[GeorgeKangas]

The word "turbocharger" was introduced to shorten the phrase "turbine supercharger", whether driven by the crankshaft or by the exhaust. Later, it came to mean "exhaust driven turbine supercharger" pretty much exclusively.

I don't have any dates for these usages.

Edit: that p-47 powertrain is an absolute beast!

[jandrese]

The crazy part is that by modern standards they aren't really developing that much power. Sure this thing puts out 2,100 HP (using 130 octane gas), but it needs a whopping 46 liters of displacement to get that.

A Veyron engine puts out about half the HP using 17% of the displacement on worse gas. You can't even buy 130 octane gas anymore. The Veyron is a notorious fuel hog, but it has nothing on a twin Wasp radial.

[bigiain]

> A Veyron engine puts out about half the HP using 17% of the displacement on worse gas.

Not at 45,000’ altitude it doesn’t.

And that Veyron engine won’t be too happy running at 80+% of its rated power level for more than a few minutes at a time.

[userbinator]

And that Veyron engine won’t be too happy running at 80+% of its rated power level for more than a few minutes at a time.

This is the part that a lot of people are unware of when it comes to engine power ratings --- aviation engines are designed to run at their rated power continuously, while most passenger car engines aren't. Even comparing a truck engine with the latter has people confused at why the power numbers seem so small both absolutely and relative to displacement. A 9L engine in a truck used for pulling semitrailers may make "only" 330HP, but it can do that continuously, and indeed will spend the majority of its life at or close to full throttle.

[czch]

But the P-47 is on fairly high power the whole time it’s running. Most Veyrons will never use 50% of their rated power.

That being said, modern metallurgy really revolutionized ICEs. Followed by computerized control.

[Gibbon1]

Not my field but the other difference is 1500 hp at 2,400 rpm. The low max rpm is because it needs to match the propeller design speed and needs to be efficient at near full power.

[lovecg]

Couldn’t you gear down?

This whole discussion makes me think what would a modern maxed out aircraft piston engine be like!

[mannykannot]

These engines were, in fact, geared down, as was common (if not ubiquitous) in large piston aero engines. This video shows an epicyclic reduction gear inside the bell-like case on the front.

https://youtu.be/EyPvpdy4dgg?t=117

IIRC, piston speed was an issue in how fast these engines could run, as, for given RPM, the piston speed is proportional to the stroke. And, for reliability and the corresponding safety reasons, aero engines are more conservatively designed than most car engines.

[Merad]

If you're really interested in the topic look up the YouTube channel Greg's Planes and Automobiles. In addition to a deep dive series on the P-47 just a few weeks ago he made a video about late WW2 "super prop" fighters. They were the pinnacle of piston engine fighter performance, but they were all canceled because they weren't needed to win the war and everyone could see that jets were the future. We'd probably struggle to beat them even with modern technology TBH.

[pbronez]

The final incremental improvement before a revolutionary change is always an interesting place to look.

[linsomniac]

Gearing adds a lot of weight, and soaks up some power. Additionally, that weight tends to be at the front of the engine, so it can mess with the CG. You ideally want an engine that produces good power at rotational speeds that keep the propeller tips moving sub-sonic.

At least, that's what I found in brief investigations long ago when I was interested in the idea of a wankel rotary powered plane.

[plantain]

Gearing adds weight and complexity, and complexity brings unreliability. Best avoided where possible.

Putting car engines into recreational aircraft has been popular over the years, but never really 'took off', with high failure rates from being run at consistent power levels way past their design goals. The best conversions are high displacement naturally aspirated engines that end up looking remarkably like the existing Lycoming/Continental aviation engine installations.

[usrusr]

Not maxed out, neither in terms of size nor in terms of wartime-only tradeoffs along the lines of "it's ok when two engines blow up due to low error margins if the performance gains they enable allow four boys more to return", but the RED A3 hn-famous from driving the Otto Celera is a modern aircraft piston engine. Apparently the only one, if you ignore the occasional automotive adaption.

[jabl]

The 130 octane gas you refer to is actually 100/130 lean/rich avgas. Quite similar to the 100LL still used today.

Towards the end of the war the Allies were using 115/145 in fighters for even more oomph.

As for fuel consumption, those WWII piston engines actually were quite efficient, look up BSFC numbers if interested. Fuel load and range were critical issues. It took many decades, energy crises and computer control for car engines to catch up.

[diarrhea]

So when you have such a turbine supercharger driven by the crankshaft, what does the turbine do at all?

[usrusr]

A crankshaft driven charger would haven been called just a supercharger, exactly like we do today. But we don't call turbine driven chargers "turbine supercharger" anymore, we call that a turbocharger.

[diarrhea]

Exactly, but GP's

> "turbine supercharger", whether driven by the crankshaft or by the exhaust.

made it sound like there's "crankshaft-driven turbine superchargers", which I stumbled over.

[agurk]

What we call a turbocharger today has two turbines in it - one that is spun by the exhaust gasses and a second one that compresses the incoming air. These two turbines are directly connected.

If you look at super chargers they're all some kind of pump driven by the mechanical energy directly from the crank. If this pump was a turbine, then you'd have a crankshaft driven turbine super charger.

So this is half of a modern turbocharger (the compressor) being driven by the crank rather than the exhaust gasses.

[diarrhea]

> What we call a turbocharger today has two turbines in it - one that is spun by the exhaust gasses and a second one that compresses the incoming air. These two turbines are directly connected.

That's incorrect, a turbocharger has one turbine, and its driving counterpart is the impeller. That impeller/compressor is never referred to as a turbine. Turbines can only ever extract work from a fluid.

Superchargers as well as turbochargers also don't have pumps, those are machines for which the working medium is incompressible (water, ...; density is not a function of pressure, in "engineering precision"). If it is compressible, it's a compressor: it affects not only an increase in pressure but also in density.

A fan also works on compressible media but is only supposed to impose some velocity. For this, it necessarily also increases the medium's pressure, but to a low degree, such that (IIRC) changes in density are negligible.

[usrusr]

Well, you can find the term "bike pump" even on newyorktimes.com and that's not about hydraulic brake levers, so there might be some difference between technical language and common usage even in English.

But I'm posting this to say thank you, I was completely unaware of this detail. In my mind, and likely in GP's mind, the term pump was characterized by the piston principle, not by the medium. And I realize now that the "pumps for air" incorrectness is much less common in English than in German (my home language).

Apparently in engineering German the distinction is exactly the same as in English, but it's completely absent from common usage. German never even adopted a verb for high pressure inflation that is not derived from pump. Other than that, the terms pump and Pumpe are extremely similar in English and in German, which is unlikely due to common Germanic roots but because of something much more recent. I suspect nautical terminology which must have been a strong language unifier before navies became a key element of national separation.

[agurk]

You're right I did misspeak about the definition of a impeller/turbine.

Never is a strong word though and there are such things as turbine pumps which are not true turbines[0]. As far as I can tell they've never been used for engine applications.

Regarding pumps they operate on a fluid, of which air is definitely classed as. [1]

[0] https://www.globalspec.com/learnmore/flow_transfer_control/p...

[1] https://en.m.wikipedia.org/wiki/Pump

[Toutouxc]

I don't get the downvotes, you're right.

A crankshaft driven supercharger doesn't need a turbine (a device that extracts power from a fluid), only an impeller (the opposite).

[sk5t]

I think what you’re getting at is that there is no turbine (only an impeller) in the case of crank/belt driven units.