One can't merely argue displacement is better or worse, or turbo is better or worse, without first defining the goal of the comparison. For instance, if you're talking about drag racing then there's a certain set of factors that go into the equation to yield the winner. If you are talking about running a road course then other factors need to be considered. If you're talking about fuel economy, of course other factors need considering.
First off you can't just take an arbitrarily sized engine and toss it in any vehicle. My guess is you'd have a pretty hard time fitting a 5.0L V8 into a Civic. I welcome anybody to try, please post some pics.
But there have already been plenty of discussions that go into who will win a drag race. Excluding the driver, things such as power, torque, weight, and the efficiency of the drivetrain (aka wheel HP) all go into whether a car will win the race. This clearly isn't an argument of displacement, it's an argument of many different factors. But toss a super heavy engine in the front of a light FWD vehicle like a Civic and take it out on the track.....that ought to be fun. Sure it may run a fast 1/4 mile, but good luck getting it to handle well with all the weight in the front 1/2 of the car.
Now if you're just looking for an engine to make power regardless of the application, then clearly a larger displacement is capable of a higher theoretical maximum power output than a lower displacement engine. However given two engines and measuring their actual power output, you can't just draw a line and say that higher displacement will have more power. You must consider such factors as the compression ratio of the engine and the overall efficiency of the entire system before making a call saying that the higher displacement engine will win.
Of course engines are usually engineered to have reasonable efficiency, but it isn't always the case. Here's a simple comparison. Take the Daewoo Leganza with its 2.2L DOHC I4 pushing 131 HP and 148 lb-ft torque and compare that to the Prelude SH's 2.2L DOHC I4 running 220 HP and 156 lb-ft of torque. Both cars are NA but we can see that displacement only has so much meaning. Just as a note for those who can't read, the Prelude clearly has much more power but not a lot more torque.
Anyhow, long story short you can't merely compare displacement and say one's better. First define the criteria, such as power output, drag racing, or track racing. If the criteria at all depends on the vehicle, then define the vehicle. A 1.6L turbo 4 in a Viper will yield significantly different results than it's native engine, equally a 7.0L in a Civic will be a little different than the normal I4. Second define the engine. Not all engines are created equal and not all are modded the same, if you want to consider mods at all. A heavily modded 2.0L I4 can push out more power than a stock 5.0L V8, as has already been shown. But a heavily modded 5.0L V8 will always be capable of pushing out more power than a 2.0L I4. Third, remove head from
and have a good discussion.
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