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This reflash is for the US 06 Civic Si two door, and the 07 Civic 2 and 4 door with K20Z3 engine.
Applications
- US 06 Civic Si with K20Z3 engine ECU part number RRB-A04
- US 06 Civic Si with K20Z3 engine ECU part number RRB-A05
- US 07 Civic Si with K20Z3 engine ECU part number RRB-A12
- US 08 Civic Si with K20Z3 engine ECU part number RRB-A12
Pricing
This reflash is specifically tuned for the USDM 06 and 07 Civic Si K20Z3.
- K20Z3-06Si ECU flash program 8600 rpm REV limit - $595
Hondata does not sell direct - all sales and payment must be conducted through Hondata dealers. The upgrade information form must be sent with your ECU.
Details
The K20Z3-06Si reflash lowers the VTEC point to 4500 rpm, advances the cam angle and raises the rev limit to 8600 rpm.
We have implemented a VTEC window from 4500rpm to 5800 rpm.
- Below 4500 rpm the K20Z3 is always on the low cam
- Above 5800 rpm the K20Z3 is always on the high cam
- Between 4500 rpm and 5800 rpm the K20Z3 is on the low cam at part throttle switching to the high cam at full throttle.
This one reflash will work well with a variety of aftermarket performance parts. It will work well with:
- An intake
- Cat-backs (as long as they are less restrictive than stock)
- A race header *
- A combination of intake and race header
(*Note that current race headers eliminate the catalytic converter and will generate a check engine light. This engine check light is for emissions and will not affect the car's performance. Race headers are for offroad use only)
You must have a minimum of an intake or header.
It is not designed to work with a stock 06/07 Civic Si and will lose power between 4500rpm and 5600 rpm if installed.
The 06 Civic employs a mass air flow sensor that automatically adjusts the air-fuel ratio for increases in air flow from
correctly designed intakes and race headers.
Intakes for this car are
critical. The intake - in particular the
size and shape of the piping around the mass air
flow sensor is the primary determinant of
fueling for this car. If you have any problems
in running rich or lean, then you must retest
with the stock intake. Race headers will not cause this engine to run lean.
The VTEC switch point on this reflash is very smooth - much smoother than previous reflashes. With a stock
air box and race header the switch point is virtually undetectable. For the reduction in VTEC "kick" and aural stimulation, we apologize, but this is the path to maximum power.
Power is gained in the midrange from 4700rpm to 6300 rpm. Power gains above 6500 rpm are negligible, although the higher rev limit will raise average power a little.
As this reflash will work with a combination of aftermarket parts we have two examples of the effect of the same reflash on two 06 Civics. (Both Civics dynoed at about 195 stock HP)
2006 Civic Si with Race header, intake and Hondata Heatshield gasket.
The following dyno chart is for an 06 Civic Si with a DC Sports header, Injen intake and Hondata
Heatshield gasket. The only change from the green to the blue dyno run was a change from the stock ECU program to the Hondata reflash.

- 4500 rpm VTEC point
- Rev limiter raised to 8600 rpm.
- 15-25 Hp gain midrange
- 15-29 ft lb torque gain midrange
2006 Civic Si with intake and Hondata Heatshield gasket.
The following dyno chart is for an 06 Civic Si with AEM CAI intake and Hondata
Heatshield gasket. The only change from the green to the yellow dyno run was a change from the stock ECU program to the Hondata reflash.

- 4500 rpm VTEC point
- Rev limiter raised to 8600 rpm.
- 10-15 Hp gain midrange
- 5-12 ft lb torque gain midrange
How do I get the reflash?
You will need to remove the ECU and via a dealer send it to Hondata. Unlike reflashes for other Honda models you will not need to send the key and immobilizer; just the ECU. Fill out this form and contact a Hondata dealer. Hondata does not sell direct. All ECUs must be sent to Hondata for reprogramming. No Hondata dealer has the equipment to reprogram this ECU.
How do I remove my ECU?
The ECU is located under a plastic cover to the right of the battery under the hood. You will need a 10mm socket. This is what it looks like - in place and removed from the car.
There are 3 bolts holding the ecu in. You
may find it easier to completely remove the
battery, but you will need to enter the codes
for your radio if you do this.



How long does it take to get my ECU back?
Turnaround is 1-2 business days.
What if Honda comes out with an ECU software upgrade?
Hondata charges $75 which includes overnight shipping and handling for any program upgrade. Print out this form and send directly to Hondata. This charge includes overnight return shipping.
Important upgrade
Honda has released an upgrade for the 06 Civic Si ECU. As of August 1 2006 Hondata has incorporated these changes 06 Civic Si reflash. the 07 model incorporates this fix. Honda lists the problems addressed as:
- Hesitation in first gear
- RPM hang when shifting
Notes:
Nitrous has not been tested. As ignition timing has not been changed, nitrous is as safe to run with this reflash as with a stock ECU.
Aftermarket cams have not been tested.
Race header / Test pipe. This will eventually give you an engine check light telling you that you have a faulty catalytic converter. We have not seen this error cause any power loss. Race headers are for offroad use only.
For consistency in dyno testing we suggest you follow the dyno procedure outlined here.
Will this affect my warranty?
Any increase in RPM limit is at your own risk. If you suffer engine damage that is related to excessive revs Honda / Acura will not cover your warranty. Valve-piston contact, which typically occurs at 10,000 RPM is the result of a miss-shift.
With regard to aftermarket parts, the law is that warranty coverage cannot be denied simply because such parts are present on the vehicle, or have been used. For more details read the K series FAQ.
Smog testing shows no measurable difference from stock.
A WHOLE DIFFERENT CAR (from what you'll be used to)... MY LAAAAAAWWWD...what have these people done to my mild mannered car.... sickyute.
Extensive report in this 8thCivic.com thread.
Its everything i hope for and more! The drivavbilty of the car is awesome now, no more hesitation and a lot more mid range pull and top end power. The midrange is where it gained the most power and that's nice because everytime you shift to the next gear you land right in the peak torque section. From stock i have gained 34whp and 31wtq with only a custom 3'' exhaust and DC race header, hondata IMG and reflash. This was all done with factory intake!! - 06redsi.
More info from this 8thCivic.com thread.

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