Comment by bob1029
5 years ago
Reciprocating machines are fairly remarkable when you consider all of the components involved, forces, etc. Even more so when you think about how long a typical car engine lasts.
These incredible forces are why rotary and turbine engines are substantially more reliable. Some gas turbines have only 1 moving part, and in some applications this moving part experiences zero wear due to magnetic/aerodynamic/active bearings.
Rotaries are a funny case. Look good on paper. Thermal efficiency issues. Smog. Seals. Noise control difficulties. Weird patches like bridge ports.
For modern passenger cars, it's kind of like overcoming the difficulties of two-stroke.
In anti-defense of 4-stroke ICE, it seems to me like we are hitting peak wacky complexity of those. Variable timing cams, turn off the cylinders, direct port injection, turbos, variable intake, complicated ECU. It's a far cry from a flathead 6 or VW flat 4.
Thank God electric cars are becoming more available, although I fear increasingly complex cooling and battery management and the 1000 things a software guy is going to add to them.
> Thank God electric cars are becoming more available, although I fear increasingly complex cooling and battery management and the 1000 things a software guy is going to add to them.
I'm hoping lithium iron phosphate starts to be used more in midrange vehicles; partly because they can be scaled up while sidestepping the potential resource bottlenecks around cobalt and nickel, and partly because they're very durable and cooling isn't usually much of an issue. Though heating might be an issue in the winter time (most LFP cells don't like being charged when temperatures are below freezing; heating might be necessary in winter).
Salesman of the future: "This motor's got five-phase windings with third-harmonic injection, baby!"
That actually is a thing, its only worth a few percent of power at the same size, and I totally expect to see it happen.
The problem with ICE industry is that nearly nothing improves much in absolute terms.
If you take a look at list of ICE records, nearly all of them were made decades, and decades ago.
Biggest piston engines - early 20th century
Most powerful piston engines - fourties
Most efficient piston engine - Jumo 204 held the record until nineties
Most power to weight - eighties
Uncounted billions put into engine RnD were mostly about scraping last few percents off everything above, and environmental compliance.
Like those distorted maps of the united states weighted by population[1], your post should be read with "environmental compliance" as the center of mass. Yet you shrug it off like a footnote. Nobody, except perhaps ship designers, cares who has the biggest piston engines.
[1] http://www-personal.umich.edu/~mejn/election/2016/
> Jumo 204 held the record until nineties
And what has happened since then? Google is showing me several engines with breakthrough efficiency in the last 10 years.
When I was a kid in the 90s, SUVs commonly got 12 MPG. The new models are 25 sometimes 30 MPG. Emissions have gotten considerably better in the last 30 years.
I’m looking and can’t find any info to back up the claim that this 1920s engine was more efficient than engines designed in the 80s and 90s. I am curious about it, not just is it true, but specifically what kind of efficiency you mean and what design features made it efficient. Do you have any sources or reading? Wikipedia talks about how the arrangement of the valves increased the efficiency, but only says this made it approach four stroke efficiency (at the time), not that it exceeded other designs. The 204 was a two stroke, and it seems to be common knowledge that even today, four strokes are more efficient. https://en.wikipedia.org/wiki/Junkers_Jumo_204
[*] more reliable in theory. Mazda RX8 and rotary engines are famous for being a bit maintenance heavy and unreliable.
The amount of engineering and brain power that has gone into making common ICE engines in cars in wide deployment reliable is staggering.
I've own an RX8 maintenance came down to adding oil every few fill ups, and changing spark plugs every 10k miles. If you treat the engine correctly, the will easily get to 100k miles, if you drive the engine incorrectly (run at low RPM), or run low on oil things won't last long. The car is a sports car and won't get you worry free 200,000 miles like Accord or Camry. Even the S2000 had similar oil usage.
Talking to the dealers I took the car too, many of the issues with related to people who didn't warm engine up, or baby the engine below 3,000 rpms causing carbon build up.
Agreed on automotive rotary. It's not in the same spirit as the gas turbine and others.