Turbocharged BMWs: Back with a vengeance

Interesting | July 5th, 2009 by 21
n55-turbo-twin-scroller

In the last ten years, BMW has successfully proven that it can generate a significant amount of controversy regarding its way of business and car …

In the last ten years, BMW has successfully proven that it can generate a significant amount of controversy regarding its way of business and car making. Just remember how much opinions the company has polarized with their stubborn but forward thinking decisions; the first X5, 2002 7 Series and the iDrive system, flame-surfacing design of the first Z4 and Bangle-styled 5, 6 and 1 Series, EfficientDynamics… All of these were subjects of numerous debates and have spawned both worship and hate, but also have skyrocketed BMWs sales and profit and have served as an exemplar to other manufacturers, resulting in many attempts to imitate the original BMW creations.

It seems that now nothing has changed: in May, BMW released a Gran Turismo version of the 5 Series, which generated negative comments about its distinctive and unusual styling and yet again, Audi has revealed several teasers of their upcoming A5 Sportback while Mercedes-Benz announced that the new E-Class family will receive a similar styled model. Interestingly enough, the two rivals feature the same dramatic sloping rear end and a sedan-like roofline.

Few days ago, BMW has released official pictures and data of the new compact SUV/crossover X1 and again, ad least two years ahead of the upcoming Spain-built Audi Q3.
As expected, rumors about the new Mercedes-Benz BLK began to spread.

Turbocharged BMWs: Back with a vengeance

Meanwhile, another novelty from BMW resulted in furious reactions, but this time from its own fan base. As you might suspect, the decision to make small turbocharged engines was not well received by the purists and enthusiasts. However, while naturally aspirated engines provide better control and more natural feel, the efficiency and weight of a turbocharged engine is crucial for the future development, which requires more power and less consumption, likewise less CO2 emissions.

What is even more interesting, turbocharged engines are actually BMWs heritage and tradition, and to be even more specific, BMW was the first European car manufacturer to offer a turbocharged car.

The BMW 1500 introduced in September 1961 at the Frankfurt Motor Show was truly a ground braking car for the time. With its rear wheel drive, fully independent suspension, MacPherson struts in front and front disc brakes, it was the first BMW that brought the company’s traditional focus on driving pleasure in a more compact and economical package. And while the 1500 had expanded BMWs reputation as a maker of true drivers cars worldwide, the next model of the “New Class” family had only secured it.

The 2002 is the one of BMWs most important models and today is considered to be the first sport sedan, a class that was later reinvented by its successor, the BMW 3 Series.

BMW started experimenting with turbocharging in the beginning of 1970s and the result came in 1972, a turbo version of their four cylinder engine, fitted in the Paul Bracq designed BMW Turbo Concept. A year later, the Turbo made its production debut in the BMW 2002 Turbo.
Performance figures were impressive: the 2002 Turbo produced 170 hp at 5800 rpm.
It was capable of 0-100 km/h in 6.9 seconds with a top speed of 209 km/h while the turbocharger kicked in at about 3500-4000 rpm.

Turbocharged BMWs: Back with a vengeance

Although turbocharging gives more power without sacrificing too much efficiency, it does not deliver the power as smoothly as a naturally aspirated engine. This is commonly referred to as turbo lag; the complete lack of power below a certain rpm. And when the turbo does start to work, it usually does so with a big kick, resulting in unbalanced driving characteristics of turbo cars.

The 2002 Turbo’s tricky handling was a direct result of the turbo lag, for which the 2002 Turbo is a school book example today. Below 4000 rpm the 2.0 engine’s power was minimal, but after 4000 rpm power boost came very sudden and especially in corners required the driver’s full attention.

Original 2002 Turbos featured a front spoiler with the script “2002 Turbo” written backwards on it. The idea was that when a driver ahead looked in his or her rear view mirror at an oncoming 2002 Turbo, the backwards written script would appear forwards to them and they would know that it was no ordinary 2002 behind them.

Production stopped after only 1,672 models were built, 1049 cars are made in Chamonix white and 615 cars are made in Polaris silver.
The reason it was a slow seller was not because it was a bad car, but because it was the wrong car for the time, the first oil crisis in 1973. All performance cars were out of favor due to soaring fuel costs, meaning that buyers wanted economy, not outright power and performance. Exactly that helped the 1975 released 3 Series, which had doubled BMW’s sales and its dominance in the sports sedan area.

Apart from rear-wheel drive and perfect 50:50 weight distribution, a hallmark of the BMW brand is also the straight-six engine, renowned for its smooth power delivery and fuel efficiency. Because the turbo lag would disturb the famous smoothness of the inline six, BMW used turbochargers only in several Formula 1 race cars in the 80‘s.
Nevertheless, an exception was made for the special edition of the 7 Series between 1979 and 1986. The 745i model featured a specially prepared 3.2 L straight six and a turbocharger producing 10 psi of boost. The car could be ordered with numerous exotic options for the time, such as heated front and rear power reclining seats and leather covered cellular telephone.

With the exception of the mentioned 745i, after almost 35 years, under the code name N54, the new turbocharged engine debuted in the 2006 BMW 335i Coupé. The N54 produces 306 hp (228 kW) and 400 Nm of torque using two small low-pressure turbochargers to remove the turbo lag. For this reason, the turbo pressure is only 0.4 bar, as the goal was to offer the same silky smooth feel as with naturally aspirated straight sixes. As a proof of this, the engine received high praise in all reviews and has been awarded with the most prestigious award in the industry, the International Engine Of The Year Award, for two times.

[youtube]http://www.youtube.com/watch?v=aHj0zbhjLZI[/youtube]

In the last few months, BMW has also presented several turbocharged engines: a twin-turbo V8 being world’s first power unit with a common exhaust manifold encompassing both rows of cylinders and featuring Twin Scroll Twin Turbo Technology, found in the upcoming M versions of X5 and X6 SUVs and a similar version used in the BMW 750i. However, the 7 Series won’t stop there, as BMW released information about their new V12 biturbo engine that will power the 760i which will be released in 2010.
A new line of straight six engines will also be released upon the launch of the new 5 Series GT, the petrol N55 (adds High Precision Injection, Valvetronic technology and twin-scroll turbocharging) and a biturbo diesel, which is seven per cent more powerful while being more fuel efficient.

Clearly, BMW pushes engine technology development more than any other manufacturer, with unbeatable 47 Engine Of The Year Awards as a sheer proof.

  • jkp

    I think, basically, the fanboys are just going to have to suck it up. For a variety of reasons, daily drivers (and no matter how good BMWs are, they are primarily daily drivers – even a significant % of the “M” cars,) are going to have to be very fuel-efficient in the years to come. As driving enthusiasts, we’re fortunate that BMW is not jumping wholeheartedly onto the “plastic-cars-with-electric-motors” bandwagon that is so popular in the US and Japan now. If anyone can produce a superb vehicle with a 4-cyl. turbo, it will be the boys in Munich.

    • Jordan

      I totally agree.

  • Stjepan

    Just wait for our next article then, it deals with four cylinders

    • Dede

      Hopefully it’s about a new turbo 4. Can’t wait to read it.

  • Mauro Corti

    @JKP

    You’re right, I do agree with you, completely. With turbo engine we will have more power, more efficiency and lighter car, I want them :)

  • Artmic

    I want to puke every time i read anything to do with CO2.
    Why are people so gullible and believe everything the press, tv-news and a bunch of UN paid for Scientists and special interest bought politicians?

    Why don’t people just do their own research on CO2 content of our earthly atmosphere, and then take a look of how much of that CO2 is contributed by humans, and then go back into history to discover CO2 levels being 10 to 16 times larger than they are now, and things were ok back then.

    • DailyDriver

      By going back in history you mean 10 million years right? By things were ok back then do you mean when there weren’t 6 billion people on earth? You must be talking about when the sea levels were around 300 feet higher on average, right over where 4 billion people live right about now?
      I’m glad you did you’re own research and figured all that out. I’m curious what methods did you use? Was it a long term study? Can you publish the results of your study so that I can review them? It seems only fair since I’m allowed to check the work of those bought and paid for scientists

      • Doug

        Hey… we (the dinosaurs) did fine with enormous CO2 levels due to volcanoes, meteor strikes, continent-scale forest fires, etc.

  • _Auday_

    IMO, I dont think fuel effecincy is exactly BMW’s reason for Turbo, I think it’s more of adding more HP in a cheaper way. Turbo charged engines are not really lighter if the numbers of cylinders are the same, and BMW did its magic with the weight of the S65 (E90/2 M3) engine using effeicnt materials, but that cost them money. They could also go back to the lighter less cylinders config and increase the RPM but that makes the engine more expensive too due to hi-RPM standing parts. So basicsally Turbo is the cheapest way to keep the engine weight Low and HP high, but not necessarly the best.

    IMO, if BMW is all about efficincy they should put all their focus on low weight materials of the car itself rather than keeping their cars going fatter and fatter, and for M cars this should go along with less cyliners, but higher-revving engines rather than turbo. This will make M engines where they should be in the real sport cars category and far from HP monsters like the AMG, RS, CTS-V, and other sports cars wannabe. Also BMW should focus on drivers feedback to get back the lost spirit of E30M3 where the driver feels one with the car.

    Unfortunately this will not happen because 1) the car will be more expensive and 2) it will not work well for HP hungery, show off people who buy M cars for the brand name, the luxury, and the raw HP. So why would BMW do it? they wouldnt, they will go to Turbo engines and leave us in the dark looking somewhere else for the Ultimate Driving Machine :(

    • pandamalone

      well, the BMW way to turbocharge an existing engine is not cheap. Actually, it’s much more expensive. Taking the N52/N54 rivalry for example. In order to achieve excellent response for the N54, BMW not only use bi-turbo charger, but also introduce the 2nd gen direct injection (DI 2) into the engine. The high pressure (~200bar) common rail direct injection system itself cost lots of money. Not to say you have to strengthen the crankshaft, engine block, improve heat releasing, to list a few. Also, i think one reason why bmw don’t come up with a 6-banger with larger displacement and instead introduce turbocharging, goes to that with the inline cylinder arrangement and given the limited room under the hood, probably a, say 3.5L NA I6, is simply too long. Just my 2 cents.

  • Zagreb

    BMW had opend last thursday a new Press Plant in Dingolfing so the Autobodyweight will be about 20 kilos lighter,also they a rumors that the new 340i Turbo in the 2012 3Series will have about 330HP,so the Car has the Power of an V8 but the consumption of an 6 Zyl.It will be a more efficiency and lighter car then the competitors have.The BMW Turbo Story will continuing.
    Remember BMW was the first Turbo Worldchampion in the F1

    • _Auday_

      20KG less is not enough to put the cars back on the right diet, the new Z4 already gained almost 300KG.
      330hp is good enough for the new 3 series IMO and I hope that BMW stops getting dragged into the HP madness. Turbo would make sense in the 3 series too, and it’s working well so far in the E90. All I’m saying is keep the Turbo and that stuff away from the M cars.

      I’m not sure what BMW winning the F1 championship with Turbo has to do with using Turbo in M cars. However I would like to mention that in that same year (1983) cars like Mclaren and Williams had the advantage in more curvy tracks because they were naturally aspirated, i.e. no Lag and more predictable throttle behavior that helps throttle steering.

  • Zagreb

    The old Z4 3.0si had 1385kg and 265HP and the new sDrive30i Z4 had 1490kg and 258HP and not a Textilroof.M BMW will in the Future had only Turboengines like the X5 M V8.

  • pandamalone

    ” new line of straight six engines will also be released upon the launch of the new 5 Series GT, the petrol N55 (adds High Precision Injection, Valvetronic technology and twin-scroll turbocharging) ”

    A little problem with this sentence.

    First, HPI (or DI 2, the spray guided direction injection with piezo injector and higher injection pressure) has already been employed on the N54, so i’m puzzled on this “add” thing.

    2nd. The primary purpose to introduce valvetronic system, is to use the valvetrain instead of the throttle valve as the controller of engine output, with the former capable of better fuel efficiency (by reducing the pumping loss) and better engine response (think about the S54B32 on E46 M3 which have individual throttle valve for each cylinder and you’ll know how valvetronic helps.). However, for DI+turbo engines, like the N54 or the rumored N55, the engine load can be also controlled by the injector (by injection different amount of fuel to the cylinder) then the pumping loss is not as significant, while engine response has already improved by the innovative control logic from BMW with help from the combination of blowoff valve and bypass valve. As a result i really doubt the necessity of introducing valvetronic into the new DI turbo engine (and i think that’s also the reason why they didn’t do it for the N54).

    Also, for the twin-scroll turbocharger, it will have a better application on I4/V8(twin turbo) engines instead of the inline 6 which is already twin-turbo charged which means each turbo charger takes charge of 3 cylinders. In this case the aid from twin-scroll might be not as significant compared to its application on I4, when1-4 and 2-3 cylinders have a 180 degree timing difference and a twin-scroll turbocharger perfectly separates this. Anyway, compared to the valvetronic, this will do more good to the engine IMHO.

    • Jordan

      The twin-scroll turbocharger I believe will only be a single on the I6 engine. It will not be a twin-scroll twin turbo. Using a single twin-scroll vs a twin-turbo BMW has been able to get more power (probably just tuning more, they could have easily got more power with the twin-turbo setup) and better fuel economy. And yes I do hope they use a twin-scroll turbo on their new I4 engines!

      • pandamalone

        yepp you are right. I later followed the the N55 thread and realized they actually use a single twin-scroll charger instead of two. I think the primarly advantage of single twin-scroll charger over twin-turbo is basically it requires less room and lighter, also with lower cost. Probably response is still not as good (though the difference might not be significant) as the tt setup. At the same time, the N55 is equipped with a VALVETRONIC system which help improve engine response. probably that’s why they are encouraged to use single twin-scroll charger. my 2 cents.

  • L1ndja

    Im sry this might be a stupid question.Why dont they just make a high revving twinturbocharged engine?I mean like taking a similar engine as the E46 M3 add twin-scroll turbocharging and sound good,improved performance and better efficiency?

    • The Lee

      The S54 engine has a compression ratio of 11.5:1. Turbo charging is nothing more than a method of artificially increasing the compression of an engine. The higher you go with compression, the higher octane you need in order to prevent detonation. 11.5:1 + turbo would likely need race gas in order to operate at an efficient and safe level, or you’d have to have the timing pulled out of it almost completely. Either way, it’s not a realistic combination for a warrantied, mass-produced engine.

      • pandamalone

        turbocharging won’t increase, by any means, the compression ratio. However even at the same CR, since the number of moles of air/fuel mix molecules are greater than that of the NA engine, the engine will experience a harder time against detonation given other factors fixed. That’s why old (none DI) turbo engines have to get a smaller CR compared to NA engines at the same tech level. However, with direct injection things become quite different. Injections can be made either during the compression stroke or even right before ignition, and with HPI there can be multi injection events, which partly solved the low CR problem for classic turbo engine. the N54 got a CR of 10.5:1, and that’s already impressive even as an NA engine. But anyway, 11.5 CR is just too high even for most NA engines, and i agree it’s hard to get a turbo engine with 11.5 CR even with the DI 2.

    • pandamalone

      The question is not stupid at all–at least not every part of it is:D To get something like turbocharged S54 is definitely not realisitic for a mass production car, as THE LEE expalined. However to explain why turbo charged engine won’t go high-revving really costs time and knowledge. One thing i’d come up with is that, as engine revs high, the exhaust volumetric rate is simply too high even a fully open bypass valve cannot handle, which in turn makes the engine breath not freely enough, as a result engine torque output drops as RPM raises over a certain number, say 5500rpm. (look at the torque vs rpm chart of N54 and you’ll know what i mean.) eventually the drop in torque cancelled the higher-revving’s contribution to power (which is equal to constant*rpm*torque), peak power is reached, and then dropped as rev goes higher. The same thing actually happens for all engines, but it’s just for turbo engines the exhaust problem makes peak power rpm comes even earlier.

      • L1ndja

        Thank you guys.

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