Difference between car and light aero engines?

I think the reason they remain virtually unchanged is because they work! Modern car engines with loads of sensors and a black box can be unpredictable, in my opinion. The reliability of the Lycoming engines used in most light aircraft have proven themselves over time...if it aint broke don't fix it. Power is not really an issue as you can get variations of engines for aircraft. The Cessna 150 is not very powerful at all but the reason being it does not need to be as it is a trainer. If you want a fast single you buy a Mooney, trainer C150, slow tourer maybe Piper Warrior or C172, faster Piper Arrow RG.
Homebuilts on the other hand use car derived engines with modifications. I looked at buying one with a VW beetle engine before, seen others with Subaru etc. I look forward to seeing the detailed tech responses on this ...effects of pressure, altitude etc.

I would have to guess that one of the reasons is weight. Because, well, don't quote me on this, but arent' car/truck engines heavier? My next thought is power. You don't really NEED a plane with a V8 engine in it because you're turning a propeller, and the only resistance there is the wind and the occasional bird/human head. Naturally, the engine has to be powerful, but not super powerful just to have the plane fly. Think of the wright brothers, wasnt it like a 12 hp engine. It only flew 20 mph, but still. And, looking at a car engine, when I stomp the gas, the RPM sometimes flies toward 6,000RPM. You don't see that sort of RPM's in anything other than jets. Most props max out at 2500, so you're just in the air with dead weight that doesn't contribute a whole lot to overall power.

Bah! You only need V8's in America where the cars are like barges and fuel is cheap.

HAHAHAHAHAHAHAHAHAH

Fuel here is over 2 dollars per gallon

Well nearly £1 per litre here which is er... (calc) £3.64 UK pounds... or $6.8 of your US Dollars for a UK gallon.
(added) and that's with the fantastically weak dollar to the pound!

wow! I didn't know that much

seriously though, i nearly died when you said it was cheap here, my dad came down and was like "what're you doing!"

Why what you doing? (or don't I want to know )

Sorry, back on topic.

I'm going to Copenhagen (in Denmark) in February and the drive to the airport (return) costs £80 in petrol (Gas in American lingo), the return to Copenhagen on the *plane* is £50. That puts it into perspective.

wow, thats a lot. Lol, i wasnt doin that, i was laughing so hard. It was the first time in 3 years i've heard the words "gas" and "cheap" in the same sentence without hearing a gunshot.

... Gunshot.

Only in America 🙂

D.

where are YOU located??? 😳

I won't get into the "Why is gas so expensive (or cheap) here," but back on the original topic:

Automobile engines have been carefully engineered to meet emissions requirements-- you don't really NEED a computer to control your engine (as those of us who learned to drive in the 1960's remember), unless you're trying to squeeze every last little bit of pollution out of the gas going out the tailpipe. Getting a lot of power out of an engine is easy, if you don't care what goes out the tailpipe. The old VW Beetles got pretty good gas mileage, but they could never meet current smog regulations.

Ed

Ed's right, we've been going on about that like a couple of hens havent we? 😀 😂