Discover why even the diet M car is well worth adding to your garage
It’s natural for any auto enthusiast to scoff at the thought of purchasing a BMW M car with more than one number on the badge. After all, we’ve already seen what BMW inline 6 engines strapped with a few turbos can do in the past (usually making around 300hp stock), so why would the M340i be any different?
While the M340i was created to replace the old 335i, it’s a completely different animal, emphasis on the word animal. Here are 3 reasons why the M340i would be an excellent addition to any enthusiast’s garage:
(For reference, we will be referring to the G20 M340i throughout the entirety of this article. Th3 G20 encompasses all 3-series cars produced from 2018 to the present.)
It’s as Fast as an E90 M3 (Stock)
Despite the M340i not having a screaming V8 under the hood (like the e90 M3), it’s every bit as fast in stock form. Let’s take a look at some quick facts regarding the performance of these two German sports sedans:
- 0-60 Time: E90 M3 (4.4 seconds) M340i (4.4 seconds)
- Quarter Mile: E90 M3 (12.7 seconds) M340i (12.3 seconds)
- Top Speed: E90 M3 (176 MPH) M340i (157 MPH)
Notice a trend? The M340i meets (or beats) the E90 M3 in every critical aspect of performance except top speed which, let’s be honest, won’t ever be a factor in everyday driving. Bear in mind, this is the M340i in its stock form, and since the B58 engine is incredibly tuner friendly, the potential to surpass even the E60 M5 in performance is there.
Better yet, the M340i doesn’t suffer from the notorious rod bearing achilles heel that was so prevalent in M cars of old, potentially saving you thousands of dollars on a complete engine rebuild/swap.
Incredible Tuning Potential
Like it’s older brother, the 335i, the M340i is an incredibly tuner-friendly platform, if you purchase a 2018-2021 model year. For some incomprehensible reason, BMW factory locked the ECU on every M340i manufactured during and after 2022, which severely hinders the potential of the platform. While there is a company in Finland called, Femto, who can unlock the ECU for these model years, the cost is well into the thousands. If you’re a gearhead looking to turn your M340i into an upgrade platform, keep this in mind prior to your purchase.
For M340i platforms that do allow for tuning, there are a plethora of available options from Dinan to Mission Performance, and everything in-between. Common Stage one M340i builds can reach 360-410 crank horsepower which is a significant step up for an ECU flash alone. Add your standard bolt-ons and you’ll be well into F80 M3 territory, and potentially teasing G80 M3 territory…
The Reliability is (Pretty) Decent
We’ve all seen the memes on Instagram and TikTok about how unreliable BMWs are, and while some of them are warranted, the B58 engine in the M340i is a far cry from the junkyard destined BMW engines of old. The N54 engine in the 335i was known for turbocharger failure, faulty cooling systems, leaky fuel injectors, and unreliable VANOS solenoids which would quickly empty the wallets of their once proud owners.
Regarding the M cars of the very same era, such as the E90 M3 and E60 M5, problematic timing chain guides and rod bearings would cause the engines to essentially boat anchor themselves, resulting in repair bills in the tens of thousands. *Gulp*
While failing timing chain guides and disaster-prone rod bearings are of no concern with this power plant, there are a few small issues that you, as the new owner, will need to address:
- Valve cover oil leaks (typical for any German car)
- PCV valve failure (will cause coolant to contaminate the oil)
- Carbon buildup (typical for any direct injection vehicle)
- Water pump failure (typical for most BMWs)
- O2 sensor failure (essential to control the air-to-fuel ratio in the engine)
- Vanos solenoid failure (BMW still hasn’t figured out variable valve timing)
There have also been a few failure reports for injectors and high-pressure fuel pumps on the B58, which seems to be BMW’s way of carrying over the 335i’s legacy. For the enthusiast who has never owned a BMW, this list may seem quite long and scary, but know that this list pales in comparison to older BMW performance cars, especially those coming from the M division.
A Stiff Salute to the Inline V6 Engine
BMW has redefined what the inline V6 is capable of with the B58 engine and the M340i as a whole. The interior is quiet and comfy, and the power matches what most V8 engines of the past were capable of while simultaneously being able to absolutely carve up any mountain road. Try achieving the same feat with a Scat Pack Challenger, or a C43 AMG; you simply can’t. To reference one of the all-time greats, Jeremy Clarkson, “This car is like the perfect dog. It’s loyal, cute, it doesn’t chase sheep, and yet, if a burglar comes, it has the power to rip his throat out.” Even with it’s (numerous) flaws, the M340i is a gem, and if you have $57,000 laying around, you should buy one, Immediately.
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