alt Hacker News> To further improve fuel efficiency and output, ZR15DDTe engine uses Nissan's unique STARC*2 concept paired with a large turbocharger.
If we are able to consider fixed RPM operation and are willing to endure turbomachinery, I don't know why we wouldn't just go all in on a gas turbine. You can reduce the number of moving parts dramatically and accept a much wider range of fuels.
Being able to engineer everything around a one fixed operating speed makes a huge engineering difference. Reciprocating engines are responsive to load and speed changes, but there are trade offs in many other categories.
You can also make a gas turbine power module quite small relative to the alternatives. Replacing the it at major service intervals could be made economically viable.
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This has been tried, but back in the day the automatic transmissions weren't really up to it, and they don't really like thermal cycling. And they're noisy. Exact opposite of modern stop/start petrol engines for urban driving.
I also suspect all attempts to keep doing combustion engines for mainstream driving are going to get gradually overtaken and lapped by BEVs.
That would be very cool. I wonder if you could get it through legislation though. I think all the legislation is based around reciprocating IC engines.
> why we wouldn't just go all in on a gas turbine
Cost, reliability.
I suspect that the improvement in efficiency is small enough at the scale of an automotive power plant that it wouldn't be worth it.
Reading around suggests that in order to achieve decent efficiency from a gas turbine, you need quite a few supporting systems that only really make economic sense at larger scales (like the 10's of MW scales, not the 100's of kW).
(Although just from a fun technology angle I'd love to see a gas turbine in a car).