These results aren't too much different than what our "virtual dyno comparo" showed earlier this year, although the K24Z7 in this Civic Si delivered a little bit less peak horsepower on average than the 2011 TSX's K24Z3 did.
As you can see below, this new K24Z7 pretty much stomps the K20Z3 everywhere south of 6000 rpms. From 6000-6800 rpms, the advantage diminishes to an extent, and the K20Z3 takes the lead beyond 6800 rpms. You can feel this on the street, too. The new Si feels much more lively underfoot and launches with much more authority. It also feels a little bit tapped out once you clear 6000 rpms or so. You can redline it if you want, but it actually feels better short shifting it at around 6500 rpms. Once underway, the K20Z3's extra rev capability and higher peak hp would make for an interesting drag race.
Click on to the next page to see how the Si's K24Z7 stacks up against the 2011 TSX's K24Z3.