BMW N54 vs. N55 Performance, Reliability, and Tunability. Prior to acquiring a turbocharged 135i, 335i or 535i it is very important to consider the distinctions in between the N54 and N55 powered BMW’s. The N54 started production in 2006 and first appeared in the 2007 BMW 335i; in 2008, the N54 was presented in addition to the 535i and 135i. BMW’s N55 engine started production in 2009 and started changing the N54 in 2010.
However, most applications built in 2010 still carried the twin turbo N54. The N55 formally changed the N54 in 2011 (with the exception of the 1M and Z4 35i). The engines have lots of similarities this post will highlight the crucial distinctions in between the two.
N54 vs. N55: Single vs. Twin Turbochargers
Perhaps, the most substantial difference between the N54 and N55 is the turbochargers; the N54 boosts real twin turbochargers while its N55 equivalent carries a single twin-scroll turbocharger. A twin-scroll turbocharger is a single turbo where the exhaust real estate of the turbocharger is split into 2 “scrolls”. Each 3 cylinders on the same shooting cycle feed a private scroll of the turbocharger which reduces exhaust reversion.
Reversion is the procedure of exhaust gases entering the combustion chamber as the gases engage with each other; this produces higher temperatures, less power, and greater emissions. What does all of this mean? A twin scroll turbocharger increases performance therefore reducing turbo spool time, increasing power, and allows the cylinders to run cooler. In spite of the benefits of a twin-scroll turbo as compared to a single single-scroll turbo, a real twin turbo setup mirrors the advantages of a twin-scroll turbo. As with the twin-scroll, 3 cylinders feed each of the two turbos consequently reducing reversion.
Out of the factory, performance does not differ much
From the factory, both the N54 and N55 engines produce similar torque and power bands. The twin-scroll design enables the turbocharger to spool a little quicker on the N55, providing peak torque 100 RPM’s sooner than the N54. This does not lead to a considerable difference– the N54 and N55 each produce very little turbo lag and feel similar to a naturally aspirated V8. On stock applications both engines carry out approximately the very same in spite of the difference in turbochargers. When comparing the N54 and N55 mod-for-mod the benefits of a true twin turbo set up become obvious.
The N54 is more tuner-friendly
BMW’s N54 twin-turbocharged engine actually comes to life when customized; I do not intend to suggest the N55 is anything but impressive when customized. The N54’s twin turbo design merely moves more air and does so more effectively. Mod for mod the N54 will outperform the N55. A big reason for the switch from the twin-turbo to twin-scroll turbo is expense and intricacy. 2 turbochargers with all of the associated hard-ware are more expensive and need extra space. Although the N54 is more effective when modified, each engine and its respective turbocharger established will produce well into the range of 400+ wheel horsepower and torque.
N54 vs. N55 Reliability: Which Engine is More Dependable?
This is always a touchy subject when it concerns conversations about the N54 and N55. Put simply, the N55 is more reputable. BMW’s N54 was the very first mass production turbocharged gasoline engine produced by BMW in years. Taking a look at BMW’s current line-up in 2017, which is mainly turbocharged, I think it is fair to state the N54 remained in lots of methods an “experiment”. The N54 was infamous for its unpleasant and common issues early on. Fuel injectors, the HPFP (high pressure fuel pump), and waste-gate rattle plagued the N54 for the very first a number of years of its production. These are among several other issues that have actually encouraged some BMW owners to prevent the N54. Nevertheless, BMW offered lots of recalls and extended guarantees to help treat the reliability concerns. You can check out all of the most common N54 problems here.
Because the N55’s introduction a number of the problems with the N54 have been resolved as BMW presented brand-new HPFP’s and fuel injectors. Waste-gate rattle is still a fairly widespread problem on the N54, however this generally does not affect the life or durability of the turbos. Furthermore, BMW uses an 8 year, 82,000-mile prolonged guarantee for waste-gate rattle on the N54. I really had my turbochargers changed on my 2007 335i under the extended service warranty (a story for another day). Long story short, I am impressed with BMW’s willingness to “make things right” and ensure the issues were resolved with the N54. While the N55 was produced to be more reputable than the N54, it still has it’s problems. Read about the most common N55 problems.
At the end of the day, the N55 is the more trustworthy engine
BMW got things right from the start with the N55– something that can’t be said for the N54. Putting aside the early issues the N54 and N55 are both fairly reliable engines. Some of the supporting hardware such as valve cover gaskets and water pumps are common problems on each, and will likely be for the long run. BMW isn’t targeting customers looking for the most trustworthy cars on the road. BMW builds “The Ultimate Driving Machine” which the two engines measure up to and after that some.
N54 vs. N55 Engine Internals
I won’t invest long on this subject as the engine internals can be another controversial subject, and for those seeking to stick with stock turbos the internals on each engine are plenty strong. The N54 comes stock with a created crankshaft and rods. The N55 features a cast iron crankshaft and rods.
Related: Failure of the BMW Professional Head Unit Display (E90-E93, E82, E88)
Both the N54 and N55 have actually cast irons pistons. Unless you are seeking to press 600+whp and a LOT of PSI through the engines then this is likely a non-issue. Both engines are incredibly strong factory motors than can deal with a lot of abuse on the stock blocks and internals.
So…Twin-Turbochargers or Single Turbo?
BMW’s N54 and N55 engines are comparable in many aspects and stock-for-stock carry out nearly identically. The N55 twin-scroll turbo provides a little faster turbo spool and provides peak torque 100 RPM’s faster than the N54; a characteristic that is not visible as each turbo established spindles rapidly and delivers impressive torque through-out the low end and midrange.
Thanks to the N54’s twin turbos and created internals, it is the more capable engine mod-for-mod. The N55 has proven to be the more trustworthy engine. N54’s are well-known for their common problems, particularly early on, but these concerns are currently resolved. If you are searching for an all-around dependable car, chances are, neither the N54 nor N55 will be at the top of your list.
Read our guide on the 8 A Lot Of Common N54 Engine Problems to learn what to look for, and how to lessen N54 reliability issues!
