The Mugen treatment gives the Civic Si what Honda calls a “track-ready suspension.” That suspension is 0.6 inch lower, the damping is firmer, and the wheels are both wider and lighter. Add to that BFGood*rich g-Force T/A rubber that is more suited to track usage than the Si’s rubber, and the result is a buttoned-down chassis that exhibits very little body roll, resists understeer, and never makes an untoward move. All of the floppiness we complained about in the base Si has been eliminated in the Mugen.
This chassis feels as though it could handle about 100 more horsepower, but with only 197 horses on tap, the Mugen couldn’t quite rocket out of corners. While lapping, keeping the torqueless engine on boil, in this case between 6000 and 8000 rpm, felt suspiciously like work as the Civic required more shifts than its competition. Mugen didn’t see fit to upgrade the braking system, which, like the Si’s, suffered from fade after only a few big, nasty stops. Still, the Mugen chassis tweaks did lop 1.7 seconds off the time of the 68-pound-lighter Civic Si coupe from the ’06 Lightning Lap.