Yes it also had slightly higher compression ratio to make use of higher octane.

 

Note the difference in Octane rating in the german owners manual between the F20C1 and F20C2 engine. Wich one was sold is the US?

I once read a copy of a car magazine test from a german Magazine. I am looking for a copy of the test, but i give up. It was somewhere in the german S2000 forum, but i am no member there anymore.
If Memory serves me, they used a S2000 on a Dyno to see wich difference the - back then - 3 different fuels we had make. We had regular 91 ROZ, Super 95 ROZ and Super Plus 98 ROZ available back then.
91 is gone in the meanwhille. Test showed that there was almost no difference in Power output and no signs of problems with the engine. The Knock sensor did a good job adjusting the ignition timing.
Nevertheless i am sceptical, i would never run the F20C engine long term with 91 ROZ / 87 Octan US

 

ah yeah , good point about the higher compression. Even with all that , wasn't the difference something like 3 hp or 3 ps ? nothing very large.

 

A good discussion on the F20/F22 series engines and more information than I can digest on a single cup of coffee this morning.

North American cars got the F22C engine (AP2 in the VIN) for the 2004 model year along with the body, suspension, and transmission "facelift" upgrades. Referring to all 2004+ cars as "AP2" is common, convenient, and incorrect other than those cars with the 2200cc engine which was only originally officially available in North America and later Japan. AP2 is an engine designation, not a chassis designation -- only so many digits in the VIN for these things -- which is why AP1 hung on to the end of production in much of the world. Don't worry we know what you non-North American guys mean if you refer to your 2004+ car as an AP2. Also note the S2000's primary market was the USA and the bulk of the car reviews come from the same source. 2004 cars were "AP2s."

Back to the @TR25's question: Without modifying the firmware in the ECU there are no ways to "tune" our cars. Aftermarket ECU (example Hondata) is required for the early cars. 2006+ cars are DBW (drive by wire) with tunable ECUs (example Hondata FlashPRO). Things like cold-air intakes, headers, and exhausts have tiny power increases with the OEM ECU only measurable with instrumentation and not all mods like these actually add power. Most do add noise which is easily mistaken for power. Pulling the cover off the intake air box sounds wonderful but tests actually show a power decrease.

-- Chuck

 

Found the test!
My memory was not 100% precise. They used Super Plus 98 Euro RON vs. Regular (Normal) 91 Euro RON. Thats about 87 and 94 US octane.
The acceleration is a little bit slower, but they stated that this is within the tolerances. ( Wich i doubt )