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Every motorist can imagine what high engine speeds are all about. But what is the nature of a concept based on such high engine speeds from the outset? |
Richter: We see this concept as the most intelligent way to deliver high power and performance from a compact engine. We are well acquainted with high engine speeds particularly in motorsport. In a modern Formula 1 engine, for example, the crankshaft rotates up to 18,000 times a minute, each of the 10 pistons covering about 25 metres of piston travel every second! We need such extreme performance in order to provide maximum thrust and torque in conjunction with the appropriate transmission. It is also the principle we apply to our M high engine speed concept.
By comparison, what engine speed is the new power unit of the M3 able to achieve?
Richter: The straight-six power unit in the BMW M3, which is an all-new engine from the ground up, revs at a speed of up to 8,000 rpm, that is a speed no other comparable production engine anywhere in the world is able to achieve. Until just a few years ago, only racing cars came in this category, reaching this kind of engine speed.
You were talking about thrust and torque - what does that mean in practice?
Richter: Ultimately, it means the power that accelerates a car. Following simple laws of physics, this thrust or torque is always proportional to the car's actual acceleration. In other words: The higher the speed of the engine - naturally always in combination with the best possible transmission ratio - the greater the torque and thrust you get when accelerating. This is the feeling of acceleration the driver will experience at the wheel. This is where he ultimately feels the power on the wheels of his car, and not, say, the - more hypothetical - horsepower claimed in the sales brochure.
Does that mean that the engine power of a car claimed on paper doesn't say that much about its actual performance?
Richter: Right. You must realise that there are various ways to develop high power. One manufacturer prefers engines with lots of cubic capacity, but running at low engine speeds. The disadvantage of such a power unit is that it takes up a lot of space, weighs a lot more, and normally consumes a lot of fuel. Another manufacturer, by contrast, prefers compact engines revving at a higher speed - which is precisely the approach we take with BMW M. So our objectives are to keep the engine relatively small and compact, to use less space and material, and, in particular, to keep fuel consumption to a reasonable level. All this, we believe, is crucial to the future of a really sporting and dynamic car.
Wouldn't a turbocharged engine be the right alternative in that case?
Richter: This is indeed the principle that some manufacturers prefer. But in our experience turbocharger technology involves the same drawbacks as a large engine revving at low speeds. A particular disadvantage certainly not appropriate today is the fuel consumption of a powerful turbocharged petrol engine in practice. And last but certainly not least, such an engine is far inferior to a high-revving normal-aspiration power unit in terms of its spontaneity.
How exactly do you define 'spontaneity'?
Richter: The customer interested in a sports car attaches great significance to the engine responding instantaneously to even the smallest movement of the accelerator. He wants to have the commands he gives with his right foot 'translated' directly into acceleration on the road, he wants his car to respond without the slightest delay. And again, this is precisely what we are able to offer with our high engine speed concept. A further significant point is the right balance of gear ratios and the final drive transmission.
What does that mean in practice?
Richter: It's simple, just like when you're riding a bicycle - riding uphill on a mountain bike, for example, you will shift down at some point in time. This means that you will now turn the pedals more often in each unit of time, but in return you are able to climb a steeper gradient. And while you could also climb the hill in a higher gear - to give you the comparison with a large-capacity engine - that would require more power. Precisely this explains the need for an ideal transmission in a sporting high-performance car.
How important is the torque of an engine in this context?
Richter: In principle high torque means a lot of thrust and good acceleration. But torque alone does not give you sporting performance on the road. Rather, you once again need engine speed and a quick response from the engine. To give you a comparison, a tractor on a farm powered by a diesel engine may well develop up to 720 Newton metres or 530 lb-ft of torque - but with the engine revving at a mere 1400 rpm, that tractor will obviously not accelerate very quickly. The new M3, on the other hand, has only about half as much torque but reaches its peak torque level at 4900 rpm and accelerates to 100 km/h in 5.2 seconds. And a Formula 1 racing car with more or less the same torque as our M Car accelerates even faster because it reaches its peak torque at an almost unbelievable 13500 rpm.
So ultimately it's the ideal interaction of transmission ratios and high engine speed that ensures superior performance on the road?
Richter: Exactly. The big advantage of this high engine speed concept is that it provides maximum performance on the road even with a relatively small engine as well as compact axle and drive units. And a point we should not forget is that large engines consume a lot of fuel, due to the proportional connection between fuel consumption and engine size: Generally, a large-volume V8 engine will consume more fuel than an equally powerful but more compact straight-six. And last but not least there is the technical challenge presented by our concept, which really motivates every engine designer and engine builder.
What exactly is this challenge?
Richter: Implementing the high engine speed philosophy in an engine in practice is by all means a demanding job. Not everybody is able to do this - if it were that easy, every manufacturer would apply this concept.
Can you explain that in greater detail?
Richter: Well, the physical loads acting on our new M3 power unit are quite comparable to the loads you will measure in a Formula 1 engine, even though the level is somewhat different. One factor you will find in both cases, however, is the significant demand made of special materials, since the specific loads we have here are roughly the same as in Formula 1. The big difference, of course, is that a Formula 1 racing car only has to last one race, whereas a BMW M engine must last for the entire lifecycle of the car.
How do you reach this goal?
Richter: There are three absolutely essential "ingredients": First, excellent engineers with good ideas; second, experience in the use of high-tech materials; third and in particular, the availability of a very special, high-performance electronic control unit. Just consider that applying our demanding concept, we have to monitor, calculate and transmit millions of data with each revolution of the crankshaft. Precisely this is why we have developed a special control unit for this purpose at BMW M - there's nothing else like it anywhere in the market.
Doesn't experience from the development of Formula 1 engines at BMW go into every M engine?
Richter: Yes, there is of course a fundamental exchange of experience and know-how, even though the two projects - Formula 1 and the new M3 - are entirely different in character. But one factor shared by both projects and technologies is that at the end of the day only the team with the highest engine speed can really beat the competition!
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