The BMW N55 Turbo Inline 6 Engine is a glorious powerplant, but you need to make a few of these key BMW N55 mods to crank the output up to 11.
UPDATED 5/2/2016: More parts for the N55 have come out since we first wrote our guide to Bolt ons for the N55 E90 and E92 335i so we’ve revised our guide with the latest and greatest parts on the aftermarket.
The following are 5 fairly straightforward N55 Mods that will take your N55-powered 2011+ BMW 335i (E9X), 2012+ BMW 335i (F30) or N55-powered F10 5-series or 2011+ E82/E88 1-series from stock to FBO – aka Full Bolt On status. Making these critical tweaks to your E9X or F30/F32 will really wake up the car and can boost your output by more than 100 horsepower. By following this stepped upgrade path, your N55-powered BMW will be ready for the next stage and be operating at peak performance.
1. A Tune
As with the N54, tuning the ECM is the easiest, fastest, most direct way to make more power, right now with your N55-powered Bimmer. Most tuners are plug and play with minimal effort required to physically install them – in fact, tuning cars these days is often so simple a child could to it. By modifying parameters like boost, timing, fuel curve, throttle mapping and other key functions, a tune will seriously alter the character of your N55 engine. Output increases are HUGE as far as “Gains From A Tune” go, and only increase as you mod the car further – you can pick up up over 120 horsepower with a Stage 3 aggressive tune (requires full bolt on) and give those ///M guys something to worry about.
Tunes allow you to adjust your engine’s programming as you add bolt-on parts, offering you flexibility to have your tune adjust with a different map as you upgrade. Several different tunes are available, so it’s up to you to determine which one is best for you. If you’re unsure, you can always consult a Modification Expert for their advice – most of our experts have first hand experience with at least one of the types of tuners mentioned below on their own cars. Here are few tunes available for your 2011+ N55:
BMS JB 4 Stage II Processor for N55 Engine (E9X) Up To +60whp/80wtq gain over stock, up to 100whp/120wtq++ gain with Stage III+ supporting mods
Benefits: Displays integrated into OEM dashboard, ideal for the power user who knows what they’re doing.
This is a Piggy-Back type system and doesn’t reflash the ECM, but rather manipulates the ECU through a number of sensor inputs. The JB4 offers more features than the other systems but you’ll need to take the time to learn how to use it to take advantage of all the clever features that it offers, like shift lights, open/closing exhaust valves on demand, boost gauge and a whole host of neat things it can do, certainly too much to list here.
Effectively, you enter the “konami code” through your existing dash buttons and the JB4 does a particular feature. The JB4 is a bit like LINUX. If you know how to use it and the tricks to getting the most out of it, it’s AMAZING, but if you want to just plug in and be done, you may want to consider other options. It’s also important to mention that if you live in California, you can basically forget about the JB4, as it’s not legal for sale to any car – racecar or streetcar – in California.
Cobb AccessPORT V3 ECU Flash Tuner BMW N55 (AP3-BMW-002) Up To +57WHP +78TQ Gain Over Stock, up to 100whp/120wtq++ gain possible with Stage III+ supporting mods
Benefits: Installs directly via the OBD II computer port, and no physical part is actually installed. Once you install your tune via the AccessPORT, you can unplug the accessport itself and leave it at home. You DO NOT have to leave it connected – the tune is there until you select “UNINSTALL”. You DO NOT have to uninstall to switch maps.
For those of you on a budget, we still have AccessPORT V2 models for N55 available for just $699. The power gains are identical and the maps are the same, but the V3 runs faster, has a bigger screen and is more useful if you plan to keep the V3 mounted and use its gauge display functions. If you plan to just leave your AP at home, a V2 is a great option.
2. An Intake Upgrade
An Intake is not always the biggest gain in power for a naturally aspirated car, but that’s not the case for turbocharged cars like our N55 powered BMWs. These cars have a lot to gain from the use of an aftermarket intake designed with performance in mind. The biggest benefits of an intake are improved throttle response and you “hear” your engine more under wide open throttle – turbo and supercharged cars will hear more turbo spool and a few horsepower at the rear wheels. In fact, your mileage may even improve with a performance air intake – if you can keep your foot out of it.
There are options ranging from “OEM++” for a like-factory look that’s low key and stealthy for those that don’t want to “look” modded, or a well engineered dual filter cold air intake can deliver up to 31HP and 7lb/ft of torque. With so many options, there’s too many to list here- cruise on over to the E90 Intake, E92 Intake, F30 Intake and F10 Intake pages to browse our full range of intakes for the E90, E92 & F30 335i. Listed below are just a few examples of the different types of intake upgrades available.
BMS Performance Intake 2011+ 135i, 335i
+10WHP Gain; Open Airbox Design, Rotomolded Intake Tube
BMS Performance Intake 2012+ 335i/435i [F30/F32]
+11whp/+7wtq Gain; Open Airbox Design, Plastic Intake Tube
BMS Performance Intake 2010+ 5-Series 2011+ 6-Series
+10whp Gain; Open Airbox Design – Rotomolded Intake Tube
Injen Cold Air Intake System N55 BMW 135i / 335i [E82/E90/E92]
+9WHP/+12WTQ Gain – Heat Shielded Open Airbox Design, Metal Intake Tube
+14whp +10wtq Peak Gains; Heat Shielded Design, Bespoke Carbon Fiber Construction, Handmade in Japan, True Cold Air Induction w/Ram Air Effect
3) Catted High Flow Downpipe
Besides a tune, a Downpipe is going to feel like the single biggest “butt-dyno” upgrade. The Downpipe is the piece of exhaust that connects from the turbocharger’s outlet to the rest of the exhaust system. The OEM catalysts are pretty restrictive and limit how quickly your turbochargers can spool. By upgrading your downpipe with a flow-optimized downpipe fitted with a high-flow sports catalytic converter, you’ll immediately notice improved throttle response, louder and faster turbo spool-up and more overall power – on average, you’ll gain about 15hp from a high-flow catted downpipe. If you want your engine to feel more responsive, a downpipe will deliver the improvement you’re after. Listed below are several popular options for downpipes – for use anywhere within the United States or its jurisdictions, we suggest only looking at downpipes with a high flow catalytic converter. You can always consult a Modification Expert if you’re unsure what the best option for you is.
4) Front Mount Intercooler aka FMIC
Dinan Front Mount Intercooler for E90 335i Shown Installed
As we mentioned in an earlier post, the N55 engine runs hot from the factory and benefits from reductions in temperature – an Oil Cooler is a necessity – and an Intercooler will further help reduce engine temperatures. An intercooler is ideally that “next step” that helps support your other modifications. The OEM Intercooler for the N55 engine is a few sizes too small- it measures just 510mm x 130mm x 110mm for just 7,293 cm3 of volume.
This reduction in volume means that intake air temperatures are way higher than they should be – and with hotter intake temps, the air is less oxygen-dense, meaning it doesn’t make as much power and can lead to detonation. An aftermarket intercooler can offer as much as a 90% increase in airflow, reducing turbo lag, increasing throttle response and spool-up.
It’s important to note that the Intercooler’s piping can be as much of a restriction as an intercooler’s lack of volume, so consider an intercooler upgrade that includes larger inlet/outlet piping for the greatest benefit from your intercooler. What’s more, nearly all aftermarket intercoolers eliminate the failure-prone plastic end tanks popular as OEM units.
TL; DR, having a front mounted intercooler means that your car can consistently produce its peak power, pull after pull – and also reduces turbo lag and increases throttle response and faster boost spool-ups – ballpark power gain estimates for Intercoolers alone range from 15-25 HP gain (at the wheels). Listed below are several popular choices for
BMW N55 Intercoolers, but these are just a few suggestions. Take a look at the options available and decide which is best for your build, or you can always ask a Modification Expert.
Active Autowerke Front Mount Intercooler for 2007-13 BMW 335i E90/E92
88% Larger Core than Stock, +12RWHP Gain
Cobb BMW 135i/335i Front Mount Intercooler
20% Increase in Cooling Efficiency, 60% Larger Core than Stock
RPi Intercooler for 2007-13 N54 BMW 335i/335is [E90/E92/E93]
35% Larger Intercooler Core than OEM; 26whp Gain
Wagner Tuning BMW N54/N55 Intercoolers Evo I Evo II
Performance I and II & Competition I and II Versions to Suit your Build & Budget
85% More Surface Area than OEM; 63% Larger Core Volume
5) An Exhaust System
Most people upgrading their exhaust do so for the sound, but on the N55, there’s some power there in upgrading your BMW exhaust system, in addition to the improvement in exhaust tone. There are quite a few performance exhaust for BMW available, ranging from quiet to aggressive. Since exhaust can be subjective, the right exhaust for you may not be the right exhaust for your friend who likes his car louder than you do – and so on. For these reasons, it’s important to do your research and look at all the options available to you before making your decision. These systems offer a gain of around 10hp at the lower end of the spectrum, and that number will increase as you add other modifications. While not the biggest gain by itself, like the intercooler, a good high flow exhaust is an excellent supporting modification that will have your vehicle ready to go to the next level. Here are just a few exhaust options for the N55. We have videos available so you can gauge sound levels for yourself, and you can always ask a Modification Expert for guidance for what sort of system is best for your needs.
E90/E92 N55 335i
HKS Downpipe-Back Exhaust for 2007-13 BMW 335i [E90/E92]
+11whp / +8wtq
Magnaflow Cat-Back Exhaust for 2007-13 BMW 335i [E90/E92]
Berk Technology Race Exhaust E82 135i
Berk Technology Street Exhaust E82 135i
Rogue Engineering E82 135i DMS Exhaust
F30 N55 335i
Eisenman Exhaust for F30 335i – an excellent choice for those who prefer to be bold.
BMW Performance Axle-Back Exhaust for F30 335i – A great choice for any build and a great way to enhance sound without overdoing it.
Remus Axle Back exhaust for F30 335i and 435i – dyno proven to improve horsepower and torque while maintaining the “German” character of the car while enhancing the exhaust sound of the N55. Like all Remus exhaust systems, this one too features OEM-level fitment and a great drone-free exhaust note.
E82 135i with N55
Berk Technology Street Cat-Back Exhaust for 2008-12 BMW 135i [E82]
MagnaFlow Cat-Back Exhaust for 2008-13 BMW 135i/128i [E82]
The modifications above will take your car from stock to FBO status, but it would be a disservice to you to not mention a few other things to consider as well. These items are great “preemptive” mods, that resolve potential issues that may arise as you modify your N55 powerplant and help increase the longevity of your engine.
-Stage 2 Hybrid Turbo Upgrade
If you’re going to go hog wild, do it the right way. Designed byVargas Turbo, this hybrid turbo setup for N55 Engines is more than a replacement. Featuring bulletproof Garrett internals and a Dual Ball Bearing center section, this turbo setup is able to capably manage 500-550 wheel horsepower with certain tunes and fuel tweaks, allowing for reliable and consistent boost from idle to redline. In short, this system will boost your output without sacrificing engine longevity.
The problem with the BMW N55 engine’s charge pipes is that they were never really designed to contain high boost. Evolution Racewerks discovered the factory diverter valves could not stand up to race use and the charge pipe itself would develop boost leaks under the harsh conditions of racing, and a new unit had to be designed.
In addition to the low boost-pressure capacity, OEM charge pipe has a silencer baffle built in which also splits airflow and causes turbulence in the intake. By removing the turbulence caused by the baffles, you’ll experience increased throttle response, decreased turbo lag and an overall higher output potential. Charge Pipe/Diverter valve combinations are available with optional blow-off valves (for those who enjoy that cool “pssshh!” sound when shifting) and even optional Methanol Injection bungs (should you add Meth later). A charge pipe will also help prevent potential boost leaks. Making this upgrade now will allow you to safely run higher levels of boost later on.
Evolution RaceWerks Charge Pipe N55
-Oil Catch Can
If you’ve ever taken your intercooler piping off and been amazed by the amount of nasty oil coating the inside of your intercooler, it’s time to consider an oil catch can. The main reason to add an Oil Catch Can to their N55 engine is to reduce/eliminate oil blow-by. Blow-by is caused when combustion in the engine forces fuel, air, and moisture past the piston rings and into the crankcase. From there, the blow-by is released by the crank case vents back into the intake pipe. This occurs on all engines, but is notably worse on turbo engines due to the higher pressure in the combustion chamber. If nothing is done, this excess “gunk” will build up in the valvetrain, turbo, intercooler, and intercooler piping, robbing your engine of performance over time. If you have a lower-mileage car, this is a great boon to your motor’s longevity.
Mishimoto Oil Catch Can BMW N54/N55 Engine
-An Oil Cooler
The Oil Cooler Shroud directs cool air directly into the cooler’s core, enhancing cooling capacity.
It’s common knowledge that BMW N55 Turbocharged I-6 engines run very hot. Basically, any kind of spirited driving will QUICKLY have your engine operating much hotter than it should be, causing your oil to stop lubricating your engine’s moving parts properly and even overheat. This overheated condition can send your car into “Limp Mode”, making your drive home a whole lot less fun. Considering that BMWs are intended to be driven hard, this can make it hard to enjoy your ultimate driving machine. Since turbochargers are exhaust driven, they’re naturally going to be hot and accumulate a lot of heat. This heat generation, and the fact that N55-Powered BMW models have a small radiator, means that under spirited driving conditions (like your favorite canyon), your coolant temperature can exceed 250 degrees – more than 20 degrees above what’s considered “hot” for other cars (230* F).
Many turbo BMW E82, E90, E92 and E93 models have an oil cooler that’s simply too small for the job. This is why if you do any of spirited driving at all or just want to extend the life of your motor, you should install an oil cooler large enough to sufficiently cool the oil, keeping your engine running cool and happy. You can read more about why your
N55 Engine Needs an Oil Cooler here.
Consider adding an oil cooler, such as the ones offered by Evolution Racewerks to keep your BMW’s oil cool and lubricating your motor like it should be to ensure many happy miles to come.
*Evolution Racewerks Sport/Competition Series Oil Cooler 135i/335i
We hope this information is helpful to you – enthusiast to enthusiast- so that you can enjoy your turbocharged BMW to the fullest and get more smiles-per-gallon out of your Ultimate Driving Machine.
Story by Nicholas Gregson in collaboration with Senior Modification Expert Alan Wei