BMW 3-Series M340i – Everything You Need to Know About the M340i

The BMW M340i is the crowned jewel of the non-M G20 3-Series lineup and there is no question that it deserves the title. Bordering on the edge of a family-friendly sedan and full track monster, the M340i exemplifies why so many people swear by BMW. 382 horsepower and enough room in the trunk for three golf bags; that’s a combo that you don’t get from many other brands. 

The 3-Series formula has always been about balancing usability with performance, and the G20 M340i strikes the perfect balance. Due to the fact that the M340i is available in xDrive form, it provides a better all-weather option for those that want M3 performance in an all-wheel-drive chassis.  In this guide, we’ll cover some of the most notable aspects of the BMW M340i.

BMW M340i Specs, Horsepower, 0-60mph, Price

The BMW M340i is an impressive car both on paper and in the real world. A lot of the M340i’s performance can be attributed to the engine that BMW chose for it. The B58B3 3.0L inline 6-cylinder is an engine that has a reputation of being a velvety heathen. Like Satan in a smoking jacket. You’ve never felt 382 horsepower delivered so smoothly. 

That isn’t to subtract from the M340i’s other crush-worthy attributes. 50/50 weight distribution has always been one of BMW’s signature traits, and that carries through to the G20. The chassis is balanced and predictable; the perfect combination when you need to get somewhere fast. The suspension also feels remarkably planted without sacrificing daily-drivability. The only way to truly understand is to drive one, but here are the on-paper stats if you can’t:

Engine: B58B3: 3.0L Twin-Scroll Turbocharged Inline 6-Cylinder

B58 Horsepower/Torque: 382hp / 369lb-ft. of torque

0-60mph: 3.8 seconds

Powertrain: Rear-wheel-drive / All-Wheel Drive (xDrive)

Transmission: ZF 8-speed automatic transmission

Weight: 3,849 lbs.

Price: Starting around $56,700

M340i Power and Tuning Potential

As with most of BMW’s modern turbocharged engines, the B58B3 has huge tuning potential. While 382 horsepower from the factory isn’t anything to scoff at, there’s a lot of room for improvement. The B58 is a relatively new addition to BMW’s 6-cylinder catalog, with its first application in 2015 with the F30 340i. 

While the B58 is new, it is heavily informed by high-performance BMW 6-cylinders of the past. The B58 is based on the fan-favorite N55 engine, yet with 20% more boost pressure, a closed-deck engine block design, and an increased compression ratio. As many of the B58’s characteristics are similar to the N54 and N55, it also shares a similar amount of tunability. That’s good news, as it was possible and easy to increase N55 horsepower significantly with simple bolt-on mods. The same can be said for the B58.

At this point, there is a growing amount of aftermarket support for the G20. Since the model is still in its infancy, there obviously isn’t the same breadth of mods as there is for earlier F30 3-Series. With that being said, there are enough available M340i performance parts currently on the market to jack up the power. 

Tunes

Since its release, the M340i’s DME has been cracked, allowing for aftermarket tuning companies to create a handful of available tunes. The most common tunes include the Mission Tuning OBD flash tune and Burger Tuning JB4 piggyback tune. Both tuning options have Stage 1 and Stage 2 options depending on your desired power target.

In general, the Burger Motorsports JB4 route is the way to go. They have a spotless record as far as BMW tuning is concerned, and the benefits of a piggyback tune far outweigh those of a DME flash tune. In addition to boosting performance by 100 horsepower on a stock M340i, the tune is heavily modifiable and can be removed at any time. It really is the easiest way to get your M340i close to the 500 hp threshold.

Purchase Here: B58 JB4

BMW M340i Suspension and Handling

In addition to having a killer engine, the M340i also includes some very cool suspension technology as well. There are two distinct suspension options from the factory. These include the standard M-Sport suspension and M-Adaptive suspension. The general consensus in the community is that the standard M-Sport suspension is sufficient for most people and feels the best on non-xDrive G20s. The M-Adaptive suspension adds another level of adjustability and is typically better suited for xDrive M340is.

M-Adaptive suspension allows the driver to control the level of suspension damping on the fly. There are three selectable shock stiffness modes, including comfort, sport, and sport+. Comfort is the softest setting, and Sport+ is the stiffest. In comparison to the standard, non-adjustable, M-Sport suspension, M-Adaptive suspension provides both the softest and stiffest ride available on the M340i. Standard M-Sport suspension falls somewhere between M-Adaptive’s comfort and sport settings. 

Both suspension setups are widely touted, so it really boils down to whether you think the added adjustability is worth the extra $700. 

BMW G20 Chassis Upgrades

Beyond the suspension itself, the M340i was designed with chassis stiffness and an improved steering feel in mind. BMW’s implementation of new aluminum wheel mount and axle components reduce unsprung weight significantly on the M340i. The overall effect is a chassis that is 121 lbs lighter than the outgoing F30 3-Series. That not only increases the M340i’s straight-line speed but also enhances the steering characteristics dramatically.

The M340i also features variable sport steering as a standard option. This comes into play most noticeably in tight spaces, as it increases the steering angle of the front wheels at large steering wheel angles. In comparison with a car with a fixed steering ratio, BMW variable steering feels sportier and more direct. One of the biggest gripes about modern BMWs is their sterile steering feel. Variable steering adds enhanced steering feel while also making navigating parking lots easier.

M340i Technology and Features

In addition to new performance attributes, the M340i also features some cool new technological advances. While heads-up displays have been available on vehicles since the 80s, BMW is getting extremely close to perfecting the space-age tech. The heads-up display in the G20 3-Series not only displays speed and speed limit information but also audio information and navigation directions. There isn’t really a need to take your eyes off of the road anymore.

For the more hoon-minded individuals out there, like me, the M340i is equipped with an advanced launch control system, that will rocket the car to 60mph in just under 4 seconds. The system is activated by putting the M340i in Sport+ mode at a stop and depressing the gas and brake at the same time. Let off the brake and anything previously in front of you will then be behind you. 

BMW’s iDrive system is getting pretty good too. Driver information is provided by a now completely digital 12.3” digital dashboard that can be customized to display the information most important to you. The M340i also features a 10.25” central digital display that functions as the vehicle’s primary display. The M340i supports Apple Car Play compatibility and includes remote start and app-based door locking and unlocking.

In xDrive models, the car is powered by all four wheels. However, the xDrive system controls the power distribution and only sends power to the rear wheels, unless it detects a lack of traction, at which point it will disperse power to the front wheels. Additionally, the car will alert you to change your driving line to prevent over or understeer during heaving braking and tight turns. Rear-wheel steering capabilities will also be automatically triggered to help prevent this.

BMW M340i vs M3 Comparison

Before the release of the G80, one of the primary selling points of the M340i was M3-ish performance in an all-wheel-drive package. Because the new G80 M3 is available with all-wheel drive, a small amount of the initial appeal of the M340i is lost. That doesn’t mean that the M340i doesn’t have its own place in BMW’s lineup. 

BMW M340i vs M3 Performance

One of the most obvious discrepancies between the G80 M3 and G20 M340i is performance. That shouldn’t be surprising to anyone, as the M3 has always been the top dog in the 3-Series lineup. In contrast to the G20, the 2022 M3 is powered by the S58B30 engine; the track star older brother to the B58 that powers the M340i. Despite having a smaller displacement, the S58 is a far more capable engine than the B58. The G80 M3 produces nearly 100 more horsepower than the M340i, which is a difference that can’t be ignored. 

The M3 is also far more capable on track for a multitude of reasons, including stiffer suspension, the inclusion of an M differential, beefier brakes, 10-stage traction control, programmable gearbox maps, and a host of other goodies. In terms of track performance, there’s really no competition.

BMW M340i vs M3 Usability

With that being said, track performance isn’t everything. The M340i is arguably the better car for everything else. While it is cool to have 480 horsepower on tap, you won’t ever use all of it on the street. You might use all of the M340i’s 382 horsepower on mountain roads, though. The M340i is also more comfortable. Its softer suspension and less aggressive seats make road trips less of a backache. 

Price is another important point to mention, as the price difference between the two is a little more than significant. The M340i’s base price is $56,000 compared to the M3’s MSRP of $70,895. Most of the $14,000 disparity goes into the M3’s more advanced and technically sophisticated performance components. It is important to question if it is worth spending that much more for a car that is worse on the street but better on the track. It really does boil down to personal preference and the size of your pocketbook!

Thanks for checking out this article! If you are interested in other G20 3-Series content, check out our 500 Horsepower B58 Engine Guide.