The BMW N20 and B48 have big reputations to live up to. They power 20i, 25i, 28i, and 30i models; a large percentage of all BMW models. Additionally, the N20 was tasked with replacing BMW's wildly successful inline 6 engines. These small 2.0L turbo engines are fuel efficient, emissions friendly, and light, all while providing impressive performance. How do the BMW N20 and B48 engines stack up?
BMW N20 Engine
Introduced in 2011, the N20 began phasing out the N52 the following year. It was a big deal. BMW is long known for their ability to build beautiful inline 6 engines. The N20 marks a big change to the inline 4, turbo engine. Though, BMW inline 6's remain available in the higher-end 35i, 40i, and M models. Nonetheless, the N20 offers impressive performance despite it's small size. The most powerful version, found in 28i models, makes 241hp and 258tq. Not too bad for a 2.0L engine. Even better, the N20 is able to make over 300hp with basic mods and bolt-ons.
BMW N20 Specs
Stock Power: 241hp
World Record HP: Estimated 400WHP
Displacement: 1997cc (1.997L)
Turbocharger: “TwinPower” Single Turbo
Compression: 10.3 to 1
Bore x Stroke: 84.0mm (3.31”) x 90.1mm (3.55”)
Internals: Cast iron internals
Block Design: Open-deck
Injectors: Bosch solenoid style direct injectors
***Specs for 2.0L BMW N20 engine (N13 and N26 have slightly different specs)
BMW N20 Performance & Mods
While BMW quotes 241 horsepower to the crank, testing shows the stock N20 is closer to 230whp. Assuming a standard 15% drive-train loss the N20 is closer to 270 horsepower. Already a solid improvement over the 3.0L naturally aspirated N52 engine. Of course, turbo BMW engines gain respectable power from simple mods. A tune and bolt-ons push the N20 to 300+whp. However, don't let engines like the N54, N55, or B58 fool you. Unfortunately, the N20 isn't as stout. It is likely best to keep boost around 22psi peak.
We've seen dynos showing nearly 400whp. Though, this is on built N20's with a larger turbo. Not too many N20 owners are truly pushing the limits. For most, it probably makes sense to upgrade to the turbo inline 6 engines if you're looking for 330+whp. This is not meant to be a knock towards the N20's performance. It's truly an excellent engine for its size. However, the N20 has it's limits and they should be respected.
Read our post about N20 mods here: BMW N20 350hp
BMW N20 Reliability
Overall, expect the BMW N20 to be a reliable engine. It seems to be a slight improvement over the preceding N52 engine. A concerning common problem is the N20 timing chain. This mostly applies to N20's produced prior to 2015. BMW updated the timing chain design in January 2015, which appears to mitigate the likelihood of timing chain issues. Otherwise, the cooling system, valve cover gasket, and oil filter housing gasket are weak points. The N20 is not alone as many BMW's are plagued by those issues.
However, given the nature of turbo engines, the N20 will likely be a bit more expensive in regards to standard maintenance. Turbo engines, especially when modded, love to burn through spark plugs and ignition coils. Not too expensive, but they can add up over time. Additionally, more frequent oil changes are always a good idea. We recommend changing the oil every 5,000-7,000 miles.
Read our post about N20 reliability here: Common BMW N20 Problems
BMW B48 Engine
Following the N20, BMW's B48 packs a solid punch for a 2.0L inline 4. Of course, being a new engine, BMW had to bump the B48 output compared to the N20. Peak power comes in at 248-255hp on 30i models. However, BMW also went a step further with the B48. An upgraded version producing 302hp is found in new 35i models. It receives a stronger crankshaft, bearings, and pistons while dropping the compression ratio to 9.5:1. Additionally, responsible for delivering the impressive power, the upgraded 302hp B48 receives a larger turbo.
Another note, the B48 is a part of BMW's modular B series engine objective. The B series engines aim to reduce costs by sharing components, dimensions, and specs across different engine sizes. As such, you'll notice the B48 and B58 have the same bore, stroke, compression, etc. Some may shame BMW for cutting costs. However, we believe it is a step in the right direction. We believe it allows BMW to focus on perfecting one design.
BMW B48 Specs
Stock Power: 248hp-255hp
World Record HP: Estimated 300WHP
Displacement: 1998cc (1.997L)
Turbocharger: “TwinPower” Single Turbo
Compression: 11.0 to 1
Bore x Stroke: 82.0mm (3.23”) x 94.6mm (3.72”)
Block Design: Closed-deck
Injectors: Bosch solenoid style direct injectors
***Numbers based on B48 30i engine
BMW B48 Performance & Mods
As with the N20, the B48 comes slightly underrated from the factory. Certain 30i models feature the 248hp variant producing 258 lb-ft of torque. Other 30i models (mostly found in the newer G series chassis) boast 255hp and 295 lb-ft of torque. Aftermarket testing shows numbers closer to 230-240whp. Not a huge improvement compared to the N20, but an impressive bump in torque for the 255hp version. Not many have pushed the B48 too hard, yet. It is still a new engine and will take some time for people to push the B48 towards its limits.
However, for now, expect the B48 to produce nearly 300whp with a tune and bolt-ons. Again, pretty similar to the N20. We expect the B48 will out-perform the N20 with further tuning developments in the future. However, engine strength is the big question. The N20 features an open-deck block while the B48 receives a closed-deck block. Definitely a sound improvement for the B48. Though the bump in compression to 11 to 1 is questionable. Generally, higher compression is not great for boosted engines. Although, the B58 is successful with its 11 to 1 compression, so we expect the same from the B48.
Read our post about B48 mods here: BMW B48 300whp
BMW B48 Reliability
This is a tough one. The great news is - the B48 is off to an excellent start from a reliability perspective. However, it's really too new to tell what may pop up down the road. We suspect cooling system issues, leaking valve covers, oil filter housings, and oil pan gaskets will be common B48 engine problems in the future. These are pretty common issues among almost all BMW's.
For now, the B48 seems to be free of any common problems. Time will tell what may arise in the future. Nonetheless, expect the B48 to be a reliable engine overall. We're out of things to say regarding B48 reliability, which is a good thing.
*We'll write a B48 common problems post in the future.
BMW N20 vs B48 Performance
Both the N20 and B48 pack small 2.0L turbo engines that produce impressive power for their size. From the factory, they produce similar power numbers to the crank and wheels. However, B48 powered 35i models see a serious upgrade. Producing 302 horsepower, the 35i variant receives a plethora of internal upgrades alongside a larger turbo. Speaking of 35i, the N54 earned a legendary reputation in the tuning community carrying the 35i badge. These B48's have a lot to live up to.
Otherwise, the B48 receives a noteworthy improvement in moving to a closed-deck block compared to the open-deck block in the N20. However, compression also increases on the B48 which isn't the greatest for strength on boosted engines. It's working for the B58, though. The N20 never earned a great reputation for strength. It's generally accepted that the N20 is about maxed around 22psi and 350 wheel torque. The limits of the B48 are still rather unknown. Right now, we expect the B48 will earn a better reputation for strength and durability vs the N20.
BMW N20 vs B48 Reliability
Expect both the N20 and B48 to be reliable engines. The N20 does have a well known problem in the timing chain. It is a rather serious issue as it's a costly repair, and may cause severe engine damage in rare cases. Otherwise, the N20 is plagued by typical BMW issues. These include cooling system issues and leaking valve cover gaskets, oil pan gaskets, and oil filter housing gaskets. Though, these issues usually don't pop up until 80,000 - 100,000+ miles.
So far, the B48 appears the more reliable engine. The B48 is without any serious common problems to date. Although, we expect the B48 will eventually suffer similar common problems as the N20, less the timing chain. That is not to say either engine is unreliable. Gasket oil leaks can be expensive repairs at the shop. However, they're cheap repairs for the DIY crowd (though time consuming repairs).
BMW N20 vs B48 Final Thoughts
As we've already mentioned throughout, the N20 and B48 are impressive performance engines for their size. Both can make over 300whp with tunes and basic bolt-ons. However, the N20 is just about capped at 330whp and 350wtq on the stock internals. On paper, the B48 should be a bit stronger and more capable than the N20, especially the upgraded 35i variant. Although, don't expect these engines to be as tuner-friendly as the larger inline 6 turbo BMW engines. Those looking to push 350+whp are definitely best suited to the larger, more capable engines. That is not at all a knock to the N20 or B48, but it is reality.
Otherwise, the N20 and B48 are both relatively reliable engines. Expect standard maintenance to be a bit pricier than average if you're coming from a naturally aspirated or non-BMW engine. Especially tuned and modded N20 or B48 engines. Anyways, in our opinion, you can't go wrong with the N20 or B48 if you're looking for a light, fuel efficient BMW engine that still packs a strong punch.
What are your thoughts and experiences with the N20 and/or B48? Leave a comment and let us know!