could be stronger than cast iron here! I am inclined to believe that the "additional" strength is afforded by the closed deck design....... of course I could be wrong!

 

[wheela]

Its hard for me to understand how aluminum could be stronger than cast iron here! I am inclined to believe that the "additional" strength is afforded by the closed deck design....... of course I could be wrong!

Wow, I was going to agree with you but thought I'd look up the properties of Alusil first. Here's what Google AI had to say about it. Apparently, Alusil is both stronger and stiffer than cast iron, and has better fatigue resistance. This one hurt a little, I was thinking atleast n55 had stronger cylider walls than s55, but that appears to be wrong. Starting to get some envy for the s55 block Learn something new every day

 

[Dumaurier7]

This one hurt a little,.......

It sure flippin' did!

Apparently, Alusil is both stronger and stiffer than cast iron, and has better fatigue resistance.

Very Impressive!

I was thinking at least n55 had stronger cylinder walls than s55, but that appears to be wrong

Yup, oh well..... I am committed and will see it through till the end, if the stock liners take a dump, I'm prepared to just do a re-sleeve and be done with it!

 

[Boorda]

Any news about cooling when using the N55 head with the S55 block and gasket?

I haven't gotten around to doing the scans and the silicone castings of the ports yet, but I promise I will add that info soon!

@doublespaces Could you please this post from @Boorda to be the first post in this thread as originally intended? It is the introductory post for this thread content, and has lots of useful info that's easily accessed in the first post of the thread. Thanks!

You see, what had happened was....

I asked @doublespaces to migrate some posts from another thread where we kinda hijacked someone's build thread.

I think what I'll do is recreate the thread fresh with the info from this one just to get things back in line.



And thanks everyone for the info, I wish we could have group editable posts, that way everyone wouldn't be waiting on my availability to make the edits. @doublespaces is this a feature that could be investigated, community posts?