Reflash - TSX


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Hondata, Inc.
2840 Columbia St
Torrance, CA 90503
  • 5000 rpm VTEC point decreased from 6000 rpm
  • 7600 rpm Rev limit, increased from 7300 rpm (for auto trans must be in sportshift mode)
  • Maximum torque gain 26 ft/lbs torque at 6000 rpm
  • Maximum power gain 29 hp at 6000 rpm
  • Peak torque increases from 169ft/lbs at 4500 rpm to 175 ft pounds at 7500 rpm
  • Peak power increases from 206 hp at 7100 rpm to 210 at 6800 rpm
  • Very wide flat smooth torque curve. 90% of peak torque available from 2000-7000 rpm.
  • Fully dealer compatible - works with all Honda scan tools and equipment

The Hondata TSX reflash is designed for use with an intake and headers. It will work very well with a stock airbox and stock headers. Testing was done with a stock cat back system.


  • $295

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.

Results for Manual Transmission TSX with no modifications

  • Red Line - Stock ECU
  • Green Line - Reflashed ECU

Click to enlarge picture

Results for Manual Transmission TSX with intake and header

  • Red Line - Stock ECU with intake and header
  • Green Line - Reflashed ECU with intake and header

Click to enlarge picture

Results for Auto Transmission TSX

  • Green line - Completely stock low milage (300 miles) Auto TSX
  • Pink line - Completely stock low milage (300 miles) Auto TSX with Hondata Reflash

The gearbox shift points have not been changed. To use the higher rev limit you must be in sportshift mode.

Click to enlarge picture

Who can use this upgrade?

Any K24A2 TSX Manual transmission owner with the ECU part numbers :

  • RBB-A02 - 04 TSX
  • RBB-A03 - 05 TSX

Any K24A2 TSX Auto transmission owner with the ECU part numbers :

  • RBB-A54 - 04 TSX
  • RBB-A55 - 05 TSX  ** New: added Jan 09 **

How do I remove my ECU and immobilizer?

The ECU is located behind plastic panels to the right of the driver's right foot and the left of the passenger's left foot. Both panels will need to be removed. You will need a Philips screwdriver and 10mm socket. Complete removal instructions are to be found on this page. Alternatively you may download and print out the TSX ECU removal pdf file(300k).

Driving Impressions

This reflash is difficult to feel because it keeps the torque delivery flat and smooth to a much higher RPM. Rather than the torque dropping 20 ft/pounds from 5000 rpm to 6000 rpm stock, the reflash keeps the torque drop to only 10 ft pounds between 5000 and 7000 rpm. VTEC transition at 5000 rpm is also very smooth with only a slight change in induction noise.


Video comparison between a stock 04 TSX and Reflashed 04 TSX.

Click picture to play (2.2 mb Quicktime)

Review from the Temple of VTEC

Tsx536: I took it to redline about 20-30 times and all I can say is WOW! You can definitely notice the difference! The car just drives differently. It's much smoother and responsive. The car pulls a little harder from 2k-3k and much harder from 3K-7K than it did before! The extra power up high in the RPM range can definitely be felt! It feels like you can take off and pick up speed much faster than before. Hondata was exactly what I was looking for! I would recommend it to any other TSX, especially any with a 5AT with cold air intake. I now consider the Hondata the official #1 best bang for the buck mod.

drkangel348: All I have to say about the Hondata reflash is that it makes the car into a different monster... It pulls so much harder now!! Its a complete different car, I'm loving it... Right now I only have the Injen CAI but I plan to install Comptech Headers and Exhaust soon... . But yeah Hondata should be the first mod for your TSX! It totally changes the attitude and performance of the car. My car is so much more responsive now, THANKS HONDATA!

vwong: When I got on the freeway, I was merging in and I was at 3rd gear around 5k rpm. I floored it to see what it was like at higher rpm. Oh my god......holly shit!!! What a difference!!! The throttle response is like instant. The car hauled ass from 5k rpm all the way to 7600 rpm. Before the reflash, I could tell that the car was a bit sluggish if I were to do the same thing. But after the reflash, the torque is readily available starting at 4500 rpm. I'm very impressed. Hondata did a good job giving us more "punch". I can definitely feel the difference. Keep in mind that my car is bone stock (engine wise). I highly recommend the Hondata reflash. So if anyone is still thinking about it, DON'T. GET THE HONDATA REFLASH NOW!!!


The TSX uses adaptive knock control. This means it will listen to the knock sensor and advance or retard the timing appropriately. This is good as it means the TSX will readily adapt to higher octane fuel and add a couple of degrees ignition advance. The TSX ECU only takes 3 or 4 power runs to adapt, and is constantly relearning. Unfortunately the side effect is that successive power runs can vary by up to 4-5 ft pounds of torque due to engine noise or knocking that is inaudible to the ear. If your coolant temperatures are too hot (>195 F) or the engine is hot from dyno runs, the ECU has a tendency to retard the timing.

All NA K24 engines we have tuned drop sharply in torque after 6000 rpm - even the 270 hp full race engines. This is a function of the long stroke of the K24 engine. The best way to change the shape of the torque curve is to improve the cylinder filling above 6000 rpm with forced induction - such as supercharging in this comparison with a supercharged K20A3 Civic

The intakes on the K series engines get very hot. They have a metal intake gasket which transfers heat from the head very quickly and are heated by hot air from sitting right behind right the radiator . Pay lots of attention to keeping everything cool and you will see results. The K24 Hondata intake gasket reduces intake temps about 15-40 degrees F. Use a cold air intake where possible.

In depth analysis for Manual transmission TSX

Lets look at a typical power run. With the stock ECU you change gear at the redline and drop around 2000 rpm onto the lowcam. Average the power readings over this range and you get 182 hp.

With the Hondata TSX reflash your shift point is 300 rpm higher and you drop in the rev range to just before the torque peak while remaining on the high cam. Average power is about 201 hp in the marked power band. This is an average increase of 19 HP from stock, even though the peak power difference is only a few HP, the area under the curve is substantially better.

Click to enlarge picture

Comparison to stock for Manual transmission TSX

This compares the dyno plots above to the TSX 6 months ago when it only had about 1000 miles (dotted pink run). With more miles on the car, the difference in base power would have been higher.

Click to enlarge picture


Copyright 2015 Hondata, Inc. All rights reserved. Warranty Information
Products not legal for sale or use in California on any pollution controlled motor vehicles.