Hondata Reflash - RSX Base 2002-2004 AT K20A3

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Reflash your 2002-2004 RSX (K20A3 engine) AT engine computer.

  • Fuel, ignition timing and cam timing optimized.
  • Rev limiter raised to 7300 rpm.
  • Power peak raised 400 rpm from stock .
  • 7 Peak hp gain depending on the dyno and modifications (results will vary)
  • 5-10 ft lb torque across the rev range
  • Fully dealer compatible - works with all Honda scan tools and equipment.

This is for an ECU reflash - the ECU is not included.  Hondata does not sell direct - the reflash must be purchased from a Hondata dealer. The ECU reflash form must be sent with your ECU.

We do not recommend the use of nitrous or forced induction for this reflash.


Within the USA this product is legal only for racing vehicles which may never be used upon a public highway.

EPA/CARB status (USA) Competition vehicles only
Model RSX
Year 2002-2004
Market US
Trim Base
Engine K20A3
Transmission AT
Part Number 37820-PND-A51 to 37820-PND-A59


Tuning notes

This car was tuned 91 octane pump gas - which we recommend. As the ignition is advanced there will be less tolerance for poorer quality fuels.

The extra low down torque as illustrated on the dyno chart, may in fact be due to the torque multiplication effect of the torque converter. With an auto transmission, very little time is spent at low RPMs. Most medium throttle openings will bring the engine to about 3000 rpm very quickly.

We do not modify the shift points. These are left at stock. The higher rev limit is accessable in the sportshift mode

When intake, headers and exhausts are added, the power peak is moved above the stock Honda redline. Extending the redline in this case, even if the power peak was not increased will increase your average power.

In the dyno chart above, a shift from 6700 rpm to 5500 rpm (stock rev limiter) goes from 132 HP to 122 HP - an average of 127 hp.

A shift from 7200 rpm (raised rev limiter) to 6000 rpm (140 hp to 132) will give you an average of 136 hp - a 9 hp increase over the typical rev range used under full acceleration.

What if you have modifications?

This program was tuned specifically for a CAI (cold air intake) as they give the best power gains.

Headers have been tested with this program.

Test pipe. This will eventually give you an engine check light telling you have a faulty catalytic converter. We have not seen this error cause any power loss.

If you have nitrous this program will probably not be suitable due to the aggressive ignition advance used.

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.

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.


The K series ECU, in order to be re-programmed must have a functioning immobilizer system. Three items must be sent to Hondata: the ECU, the ignition key and the immobilizer. The immobilizer works as normal after the ECU has been re-flashed.

Tools needed:

  • Philips screwdriver
  • 10 mm socket and drive
  • Time needed : 10-15 minutes

Removing the immobilizer (Civic Si, RSX / Integra)

Under the steering column remove the three philips screw holding on the bottom plastic cover.

Depress the bottom cover along its top edge where it meets the top cover to separate the plastic clips. Rotating the steering wheel 45 degrees can help.

Lower the steering column and remove the bottom plastic cover from over the height adjustment lever.

Unclip the green connector immobilizer connector and unscrew the securing two philips screws.

RSX ECU removal

The ECU is located in the passenger's footwell. The kick panel is removed after depressing the centers of three small plastic buttons around the front covering panel.

Unplug the three wiring connectors and remove the two front most 10mm locating bolts, plus the rear bolt. The ECU will slide out easily - if it does not, then check that the rear bolt has been loosened or removed.

K20A3 Civic Si ECU removal

The Civic Si's ECU is located in the passenger's footwell behind the glove compartment.

Unclip the lower plastic panel:

Unplug the three ECU connectors.

Remove the lower two 10 mm bolts.

Open the glove compartment and push out from behind the two bump stops. The glove compartment will drop after this is done.

Undo the last 10 mm bolt and slide the ECU down.