Hondata Reflash - RSX Type S 2002-2004 Type R

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Reflash your RSX Type S (Type R specification) engine computer.

  • Fuel, igniton timing and cam timing optimized.
  • Rev limiter raised to 8800 rpm. (ITR ECU uses a 8500 rpm rev limiter)
  • VTEC point lowered from 6100 (ITR ECU) to 5200 rpm.
  • 8 peak wheel hp increase over an ITR ECU.
  • Peak power raised 200 rpm (8100-8300)
  • Peak torque now at 6300 rpm, down from 7600.
  • Significant midrange torque increases form 5500-7000 rpm
  • 15 ft/lb torque increase between 2500-3500 rpm.
  • 20 ft/lb torque increase at 6300 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.


  • K20A engine or K-Series engine built to K20A specifications (ECU part number PRB A01 through PRB A08)

We do not recommend the use of nitrous or forced induction for this reflash. For these applications use the K-Pro.


  • K20A ECU flash program 5200 VTEC and 8800 rpm REV limit - $295
  • K20A Flash upgrade - $200

The upgrade price applies to any K20A2 (RSX type S) owner that already has a Hondata flash program.


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

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


The engine tested here is a JDM K20A engine with Hondata intake gasket, CAI (cold air intake) and cat back. Headers and cat were stock RSX. Also tested was a bored and tapered 64mm throttle body. The major variations this engine has compared to the US K20A2 are:

  • Cams (same lift and more duration)
  • Compression (up from 11 to 11.5)
  • Intake manifold (wider runners)

Three programs were tested.

  • The stock ITR ECU
  • The K20A2-4 flash program
  • An optimized K20A2 program

The RSX K20A2-4 program performs substantially better than the stock ITR ECU adding significant torque from 5500-7000 rpm.

The K20A program optimizes the fuel and cam timing, adding about 5 ft lb more torque for the high cam.

ECU re-tuning – Comparisons to the ITR ECU

  • 216 peak HP at 8300 rpm depending on the dyno and modifications
  • 8 peak wheel hp increase from the ITR ECU.
  • Power peak raised 200rpm (8100-8300)
  • Significant midrange torque increases form 5500-7000 rpm
  • 15 ft/lb torque increase between 2500-3500 rpm.
  • 20 ft/lb torque increase at 6300 rpm.
  • Peak torque now at 6300rpm, down from 7600.
  • Rev limiter raised to8800 rpm. (ITR ECU uses 8500 rpm rev limiter)
  • VTEC point lowered from6100 (ITR ECU) to 5200 rpm.
  • Fully dealer compatible- works with all Honda scan tools and equipment.

This is a magnified view of the torque curves seen above.

What if you have modifications?

This program was tuned specifically for a CAI(cold air intake) as they give the best power gains. All future tuningwill be done with either the stock or CAI intake.

Headers will be tested at a later date. This program should work OK with headers.

Test pipe. This will eventually give you an engine check light telling you have a faulty catalytic converter. We havenot 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.

Tuning notes

This program is a highly optimized version of the K20A2-4 program. Ignition was retarded from 1800-2200 rpm as 91 octaneand 11.5 compression caused knocking. This (and the knock sensor retarding the ignition) is the cause of the slight low RPM power drop.

Fuel was added to all high cam fuel map.Additional fuel was needed above 8500 rpm where the engine ran very lean.Part of the reason additional fuel was needed was that the Hondata gasket was providing colder air while the ECU was providing the same fuel. TheHondata gasket caused the engine to run about 0.2 points of an air fuel ratio leaner.

Cam timing has been highly optimized for this engine. The intake cam can move 50 crank degrees. 25 degrees of movementis needed to generate the best high cam power figures.

We tested a 64 mm (+2 mm) bored and tapered throttle body. It produced statistically insignificant results (+ 1 HPfrom 7500 rpm up.) We have seen combinations (short ram cold air 50 cmstraight velocity stacks on a K20A engine mounted in a Lotus.) where thebored throttle body makes a difference.

Dynojet comparison

These three programs were also tested on the Jackson racing dynojet.

Note that this car had heavy 19” wheels and tyres. The gearbox also has different ratios to the type S. The time taken to make the acceleration is longer than the Dynapack. This will also affect power readings. Dynojet testing was done the day after the Dynapacktesting that generated the graphs above.

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

How does this compare to the Type S?

An RSX Type S with CAI, Hondata flash program and stock exhaust makes between 190-200 peak HP on the Dynapack. When examining these figures take into account that the ITR had a cat back, giving it a few more HP, and the RSX's engine had only a few miles giving it a few less HP.

You can see that the main improvements are on the high cam by the amount of 15-20 HP.

This is a magnified view of the torque curves seen above.

How would the K20A flash program work in a Type S?

Without the ITR cams this will just cause poor fuel economy and lower performance.

How would the K20A flash program work in a Type S with ITR cams?

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.

It works very well.  In fact, it works better than the stock ITR ECU.

Rev limits and Valve springs

Based on information from TODA Japan, theType-S and Type-R have the same exhaust valve springs. However the intakeside uses F20C (S2000) intake springs for the outer spring and a Type-Rfor the inner spring. TODA also mentioned that Honda is now using singlesprings of a higher grade material for the newer Type-R's.

The interpretation here is that the stockvalves are good. We have had a test vehicle (K20A2 in a Civic Si) runningwith an 8900 Rev limit for 2 months now. In this car you change gear whenthe Rev counter points to 20 mph!

Any increase in RPM limit though is at yourown risk. If you suffer engine damage that is related to excessive revsHonda / Acura will not cover your warranty. If this of a concern, upgradeyour valve train or use a program with a stock rev limit.