Life & Death of BMW\’s Naturally Aspirated Engine

E46 M3 CSL

The naturally aspirated gasoline engine is dead. As dead as 15 ” wheels and roll-up windows. A generation from now no one under 25 years old will even know the experience of winding up a BMW inline six without a turbo sucking exhaust gasses out of it.

The need for efficiency and ever increasing performance have dictated a sea-change that will alter what we ‘ve known BMW ‘s to be forever. Consider the following the fact: the E9X M3 will be the last naturally aspirated M product. Or (even more shocking) that the current 128i, 328i and X3 28i are the last naturally aspirated BMW products to be sold in the US. Once those three models are gone it ‘s all turbos for as far as the eye can see.

From the 16 valve V8 found in the 507 to the 500 hp V10 under the hood of the E60 M5 BMW has had a long and storied history when it comes to the engines that motivate its cars. The soul of these cars have been unadorned with turbos or superchargers (with an exception or two) from the early part of the 20th century until the early 2000s. Production BMWs have been celebrated as naturally aspirated affairs. It ‘s a simple theory at the the heart of complex machine; perfect weight distribution and nothing in the way of complete control and feel. For engineers in Munich that meant anything within the engine that would reduce the ability to rev (heavy flywheels aside) or the connection from the driver ‘s foot to acceleration wasn ‘t a part of the package. And for many years it made sense at every level. Turbos were meant for such lowly brands as Audi who had to make do with the scraps of a VW empire. Or Porsche,saddled with flat six architecture that was mandated by hanging the engine out the back.

BMW E30 M3

Over the years BMW excelled at this formula. For more than a generation engineers in Munich continued to perfect the formula. From the smallest inline six to the largest V12, every BMW engine held true to the theory that control and performance meant forced induction was not part of the answer.

Even despite the radical turbocharged engine on the 2002 Turbo, race cars such as the 320i Turbo or the legendary 1.5L M12 in the Brabham F1 car (which produced over 1300 hp in qualifying form), BMW was dedicated to its formula in street cars.

In series production the book-end came in the form of an inline six and a V8. The last top-line naturally aspirated inline six was the quick-revving 3.0L N52 that produced 272 hp in European form. But perhaps the pinnacle of BMW ‘s long history with naturally aspired six ‘s came with the E46 M3 and the S54B32. 333hp in US form (and up to 355 in CSL trim) the 3.0L sounded and revved like a race-car.

But if you ‘re talking about the ultimate naturally aspired BMW engine, that would technically have to be the S85B50 V10. With 507 hp at 7750 rpm the 5.0L V10 blew away all comparable engines when it came to displacement vs power. With a 8250 redline the V10 was inspired by the high-revving BMW F1 engines of the era. It didn ‘t sound as great as the V8 it replaced (we ‘ll blame EU noise laws for that) but it was dramatically more exotic.

Then BMW did one better and sliced off a couple of cylinders to create the high-revving 4.0L V8 for the E9X M3. The S65B40 produced 414 hp and a 8400 rpm redline that defied all belief. While some of the BMW historical M3 character was lost with the S54B32, the new V8 threw the gauntlet down on the competition and helped continue the M3 ‘s dominance over the Audi and Mercedes competition.

And then just like that the 8,000 redlines were gone.

Progress should give us more of what we want. But we ‘re finding out the future is too complicated for that. Yes the new era of BMW engines develop more torque and are better at every day drivability. But there is a character that will soon be forever lost with these engines. The honesty of a naturally aspirated engine will soon be forgotten and in its place the induction sound and endless torque. Yet another old technology that progress has made irrelevant.

My fear is that the accelerator will soon become the go button and the nuances of power delivery we all know and love will be gone. And gone too will be listening to an engine take on new character at every thousand RPM up the dial – the very soul of an engine.

So what do we have to look forward to? Speed for one. We know that BMW will up the ante in every way with these new turbocharged monsters. We also should expect smaller engines producing the same if not more power. And that means less weight and (most importantly in the eyes of society) much higher efficiency.

All is not lost but quite a bit of what BMW has hung their hats on for the past 40 years will be. Thus it ‘ll be up to the mad scientists of Munich to find BMW ‘s voice in this new world. They have a a tough road and there ‘s an enormous amount at stake. But if there ‘s one thing we ‘ve learned to do, it ‘s to trust them when it comes to designing and building powerplants.

Or you can just start scouring eBay for that pristine E46 M3.

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  • JonPD

    Feels like the passing of a old friend! I know BMW has more fun planned for our future. I also generally speaking turbos and superchargers do not have the long term reliabity of non-aspirated motors and usually higher repair bills.

  • Evan

    I fully understand the efficiency and power attributes of a turbo engine, which has it’s own character. But my soul will forever long for that BMW inline six start up sound and that smooth rev all the way to the redline. Opening the sunroof and windows on a crisp fall day just to hear that engine sing. There is and will never be anything else like it.

    Sad news.

  • lava

    OT but did the layout just get tweaked recently? Seems the header image now bleeds out to the background? Looks great.

  • jayparry

    “Turbo’s were meant for such lowly brands as Audi”

    What is the apostrophe for in this sentence? Don’t allow grammar to go the way of the naturally aspirated engine.

  • Max

    The 3.0 straight six cylinder engine (N52B30) that was used in the Z4 3.0si was probably one of the best machines ever built in engineering history. AutoBild (German) once did a 100,000 km test with a 130i and finally disassembled the whole engine – with the result that after this amount of milage 99 % of the engine parts looked close to factory-new. It was the best test result ever achieved by an engine so far.

    The sound of revving up this machine (adding an Eisenmann 4-pipe steel sport exhaust) in a topless E85 on a lonely road through the Alps will create perhaps more endorphins than any other activity in the world (literally any…). I have to agree that this pure, natural sound along with the sheer unbelievable smoothness and ease of the acceleration will ever remain in my mind.

    Nevertheless, I have been lucky enough to drive the same roads in an 335i convertible, and yes although the sound is different and yes although the smoothness and response of the engine has suffered a little bit (which you will only notice if you have the direct comparison) – this IS evolution. The power, the torque, the endless will of the car to run forward is simply amazing.

    So in the end I have to agree that is a shame that those wonderful natural pieces of engineering genius will disappear – but it is good to know that their idea will live on in their aspirated successors.

  • http://www.bridger.us/ Gabe

    OT but did the layout just get tweaked recently? Seems the header image now bleeds out to the background? Looks great.

    Yes. Thanks! Changes like this for MF are coming as well (among others).

  • Micah

    Placing the blame for the demise of BMW naturally aspirated engines soley on demands for increased efficiency/performance is somewhat disingenuous. We all know that both demands can be met by reducing weight for example. Furthermore, among German performance car makers, both Porsche & Mercedes continue to produce high-performance, high-revving NA engines with better sound & throttle response, greater simplicity, lower weight, and lower thermal demands when driven hard relative to similar turbocharged engines.

  • http://www.bridger.us/ Gabe

    Placing the blame for the demise of BMW naturally aspirated engines soley on demands for increased efficiency/performance is somewhat disingenuous.

    It isn’t if you talk to M engineers.

  • Bimmer Bob

    Wait until electric cars take over the model line. In a matter of a single generation, driving will dramatically change. Turbos will seem like so much fun!

  • chad

    i’m not sure how much of the efficiency argument i am buying. the e46 m3 got nearly 30-mpg at 70-mph on the highway. porsche seems to be making engines which are NA, more powerful than before and get better fuel economy.

    and it is not the increasing weight of cars that is soley killing fuel economy- it is also consumer demand for more and more power.

    i’d argue that BMW, the M-division, are saddled with the task to make MORE power all the time and maybe FI is the best (easiest, cheapest) way to do it? maybe FI is a business decision? maybe it truly is the best solution to the matrix of problems BMW/M deals with when designing a performance car?

    just so everyone is clear where i stand- i regret selling my 2005 M3. i look at ads constantly for another or a near new M coupe. S54 has my heart.

  • Labrat

    If the NA inline 6 is bound for the dustbin of history, then I’m glad I bought my 125i with the N52. I’m a (very) late convert, and it looks like I made it just in time. I love driving slowly in car parks, just to hear that gorgeous sound. It might not have the grunt of the 135i, but the sheer smoothness and balance on the road just sweeps me away.

  • Dylan

    Hanging onto my E30!

  • GJR

    Time to go put another coat of wax on my E39 530i…

  • goat

    @ chad – not just consumers demanding more power (which can be delivered to them via weight reduction to give an equivalent gain in power/weight) but I think it is also the fact that so many cars are only sold with automatic transmissions. :/ And the driving experience with automatic transmissions greatly benefits from torque at low revs and a flat torque curve – the (low inertia) turbo’s calling card.

    Either way, bittersweet about this. I am an NA motor fan first and foremost for the throttle response, the “cammy sound”, and building rush of power to redline, and the longer term durability. But I also can’t deny the fuel economy gains of a smaller turbocharged motor compared with an equivalent power NA motor. And there is definitely a satisfaction to the feel of a “swell” of torque @ 2000rpm or even lower – but I’ll take that with a 6MT please! :)

  • SmokinJoe00

    I’m on my 7th Bimmer with 3, 5, X, and M’s. My latest e92 M3 is by far my most pleasurable to drive, although I still love my ole’ e39 M5 design/styling (RIP). I’m saddened by the loss of the NA engines. I know, I know, we may have short memories if the new-gen engines are as reliable, fun and performance filled. I plan to purchase another of the last model year e92′s and keep it!!!

  • E90330

    This certainly makes me appreciate my ’06 330 even more!

  • dr

    and back will come the days of engines failure before 150k miles, the junk yards will be full of turbocharged cars and you wont be able to even give away a modest mileage car because of the looming repair costs…and bmw will be fighting the reputation that their cars are known for early engine failure for a decade.

  • Joe C

    Gabe, a beautiful elegy. Great piece.

  • bthayer23

    Don’t forget the M21 diesel engine had a turbo. We had an ’84 524td for a few years. Once you got the revs up, that thing could move.

    And I think the death of the NA inline six is a long ways away. There are plenty of E30s and E36s still on the road.

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  • David

    With all of the amazing technological advancements in the world. I believe it is now time to find out just how much the thermal efficiency of the internal combustion engine can be increased. Personally I look forward to seeing what BMW is capable of engineering.