the maddman said:
Yeah, but it's the little 4 that's impressive to me. They get a lot of power out of a tiny bit of engine.
HP per liter is just a number.
If you rev the piss out of an engine you're gonna make good power for the size as long as you have nice head(s) and a cam.
A better way to rate engines is BSFC.
Brake Specific Fuel Consumption is the ratio of fuel consumed (in lbs. per hour) to horsepower produced. This ratio is a direct indicator of how efficiently the engine converts fuel into power.
So it's one thing to rev the piss out an engine and it's another for to be efficient at turning air and fuel into power.
When you hear people saying rotary engines *rx7/8* are inefficient, this is what they're talking about.
The problem with rotaries is thermal loss(huge combustion chamber) and the combustion chamber shape isn't good.
The reason the exhausts are so hot on those is cuz they lose a bunch of heat out the exhaust.
I like high reving engines as much as the next guy, but making a bunch of power at hig rpm and about 0 torque isn't impressive.
When HP liter drops to the 40< range than that's when it gets pathetic and when you pull out the HP/liter argument since theres no reason a modern passenger V8 should make such little power for the size of the engine,
I personally think shooting for 1HP/Cubic inch is a good goal like American v8s go for.
Generally speaking the v8s still make plenty top end while still having lots of bottom end.
Fun facts: the LS7 in the C6 z06 makes 71hp/liter.
Pretty decent for a pushrod engine.