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The Hondata Reflash THE best bang for the buck on your 04-06 TSX

The engine in your TSX is controlled by a computer, which should come as no surprise. The computer, like all computers, are dumb. They just do what some programmer somewhere told it to do. Meaning, your car is running on a program made by some nameless, faceless engineering group at Honda to be the best Honda it can be.

Unfortunately for you, that does not mean it is the best PERFORMING Honda it can be. Engineers have to report to the company which needs to report to its customers. Not all customers are power-hungry pedal stoppers like you and I are. Therefore, there is almost always some power left on the table somewhere.

The Hondata Reflash for the 04-06 TSX is a revamped set of parameters that is downloaded onto your stock computer to de-geek it. Ironically, the program of the reflash was developed by the biggest Honda-geek of them all, Doug who is the head honcho at Hondata. That anyone, for a mere few hundred bucks, can get a fully optimized ECU tune by one of the modern-day masters is nothing short of a no-brainer.

During a recent dyno testing stint at Church Auto Testing in Wilmington, CA, I had the opportunity to do a little before-and-after test of the reflash on my personal HTSpec TSX. This 2004 model has about 120,000 miles on it and minimal mods (just an CT-Engineering Carbon Icebox, UR Underdrive Pulleys, and a Fujitsubo exhaust). Check out the before and after dyno graph:

Holy crap, just look at what happens past 5000 rpm! The Torque curve on the stock tune goes pretty abruptly down and after the reflash it very certainly is going UP. All the way to a peak of 189 ft-lbs. We are making really good torque which is fairly consistent from 3500 rpm to about 6000 rpm, where it tapers off near redline. But man, look at 6000 rpm, we go from about 156 ft-lbs all the way up to 180 ft-lbs! a 24 ft-lb increase for under $350???? Up, YES PLEASE.

So how is all the power being made? Well, it is all in the tuning. There are three major variables that are adjusted in a K-series engine: fuel trim, ignition timing, and cam phase. Fuel and ignition we know about. The fuel is usually more on the rich side to protect the engine from knock, and while the computer is over-protective in this way it is such at a detriment to power. The fuel is backed off ever so slightly in a still-safe manner, which has a big affect on power.

Ignition timing, also in an effort to reduce knock, is very eager to retard itself. Yes, retarding ignition timing is bad for power. By making the ignition timing a little more aggressive, the engine is able to spin faster and harder thereby producing more power.

What about the cam phase adjustment? The intake cam on the K-Series engine has a special gear on it with a mechanism called a VTC forming the hub. This special gear can move to advance or retard the intake cam at different RPMs, at the will of the computer. You may know that cams can be degree'd to make power at certain RPMs, but the VTC has the ability to CONSTANTLY tune the cam as you are driving! The main reason Hondata can get such good power numbers is because they can tune the VTC to act in a way that is a lot more efficient for making power than stock.

All of the adjustments Hondata makes are completely safe and literally invisible to anyone "looking" at the computer. Your Smog guy won't know it is there, and the car will still pass emissions test just like normal. The dealer won't know it is there and cannot void any part of your warranty. There are no engine lights that come on, no special fuel additives needed, nothing like that. Just get the reflash and motor-away!

Related Items

Hondata Reflash, 2004-05 Acura TSX (ALL)
Hondata Reflash, 2004-05 Acura TSX (ALL)

Honda Genuine OEM VTC Actuator, Honda K-Series (50 Degree RSX-S RBC Spec, Option Phase Limit Pin K24A2), 14310-RBC-003
Honda Genuine OEM VTC Actuator, Honda K-Series (50 Degree RSX-S RBC Spec, Option Phase Limit Pin K24A2), 14310-RBC-003


Joshua Ruiz
06-09-2016 10:21 AM at 10:21 AM
Will there be any gains on an automatic TSX
Administrator Note:
Yes the gains in engine output would be the same on an automatic TSX.
03-18-2016 02:32 AM at 2:32 AM
Is the only thing I have to do is take off my ignition and ecu and send it in? Also I'm planning on running an rbc, cold air intake and exhaust. Would u recommend I use this same reflash? I have an 05 automatic
Administrator Note:
Yes, this is correct! This reflash is very effective with all kinds of bolt-on modifications, although a custom tune becomes more important with more involved modifications such as intake manifolds and camshafts.
10-04-2015 10:48 AM at 10:48 AM
So how does this reflash effect mpg at highways speeds. My 04 6mt is lucky to hit 30mpg running 70mph + due to the gearing. Wondering if I'll use more fuel cruising at 3500rpm.

Also, if I don't want to do exhaust, only an intake, will this reflash still give me noticeable gains as in better 0-60 or only pulling power on the highway while in VTEC?

Also not seeing the carbon fiber style CT icebox on their website....
Administrator Note:
I didn't record my fuel economy, but others have mentioned improvements in MPG (of course, others mention the opposite, due to "lead-foot" syndrome). Fuel economy has more to do with where your foot is than where your RPM is, though.

Yes, the reflash needs NO supporting mods to really impress you.

The carbon box was discontinued some time ago, unfortunately.
alexander larosa
09-23-2015 12:10 PM at 12:10 PM
i just had the reflash done an i notice a difference right away idle was improved an the driving makes it more fun to hit VTEC. I'm sure changing the clutch an using a light flywheel would be nice. But wanted to know could adding a bigger throttle body or the 06-08 tsx cam help???
Administrator Note:
Yes adding the cam and a 45 degree pinned VTC (available on Heeltoe) will definitely help, but you'll need the Flashpro to tune them. The Reflash won't do it, sadly.
Jeff M
10-18-2013 12:33 PM at 12:33 PM
I have been running the reflash in my 05 6 speed for 90K miles now. Being a family man, this was the only mod I could do on my car, and I am so happy that I chose it. 0-60 in 1 shift, much better freeway speed passing, and no deleterious mechanical issues produces. Truly, the best mod you can do for a 04-06 car.
03-19-2013 04:03 PM at 4:03 PM
Fuel consumption: I have not noticed a dramatic change at all. But the rush after 4000 rpm is QUITE noticable.
12-04-2012 09:46 AM at 9:46 AM
Thanks for the great article! Any idea about fuel consumption after Hondata given exact same driving habits?
G. Baker
10-26-2012 08:34 PM at 8:34 PM
This was a great additon to my 04 TSX with the CT Icebox also. It initiallly feels slower, but pulls strong and smoothly all the way to 6K rpm. It drives a bit different, and you will have to resist reving it hard as you enjoy the added power and torque.

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