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Originally Posted by luxman999
So what is the real advantage of turbo charged 3.0 liter engine over naturally-aspirated 3.5 liter? Does it have better performance, better reliability, better gas mileage or cost less? I think answers are clear NO to all. I really don't know what BMW guys are smoking these days.....
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Sorry if any of this has been answered already:
A well tuned bi-turbo setup delivers:
-Excellent torque
-Excellent power curve (note the 1500-5800 rpm torque plateau - talk about awesome highway performance/passing and in-gear acceleration)
-Better fuel economy under partial throttle (which is how most driving is done, of course)
-Lighter block weight (important for balancing the car's chassis - the 4 liter V8 used in the 540i, for example, is 70 kg heavier than the N54)
Forced induction essentially provides all the advantages of a larger naturally aspirated engine with fewer of the disadvantages (particularly in terms of day to day fuel economy). We will likely see this engine, at 3.0L with HPI, getting better than 30 mpg on the highway. Lexus' DI 3.5 rates at 28 (despite a six speed trans and very conservative - judging by how it behaved when I drove it - transmission behavior), and the BMW non-DI N52 3.0 is currently rated at 30.
Cost and reliability depend upon the setup and are impossible to determine from this side of things.
I don't know about you, but I love the torquey nature of the M52TU in my E46. I love being able to pass in 5th gear on the freeway with a lowly 2.5 liter engine. The low and mid range torque in the older BMW I6 engines was always a big selling point for me...this engine restores my faith in that ideal.