¶ N2x Forged Internals Guide
This guide will touch on some of the specifics required when you build an N2x engine block.
(The N2x Platform shares around ~80% of its engine parts with the N55 and about ~60% with the S55, the N2x also shares some similarities with the BMW Prince Engines (N14, N18 etc)).
Please note, below information is an additional guide - this should be used in conjunction with the BMW N20 / N26 rebuild guide located in either BMW TIS/ISTA or equivalent.
Required Parts and/or Procedures for forging the N2x:
- Timing Chain, Oil Pump Chain, Chain Guides, Drive Sprockets.
- If you're rebuilding the motor and it's been built before JAN 2015 for Automatic Gearbox or JAN 2016 for Manual Gearbox then its best to get this over and done with whilst the engine is open.
- Notching The Cylinders For Upgraded Connecting Rods.
- Notching the base of the cylinders is usually required for H-Beam connecting rods due to their width being quite large as apposed to I-Beam connecting rods. The stock rods are a type of I-Beam configuration, typically you would use H-Beam high TQ motors and I-Beam for high HP and High revving engines. However over the years the technology has improved dramatically in forged connecting rods that I-Beam and H-Beam rods perform very similarly. At this time there are no I-Beam Connecting rods available for the N2x.
- Here is a video regarding the notching from Brintech Customs in AUS.
- Installing Sleeves Into The Engine Block.
- The N2x engines are made in the factory with the following: (This is taken from the BMW Technical Documentation).
- What this means is that the Cylinders require either a replacement or performance sleeve to be installed or for the block to have the arc spray process re-applied when new pistons and piston rings are required. Do not attempt to re-use your original piston rings on new pistons or forged pistons and ensure the piston rings match the cylinder they have been ring gapped for (google piston ring file fit/ring gapping). If you attempt to reuse old piston rings, or do not re-hone/bore a cylinder for a new set of rings/pistons you will more than likely end up with compression issues, oil blow-by or burning and low power output.
- Note: it is worth mentioning that we have seen examples of built N20s with closed deck insert/conversions and reapplied plasma arc spray coatings running in the 400-500whp range (Based on Dynojet) running around 30-38psig, however these cars haven't been operational at these high power/boost for a long period of time so we cannot gauge the longevity of the factory plasma arc coating as of yet in these extreme conditions.
- Since its always best practice to re-hone a cylinder even if its by just a couple of thou (thousands of an inch) due to small thickness of the arc spray process a Sleeve must be installed and is preferred over the factory arc spray process although as previously discussed it is challenging to find a shop that can have the arc spray process replied during an engine build process. There are 3 common options available on the market listed below:
¶ First we have the most common and cheapest Sleeve option the "Parallel" or "Repair" Sleeve:
- The "Parallel" or "Repair" Sleeve is good for those that need to repair the block close to factory specification if re-applying the arc spraying process is not available. The problem with these sleeves on the N2x platform lies in 3 areas:
- Using these sleeves with the Athena "Cut-Ring" Head Gasket, this gasket which incorporates a "Seal Wire"/ "Fire Ring" that is free floating from the rest of the gasket is quite thick and during the head torqueing process it places an immense amount of strain on the sleeve. If the sleeve is not installed correctly then the sleeve will begin to drop during the first engine heat cycle and you end up with a blown head gasket and loss of cylinder compression. The sleeve will continue to drop until it eventually bottoms out in the block, however finding out when this will occur is time consuming and costly (It only took me 6x to find out when my sleeve would stop dropping).
- Installation Error/Sleeve Mis-match, we've seen this too many times on this platform and it needs to be addressed. Most of the "Parallel"/"Repair" Sleeves we have seen are usually a "close enough" match from another engine application such as a diesel engine that is very similar but not identical to this engine. What we have seen is engine builders choose a sleeve that has either too large of an Outer Diameter or too small of an Outer Diameter. Those that use too large of an Outer Diameter results in the machinist carelessly machining into the coolant passages between cylinders which no matter the amount of sealant the engine builder may use will allow the coolant to leak down the cylinder between the aftermarket sleeve and the OEM aluminium cylinder wall resulting in coolant mixing with oil. Those that use too small of an Outer Diameter result in the cylinder wall thickness being too thin and under high horsepower or detonation can crack the sleeve, resulting in a failed motor.
- The last issue we have seen with these types of sleeves is when used under high performance applications, the sleeve drops as they're just not fit for purpose the immense cylinder pressures cause the block to warm up and the N2x uses quite a soft aluminium composition, which once warm combined with high power will see the sleeve drop, head gasket fail and another engine rebuild.
- You might think "what if I got a really good engine builder and a custom "Parallel"/"Repair" Sleeve made" if you did manage all of this, you could still experience the issue highlighted in point 3. which is why we only recommend such a sleeve for OEM style rebuilds where the engine power won't exceed standard stage 2 OTS levels. It is also recommended that if you do use this method you ensure the right type of material the sleeve is made of will be fit for the application it is being used for so it doesn't prematurely distort or crack. If you have access to re-applying the arc spray process then we would recommend you do that over a "parallel"/"repair" sleeve as its a lot less prone to the issues highlighted above.
- The "Parallel" or "Repair" Sleeve is good for those that need to repair the block close to factory specification if re-applying the arc spraying process is not available. The problem with these sleeves on the N2x platform lies in 3 areas:
¶ Flanged Sleeve this is a sturdier option and is denoted by flanged top or "hat" on the sleeve:
- The "Flanged" sleeve is very common in the BMW engine building world mostly in the 6 and 8 cylinder engines. The flanged top of the sleeve has more surface area and helps the sleeve stay seated in the block and eliminates the sleeve from dropping. The 3 issues we have seen with these types of sleeves in the N2x platform are:
- Cracked sleeves in high performance built engines, this is bound to happen if you use a sleeve that has too thin of a cylinder wall thickness especially when paired with an "Open Deck" block design, most of the "Flanged" Sleeves we have seen are usually a "close enough" match from another engine application such as a diesel engine that is very similar but not identical to this engine or use a material not designed to handle high boosted/nitrous applications. However should you elect to run a sleeve that is quite thick in wall thickness you then run into the likelihood of machining into the coolant passages between the cylinders and allow coolant and oil to mix. The best option we can suggest here to avoid this issue if you want to use this method is to have Darton Sleeves Inc, create custom "Flanged" sleeves that allow maximum wall thickness without causing the machinist to machine into the coolant passages between each cylinder.
- The next issue we have seen with these types of sleeves is again cracking of the sleeve, but due to the cylinder moving around under high boost due to the nature of the "Open Deck" design of the N2x. To combat such an issue having the deck "Closed" would help eliminate "Sleeve walk" and minimise chance of cracking.
- The last issue is sleeve material, you want to ensure the sleeve is constructed from a robust material so it doesn't distort or crack under high horsepower applications. Darton Sleeve's flanged sleeve material has so far been tested and is yielding great results over previous flanged sleeve solutions used on this platform.
- The "Flanged" sleeve is very common in the BMW engine building world mostly in the 6 and 8 cylinder engines. The flanged top of the sleeve has more surface area and helps the sleeve stay seated in the block and eliminates the sleeve from dropping. The 3 issues we have seen with these types of sleeves in the N2x platform are:
¶ The final sleeve option for the N2x is the Darton MID Wet Sleeve:
- This sleeve has been custom made by Navardi Tuned in conjunction with Darton Sleeves International Inc, and Brintech Customs Australia. This type of sleeve is designed to replace the entire aluminium cylinder wall and all the sleeve to be one solid piece rather than 2 different pieces of metal. This allows for better heat transference (lower cylinder temperature) and for better rigidity and strength. These sleeves also incorporate a closed deck design which is what we highly recommend if you are going to run a flanged sleeve, given this is the case from a cost perspective this solution ends up being the same or close to a "Closed Deck + Flanged Sleeve" solution. Below are some of the "Pros" & "Cons" of this setup:
- Pros:
- Integrated closed deck solution.
- Thicker cylinder wall thickness, which allows for more abuse and greater horsepower limits.
- Better heat transference of the cylinder.
- N2x Darton MID Wet Sleeves have been designed with 3x sealing O-rings whilst most Sleeve options are designed to be an "Interference fit" (which means they are slightly larger than the object they are being installed into, usually about 100 - 200 Thousands of an inch larger). This Darton offering allows for the sleeve to be easily replaced due to the 3x sealing O-rings they are not an interference fit design but rely on the O-rings to seal the sleeve to the block and prevent coolant from leaking into the crankcase. This type of setup is inherently better than an interference fit sleeve because if you have to replace a sleeve you need to replace it with a slightly oversized sleeve to maintain the interference fit and a good mechanical seal. These types of sleeves also allow replacing/repair individual cylinders especially if one or more cylinders are damaged beyond repair.
- Cons:
- Price, they can be more expensive per sleeve than a flange sleeve, however as stated before on this platform we strongly recommend closing the deck to stop sleeve/cylinder walk under high boost/horsepower applications.
- At this time these sleeves for this platform are made to order, and due to the ongoing pandemic Darton's manufacturing lead times are 12-18 weeks (pre-pandemic it was about 4-6 weeks).
- Installation cost, some shops may charge a higher install cost over other sleeve options as they cannot use a standard boring machine on this engine block. At minimum a 3 axis digital CNC machine needs to be used to remove the precise amount of material down to the nearest 10 or even 1 thousands of an inch.
- Finding a machinist/engine builder with a 3 axis CNC machine, you may find it challenging to find a shop local to you that owns or uses a 3 axis CNC machine. This may not be an issue for some people but it needs to be mentioned.
- Pros:
- This sleeve has been custom made by Navardi Tuned in conjunction with Darton Sleeves International Inc, and Brintech Customs Australia. This type of sleeve is designed to replace the entire aluminium cylinder wall and all the sleeve to be one solid piece rather than 2 different pieces of metal. This allows for better heat transference (lower cylinder temperature) and for better rigidity and strength. These sleeves also incorporate a closed deck design which is what we highly recommend if you are going to run a flanged sleeve, given this is the case from a cost perspective this solution ends up being the same or close to a "Closed Deck + Flanged Sleeve" solution. Below are some of the "Pros" & "Cons" of this setup:
¶ In closing:
Due to the large amount of failed built/forged engines we have seen, we highly recommend a Darton MID Wet Sleeve as your first solution, with the second solution being the "Flanged Liner & Closed Deck Conversion". We really do not recommend leaving the deck open for applications above 400WHP at boost pressures above 30psig (DynoJet based) as we have seen it crack the sleeves. given the average total cost of a Darton MID Wet Sleeve solution coming in close to a flanged liner + closed deck solution it would make more sense to go the Wet Sleeve as it has more inherent benefits over the flanged sleeves. For retrospect using a standard 84mm piston, the Darton MID Wet Sleeve has around 3.5mm of cylinder wall thickness between cylinders and about 8mm of wall thickness on the "thrust & non-thrust" sides of the cylinder (part of the cylinder exposed to the coolant jacket that takes the most abuse during engine combustion). For comparison an appropriate flanged liner usually sits around 1.8-1.9mm of cylinder wall thickness the entire way around.
¶ Closed Deck Conversion Information.
- As stated in the "Installing Sleeves into the engine block" section, closing the N2x engine block deck is highly recommended as we have seen on 30+PSIG setups if the block is left in its original open format the factory cylinders can begin to move around. Whilst this is slight it can be enough to cause a head gasket to fail or for a sleeve to crack if the force/movement is great enough. Closing the deck can and to the overall cost of the engine rebuild, there options to chose a hybrid design instead of a fully closed deck solution which is a cheaper alternative but it too will have its limits. My philosophy is do it once do it right, learn from my failures and avoid cutting corners where possible on this platform as it can become a nightmare very quickly.
- Open Deck Design (N2x Pictured):
- Semi Closed Deck Design (N2x Pictured):
- Fully Closed Deck Design (N2x Pictured):
- Required OEM Replacement Bolts & Gaskets.
- These parts must be replaced when rebuilding the N2x engine as they are either "Torque to Yield" or Gaskets that should be replaced (Torque to Yield "TTY" is a bolt or fastener that once tightened into place is stretched and can no longer be reused as it will never hold or regain the same amount of tightening torque):
- 16 x M8 x 30mm OEM Bed Plate Securing Bolts (OE 07129903926)
- 4 x M8 x 40mm OEM Crank/Flywheel Hub Bolts (OE 07119907475)
- 1 x Crankshaft HUB Seal (OE 11118618864)
- 1 x Crankshaft Flywheel HUB Seal (OE 11117587168)
- 2 x Spark plug / Injector Bucket Gaskets (OE 11127589830)
- 1 x Valve Cover Gasket Set OEM (OE 11127588418)
- 1 x M10 x 30mm Oil Pump Drive Gear Bolt OEM (OE 11277619309)
- 1 x Oil Filter Housing to Cylinder Head OEM Gasket (OE 11428637821)
- 2 x Oil Pan Bolt (OE 11137603830)
- 20 x Oil Pan Bolt (OE 11137603833)
- 1 x Vacuum Pump Seal (OE 11127507217)
- 1 x Valvetronic Seal Plate (OE 11377502022)
- 1 x Oil Pan/Sump Gasket:
- RWD vehicles: (OE 11137627512)
- AWD vehicles: (OE 11137627511)
- These parts must be replaced when rebuilding the N2x engine as they are either "Torque to Yield" or Gaskets that should be replaced (Torque to Yield "TTY" is a bolt or fastener that once tightened into place is stretched and can no longer be reused as it will never hold or regain the same amount of tightening torque):
¶ Cylinder Head Cracking Current Prevention Method.
- For those that are not aware the N20 Cylinder heads are known to crack around the spark plug seat and down underneath the valve seats causing compression loss and and engine idling/start-up issues. The working theory on what causes this is due to the small & thin amount of material exposed to the combustion chamber from the spark plug seat, if the engine runs too hot or too lean, or experiences detonation the material cracks and increases over time and heat cycling.
- Attached is a video from Brintech Customs Australia detailing the issue and the current method deployed to prevent the issue happening from a good condition cylinder head:
- Its estimated but of the wrecker cylinder heads we have seen at least 50% of them have these cracks not all are major and can be repaired, but the cracks that spread to the valve seat make the cylinder head unusable.
- Modification Of The Engine Block To Suit 10x 11mm ARP Head Studs (Including Head Stud Torque procedure). (Stock headstuds fail over 30psi of boost!)
- The stock head bolts (OE 11122212157) are fine for 30PSIG of boost, however they are a once off use component. The most appropriate upgrade is going to ARP2000 Head Studs currently the EVO X (Mitsubishi 4B11 Engine) ARP2000 & CustomAge 625+ Head Studs are compatible with the N2x Platform. However modification must be made to the 4x corner bolt holes to fit 10x 11mm studs, factory design uses 6x 11mm and 4x 10mm bolts from a performance point of view the 10mm studs are weaker than the 11mm and will be your first point of failure.
- To modify the block to accept 10x 11mm studs the 4x corner threaded holes must be modified using a "Time-Sert" they're like a helicoil but better and stronger, we do not recommend using a helicoils on engines in critical areas (cylinder head, crankshaft area etc.) as they are prone to failing. The go to standard is Time-Sert or Big-Sert if you manage to damage a installed Time-Sert. The Time-Sert you need is: M11 x 1.5mm x 30mm Thread Diameter: Metric 11mm Thread Pitch: 1.5mm Time-Sert Depth/Length: 30mm
- You will also need to drill out the 4x corner head bolt/stud holes in the Cylinder head to suit the larger head stud diameter, a 12mm or equivalent drill piece does the job.
- Links to the Time-Set kits (note Big-Sert not listed it is rare you may need to use them):
- Inserts: https://amzn.to/2V5FSCL
- Time-Sert Installation Kit: https://amzn.to/3hneRn7
- Torque procedure for the Head studs is as follows:
- Follow the ARP TQ specifications for your studs, however the TQ sequence is as follows:
- Once the initial head stud TQ procedure has been complete, recheck TQ after to ensure that any air pockets in the ARP lube has released - for added security if you want, rechecking the head stud TQ after a 500km break in will ensure the head studs are maintaining their final TQ spec.
- Below is a video of the Time-Sert process:
- Modification Of The ARP Main Studs To Allow Clearance For The Oil Pump/ Balancer Module.
- Due to tight clearance with the oil pump and balancer shaft module aftermarket ARP main studs will be required to be installed without the washer and to have excess thread/stud that protrudes out the top of the nut/fastener to be removed.
- Please refer to the below photo, notice the tops of the studs + nuts/fasteners is inline with the base of the engine block:
- Torque procedure for the Head studs is as follows:
- Follow the ARP TQ specifications for your studs, however the TQ sequence is as follows:
- Please refer to the below video:
Forged Internal Part Options:
- Connecting Rods, "Conrods", "Rods".
- Parts are listed from "Strongest" to "Weakest" (generally Stronger/Higher HP rated parts are more expensive):
- CP Carrillo Conrod with Carr Rod Bolts
- CP Carrillo Conrod with WMC Rod Bolts
- SP Components (Sold through VAC Motorsports)
- Max Speeding Rods with ARP L19 Rod Bolts ~ rated to around 800 crank HP.
- Max Speeding Rods with ARP2000 Rod Bolts ~ rated to around 600 crank HP.
- Parts are listed from "Strongest" to "Weakest" (generally Stronger/Higher HP rated parts are more expensive):
- Forged Pistons.
- Parts are listed from "Strongest" to "Weakest" (generally Stronger/Higher HP rated parts are more expensive):
- Piston Coatings are optional and can improve the durability of the piston, but I would only recommend using them when looking into a 600+HP N20. VAC Motorsports offers this option.
- Default piston pins are a chromoly material, however for additional cost you can upgrade these to heavy duty/steel piston pins. I recommend upgrading the pins if your goal is for the 800+HP range. VAC Motorsports offers this option.
- Pistons come in 2x off the shelf sizes 84mm and 84.5mm, since you have to sleeve the block, suggest going for the 84mm so that if you have to replace a piston and need to go up in bore size you can, without having to install a new sleeve. Custom sizes can be made however 84.5mm is the safe max for Flanged Sleeves / Parallel Sleeves, whilst the Darton MID Wet Sleeves were designed to take a maximum piston size of 85mm.
- Pistons come in 3 standard compression ratios: 9.5:1, 10.0:1 and 11.0:1. Depending on your turbo setup I would recommend a 9.5:1 or 10.0:1 compression piston just due to the cylinder head design using 11.0:1 Compression piston will end up limiting your achievable power. Just remember Head Gasket thickness and "decking" or resurfacing the engine block or cylinder head will increase or decrease total engine compression (thicker gasket usually = lower compression).
- Piston options (2618 forging is material used normally in top fuel engines, its an extremely robust and strong material compared to 4032 forgings):
- CP Carrillo 2618 Forging Piston.
- Head Gasket Options.
- Athena Cut-Ring Head Gasket 1.21mm thick.
- This composite gasket includes a fire ring that mechanically locks into the cylinder head to increase combustion seal. This is an aftermarket performance oriented Head Gasket for applications in the 35+PSIG range.
- BMW OE Head Gasket (OE 11128676514) 1.0mm thick.
- OEM MLS Gasket, requires a fresh engine block and cylinder head resurface to seal correctly, with a surface finish greater than 60RA.
- BMW OE Head Gasket (OE 11128676519) 0.7mm thick.
- OEM MLS Gasket, requires a fresh engine block and cylinder head resurface to seal correctly, with a surface finish greater than 60RA.
- Athena Cut-Ring Head Gasket 1.21mm thick.
- Connecting Rod Bearings.
- Due to the different sizing's these bearings can come in, you should have your shop/builder source the correct sized bearings. However the recommended upgraded bearings are ACL Tri-Metal Racing Bearings or King Bearings GPC Bearings from King Racing . You can get the bearings coated with a low friction coating such as a Calico Coating, VAC Motorsports offer this as an off the shelf item however they offer OEM bearings coated in a Calico Coating. If you want to have your bearings coated, it would be best to reach out to Calico separately.
- Crankshaft Bearings.
- At this stage the only offerings are OEM or King Bearings, given the vast array of sizes the main bearings can come in, it is best to let your shop/builder order the correct size for your application. Again Calico Coatings can be applied to these bearings if you reach out separately to Calico. The Calico Coating is a low friction coating/film applied to the bearing.
- Valve Lift Modification.
- BimmerMILVS offers a Valvelift modification that increases the Valvelift of the intake VVL (Variable Valve Lift System aka Valvetronic) by 1mm, increasing lift increases air into the engine resulting in more power.
- Head Studs.
- Currently the Mitsubishi EVO X (4B11) ARP2000 and ARP CustomAge 625+ Head Studs are the go to aftermarket head stud. Please refer to the information in "Modification Of The Engine Block To Suit 10x 11mm ARP Head Studs".
- Main Studs.
- Currently BMW M50 ARP2000 or ARP CustomAge 625+ Head Studs can be used as the N2x Main Studs. Please refer to the information in "Modification Of The ARP Main Studs To Allow Clearance For The Oil Pump/ Balancer Module".
- RWD Oil Pan.
- Given the issues the RWD Plastic Oil Pan / Sump has under high lateral left and right turns including issues of oil starvation under hard braking, it is advised that if you drive your vehicle in extreme or track like situations to upgrade your engine with a baffle kit. Currently Navardi Tuned offers an Aluminium RWD oil pan from URO Parts modified with a custom Baffle Kit made by the guys at Brintech Customs Australia.
- Given the issues the RWD Plastic Oil Pan / Sump has under high lateral left and right turns including issues of oil starvation under hard braking, it is advised that if you drive your vehicle in extreme or track like situations to upgrade your engine with a baffle kit. Currently Navardi Tuned offers an Aluminium RWD oil pan from URO Parts modified with a custom Baffle Kit made by the guys at Brintech Customs Australia.
- Auxiliary Mods/Information:
- If building a motor especially the N2x series engine, ensure you have all the correct supporting mods for your engine/turbo setup (This is more a checklist of what you may also want to consider, it is not required for building a motor):
- Upgraded Charge-pipes.
- Upgraded FMIC.
- Upgraded Intake.
- Upgraded Turbo Inlet.
- Upgraded Performance Exhaust.
- Upgraded DV Module.
- Oil Catch Can.
- Upgraded Coil Packs (If Necessary).
- Meth Injection (If Necessary).
- Upgraded HPFP Solution.
- Port Injection (If required).
- Upgraded DI Injectors to S63TU DI Injectors (OE 13647599876).
- Appropriate Spark Plugs and Gap.
- External/Aftermarket Oil Cooler Setup (look at N55 solutions) ensure you use an oil thermostat! so your engine doesn't take forever to warm up and you damage your bearings/internals etc cold oil is less vicious, meaning its more thick and can take longer to coat surfaces.
- Upgraded LPFP If Required (Not needed for anything under 450WHP based on DynoJet).
- Rotating Assembly Balancing
- Crankshaft Polishing
- Cylinder Head Porting
- If building a motor especially the N2x series engine, ensure you have all the correct supporting mods for your engine/turbo setup (This is more a checklist of what you may also want to consider, it is not required for building a motor):
- Cylinder Head Valve Train Specific Upgrades: (TBD)
- N20 Forged Engine Build Videos:
- Part 1:
- Part 2:
- Part 3:
- Part 4: