most N.A. engines make max torque at around 4,000-4,500 RPM
BMW's 3.0 n52 makes max torque at 2,400 RPM and it's also NA with vvt
how do they achieve that?
does more torque at lower RPM destroys the gearbox faster?
and why doesnt any other car makes makes their NA engines more flexible?
at the end it improves fuel savings not only acceleration and engine flexibility
i heard the e90 330 has this engine and its very reliable
That's just the nature of how the engine was designed. Every engine is different...a Toyota 4 cylinder is going to be completely different from a BMW 4 cylinder (same with 6 cylinder engines). BMW's VVT system is also VERY sophisticated as well, which could also play a role in all this. Which NA engine did you compare this N52 engine with? This is a 6 cylinder NA engine, so you cannot compare it with a 4 cylinder NA engine...the NA 6 cylinder would make peak torque a lot faster than the NA 4 cylinder. Let me know which NA 6 cylinder engine you compared this engine with.
And yes, this is probably the most reliable BMW engine you can get.
"most N.A. engines make max torque at around 4,000-4,500 RPM"
Which engines are you referring to?
Straight 6 engines have historically made their torque at lower rpms. That's why they were in many commercial vehicles back in the day because they could haul a lot of stuff because of the torque they produced quickly, and where speed/hp wasn't as important. How BMW does it in their engines to achieve modern day metrics, is very complicated engineering which is why it cost so much to repair when they have failures.
actually i did compare this engine with 4 cylinder engines, didn't knew it matters.
some of them have really terrible numbers like the old corolla with dual vvti system that makes peak torque at 5,200
on the other hand there are more flexible 4 cylinders like the honda accord 2.0 155 hp that makes it at 4,000