ECUS, Turbos, just engine performance tech overall. I mean shit my ZL1 compared to 5th gen. Once my TB and blower come back from being ported I’ll probably be sitting at around 750whp, whereas you’d have to completely swap the blower in a 5th gen to get there

Adjustable valve timing plays a big part. Every manufacturer has its own version of adjustable valve timing. Computers preform instant adjustments according to RPM and load so the engine runs as efficiently as possible.

The biggest technological change in most industries in the last 20 years has been computer software related. Same with the auto industry. Better computer modeling of the flow of gases in the engine (CFD) allow for better fine tuning of all passage ways and allows higher compression because of a better understanding of when the mixture will combust. Butter ECUs allow for better optimizing of the engine for different conditions (different loads, rpms, fuels mixtures, temporaries, etc). Better automation allows for more rapid iterations in physically testing everything which also resulted in an advance in material science.

The G80 has two big turbos. A more interesting discussion would be around how powerful small engines have become, like the Yaris GR with a 1.6 and 500-600bhp some are running.

In generally the biggest advancement on ICE engines on last 20 yrs are materials (lower internal friction), better control of mixture forming and burnign (better control electronics, direct injection, etc)

Not all of these advancement are nessarily for good in terms of durability IMO.

But for you question, take std.M54B30 and slap couple of turbos to it and it gives easy 500hp. Rebuild it to suite and you have more with reliabilty, so you dont need modern engine to make power, those turboes does most of the work.

Look in to the LF4 engine design from GM. Lots of cool tech in that one.

The e46 m3 had a v8 or a v10 that made 500 horse or aomeshit lol.

Direct injection.

You have already named the big difference, and that is the turbo.

But comparing na VS na comes down to tighter tolerances and better fuel mixing for a more complete combustion.

The real freak is the Porsche GT3RS engine. All-motor 4 liter Flat six making 500 horses.

I don’t know what service intervals are like but the only things comparable imo are the LT6 and GT350 motor.

Turbos are less impressive imo because even in the 90s there were insane power levels from turbo charged engines, really even the 80s, it’s just that the power delivery got more linear with twin scrolls and sequential turbo systems.

There still is lag though. My M177 even lags sometimes. Rarely but it happens. NA motors don’t have lag but are generally peaky below 8 cylinders.

Precision through computer simulations, take 2jz for example, a huge and over-built in every corner of the block, but it’s extremely heavy and inefficient especially being a cast iron block.

Modern engines are smaller, lighter where mass are only necessary added based on the engine’s weak points. Materials selections have also improved for better costs to strength.

Advancements have come from materials, intake and exhaust efficiencies. Motor size doesn’t matter like it used to back in the day of carbs, the old way was crude and so inefficient compared to the modern stuff.

The gains with the modern stuff is so small and minor, a few hp here and there but over the course of decades it became impressive. Turbo’s were never really all that great until recently and they have so much room to go…plus hybrid systems, you’ll be looking at extremely quick cars.

Problem is EVs are taking over, so much faster and r&d into ICE is going to stop.

The E46 M3 makes a lot of power per liter but in general modern engines make more power because of Higher revving (7000 not 5500rpm), variable valve timing, knock sensors that allow ignition timing to be right where it needs at all rpm and load to be without a power killing always-on safety factor, and direct injection.

Imagine modern engine materials and controls with early 2000s emission regulations. Now that would be power

Head design is a big one. Look at a fox body Mustang 5.0 and a current 5.0 ; DOHC, variable cam phasing, and direct injection. Put sophisticated intake manifolds on there (which go back to the 80s as a widely available tech) and you get a lot more power, when you consider things like the higher compression ratios the tech enables.