Hondata Reflash - RSX Type S 2002-2004 K20A2

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Reflash your 2002-2004 RSX Type S engine computer.

  • Fuel, ignition and cam angle optimized.
  • VTEC point lowered to 5200 rpm for cars with intake systems.
  • Rev limiter optionally raised to 8600 RPM (see valve spring tech information).
  • 12-20 peak wheel hp from a stock RSX depending on the dyno and modifications.
  • 15-20 ft/lb torque increase between 2500-3500 rpm.
  • Peak torque now at 3200 rpm on an unmodified RSX.
  • Very flat smooth torque curve. 95% of peak torque available from 2500-8000 rpm.
  • 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. For these applications use the K-Pro.

Two  programs are available.  They both are based on the performance program above and vary only in rev limits:

  • K20A2-2: 5200 VTEC point and stock REV limit
  • K20A2-4: 5200 VTEC point and 8600 rpm REV limit


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

Sales Region US Only
EPA/CARB status (USA) Competition vehicles only
Model RSX
Year 2002-2004
Market US
Trim Type S
Engine K20A2
Transmission MT
Part Number 37820-PRB-A01 to 37820-PRB-A08


The results we list below are for an unmodified RSX. The dyno we used was Dynapack, a very accurate and repeatable dyno which bolts onto the front hubs eliminating wheel and tire factors. As a result the Dynapack reads about 10 hp higher than a Dynojet. For a fair comparison we tested on Jackson Racing's Dynojet. Fuel used was 91 octane pump gas.

This test RSX has less than 1500 miles so the engine is a little tight.We would expect more power after a switch to synthetic and a few thousand more miles.

Findings in brief

Cold air, cold air and more cold air. The intakes on the K series engine get very hot. They have a metal intake gasket which transfers heat from the head very quickly and sitting right behind right the radiator are heated by hot air. Pay lots of attention to keeping everything cool and you will see results. The K20 Hondata intake gasket reduces intake temps about 15 F (10 C) giving you about 3 % or5 HP. See the upcoming Tech section on K series intakes - keep it cool.

Long cold air intakes work the best. The long cold air intake we tested with added significant torque between 4000-6000 rpm compared to a short ram. Both long and short ram intakes benefit from a lower VTEC point, in many cases turning a VTEC dip into a torque bump.

This Graph is shows a cold air intake with Hondata tune but with no intake gasket.

The RSX runs rich in stock form. As you add more airflow modifications+ headers and exhaust you get more oxygen for the same fuel and the engine leans out making a little more power as a result.

For consistency in dyno testing we suggest you follow the dyno procedure outlined here.

What if you have modifications?

We have tested short ram, cold air intakes, headers, test pipes and exhausts and have done some preliminary work with ITR cams. The programs have been tested to work well with any intake.

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

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.