For example, why does 5.7L V8 Tundra Engine make 381HP/401 pound-feet and a 2.3L 4Cyl Focus RS make 350HP when other V8’s can make ~700HP.
In: Engineering
In the samples you’re talking about, mostly rotation speed.
To a *very* rough approximation, power scales with displacement and speed. There are lots of other things involved, like /u/TheJeeronian describes, but if you want to get more power out of an engine you can increase displacement or increase crankshaft speed. Turbo/supercharging is effectively a displacement increase (by compressing the air more, you can make a smaller displacement engine hold more air).
A 350HP 2.3L is going to be running at about twice the RPM (ish) of a 381HP 5.7L. A 700 HP V8 is really screaming. Something insane, like an F-1 race engine, is a low displacement V6 but it’s going about 15,000 RPM.
The *stress* on the engine parts scales really strong with speed, especially at high speeds. A big engine, like a 5.7L V8, can generate a lot of power without spinning that fast. This means many of the parts, though physically big, don’t have to be as proportionally strong or precise. This means less exotic materials, easier tolerances, higher durability, less issues with weird stuff like valve float, etc. This is why pickup engines happily go 250,000+ miles while dragsters and race cars throw a piston every couple of races.
Making big things go *really* fast is very difficult. Balance becomes a huge problem, bearings get ludicrously expensive, lubrication failure becomes instant catastrophic disassembly rather than giving you seconds/minutes to shut down, etc. Rocket engines turbopumps live at the bleeding edge of this spectrum…truck engines live at the far other end, with the only thing past them being large ship engines.
Edit:typo
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