A bit late to the party, but the combustion chamber on the S55 head may well be slightly different to the N55. CP, Mahle, and other big name piston manufacturers list the same pistons for both N55 and S55 but in the S55 their pistons have a 10.2 (standard) compression ratio, but in the N55 the compression ratio is stated as 11. It could be that one person/company has tested it and they all copied each other, or it could be that there are, in fact, changes between the S55 and N55 head confirmed by several big piston manufacturers.
Head ports could therefore likely be different as a result too.
Head ports could therefore likely be different as a result too.
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.
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.
Check back regularly as I will do my best to maintain this first post with shortcuts to various posts and resources.
Technical Documentation
N55
- Technical Training
S55
Other Resources
N55
S55
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
- 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:
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?
Question Queue
- What's involved in adapting the S55 cooling system to an N55?
- Not Possible
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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?)?
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?)?
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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.
Great to know, thanks for sharing!
So both s55 and n55 start out at 10.2:1. If the same aftermarket piston still yields 10.2:1 in an s55, but 11:1 in an n55, that would mean more head volume in the n55 head vs. s55 head, right? If so, then if you swapped an s55 head onto an n55, you'd increase the compression ratio to higher than 10.2:1, and could potentially (depending on the specific differences in geometry) be placing the spark plugs closer to the pistons? Am I thinking about that correctly? Those things may or may not be a problem, but would definately be good to know about if one was swapping heads.
Wow, that sounds awesome, thanks again for pulling this all together, great resource for the community!
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
Wait, I think what I said above is backwards... It would be less headspace in the n55 vs. s55, right?
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)
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'll modify the first post so that we can start to capture engine revisions for each platforms as well.
N55 - Single Oil Pump
M2 N55 - Dual Oil Pump System (not sure about the correct name)
S55 - Same as M2 N55
M2 N55 - Dual Oil Pump System (not sure about the correct name)
S55 - Same as M2 N55
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.
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.
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
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 manifoldI 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
If I come across any of those I can scan them tooI need a 3d scan from the N54 intake ports and the B58 manifold
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 winAttachments
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...
I did manage to get some good scans of my 8HP75Z tranny though...
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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
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