Let's get to the numbers. Recall that the AEM V2 lost some torque below 3000 RPMs. That loss in torque is still present. However, we should note that the Dynapack software does not perform SAE corrections for temperature and humidity for the torque graph. The torque graph shows the raw, uncorrected data. On the other hand, the horsepower graph shows the SAE corrected data. Looking at the horsepower curve, we note that there is only a slight improvement in horsepower after the flash upgrade. The dark blue curve is the stock run. The green curve is the AEM V2 run. The teal curve is the AEM V2 and Hondata run.
The reason we don't see much improvement is most likely due to the fact that the K20A3 program was optimized for cold air intakes. The AEM V2 is a short ram intake which sits under the hood.
Don't despair at the marginal improvement in peak horsepower. Remember that the main reason we got the Hondata flash upgrade was to raise the rev limiter. Notice how the power hits a peak around 6400 RPMs but tails off to the stock peak power level at the rev limiter (Note - the Dynapack does not read engine speed directly, it calculates it from the hub so that the RPM shown is not exactly the same as the engine RPM). We have 900 more RPMs to play with and the power between the original and new rev limiter is higher than the stock power. What does this mean? It means you go faster! In the stock configuration, the Civic Si cannot reach 60 MPH in 2nd gear. After the flash upgrade, you can get to 60 MPH in 2nd gear. Most of the claimed 0-60 gain comes from the fact that you don't need to shift to 3rd to get to 60 MPH. Mission accomplished!
Well, not quite. We still need to determine why low end torque and power was lost and whether we can fix it. Hopefully, later this year, we will be able to get our hands on a KPro programmable ECU and properly tune the car. The KPro may be overkill for our current modifications, but it will be necessary as the project continues.
As for every day driving, the extra 900 RPMs comes in handy for quick freeway merges. Fuel economy has not changed. I am still averaging 28 miles per gallon or more (mostly freeway, some city).
I have read threads at various Honda websites where people have stated that the Hondata flash upgrade is too expensive and not worth the money. However, those people are missing the point. Though the flash upgrade gives you a marginal increase in horsepower, you get a higher rev limiter. The higher rev limiter means that you can hold each gear longer, which results in getting more speed per gear, which means you need to shift less. For whatever reason, if you are concerned with your 0-60 time, there is no better price/performance modification than the Hondata flash upgrade.