N55 vs S55: Technical Differences, Compatibility & Performance Potential

[Boorda]

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

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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

​

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[wheela]

Thanks for putting this together!

A comment about the rods - this may depend on year of n55, but per realoem, the rods in my n55 (2015 e84 n55 with pwg) cross-reference to the s55 engine. Anecdotally, I've heard they changed the rods after the earliest n55's (2010 and potentially 2011?)?

 

[Boorda]

Thanks for putting this together!

A comment about the rods - this may depend on year of n55, but per realoem, the rods in my n55 (2015 e84 n55 with pwg) cross-reference to the s55 engine. Anecdotally, I've heard they changed the rods after the earliest n55's (2010 and potentially 2011?)?

Perfect, thanks for contributing!

I'm actually working on an AI Agent specific to searching through RealOEM to find nuances like this.
You'll also be able to ask it questions and it will make comparisons and pull the info for you.

 

[wheela]

Perfect, thanks for contributing!

I'm actually working on an AI Agent specific to searching through RealOEM to find nuances like this.
You'll also be able to ask it questions and it will make comparisons and pull the info for you.

Wow, that sounds awesome, thanks again for pulling this all together, great resource for the community!

 

[wheela]

Totally anecdotal, but I've also come across comments that after initially launching s55 with the magnesium oil pan, bmw switched s55 to an aluminum pan somewhere along the line. Maybe that's something an AI tool could identify/confirm/deny

 

[Ali_X]

Thanks for putting this together!

A comment about the rods - this may depend on year of n55, but per realoem, the rods in my n55 (2015 e84 n55 with pwg) cross-reference to the s55 engine. Anecdotally, I've heard they changed the rods after the earliest n55's (2010 and potentially 2011?)?

I also believe and correct me if I'm wrong but the N55 EWG produced from July 2013 installed on the 235, M2 and x4 40i (N55 engine) has a forged cranckshaft and a revised cooling system and oil pump regardless of xdrive or not.
Only the M2 and 235iR have the S55 oil scavening system (dual pump, sump)

 

[Boorda]

Totally anecdotal, but I've also come across comments that after initially launching s55 with the magnesium oil pan, bmw switched s55 to an aluminum pan somewhere along the line. Maybe that's something an AI tool could identify/confirm/deny

I also believe and correct me if I'm wrong but the N55 EWG produced from July 2013 installed on the 235, M2 and x4 40i (N55 engine) has a forged cranckshaft and a revised cooling system and oil pump regardless of xdrive or not.
Only the M2 and 235iR have the S55 oil scavening system (dual pump, sump)

I'll modify the first post so that we can start to capture engine revisions for each platforms as well.

 

[JohnDaviz]

N55 - Single Oil Pump
M2 N55 - Dual Oil Pump System (not sure about the correct name)
S55 - Same as M2 N55

 

[Boorda]

Ok, silicone came in today, so here in the next couple of days I'll get those port molds made for the heads.
Im thinking if I dont have enough silicone, I'll do at least three ports and then average the volumes; this will be done for each head's intake and exhaust sides.

 

[wheela]

I can also 3d scan the intake valve port of an n55 head I have in the garage and upload an .stl file of it for comparison. Once I'm done with my big turbo mock-up, I can also do the same for the exhaust ports and combustion chambers

If anybody wants to send me an s55 head I can do the same for that

 

[JohnDaviz]

I can also 3d scan the intake valve port of an n55 head I have in the garage and upload an .stl file of it for comparison. Once I'm done with my big turbo mock-up, I can also do the same for the exhaust ports and combustion chambers

If anybody wants to send me an s55 head I can do the same for that

I need a 3d scan from the N54 intake ports and the B58 manifold

 

[wheela]

I need a 3d scan from the N54 intake ports and the B58 manifold

If I come across any of those I can scan them too

 

[Boorda]

@wheela What scanner are you using?
I have an Einstar Vega, but it has trouble getting into dark places like ports.
Other than that, it's F'n amazing for a consumer level scanner.

 

[wheela]

@wheela What scanner are you using?
I have an Einstar Vega, but it has trouble getting into dark places like ports.
Other than that, it's F'n amazing for a consumer level scanner.

Nice I got a Revopoint Miraco 3d scanner. I haven't tried the intake ports yet, so we'll see how it goes. I think its a pretty good scanner - my scans so far aren't that great yet, but I never watched any tutorials or anything so I don't really know what I'm doing with it, lol I always seem to lose tracking while scanning, it's a little frustrating. I was able to scan my block, water pump, and intake ducting well enough to design a turbo inlet for my kit though, which was my main purpose for getting the scanner, so I'll take it as a win

 

[Boorda]

Thats pretty damn good. I got mine primarily for same thing, but I havent gotten to the point of designing the intake for my new build.
I did manage to get some good scans of my 8HP75Z tranny though...

 

[wheela]

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

 

[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