[n86121]

Other than FADEC being simpler, and electronic ignition being easier to start,
I can't imagine there is any noticeable gain in efficiency, miles per gallon, or power speed.

Unless I am missing something,
automobiles gain their 'efficiency' by handling constantly CHANGING power requirements more precisely.

I remember from my Princeton aersopace design course, a car on a level highway at constant highway speed needs on order of 20 HP (or less) to overcome all friction, internal and external: air, internal friction, wheels deforming, etc.

Thats why cars are all looking the same. They all ready the same market studies for what the market wants, and they are all engineering the same few variables to optimize drag and friction. They also become lighter to require less HP to accelerate fast, but super acceleration is more for marketing than regular use.

That is also why a tiny car engine that can provide efficient cruise at low power, with high efficiency, and also have massive turbos and other add-ons that adjust changing fuel, air, timing; such as for ACCELERATING the mass of the vehicle, or improved performance, etc.

My son's 350HP sports car still gets 30+ miles per gallon, when turbo's not accelerating it. But hard acceleration and it drinks fuel. Physics.

Our airplane engines operate more like an industrial powerplant: Many hours at mostly steady state, within a very narrow band of RPM and mostly constant power at a given altitude.

There are only three variables: How much fuel, how much air, and when to ignite it?

There are also other clever things one can do to improve volumetric efficiency: Intake systems with less drag. Larger valves to breathe easier, etc.

I had a Lotus in the 70's that had a 45mm carb on EACH cylinder, a flow through exhaust, and 4 LARGE valves per cylinder. I recall the exhaust vales were huge. It got 250HP out of a normally aspirated 4 cylinder engine, sounded like you were at Le Mans, and was a rocket, AND got great mileage when you weren't flooring it.

At a steady state, I BELIEVE our aircraft engines are pretty much optimal for fuel, air, timing, and exhaust. They may not operate very well outside of that, but we don't operate them out there for long anyway.

So I dont understand where the gains can come from?