rennsport99

I've always been curious why consumers view turbocharged engines as an inferior engineering achievement, while a high-revving normally aspirated engine seems to get all the acclaim. While I'm not an engineer (by degree) or mechanic (by trade), I've been modifying my own cars for some time now, mostly performance upgrades. I've blueprinted both NA and FI engines, and can honestly say that designing a turbocharged engine is orders of magnitude greater in difficulty than a normally aspirated engine. Building a high-revving engine is not difficult at all. Virtually any normally aspirated engine can be made to rev beyond 8K and put out over 100HP/liter (yes, even a meager 4cyl found in a Kia can be re-built to put out 100HP/liter). All you need are stronger connecting rods, a reinforced crank, high-compression forged pistons, more aggressive cams, a ported and built cylinder head, plus headers. These are all parts that are available "off-the-shelf" from various manufacturers (both OEM and aftermarket). The tuning is also rather straightforward and can usually be banged out in a day on a chassis dyno.

However, when it comes to designing a turbocharged engine, I can vouch that not only do you need all the parts I mentioned above, but you also need to design extra components such as an exhaust manifold, wastegate dump, plumbing for both hot/cold sections of the turbo, a heat exchanger system and an intake manifold. Then you have to deal with the tuning process, which is a complete nightmare for an engineer. Whereas a normally aspirated engine is "predictable" in the amount of airflow it sees at a given RPM, a turbocharger is variable in its boost output, which means you can see an unlimited amount of variance in airflow at a given RPM. Then you have to factor in elevation and temperature differences as well. By no means an easy feat, which is why you see tons of normally aspirated upgrades for BMWs, but rarely a solid/reliable turbocharger upgrade.

I'm truly baffled when people criticize BMW for going back to its turbo roots (yes, BMW was the first automaker to run a turbocharged engine in a mass production vehicle and managed to run them with great success in Formula 1 as well). Not only are turbocharged engines much more efficient and "fun" to drive, but they are engineering marvels that should be recognized for their complexity.

designo

Because they use power adders! The engine itself thus becomes inferior.. ( but in what sense? )

danzanchy

i thought that turbo'ed engines have easier tuning capabilities... this is the idea i'm getting from looking at performance parts for 535s vs 545/550s

but nothing appeals to me more than to know that an N/A engine is producing massive amounts of power without forced air... and the sound is just sexy on an 8+ cyl N/A but I must admit that i love the sound of turbos spooling just as equally (i've wanted an evo for the last 5 years because of its turbo setup but never bought one ) maybe i just love the sound of power

pukka

Actually, GM was the first to market a turbo in a cars, SAAB was the first to introduce it in mass production vehicles. Renault was the first to use it in F1.

For years, BMW has established its reputation by churning out high revving N/A motors while everyone else focused on either large displacement engines (GM, M or some form of FI (Toyota, Nissan).

IMO people are being critical because BMW is showing signs of going along with everyone else. I remember quite a few threads on this forum debating the 535 and 550 engines. The irony is that many of the 550 owners who dogged the 535 for its turbos wouldn't hesitate to buy an F10 55x with the same thing.

flyingpuck

I LOVE the sound of my V8, but whatever works, will get my vote in the future!

swajames

I'd disagree with the contention that designing a forced induction engine is orders of magnitude greater in difficulty than a normally aspirated powerplant when we're talking about the traditional M engines, and most specifically the S85 in the M5/M6. There's a tremendous engineering challenge associated with the development of an engine and a valvetrain that can run reliably with an 8500 RPM redline. Were it not for the limiter, these engines could probably run close to 10,000 RPM with reasonable reliability. That's no mean feat.

To your primary point, I don't think that a forced induction engine (and particularly the M version) should be viewed as inferior to a normally aspirated unit, BMW is clearly capable of building tremendous engine in either flavor. I've always been of the view that one isn't necessarily "better" than the other, they just go about their business in a different way. I've made the same points before when comparing the S85 to say the LS9/LSA powerplant in the ZR1 and CTS-V - they simply use different means to achieve the same end, and each has its inherent advantages and disadvantages.

The problem, however, is that the engineering philosophy of the M brand as a whole is undergoing a change - and not everyone buys into or appreciates these changes. For me, the hallmarks of an M engine are and will always be a very high revving, highly strung powerplant that needs to be worked very hard to give its best - because that's the philosophy that characterizes racing engines in general. The change to forced induction will lead to reduced redlines and the engines will lose some of their soul. And when the engines lose soul, the car loses soul. M is all about flawed genius, and it is these flaws that we've come to love. The powerplant change is just part of a trend towards the "commoditization" of the M brand. M never stood for all wheel drive, automatic transmissions, high centers of gravity and turbocharging. So - the turbo engines will, bo doubt, be very capable - but for me, they're likely to lose their soul. And that's not a good thing.

Krozi

Well said

skelevirus

Jeezus Swahili I couldn't of even thought it better let alone said it better myself

+2million kroz

but what about a Porsche for example 911 gt3 or 911tt?

See I don't think a turbo engine loses or gains any stigma when comparing in a co. like Porsche I think people really only groan about turbos when recalling memories of all the crappy 80's GM turbo POS that notoriously sucked.

I myself would take a GT3 just for the fact that the tt actually scares the hell out of me

m630

+1

Its not that FI is bad, its just not an M. I'm sure the new TTs are great from bmw, and they do just fine in the normal lines, but when the past 25+years of ///M philosophy has been based on NA power and they appear to be doing a 180, then you hear the tradionalists barking, like I often do. We never say that the turbo is bad, its just different in the way it delivers power and audible extascy, and when speaking of M, its near heresy to speak of FI...its the intangible that is at the souls of the beast, and the S85 will forever be the Ultimate aspiration of what NA could be

z06bigbird

Beef up the top of the engine without addressing the lower part will result in problems in lower half of engine.