[Korvo]

I test drove a 340 before buying my 335 and the 335 was fairly disappointing compared to the 340. The transmission made a difference, but the 340 felt like a rocket. Then I got MPPK on my 335, which made my 335 feel like the stock 340.

Bottom line, I tuned my 335 and it's much faster than both originally were. Go with the nicer car.

[antzcrashing]

I feel the exterior improvements of the 2016+ are worth it. LED tails being a big aspect. The engine is an improvement too. I suggest targeting 2016+ if it is in budget

[Wires]

Couple notes in overall driveability:
1) B58 has larger turbo and air to water intercooler. You get better torque at all RPM's and consistent power over consecutive pulls.
2) Sure tuned, they will put out the about same power at WOT, but nobody drives WOT all the time. On demand torque is better with the B58's larger turbo.
3) B58's air to water intercooler eliminates the charge pipe in the N55, and there are a bazillion posts about N55 charge pipe failures. The M cars use the water to air intercooler, not air to air intercoolers.

I had a N54 (Dinan S2) and now the B58 (Active 8 PB). Just speaking from power delivery, the B58 is much better. And the whole F30 vs E90 change nets me 20% fuel savings over my N54.

For me, the 340 is a hands down win.

[Wires]

Originally Posted by RPM90

My S4 experience has been ruined by how astoundingly awful Audi implemented that AT in this car.

First off, stellar writeup! You captured a lot of my feelings between the models.

I've heard many on the Audi forum complain about the S4 / ZF 8AT driveline. Interestingly enough, we bought a 2018 SQ5 (3L / ZF 8AT), which should be the same S4 B9 driveline. Perhaps they heard you complain about the S4, as this one is tuned drastically different. I find my SQ5 ZF 8AT to have very firm and crisp shifts (up or down), and is a lot crisper shifting than my 340 is.

One thing it does that I wish the 340 did was bump up the idle revs when you are in sport mode. The Audi goes from 600 to 900rpm (at which the torque converter has started to load up). Makes that launch pretty exhilarating!

[BMW in NE]

Originally Posted by cfm56d7b

I also prefer B58 after owning N55 equipped 335. B58 has many changes which make it a much better engine.

+1

[Usef_Afande]

Originally Posted by RPM90

I had a 2012 335i Msport, and then I got a 2016 340i Msport to replace the 335i.

Both were configured pretty much the same.
2016 received the new B58 engine, along with suspension updates and revised tuning.
The ZF 8spd AT also received some updates and upgrades, as well as revised tuning.

The 335i Msport was very nice.
The 340i Msport improved all of the nice things about the 335i.
Some improvements more noticeable than others.
For example, the B58 engine revs smoother and higher, and pulls across the rev band better all the way to red line.

I had both models for 3 years each.
In my direct and longer term experience, I can easily give the nod and preference to the 340i Msport, with no disrespect to the 335i which is the same chassis the 340i is built on.

The steering feel is very slightly improved in the 340i.
But this is one area where there isn't a clearly noticeable improvement or difference.

The adaptive sport suspension was nicely improved, and there is a better and more effective distinction between comfort/normal and sport modes.
Damping quality was improved, though spring rates remain as poorly selected as pre LCI sport suspensions.

The improvements to the AT are very nice and noticeable, as the trans shift quality is smoother and smarter in the 340i, and manual mode shift quality was nicely improved to feel smoother and more direct.
BMWs application of the ZF AT is simply amazing, and demonstrates how greatly improved a modern torque converter AT is.
My current Audi S4 uses this same AT, and Audi managed to completely f**K up how great this AT is.
ZF should take up a law suit against Audi regarding defamation of character, as Audi has clearly blemished ZF's image and reputation regarding their 8spd AT.
My S4 experience has been ruined by how astoundingly awful Audi implemented that AT in this car.

Handling and feel is slightly improved in the 340i, as BMW's work to improve those qualities was successful. The 340i Msport w/adaptive takes a quicker and firmer set in turns.
And on highway cruising the dampers are less "busy". The effect is subtle, but having experienced both models for longer terms I noticed the improvements.

Handling, overall, is thus improved with the 340i.
I do not know how someone could say the handling of an equivalent optioned 335i Msport is better than the 340i Msport.
Clearly and obviously that is not true.
And weight increase in the 340i compared to the 335i is not at all noticed.
As for the 3 series that has the better and best feeling and more responsive front end and handling, that would be the 2.0 engine variants, as the lighter weight and more centralized weight distribution due to the engine, gives the 328i/330i that award.

The claim of the 335i being the better handling model is not true in my experience having both models for 3 years each.
And, pro reviewers experienced and stated the same things I experienced.
The 340i and Msport is an incremental improvement over the 335i and Msport in every area.

And, the B58 has a noticeable increase in overall power as it pulls stronger at all RPMs.
Also, the B58 breathes better at the top end as it pulls strong all the way to red line where the N55 started to drop power near red line.
That is why the all around performance goes to the B58. And let's be clear, the N55 is also a fantastic engine.

Along with all that said about the B58 and N55, I achieved an average MPG improvement from about 26mpg with my 335i to about 27.5mpg with the 340i.
Both cars were driven in the same manner, on the same roads, by me.
That demonstrates that indeed BMW achieved better overall efficiency with the new B58 engine.

If the cost difference is negligible, then I recommend the 340i.
But, you have to make the decision for yourself.
A 2015 335i with same options and same mileage and condition as a 2016 340i should cost less.
The difference then will be any warranty time and/or mileage left.

A 2015 model will have less manufacturer warranty compared to a 2016. And where either model year's warranty ends will depend on when the car's "in service" date began.
If the 2015 was early in the model year, and the 2016 was later, then there can be more than just 1 year's worth of warranty coverage difference.
If the in-service dates of either model year is only a couple of months, then the remaining warranty time and miles may not make as much difference.

As for reliability, I did not have any major issues with either model year.
Both the N55 and B58 engines are fantastic, with just a slight power advantage to the B58, along with the higher rev range and top end power of the B58.

Also, I have no idea why anyone would conclude that the 340i is slower than the 335i.
That is not my experience at all, and the clear majority, if not all reviews, have shown the 340i to be faster than the 335i when compared to it's trans type and drive type counterpart.
Be sure to compare the correct variant and trans type when considering acceleration and handling performance and differences.

My 340i Msport felt more powerful and than my 335i Msport.
And some of that was due to the smoother and more linear power delivery of the B58, along with it's ability to keep breathing and pulling strong all the way to red line.
The N55 also has a very strong and linear pull, just to a slightly lesser degree by comparison.
And the N55 couldn't breathe as well at it neared red line, and that is a known aspect of that engine as well as the previous N54, which I had in my 2009 135i.

Those who use one specific test to confirm their own needs are simply choosing to fool themselves for personal reasons.
Remember, the only way to test which car is or may be faster than the other is to test them side by side on the same track, doing multiple runs.
BMW didn't build the 340i with the B58 in order for it to be faster.
They went for efficiency increase, and to improve the ride, handling, and feel of the pre LCI F30, especially with all of the complaints from previous BMW owners and reviewers.
I've not read any reviewer who stated the LCI 340i was less than the 335i, or that it performed worse than the 335i.

As for reliability, remember, there were some mechanical changes to improve the 2016 LCI model. The overall car is still the same.
Those who say that someone should wait a year or more so that "bugs" can be worked out are overstating that very old school claim.
The 2016 model year was an F30 face lift, not a completely new chassis.
Since the F30 had been in production for at least 3 model years, the 2016 actually benefits from the improvements made on the assembly line over that time on the same chassis.
The only major significant difference in the 2016 LCI was the new B58 engine for 3 series.

Those are my thoughts on your questions.

Appreciate the write up.. super informative..