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BMW Unveils New Biturbo Petrol Straight Six Engine
Text & photos courtesy BMW AG
02-20-2006




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The force is with BMW as a new biturbo petrol engine blows in at the Geneva Motos Show

225 kW/302 hp and 400 Nm for hugely-powerful all-aluminum 3.0-litre six

High-precision direct petrol injection cuts fuel use by 10 percent

Turbo lag banished by intelligent biturbo technology



BMW is not re-writing the laws of physics, just the laws of forced-induction. Turbo lag has been vaporised, fuel consumption slashed and torque ramped to the max, as BMW unveils yet another benchmark-setting power unit.


Backing up its global success with the innovative 507 bhp V10 powerplant for the M5 and M6 super cars (2005 Engine of the Year), and the VALVETRONIC magnesium-aluminum straight-six engines introduced in 2005, BMW is set to tear the wraps off a production-ready biturbo version of its acclaimed petrol-powered six-cylinder. Retaining the familiar 3.0-litre capacity, the new all-aluminum engine boasts a pair of turbochargers, each feeding a trio of cylinders.

When combined with the efficiency and flexibility of acclaimed BMW VALVETRONIC and double-VANOS technology, the new engine is able to produce an immense 225 kW of power and 400 Nm of torque. It is armed with a Table Mountain-like torque profile that defies the term curve. Peak torque of 400 Nm is delivered between 1,500 rpm and 5,800 rpm and the engine boasts a 7,000 rpm red line.

The biturbo six-cylinder has the same power and more torque than the muscular 4.0-litre V8 engine fitted to the 740i. The new engine further entrenches BMW as the manufacturer of the world?s most intelligent, advanced and dynamic engines for the enthusiast driver. However, in keeping with BMW philosophy, the substantially enhanced performance does not come at a substantial cost to the environment. Fuel consumption, previously a bug-bear of high-performance turbo-charged engines, has been radically reduced thanks to high-precision direct petrol injection, used for the first time on a BMW six-cylinder motor. The V12 powered BMW 760i/Li features direct petrol injection for its 6.0-litre engine.

A further traditional turbo-engine wrinkle has been ironed out by BMW engineers: turbo lag. In the new engine, this has been completely removed, thanks to low inertia turbochargers. The driver need only brush the accelerator pedal to receive an immediate surge of power and performance, as the engine delivers an electrifying response. While turbocharger technology is almost as old as the internal combustion engine itself, in combination with cutting-edge high-precision direct petrol injection technology BMW engineers were able to write a new and exciting chapter in the history of forced-induction.

The foundation for all this power and torque is drawn from the exemplary characteristics of the magnesium-aluminum 3.0-litre engine which is rated at 195 kW/265 hp (as fitted to the BMW 130i and Z4 Roadster). This in itself is quite outstanding for a normally aspirated engine. Compared with the proven 3.0-litre normally aspirated magnesium-aluminium engine, the all-aluminium engine featuring new biturbo technology increases overall output by approximately 15 percent. Peak torque shoots up by an even more impressive 30 percent. The resulting 225 kW/302 hp and 400 Nm of torque deliver outstanding thrust and driving power all the way across the rev range.

The only way to achieve such an increase in power and performance with a normally-aspirated engine would be to significantly increase engine size, which would also mean a corresponding increase in weight and the negative effects on the car?s overall balance. The BMW combination of turbocharger technology with high-precision petrol injection is a particularly efficient way to meet even greater demands in terms of output and torque. And for comparison, the new straight-six biturbo weighs about 70 kg less than an approximately equally powerful eight-cylinder normally-aspirated engine displacing 4.0 litres. That is about the same weight as a moderately sized passenger.

Direct petrol injection also offers a significant fuel consumption saving of about 10 percent compared with a similarly powerful turbocharged engine that uses regular fuel injection. Turbines made of high heat-resistant special steel can withstand temperatures of up to 1,050 ?C and therefore do not need the cooling effect of extra air flow. Particularly under full load, this means a significant decrease in fuel consumption.

High-precision fuel injection allows an even more exact dosage of fuel as well as a higher compression ratio ? ideal conditions for increasing engine efficiency and significantly reducing fuel consumption. All this is made possible by the central position of the piezo-injector between the valves. Fitted in this position, the innovative injector opening to the outside is able to distribute fuel in a conical burst ensuring particularly smooth distribution of fuel within the combustion chamber.

Apart from its low weight and class-leading fuel economy, the new biturbo engine is able to offer yet another unique BMW feature. This is supreme smoothness and refinement, precisely the virtue which has made BMW straight-six power units the benchmark for refined drive technology, acknowledged the world over. Indeed, the natural perfection of the straight-six layout gives the engine perfect balance in terms of free mass forces, avoiding vibrations even at high engine speeds.

A further important point is that this turbocharged version of BMW?s six-cylinder comes with the same hollow, extra-light camshafts as on the normally-aspirated engine, as well as an electrically driven coolant pump operating only as required. Developing this new straight-six with biturbo technology, BMW is opening
up a new chapter in the long history of the turbocharged engine, which dates back to 1905 and the work of Swiss engineer Alfred B?chi.

Initially turbo-charged engines were restricted to marine and aircraft engines. It was only much later that the technology migrated to cars. BMW began its association with turbocharged road cars with the now famous 1973 BMW 2002 Turbo road car. But BMW regularly sets important milestones in engine development.

During the late 1960s, BMW was the first manufacturer to use turbocharged engines in touring car racing.
And in 1983 a BMW Brabham driven by Brazilian racing driver Nelson Piquet became the first turbocharged F1 car to win the Formula 1 World Championship. Even back then, BMW?s engine specialists were able to extract far more than 1,000 horsepower from an engine displacing just 1.5 litres.


Now BMW is ready to open a new chapter in turbo-charged petrol-engined road cars and reset the bench-mark for dynamic driving with forced-induction. Over and above the drivetrain conceived and built for supreme dynamics, this technology provides the starting point for a lean-burn direct injection concept and thus serves to successfully optimise fuel consumption also in other performance classes.

In this way BMW is once again proving its competence in engine construction, developing modern drive concepts and at the same time enhancing that sheer driving pleasure of BMW to an even higher standard. BMW will announce at a later date which of its vehicles will receive this new engine.

big_ipaq

Here we go... Where is that diesel 3l engine from 535d now?

colejl

Sounds great - I'd have to try one on the road... Might even tempt me out of the diesel!

However, I can't help thinking the standard tune is still a little low? (This thing will chip nicely though!)

I'm surprised it's not a sequentional turbo like the 535d...

KAF

Probably does not need it, petrol engines are much more responsive than diesel so turbo lag would be less noticeable.

big_ipaq

Is it not?!?

colejl

Retaining the familiar 3.0-litre capacity, the new all-aluminum engine boasts a pair of turbochargers, each feeding a trio of cylinders.

That's one turbo for 3 cylinders... This 2 turbo's for 6...

colejl

That's true but off-boost even petrol turbo's seem slow and sluggish!

It looks like BMW have bolted on 2 'small' turbo's - that's why there's 'no lag' and not a fantastically high specific output...

The sequential approach would of been better but modern economics is forcing the issue of consumption and emissions. Bottom line is it's 'better' than the 4 litre V8 (I expect the 540i to disappear in the UK and be replaced by the 535i)

big_ipaq

I doubt it. 540i is one of the youngest in the range... Isn't it?

BetterMakeWay

Exactly...although the article convinced me in a way, i would still want to drive this car when i get the chance to, so i can clearly make statements. The level of tune is rather small. The advantage of the engine is the torque curve but the hp gain is small. I bet it uses small (rather small) twin turbochargers so they can spool up quickly but what happens when you aproach the redline? I mean yeah i read the article BUT in real life testing will the power drop a little as the revs go higher and higher. Not drop, i mean keep the same pase, keep the same rythm? Sice it's not sequential turbo wich imo would have been the better concept (but hey i'm not an engineer) that means each turbo spools up fast and looses it's grunt as the revs keep climbing (to the red line). Where in the diesel that doesn't happen. 1 tubo looses grunt the other big one cuts in and takes over. Sudden brake-->speed drops--->rpms drop no problem the little one starts to work out in an instant.

That's why i'm saying i would have to drive test this engine with much attention. I'd like to see how it holds up, and also i'd like to see the comments from the best magazines/tv shows, even compares. I have a hunch that if you drive the car VERY HARD (almost racing it) it will feel more like a NA engine at the high rpms (meaning it will deliver as a NA). Also i was thinking about the turbo size on the petrol...meaning that if they are small enough to kill turbo lag then at very high stress they might give too much heat on the engine. 1000+ degrees Celsios is alot (not necesarely for the turbo) but for the engine itself and all near components. I think a good intercooler should cover it up...but from what i understood intercooler was not an option or i missunderstood?

And btw the 3 liter TT engine isn't beaten yet. It's still 160 NM away from the petrol and also let's not forget a new unit is to arrive, a little lighter and with insignificant hp increse. I have to addmit that if i'm worng and that 3 liter TT petrol delivers as it shoul, the right way, then it's a freaking good alternative to the 4 liter V8. IF IT"S THAT GOOD then i'm afraid bmw just killed the 4L V8 market segment. Just my opinion.

525dse

"Peak torque of 400 Nm is delivered between 1,500 rpm and 5,800 rpm and the engine boasts a 7,000 rpm red line. " that engine will make the 3 series coupe a rocket! well feel it. it may have alot less torque than a 535d, but it covers alot more of the rev range...