Since the initial release of the N54 in 2007, BMW has earned a reputation for building a line-up of turbocharged engines that are capable of significant power gains with a tune and basic bolt-ons. The N20 was BMW’s first turbocharged, direct-injected 4-cylinder engine. From the factory the strongest version of the N20, found in 28i variants, is rated at 241hp and 258tq. However, real world dyno testing suggests those numbers are slightly underrated with the engine producing similar numbers to the wheels. Depending on the assumed drive-train loss, this would put the N20 in the ballpark of 275hp and 290tq at the crank. A stout performance for a stock 4-cylinder, however, as we know with almost any turbocharged engine, there is a lot of untapped power that some basic mods can unleash. Though, the question is – can the stock components handle the newfound power?
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A Look Into the BMW N20
There seems to be quite a bit of information floating around forums that the BMW N20 is a relatively weak motor. Although, for some reason, it is challenging to find any solid evidence the N20 is truly as weak as some suggest, but that is not to say the engine is flawless. It has been plagued with a major issue involving the timing chain, which in some cases may lead to complete engine failure. BMW updated the timing chain in 2015, which seems to have solved the problem for the most part. We will write a more in-depth post regarding the timing chain issues in the future, but for now let’s examine the more exciting aspects of the N20.
As stated, the engine is underrated from the factory and already provides respectable performance for a fuel-efficient 2.0L engine. However, for some enthusiasts, a little extra power can go a long way. Like other turbocharged BMW engines, the aftermarket industry is littered with tunes and basic bolt-on modifications. Common mods include tunes, air intakes (CAI), catless downpipes (DP), and upgraded front mount intercoolers (FMIC). Typically, when all mods are combined the engine may be referred to as full bolt-on (FBO). An FBO N20 engine with a small E85 mixture is capable of producing upwards of 350hp and torque. However, the question remains – can the N20 really handle that much power?
As a disclaimer, it is important to note that putting a specific number on the upper limits of the stock internals and block is tough. The N20, as with any engine, may be capable of producing higher numbers than the engine can tolerate in the long-run during “glory runs” on the dyno. Additionally, every N20 is different. Some may be able to produce power and torque significantly above stock levels without issues, while other engines may let go much sooner. With that being said, lets dive into the generally accepted upper limits of the N20.
N20 Tuning Potential
The safe upper limits of the N20 appear to be somewhere in the lower-mid 300whp and wheel torque range. This is roughly where you will end up with full bolt-ons and some E85 in the N20, and the general consensus is not many owners are pushing their cars beyond this limit without upgraded rods at the least. You may be able to push the car a bit harder on the stock engine, but here are a few things to consider:
- Limit boost from stock turbos to 22psi
- Use data logging to your advantage – watch for lean conditions
- Oil starvation under hard braking or cornering
On a stock turbo N20 it is highly recommended to keep boost in the lower 20’s with 22psi being towards the higher end of the safety margin. Additionally, the N20 is known to have issues with running a bit too lean. This is concerning when pushing the engine towards it’s limits as lean conditions are more likely to cause engine knocks. Lastly, hard braking and cornering may cause the N20 to go through a period of oil starvation. Obviously, on a stock motor oil starvation is still a horrible thing, however, increased power may lead to more significant issues due to oil starvation.
The Importance of Having the Right Tune
I believe some consider the N20 a weak motor, because it is more finicky than the 6-cylinder N54 and N55 engines. There are many N54/N55 owners and tuners who have no idea what they’re doing. They toss a few mods on the car, turn up the boost, dump some E85 in the tank, and let it rip. In most cases, the engines hold up very well on stock turbos as they are simply not making enough power or torque to do significant damage without major abuse. In my opinion, the N20 is a relatively capable engine from the factory and performs well for a small 4-cylinder, however, they do require a bit more attention and knowledge than their counterparts.
It is highly important to ensure you are running the right tune on your N20. You cannot simply toss on some bolt-ons, E85, and crank up the tune to be as aggressive as possible. Ensure you have the right supporting and cooling mods, and your tune is properly accounting for the mods you are running. For example, running an upgraded FMIC will assist in keeping IAT’s to a minimum, thereby reducing the change of engine knock. Additionally, upgraded fueling components for heavy E85 mixtures will help the fuel flow and reduce the likelihood of the engine running too lean. In other words, keep the tune modest and do not push things too far. The extra 10hp from an aggressive tune is not worth the significantly increased risk of blowing the motor.
The N20 has earned a reputation for being a weak BMW engine, a reputation that I believe is falsely warranted. I am not saying it is as capable as the N54, N55, B48, S55, etc but is that what anyone would expect from the engine? It is a 4-cylinder 2 liter engine that was designed with entry level BMW models, not a 6-cylinder engine designed for mid-range or higher end models. If the N20 could really handle 500whp without breaking a sweat why would any enthusiast get excited about the 425hp M3 or 300hp N55?
The N20 does exactly what it was designed to do, and then some. A tune and simple bolt-ons can propel the engine into 300+hp and torque territory; respectable performance which remains fuel-efficient and enjoyable to daily drive with enough power on tap to have some good fun when called upon. However, the N20 does have its limits which may be a concern when looking to push things too hard. Equip your N20 with full bolt-ons and the appropriate supporting mods and a conservative tune. Do this and you will likely have a wonderful experience driving an engine that is powerful, reliable, responsive, fuel-efficient, and an all-around enjoyable driving experience. Treat the N20 like its BMW’s twin turbo S55 engine found in the M3/M4, then you may join the crowd of owners complaining the N20 is too weak.