For several years now, the writing has been getting clearer on the wall. NA engines are becoming niche, and there's little evidence that automakers are running off to design new NA engines from scratch apart from a few modifications year on year.
A casual look at this year's 2015 Ward's 10 Best engines shows that 8 out of the 10 winners are forced induction and 6 are specifically turbocharged engines. (Incidentally, my favorite "sports" car is on this list with its fine 6.2L supercharged V-8... actually this makes it twice in a row as it had won in 2014 as well).
An article in June's Engine Technology International puts some figures to the case for turbos. Apparently, even the worst turbocharged engine will get you an honest mean effective pressure of 15 bar. Put into other words, these low end turbocharged engines already put out a specific power of 100 kW/liter, which is roundabout the same figure the best NA engines muster today.
There's really no competition, or is there ? What can possibly compete?
Electric superchargers are independent of parasitic losses but lose a ton of power in energy conversion. Further, they are only transient devices. Commercial entries to "electric boosters" have been labeled a scam. They don't work.
PHEVs offer promise, since they supply instant torque on startup and eliminate the need for turbo assisted low speed torque. Hybrids also cut back on range anxiety since you can technically always fall back on an IC engine. However, battery costs are looking prohibitive for most people right now. In countries like the U.A.E where I live, the electric infrastructure is only starting to pop up, and in minuscule amounts.
At some point in the next few years, I'll buy a new car and it won't be special to tell others it's turbocharged. I'll most likely get disgusted looks if I say it's NA.
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Ward's 10 best engines of 2015 (link) :
127-kW Electric Motor (BMW i3 electric vehicle)
6.2L OHV V-8 (Chevrolet Corvette Stingray)
6.2L Supercharged OHV V-8 (Dodge Challenger SRT Hellcat)
1.0L Turbocharged DOHC 3-cyl. (Ford Fiesta)
100-kW Fuel Cell (Hyundai Tucson FCV)
1.5L Turbocharged DOHC 3-cyl. (Mini Cooper)
3.0L Turbodiesel DOHC V-6 (Ram 1500 EcoDiesel)
2.0L Turbocharged DOHC H-4 (Subaru WRX)
1.8L Turbocharged DOHC 4-cyl. (Volkswagen Golf)
2.0L Turbocharged DOHC 4-cyl. (Volvo S60)