What makes different engines provide more/less power than other engines?

I'm an engineerlet and also don't know any car engines so please bear with me

What makes different engines provide more/less power than other engines?

For example, the engine on the Brough Superior SS100 was a 998 CC V-Twin, yet only produced 48 horsepower with a top speed of 100 MPH.

Meanwhile, the Kawasaki Ninja H2R, a 998 CC I4 produces 310 horsepower with a top speed of 250+ miles an hour.

Of course I know inline engines produce more power than V engines, but why?

Why do engines of the same displacement and orientation produce (significantly) more/less power than others?
Why do giant two-stroke 1500CC engines of motorcycles from 100 years ago produce less power than a lawnmower today?

more air and more fuel

but if they have the same displacement, wouldn't that imply they have the same amount of air in the combustion chamber to begin with?

this. car weight also impacts heavily. the more air part is the entirety of how a turbocharger works actually

but heads intakes exhausts and all of that could be different

H2Rs are supercharged too arent they?

Cam profiles
Bore vs stroke
Compression
Internals strength
Layout
Displacement
Ignition type
Valvetrain type
There's more. But there's a lot of variables.

yes, I forgot to take that into account

no, some vehicles can't flow as much air and fuel into the combustion chamber

just because they displace the same amount of air doesn't mean it does a good job of flowing it in

also you fail to account for RPM, more RPM means higher capacity to flow fuel and air

It might help you if you look at the principles involved in *increasing* power in one engine
At first glance upgrading the intake and exhaust can give you more horsepower without changing displacement, right? This improves the 'breathability' of the engine, allowing it to suck and blow more air through the restrictive system. Porting and polishing heads, camshafts that keep intake valves open slightly longer, etc etc
Compression ratio is also important, many modern engines use a relatively low compression ratio so they can burn lower octane fuel and not produce high-temperature emissions.

As user mentions, it's all about breathing. For a naturally aspirated motor, having sufficient fuel supply is rarely difficult. IME, the biggest dictator of power, both peak and "under the curve", is head and port design. It's not about flowing ALL THE CFM, but moreso creating a proper surface finish, allowing the air to enter the combustion camber efficiently, as well has having it exit that way.

For example, Two engines, 10:1 compression, identical cam profiles and valve size, same manifolds, injectors, etc.

One has a beautiful straight shot into the port. The other needs to make a hard 90 before entering the port. Which will make more peak power?


Another issue not mentioned is air velocity, but at that point you're getting into engine specific tuning. Basically, using resonance chambers, variable geometry manifolds, etc, you can increase cylinder filling below WOT and peak power. All about that midrange.

The first engine is an air cooled OHV engine with low compression that used a carburetor. It could achieve 5000 rpm.
The second engine is a water cooled inline 4 DOHC engine that is supercharged and has fuel injection. It could achieve 14000 rpm.
Among better fuel management, much higher compression, forced induction, superior cooling, and better internals it should be obvious.
The first engine is also burning much worse fuel. The replacement for displacement is technology.

IC engines are far from achieving 100% efficiency. So there are essentially two ways for achieving more power are better efficiency (higher compression ratio, better air fuel mixture control, more aggressive spark, tighter tolerances between piston and walls, lower friction between components, etc) or more airflow (forced induction, tuned intake and exhaust manifolds/ports, bigger bore, more valves, bigger valve lift, more RPM, colder intake temperature, etc).

What I don't get is how there can be such a massive gulf between engines.
Around 2000, a 3.8L V6 Mustang only got about 190hp, while a Ferrari with a smaller 3.6 V8 got more than twice that.

read this, then read Vehicle Dynamics by Pauwelusson.

all the math reduces to HS level algebra so no excuses about it being too complex.

There are many variables, forced induction, rev limit, compression ratio, number of cylinders, number of valves per cylinder, valve timing, size of bore and stroke... A high revving high compression engine with many cylinders and a short stroke will make a lot of power, although usually at the expense of low end power and reliability.

Think about how much money was spent producing both of those engines user. Before we even touch on the engineering differences, understand that mass production dictates a great deal of compromises in engine design. Ford could have sold an engine with competitive output to that Ferrari motor, but nobody was gonna buy a 65k mustang. Often time it just boils down to cost.

Compression rating and cylinder displacement length and diameter.

Taller cylinders and rods have more torque and lower RPM. Tighter cylinders need less fuel. Larger cylinders suck in more air to burn that fuel requirement. Shorter cylinders and rods have more top end horsepower with longer ramp up time without variable timing. RPM rating is from the crank speed, not by the cylinder cycle. Engine works harder with less cylinder rods turning the crankshaft. Road and head wight affects response time, ramp up, and engine durability.
Variable valves change the conditions of the cylinder such as trapping some of the exhaust in the cylinder to maintain a combustible compression at higher RPM's, but at that point only increases engine crank speed but not power under a parasitic drain.

>mass production dictates a great deal of compromises
Ok, but what about say, a corvette engine?
I don't have those specs in front of me, but wouldn't that be coming closer to the Ferrari output, but still mass produced?

Mechanical efficiency, less friction, tighter clearances etc

The high end Corvette's supercharged V8 is used in other cars, lower trims, some Cadillacs. Its not just powering one car. Its also so monstrous that they had to include 11 intercoolers to keep it at safe operating temps, and despite all that they were still having cars overheat, so they had to redesign two of the intercoolers and mount them in different locations.

That right there *is* an example of a mass production compromise. They wanted to pull extreme power out of an engine not up to it, and put it in platforms it doesn't belong in.

Thanks for the explanation.
I always believed that power didn't come down to just numbers, but lacked the knowledge as to why.
As such, I had been under the impression that most of the additional cost present in low production number engines was due to brand markup, not quality.