Why do I compare exactly these two engines?
Both are BMW 6-cylinder aggregates. I believe that BMW considers (all symptoms show that) exactly the 6-cylinder engines for the “main” in their product range. Yes, of course, if you ask the manufacturer itself, the formal answer would be something like “for us, all aggregates are equally important “, but facts speak by themselves. The largest amount of cars of the BMW premium segment is sold exactly by these engines (at least in relatively close past); typically – these engines, as first ones, are equipped with the newest technologies. Only after, the “dwarf versions” or the 4-cylinder (or even 3-cylinder) are made. Yes, of course, there are also V8, V10, and even V12 composition engines, intended for completely mad “petrolheads”.
In my opinion, N53 demonstrates the highest technology point of the petrol engine era.
It is clear that BMW, like many other car manufacturers, will not develop any new petrol engines. B58, instead, will be the honor to be the last “full-fledged” power aggregate of the petrol car. In the range of the cars, hybrids or full electro cars will appear, but the petrol classic (“fuel graveyard”) will be finished by B58.
Formal data of both engines:
N53B30O0: 2996cm3; 320Nm and 272hp; atmospheric engine with Stratified charge;
B58B30M0: 2998cm3; 450Nm and 320hp; turbocharged engine
Both engines in my comparison test are installed on cars with a similar weight: both cars are equipped with a manual gearbox. Differential gears also are identical: 3.23. I believe – quite fair conditions for comparison.
Before I move to compare the engines, I would like to talk about formal power parameters. Here, the real measurement of N53B30O0:
Dyno measurement looks fair because the numbers of both parameters (torque and power) correspond the ones indicated by the manufacturer. As we see, the torque is practically unchanged in a range of 1500 .. 6000RPM; instead, in the range of 6000 .. 7000 RPM, full power: 200 kW is available. At least 70% of max torque is already available (at least 210 Nm) at idle. All parameters correspond to the ones indicated by the manufacturer.
Let’s see the technical data of the B58 series engine. BMW, though, has not compared the basic parameters of this engine with N53, so we can not see them in one chart together:
As we see in the comparing chart with the “old” N55:
a. at range 1300 .. 5000 RPM full throttle (450 Nm) is available;
b. at range 5000 .. 7000 RPM full power (240 kW) is available;
c. from 1000 RPM already around 300 Nm are available.
The technical specification looks impressive!
How did BMW manage to reach full throttle already from so low RPM? BMW is proud of its use of Twin-scroll Turbo turbocharge aggregate with an electrically manageable wastegate. This “double” turbocompressor is used in the so-called “pulse” mode. What it is, and how does it work – in one of the next entries.
BMW does not indicate in what conditions the measurements are done and so beautiful torque curves are got, so I will reveal the “secret”. Such curves are obtained in static conditions. The engine (or the car) is placed on the dyno stand; in each RPM range, the stable speed with max required torque is maintained. So, this curve does not include the dynamic turbo lag of the turbocharger. In this graphic, the turbocharger is already “on full speed” – works “with full power”.
It is clear that for the turbocharger (for efficient performance) are necessary:
a. appropriate (sufficient) kinetic energy of the exhaust gases;
b. time, to overcome the inertia of the mechanical part of the turbocharger.
In continuation of the entry, when talking about the B58 engine, I will often call on these two criteria.
But now – finally, I move to the comparison of both engines.
N53 is unique with its immediate reaction to the accelerator pedal. Even in idle, when even slightly pressing the accelerator pedal, there is a feeling that the engine has no flywheel at all. There is a feeling that the mechanical inertia is 0. Even from idle, almost full throttle is available – even in first gear, releasing the clutch, the engine will accelerate smoothly and immediately. The engine reaches 7000 RPM without problems (even with the sense of “ease”), it has no slightest signs of tiredness. MSD80 perfectly balances the performance of cylinders that pressing/releasing the accelerator pedal; not even the slightest vibration or “stiffness”/unevenness can be felt.
I would like to compare the N53 engine with a sophisticated lady.
Gracious. Nuanced. Yes, relationships with the “queen of the ball” can not be cheap. Yes, this engine has its “special” days – desulfation of the NOx catalytic converter. But – the good moments give such a driving pleasure that no other BMW engine does.
B58 is different. B58 reminds me of a professional “strongman” with weakened mental abilities.
This “freak” has a lot of strength. But the main problem – its reaction is slower. You can not hail to him – “let’s run”! No, at first he has to drop the dumbbells, then the question “what? where? why?” would follow. Yes, if you explain promptly, what to do, he “does” almost all other competitors. His muscle mountains limit swift movements, so don’t hope for a lightning-fast reaction or a light run at a huge speed.
Do you need a technical explanation? Here you go!
Pay attention – if the car is equipped with an automatic gearbox, in Sport/Sport+ modes, when starting the fight for a tenth of seconds till 100km/h, the DME of this engine maintains around 2200 RPM. Why? The turbo aggregate would have the energy of exhaust gasses to turn it on! In addition, these RPMs are maintained for 2+ seconds. Why? For the inertia of rotation elements of the turbo-aggregate to be overcome – to gave enough force for them to start to turn. If at least one of these conditions (RPM and/or time) is not fulfilled, the engine’s reaction is… None. The “strongman” stands with the dumbbells in his hands for around two seconds, peeking stupidly. Yes, then comes the growl, but even in Estonia, already a new day has started. The reaction of the engine at the moment of start is worse than I expected. B58 has a turbine of relatively low boost pressure; compression is 11:1 (very high for a turbo engine). I would expect at least half from a max torque. No, not even close to half is available!
The second nuance – even in Sport/Sport+ modes DME in Overrun modes works in such a way, how the driver “commands”; it means – it does not maintain the minimum required torque for the turbocharger needs. If the driver releases the accelerator pedal, the turbocharger “stops”, and after a moment, the old story continues – the “strongman” stands with the dumbbells in his hands. Good news – if RPM is at least 2000, around 270 .. 300 (from 450) Nm are available already without the involvement of the turbocharger.
Both previously mentioned nuances/problems are largely suppressed by the automatic gearbox. People, who use automatic gearboxes, are already used to it, that nothing happens at the same moment. Additionally, the automatic gearbox will maintain the required RPM at the moment of start and will “release the clutch” “correctly”. Also, it will not allow the drop of the RPM below the norm – on a large scale; it solves the second problem.
When the engine is turned to redline, you can feel that above 5000 RPM, the torque starts to drop. Till 6000 RPM subjectively, this drop is not so pronounced, but it does not give any pleasure to turn B58 till 7000 RPM. Unfortunately/luckily, it has to be done if you want to reach the max acceleration. Drop of the torque by large RPM is not so swift that it would be more profitable to switch to the next gear faster than reaching 7000 RPM.
Here I want to remark, in my opinion, an important nuance. BMW in the NBT screen offers the performance indications – the parameters of power and torque developed by the engine.
Unfortunately, in the clockface of the torque indicator, a significant indication is missing – max available torque of the engine in the exact conditions. Of course, when driving in a “race” mode, the driver has no time to observe these indicators, but this parameter would be mega useful in the “self-learn” stage!
One more nuance, which is quite complicated to get used to. Pay attention to the tachometer:
As we see, to inform the user if the engine is permanently turned off or at the moment it has been turned off by the Start/Stop system, BMW has introduced this “Ready” mark. But now all RPM scale has been shifted! Where previously was 2000RPM, now it’s only around 1000 RPM! This nuance is very significant when driving in “mode” “I’m ready to demonstrate the performance of BMW”. This mode suggests relatively peaceful driving, but at the same time – being ready to conquer other “not-cars”. Of course, the driver is not checking the tachometer all the time, but still – with ar peripheral vision, its indications are seen. The situation gets complicated by the obstacle if such a tachometer is regularly replaced with a “regular” one, for example, if the everyday car is some E series car.
It is possible that my writing was not relevant for those who use the automatic gearbox. It is possible that it was not interesting to those driving every day with turbo engines and have developed the driving skills to perfection. Till now, I was (and still am) the advocate of the atmospheric engines. Now the time has come when even BMW does not manufacture atmospheric engines anymore. Even more – in newer models, there are no manual gearboxes available! I’m forced to adapt.
Does B58 give the pleasure of driving? Yes, it does. It is completely different from N53. It is harder to drive with this engine if you want to “squeeze” the maximum from it. But, exactly this – not simple management is exactly that, what attract the manual gearbox lovers.