• Hondata Reflash - RSX Type S 2002-2004 K20A2

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.

Location: Baltimore

Wow! what a difference. It pulls like a totally new vehicle. I had to turn around and hit it the other way back home. Needless to say, I was fighting a smile the whole way home. I was giddy for the first time since I was 16 years of age. All I have to say is; well done Hondata! For $290 I received a re-flash that made more of an impact than all of my bolt-ons combined.

Location: San Jose

First word out of my mouth when I tested it was HOLY SHIT! 
Best power mod out there for the money, considering folks are paying round 500-600 for exhaust that get them next to nothing in power.  Good low-end tq for driving round town. It pulls in 6th gear now, so no more downshifting to pass slower traffic. VTEC is amazing, feels like you?re in vtec forever, and you?re in vtec for 3600rpms. From 5200 all the way up to 8800-8900. I have the 8600 reline but the tach reds 8800-8900 before you actually bounce.cation: NY

Location: NY

You will definitely feel the power gains when you are driving your car hard. In particular, the mid range powers between 4 to 6,000 RPM the vtec engages much smoother and a lot more quietly. As before the car pulls like an animal above 6000 and is very eager to run right up to the new 8,600 rpm limit. It almost feels as if there are two VTEC in the car 5,200 engages the first one with a slight push and that second big push comes at about 6,000, above that hold on tight and get ready to shift, because your revs move very fast through the band. A word to the wise be careful, this new rev limit is addictive, and the car wants to go there, it does not tail off at all above 8,000 and you are going to be very tempted to push it deep into the red a lot! Think of your valve springs and how much it will suck if you bend one. Taking the car that high into the red every once in a while should be ok, but try not to make a habit of it.  I think you will feel the New ECU the most, when you are not expecting it. In particular, every day driving. I put the ECU in sat. night and drove the car very hard , it was very fast. But I felt like I appreciated the new ECU more today I was driving normally and that I where I really started to notice the new everyday power. Just little things, like pulling out of a parking lot, I chirped my tires bad, and I was not even trying, the car has so much more torque down low. It is so nice because unlike before you do not have to run the car into V-TEC range to get it to go anywhere. And that means that the car is a lot quieter when you want it be.
Overall, this the best 600.00 bucks I ever spent!


Location: NW Houston

WOW... thanx...
This mod just seems too perfect.  Besides the fact that you can only use it for N/A applications... it sounds like the best mod for the car

Alpha Zero
Location: SF Bay Area

First word out of my mouth: HOLY SHIT. As with everyone who has tried out an S with the ECU. It's just totally amazing. Its kind of fun to watch the needle dip so far into redlines. Mid range is where you notice the biggest difference though. 


I can feel the car pull very well at low end and also it flies at high-end speeds. The car also no longer has the vtec lag as it did before.

Location: Oceanside, CA

Well, I finally made it to Hondata today and had my ECU reflashed. Doug and Matt were great and spent a lot of time with me. The car runs great! It pulls MUCH harder from low RPM's all the way to it's new redlined of well over 7000!!! Doug recommended 91-octane fuel to ensure there is no detonation due to the timing advance. A very small price to pay for a very noticeable gain in power. The drive home was a lot of fun; I can't wait to get this thing to the track and see what my times will be like now.


Got my ECU back yesterday. 2 words "Well Tuned." The power delivery is smooth all the way up to 8600 and VTEC has a silky smooth delivery. No more loss in power before engagement like the old program. Thanks Hondata

Location: Mt. View, CA

Yes, Hondata ECU upgrade is without a doubt the best mod out there right now. Power down low, wider vtec band, and extra RPM to boot.

Location: Texas

I've also noticed that I cruise in a lower gear than usual. The car is definitely smoother. BTW, my gas mileage hasn't changed since getting the ECU although it's only been 1 tank of gas since the upgrade.

Location: So Cal CA

Well I got my car flashed yesterday with program 4. I had it done at Erick?s Racing in Torrance CA (right down the street from Hondata), took about 30minutes and I was out of there. They are very nice and I recommend them. The first words out of my mouth and my friends, was HOLY SHIT! Way worth it for just the torque down low alone... The power up high is great too. It pulls so much better. I was kind of dreading the not noticeable VTEC change over (cause I like the change in noise and power it throws people off). But I can tell you its way better now. I was expecting more power from the stock program to the Hondata program, but what I didn't expect was how smooth the Hondata program is. It?s amazing. Best 581 dollars I spent on my car. The power is very noticeable. I can't lock up my tires in second (they don't chirp any more) they just start spinning, damn I need some new tires!

Location: Plano, TX

Got mine back today, put it in..
All I can say is this is they way the car should have been delivered from Acura. Everything is smooth...it's not a different car or anything it's just the way it's supposed to be. I found myself on the brakes a lot more than usual I got the stock limiter but I have bounced off it a few times just tonight because it gets there quicker and it seems disappointed to shift so "early". Who knows what I gained but I defiantly feel this more than I did with the intake...probably because the gains are everywhere not just in one area. I found myself in a lower gear than usual when just cruising around...I'm tellin' ya Acura should either mimic this or pay Hondata a butt load to program every ECU.


Got mine back today at 10:30am. I left work at lunch went home and installed it. I have to say that the difference is nice. The low end is much stronger now. At one point today I noticed I was cruising at 35 mph in 5th gear and it could still accelerate well. I can say that the car is definitely nicer to drive now. The power delivery is much smoother, more linear. There is a slight bump at 5200 (VTEC) and 6000 RPM but, not like before. The car pulls hard from 3000 to redline. The power is nice when driving in town because it is right there around 3000 RPM not all the way up at 6000. The only problem is that the speed is deceiving. It increases faster than it feels. I can see I'm going to get some tickets with this mod.
The stock tires really suck with this mod. They spin way to easy. I'm going to install my new wheels and tires and I'll see if that helps.
IMO I would say this is the best performance mod I have installed yet. I think it is definitely worth the money.

Location: Des Moines area

I just got the reflash program 4 and holy sh*t what a difference. I can feel it pull harder all through the rpm range. Nice and smooth and a lot of power!. I'm really blown away. It made a night-and-day difference.

Location: KY

I installed my Hondata ECU and intake gasket this week and wow what a difference! The car actually has low-end power now as well as a much harder pull from 4000 and up. The intake sounds amazing and gas mileage seems to be about the same. Not sure that it is a Z killer just yet, but this is definitely the best money I have ever spent on a car.

Location: New Jersey

I just got my ECU back from Hondata today!!!!!!!!!
I must say that this has been my most significant mod out of all of them.... it was everything I expected and more.
I feel more torque in low end and the acceleration is more responsive witch is what my car really needed...I never been more happy with it since my first mod (injen)...vtec creeps up so much faster and there?s no difficulty at all staying in it...redline difference is amazing, I don?t feel the car winding down at all.... it just wants to go faster.... car puts out a nicer smoother tone and runs smoother as well...I was hardly able to get out of my car today all I did was want run errands and drive.
Location: Arizona

Got my ECU back from Hondata today. Wow wow wow! I think this has been the best mod so far. There is more power everywhere. With the stock ECU, the RPM would climb so slow in the low end before vtec, but now its much quicker. More low-end torque, which is great for everyday driving. 5200 vtec is great, pulls slightly harder, then at 5800 even more, I actually feel a bump in power there now, instead of a dip. It still wants to keep going all the way to 8600, more power all the way. Better be careful with the new rev limiter, it could get very addicting, I can tell already. I've pushed it up there a few times, seems like fuel cut off isn't until at least 8800, I don?t know, the needle seems really really far into the red, past 8600. It feels faster and faster the more I drive, so the ECU is still learning.
As for the tone of vtec, it is much different than before, no more baaaaaaaawwwwwww, now I just hear my exhaust screaming. I actually like it better now, I think it sounds nice. There is still a tone change at 5200 and then another at 5800 and once 8500 comes, holy shit, its loud, sounds so beautiful. This baby screams!
Thank you to Hondata and Clubrsx! The order went very smoothly.
This is how the car should have came from the factory

Some 2002 onwards and all 2006 onwards ECUs are flash programmable. The ECU can be repeatedly reprogrammed without removing or replacing and internal components.

How do you get your ECU reflashed?

  • Fill out this form
  • Contact your dealer. All sales are made through Hondata dealers.
  • Your dealer or you will need to remove and send your ECU, immobilizer and key to Hondata.

Do I need to send the key & immobilizer?

Only for 2002-2006 RSX and 2002-2005 Civic Si reflashes. All other reflashes do not need to send a key or immobilizer. Flashing the ECU does not in any way alter the immobilizer operation.

How long does it take?

The ECU will be reprogrammed and shipped out the same day it is received. Shipping in the continental USA is FEDEX next day.

Will this affect the fuel economy?

Assuming you drive the vehicle in the same way, no. Fueling at cruise is the same as stock.

Will this affect the engine life?

Provided your engine is maintained correctly this modification should not affect the engine's life.

Will this affect the warranty?

It should not.

Federal law sets forth requirements for warranties and contains a number of provisions to prevent vehicle manufacturers, dealers and others from unjustly denying warranty coverage. With regard to aftermarket parts, the gist of the law is that warranty coverage cannot be denied simply because such parts are present on the vehicle, or have been used. (see Federal Warranty Laws for details). The warranty coverage can be denied only if the aftermarket part caused the malfunction or damage for which warranty coverage is sought.

If a dealership denies warranty coverage (more details here) , they should be willing to do so in writing. Have the dealer describe the failure which is causing your problem AND how the dealer believes the aftermarket product installed is responsible for the problem. Keep an accurate log of all contacts and correspondence in addressing the warranty denial. Hondata will provide any technical information the dealership requires.

With any increase in rev limit there is an increased risk of valve damage. To minimize your risk use the Hondata program with the stock rev limit. All reports of valve damage we have heard have been as a result of miss-shift. The Type S valve springs are good. We have tested a Type S with an 8900 rev limit in a press test vehicle for several months with no problems.

Will any settings be lost?

Your ECU will lose some idle settings and fuel trim when it is unplugged. It will relearn idle automatically if you leave it idling for 10 minutes. As you drive the car it will relearn fuel trim values in a matter of minutes.

Can a Honda/Acura dealer erase this program?

Only if another Honda/Acura update is released could a dealer erase your existing program. If Honda/Acura comes out with an upgrade you are not obliged to have it installed. If you do not wish to have the dealer program installed there is a wire you can disconnect or cut, to prevent reprogramming. The charge for restoring an erased program is $75 (cashiers check or money order) shipping included.  You can also remove pin 7 from the OBD2 port to keep the dealer from reflashing your ecu (DO NOT CUT THIS WIRE).

What about bolt ons?

Most programs have been tested to work well with a variety of intakes and exhausts. No retuning is necessary after an intake is added.  Some programs as tuned specifically for an intake or exhaust, and if so, will mention this in the reflash notes.

If you currently run nitrous, these programs will probably not be suitable due to the ignition advance used. If you want to use nitrous and this program now, you must install a nitrous system that retards ignition.

What about turbo-charging and super-charging?

Use the K-Pro or FlashPro.

What octane is recommended?

For high compression engines (K20A2, K20Z1, K20Z3, K24Z7) 91 octane fuel or better is recommended.  For all other engines there are gains from using higher octant fuel, as the ECU will automatically advance the ignition timing if no knock is detected.

Rev limits and Valve springs

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

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

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


With the stock airbox the VTEC point needs to be set at 5800 rpm. With intakes the power curve benefits from a lower VTEC point. VTEC switching point is important. Switching at the wrong RPM can cause the engine to drop power for the next 1000-1500 rpm. We have found 5200 rpm a good point for cars with intakes.


The immobilizer feature on the US Spec RSX is the most advanced to date. The ignition key, the immobilizer box and the ECU are all matched. It there is not a match there will be no fuel or spark. Japanese ECUs have less protection and are more easily bypassed.

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.

Hondata Reflash - RSX Type S 2002-2004 K20A2

  • Brand: Hondata, Inc.
  • Product Code: Reflash - RSX Type S 2002-2004 K20A2
  • Availability: In Stock
  • $295.00