As soon as we got the car back from the SEMA show (thanks for shipping it back, American Honda - saved me another drive!) we delivered it to Hondata in Torrance, CA. If you didn't know by now, Hondata is the expert source when it comes to tuning the OEM Honda ECU. While Hondata began by developing a replacement system for the original OBDI ROM-based Honda ECUs, their business has truly blossomed since the introduction of Honda's flashable K-series ECUs.
The 2006 Si's ECU, unfortunately, is not like the earlier K-series units. As far as we know, it is completely new. Even worse, the engine management system now incorporates both a MAP (manifold absolute pressure) and MAF (mass air flow) sensor - most likely in an effort to better control emissions. This meant that Hondata needed to not only crack the new ECU (something they seem to get quicker and quicker at), but they needed to figure out Honda's control scheme for fueling using both the MAP and MAF sensors. So far, they have been successful on one of these two tasks. Fueling has not been cracked to date, but Hondata can now control everything else - cam timing, ignition timing, rev limiters, VTEC, etc.
On our Si, Hondata managed to increase hp from 224 hub hp on our Dynapack 4000 to 231 hub hp just using a rough cam timing map and adding some ignition timing. Fuel was not altered, because at this point, it can't be. Also keep in mind that this was not a full tune as it takes quite awhile to reflash the computer at present. This 231 hub hp on our Dynapack equated to 213 whp on Sport Compact Car's Dynojet 248c (a little lower than we expected, but they had virtually nothing in the way of cooling airflow in their test center, so we'll cut them a break). We did have a little drivability issue at low rpms, but this was present before Hondata got ahold of the car, so it may have something to do with our mods and the MAF sensor. The rev limiter also was a bit harsher than stock. The good news is that Hondata now has a totally stock production Si to work with, so we expect development to proceed apace from this point onward. NOTE: Check back soon for dyno plots. ed
After our visit to the racetrack, Doug from Hondata did a little more fine tuning on the car. In particular, he played with the ignition timing a bit and found 2-3 more hp across the board. He also fixed our rev limiter issue (the rev limiter is actually encoded in several locations in the ECU maps, and you have to change them all to get the desired effect). Given what other K20s with our camshafts have made in the past, we feel that another 5-7 hp is available with full tuning (whenever that occurs). We also feel that our DC race header, while great for a basically stock car, is a little too small for our big cam setup. We hope to find another 5-8 hp with a more appropriate header.