Original thread: http://www.civictype-r.co.uk/forum/viewtopic.php?f=31&t=39655 

Author: Conradb

This FAQ was written primarily for US verions of the Acura RSX and Civic Si, but most of it also applies to your Civic Type R (with the vexing exception of the missing wideband). It should answer most questions about both the Hondata reflash and the Hondata K-Pro. The information is based on my own experience with the Hondata reflash and K-Pro. I also attended the Hondata seminar and took lots of notes (see bottom of this FAQ). Many thanks go to Doug and Derek at Hondata. Corrections/suggested additions to this FAQ are welcome.

What is “Hondata”?

Hondata is a company in Torrance, California that specializes in Honda performance products, and especially reprogramming of Honda onboard computers for optimal performance.

What products of interest do they have for me?

Three. They offer a reflash for the Acura RSX computer, which we call “ECU,” for Engine Control Unit. They offer the K-Pro system, which consists of a hardware modification to the Acura RSX base and Type-S ECU (as well as the US Civic Si and the Euro Civic Type R) and PC software to program the ECU. And they offer an Intake Manifold gasket which keeps the manifold much cooler than the thin stock metal gasket.

Does Hondata work with the new 2005 US RSX?

The 2005 US RSX-S (PRB-A13), Base and Auto have different wiring and a completely different ECU from the 2004. None of the existing reflashes work with this ECU. However, Hondata created a wiring adapter harness so that a 2002/2004 K-Pro ECU can be used in an 05. The 2002/2004 oxygen sensor is also needed.

Does Hondata affect my warranty?

Hondata says: (In the US) a dealer cannot deny warranty simply because you have changed a part – see the Magnuson-Moss Warranty Act. SEMA has information on their website, otherwise do a search. Basically a dealer has to honor the warranty unless they can prove the part you changed caused the fault. e.g. altering your wheels & tires should not effect a warranty claim on the a/c. This sounds straightforward but often many things fall into a gray area, for example, supercharging the engine and then trying to warranty a transmission failure. Did the transmission fail because of the extra engine power? Much depends on the relationship with your dealer. Many dealers will try to scare the customer telling you ‘change anything and you will void the whole warranty’, whilst other dealers have a much more after-market friendly approach.

I heard Hondata increases the rev limiter. Is that safe?

Hondata says: “The JDM J20A has a 8600 rpm limiter, whilst the US K20A2 with the same internal parts has a 8100 rpm limiter, so we are comfortable increasing the rev limiter to 8600 or 8800 rpm. One important point is that hitting the rev limit places a lot of stress on the engine, no matter where the limiter is. It is better to rev to 8500 rpm than hit the limiter at 8100 rpm. Also do not hold the engine on the rev limiter if you miss a gear – I’ve seen more than one engine expire this way. Another factor with the rev limiter is that the early K20A & K20A2 engines had weaker dual intake valve springs. Honda upgraded these some time in 2002 to a single valve spring (supposedly from the S2000). Owners of the earlier engines should consider changing the valve springs if they race the car. You’ll lose a little power doing this. Connecting rods are a point of debate at the moment. We know they can fail at 9500 rpm, so setting the rev limit below 9000 rpm seems like a good idea.

What’s the difference between the reflash and the K-Pro?

The reflash consists of a one-time changing of the stock ECU programming. You send in your ECU, immobilizer and key, and Hondata will program the ECU and send it back to you. The K-Pro system lets you program the ECU yourself after Hondata has added a daughterboard and a USB connector to your ECU. You can then connect a computer to the ECU, run the Hondata K-Pro ECU Manager software and either load one of the several “calibrations” Hondata ships with the software (many run well without the need for further tuning), or have a tuner create a custom calibration for your car.


How do I get the reflash?

First, Hondata does not sell directly. You must order the reflash from a Hondata dealer. In the US, if you order from Hondata dealer, you will receive a box with a Fedex label. You remove the ECU and the immobilizer (it sits around the ignition key lock of the car) and send both, plus your car key, to Hondata. Hondata will do the reprogramming and overnight the box back to you the same day they receive it. In most instances, you get the box back 48 hours after you send it. You then put the immobilizer and the ECU back in the car. All done.

Why do I have to send the immobilizer and key?!!

Because the immobilizer reads the information embedded in the key. Only if it matches will the immobilizer give the ECU the go ahead to start the car (or do much of anything). Hondata needs the key and immobilizer to reflash your ECU.

How much performance will I gain from the reflash?

That depends on the modifications on your car. Most people see improvements throughout the powerband. The most dramatic increase is around 5,800 rpm where wheel horsepower gains can be 15-25 and torque gains almost that much. The big midrange gain is primarily because Hondata lowers the VTEC point. There are also gains at the top of the rpm range, though they are usually less.

Is it true that Hondata changed the VTEC point in the Hondata 4 reflash?

Yes. Initially, the Hondata 4 reflash had a fixed VTEC point at 5,200 rpm. This fixed point has been changed to a VTEC window. At full throttle the engine will go into VTEC at 5,200 rpm and at part throttle as high as 5,800 rpm.

I have the Hondata reflash. Can I upgrade to the K-Pro?

Yes, Hondata offers a special price for existing Hondata customers. Instead of US$999 for new customers, the upgrade is US$500.

Can the Hondata reflash be detected by a service technician?

It can, but only if someone is specifically looking for it. Each ECU has a CVN (Calibration Verification Number). Any change to the ECU’s programming will change that number. Experienced Honda mechanics will also be able to tell by other parameters changed by the Hondata reflash (and, of course, by how much quicker the car is).

How did Hondata get all this extra performance?

By carefully examining the K-series engine with its unique combination of VTEC (Variable Timing Electronic Lift Control) and VTC (Variable Timing Control), then optimizing the conservative factory settings. Hondata did over 2,500 dyno runs while developing the reflash and K-Pro.


What’s in the package when I get the K-Pro back?

You’ll get the modified ECU (it will now have a USB port and a Hondata sticker on it), Hondata software on a CD (for Windows XP, no Mac or Linux versions), a 6-foot long USB cable, a jumper for Nitrous applications, instructions, and two Hondata stickers.

Do I have to send in the key and immobilizer?

Not according to Hondata: “No key and immobiliser is needed. As long as you install that ECU back into the car from which it came, the immobiliser will function. If you want to use your programmable ECU in another car you will need to switch off the immobiliser in the software.”

I don’t have a laptop. Do I need one for K-Pro?

Yes, you need one if you want to datalog or upload calibrations into the K-Pro. You can, of course, set up a desktop PC in your garage and upload a calibration from there, but that is definitely not what the K-Pro was designed for. Used laptops with enough power to run the K-Pro software and datalog at a decent rate can be had for less than $400 on eBay and other places.

What do I do next?

First, install the Hondata software on the notebook computer you will use. If you have an internet connection, fire up the Hondata K-Pro ECU Manager and use Help>Check for Updates to see if a later version is available. At this point you can also install the USB driver needed for the computer to communicate with the ECU. The ECU does not need to be in the car for that. Simply connect it and Windows will find the ECU and ask you for the driver. Point Windows to the Hondata directory and it will install the driver.

Next re-install the ECU. Note that the USB port on the ECU points forward. Once installed, the port will be next to inaccessible, so install the ECU with the USB cable plugged in. Now start the car and see if all works okay.

I installed the K-Pro and now have a yellow key-like light flashing in my dash.

That’s the immobilizer-off warning light. Hondata’s calibrations come with the immobilizer function turned off. You can turn it back on in the ECU Manager under Windows>Parameters>Misc.

I got my K-Pro and installed it, and now my fuel pump does not seem to work!

Do you by any chance have a PRC ECU and didn’t tell Hondata? If so, they may not have made a circuit board alteration affecting the fuel pump. To check, remove the circuit board from the case and look near the connectors for jumper J160. There should be two solder pads bridged with a piece of wire. If not solder a piece of wire across.

Does the engine need to be off when I upload a calibration?

There are two types of uploads. When you upload a calibration that is not already in the ECU, the initial upload will take about 30-45 seconds. The engine must be off for that. However, if you then make changes to an already loaded calibration, the incremental upload will only take a couple of seconds to upload into the ECU, and the engine can be on for that. I recommend that the engine always be off for updates.

But I don’t even know what calibration is on my ECU!

My own ECU was sent in with Hondata 4 on it and came back with something else. Unfortunately, the ECU Manager software does not tell you what calibration is loaded. What you can do is download the calibration and check the values. These days, Hondata usually loads the plain vanilla “factory” calibration.

What is a “calibration” anyway?

A “calibration” is a set of tables and parameters specifically prepared for certain engine configurations. Each configuration has two cam angle tables (one for the low-speed cam and one for high-speed cam), a total of six fuel tables for the low-speed and six for the high-speed cams (one for each angle of 0, 10, 20, 30, 40, 50 degrees), and six ignition advance tables each for the low-speed and the high-speed cam. In addition, many parameters can be set.

What are some of the important parameters?

We already mentioned the immobilizer. Other important ones include setting the Rev limit, setting either a VTEC point or VTEC window, setting idle speed, setting things so that the MIL light flickers when the engine knocks (a common occurrence when you start out with a calibration), and others.

VTEC Window? What’s that?

The K-Series engine can either switch from the low-speed cam to the high-speed cam at a specific rpm point (the “VTEC point”) or it can switch during an rpm range depending on manifold pressure (a “VTEC window”). You can set the lower VTEC boundary to, say, 4300 rpm at 98 kPa (full throttle) and at 5800 rpm at 24 kPA (light throttle). Inbetween those two points, the engine will switch cams on a linear curve.

What is “datalogging”?

Datalogging is one of the best features of the K-Pro. You connect your notebook PC to the K-Pro to record a total of over 40 sensor values. When you’re done recording (all recorded data is on your notebook, not the ECU) you save the datalog file with a descriptive name (like “myrsx_august24_fromwork”). You can then examine the data at your leisure. This is hugely educational and can also help you find what’s wrong (or not optimal) with your calibration.

What is the recording “frame rate”?

Each set of sensor values the K-Pro records is called a “frame.” The “frame rate” is the number of frames the K-Pro records every second. That number is not fixed. It depends on two things. 1) How many of the K-Pro’s windows you have open (those that display live data during datalogging slow things down a lot), and 2) how fast your computer is. With a modern notebook and a newer version of the ECU Manager you may see as many as 60 frames per second with all windows closed, and as few as 10 or 12 frames per second with all windows open (and perhaps other Windows programs open). For best data analysis you need as many frames per second as possible.

I have a fast notebook and all windows closed, but my frame rate is still low!”

Datalogging was much, much slower with older versions of the ECU Manager. Make sure you have the latest one! Another possibility for sluggish datalogging is the Windows Power Settings problem. On battery power Windows is slowing down the CPU to conserve battery. If it’s possible in your notebook, create a special “datalogging” power setting with CPU full power, the disk never going to sleep and the notebook never going into standby.

How do I look at the data from the datalog?

You load a datalog, then click Windows>Graph. Initially there is only one default graph. You can create your own custom graph templates via Options>Graph Templates. You can add as many custom graphs as you want. Each one can have between one and four graphs, and each graph can track between one and four sensors.

I am looking at graphs. All I see is lines.

Since you can display up to four graphs, it’d be confusing to have graph labels for all four. Therefore, each sensor displays a curve within a minimum and a maximum value. You can set minimum and maximum under Options>Sensors. Also, you can click on any point in the graph. A vertical dotted line will appear. If you have the Sensors window open, the exact value for each sensor can now be seen.

What does “Table follows VTEC” and “Tables follows Cam Angle” mean?

Open a datalog and also open the “Tables” window. Now move through the datalog in a Graph. With neither of these options checked, the table will never change. If you check the “VTEC” box, the table will toggle between low-speed cam to high speed cam depending on what point in the log you’re looking at. If you click “follows cam angle” the the software will always bring up the proper cam angle table. If you click both, it will switch both cam angle tables and low-cam/high-cam.

Will my gas mileage go down if I install the K-Pro?

According to Hondata: “As long as you have a working o2 sensor and run in closed loop, fuel economy is pretty much invariant. Closed loop ensures the A/F ratio is close to 14.7:1 while at part throttle, so the only variables to tune are ignition and cam timing. Hondata did some testing last week on the dyno, changing ignition and cam timing, measuring the manifold vacuum to achieve a certain power at certain rpm (30 hp at 3500 rpm to simulate highway cruise). The maximum power (lowest manifold pressure) was at anywhere from 36-44 degrees of timing at part throttle, which matches the stock ignition maps fairly well. Maximum power for cam timing was between 10-20 degrees advance, which is slightly less than the typical stock setting of 30 degrees at cruise. Typcially we see from zero to a couple of mpg inprovement over stock with a tuned ECU.”

I loaded a calibration and now my car is knocking.

That is a common occurence when you first load K-Pro calibrations. They are very aggressive and you’ll likely have to retard igniton here and there to get rid of knocking.

What is knocking and how do I get rid of it?

Knocking occurs primarily for one or more of these three reasons: a) bad petrol (combusts at lower temperature/pressure), b) too much ignition advance (flame ignites in various places), and c) too lean a air/fuel mixture (temperatures get too high and mixture ignites). If you already use the best petrol you can get, datalog your driving and then examine the points where the engine knocks (i.e. where the knock count increases). If you’re running very lean there, increase fuel. If you’re air/fuel ratio looks okay, select the area where knocking happens and reduce ignition advance across all tables by two or three degrees. If you are not comfortable with this, have a tuner or mechanic do it. Do not drive with lots of knocking.

Why across all cam tables when knocking only happens in one ignition table?

It may look like only one because you see that highlighted 2×2 square in the table. In fact, the Hondata program interpolates an actual value by looking at the four closest values, and also interpolates across cam tables. A total of eight values determine the actual value the ECU uses. This is why you need to make the initial corrections across all tables.

Why does ignition advance at idle show zero?

According to Hondata, idle uses a special emissions ignition value.

I loaded a friend’s calibration and in the 2-D graph, values are off the map!

That happens when you look at a really old calibration with a newer version of the software. Hondata says: This is caused by the tables being uninitialised from columns 14-16 when you load an old calibration. You need to replicate column 13 into 14-16 to fix this for pre 1.1 calibrations.

My air-fuel ratio is always 11.48 at full throttle. Why?

The K-Series’ wideband oxygen sensor (US only) reads down to 11.48. Most likely you’re running richer than that.

Can I get wideband in my Euro CTR?

Yes. Some claim it’s not worth it because the integrated wideband only reads to 11.48 and to get an external wideband. That is nice for dynotuning, but not for datalogging. Having K-Pro wideband logging is invaluable for tuning. Unfortunately, you do need both the US ECU (upgraded to K-Pro) and the US sensor. One pin in the wiring harness needs to be changed, and one added. CPL has done this to their car. The US ECU also cycles the O2 heater so as not overheat the sensor.

How does the K-Pro work with a race header that doesn’t have a secondary oxygen sensor?

The K-Pro uses the US-models’ primary (wideband) oxygen sensor to determine air-fuel ratio and for open/closed loop operation. The secondary sensor simply determines if the cat is there and the primary sensor is working. Without the secondary sensor, the ECU will cause a P0134 error code that can be disabled in the K-Pro Parameters window.

What happens if I disable OBDII in the Parameters window?

Disabling OBDII turns off monitoring of the following sensors: secondary oxygen, fuel tank pressure, electrical load, and atmospheric pressure. This means OBDII tests cannot be conducted. Closed loop operation is not affected.

Some non-Type-S ECUs (like the Japanese market PRC ECU) do not support some of the sensors. If such an ECU is used, those sensors must be disabled or else you get an error code.

Can I run the K-Pro without either of the two oxygen sensors?

Hondata says: “I run my race car with no o2 sensors without any problems. You will need to disable everything and run open loop. As far as tuning goes, as long as the dyno has a wide band there should be no problems. However for a street car it generally is a bad idea to run open loop unless you spent time on the part throttle fuel maps and get them close to perfect.”

Can I use (brandname) cams with K-Pro?

Hondata says: “For anything other than stock, Toda or IPS cams you need to mock up the cylinder head and measure clearences. To do this properly you need a pin to lock the high lobe and an indexed intake cam sprocket. Once you have established the maximum safe advance on the intake you pull apart the intake cam sprocket and pin it so that the cam has a physical stop. From memory with crowers cams this is at about 30-35 degrees advance.”

How does one tune the K-Pro?

There are three major ways: 1) If you know what you’re doing you can tune/tweak it yourself by making sure the air/fuel ratio is optimal in all areas and that the car does not knock (of course, that way you won’t have dyno numbers to see what your changes did). 2) A tuner can tune your car by starting with one of the base maps and then optimize that map on his dyno. 3) A tuner can start from scratch, like Hondata did, create dyno curves for each cam angle, then create a composite curve and dynotune this to perfection. That runs into money.

I use a turbo. Does the K-Pro work with it and how do I tune it?

Here is Hondata’s advice:

You can start with the reflash and upgrade to the programmable to work with any turbo kit. The K series Honda ECU (and K-Pro as well) require and work best with high impedance 12 ohm injectors. RC Engineering sell these in 440, 550, 650 and 750 cc in size. The K-Pro works very well with any boosted engine with the stock MAP sensor up to about 12 pounds of boost. No piggybacks are needed or recommended. K-Manager also supports a 3 bar map sensor upgrade. Proper tuning of a boosted engine includes:

1) Setting the cam angles
2) Retarding the ignition timing as boost increases
3) Setting the optimum VTEC point for part and full throttle operation
4) Tuning the part throttle and full throttle fuel maps to match the injectors
5) Altitude compensation – making sure that altitude the ECU sees the correct boost pressure to deliver the correct fuel and ignition. At wide open throttle on a stock ECU the ECU reads not the boost pressure in the manifold, but the pressure in the ECU case. At altitude this advances the ignition and leans the fuel. This is not what you want in a boosted car if you want reliability. The K-Pro fixes this.
6) Closed loop control. On boosted cars we have tested running stock ECUs, the ECU will hold 14.7:1 air fuel ratio after a gear change for several seconds and when going to boost from a cruise. You will never see this condition on a dyno run, but on the road it is far too lean for a boosted engine. The K-Pro fixes this by switching off closed loop when a preset level of boost is reached.

Of course you can skip some or all of these steps and you will still probably be pretty happy, but you will be down on power and compromising long term reliability. So, as long as you know what is necessary to do to have a well tuned engine, (and this will require tuning by an expert) you can make the best decisions for your purchase. I suggest also, you talk to some companies who tune boosted engines for a living and ask their opinions.

Does the K-Pro work with Nitrous?

Yes, exceptionally well. There is an entire control panel for nitrous operation, and Hondata can back it up with extensive nitrous testing in their own cars. The K-Pro switches on nitrous based on rpm, throttle position, vehicle speed, and air pressure. It also switches off nitrous before the fuel cut-off.

Why does Hondata recommend a dry nitrous system

Hondata says: “If you have a wet system and hit the rev limit two things will happen: 1) The rev limit will not be there and you will overrev. This is because the ECU cuts the fuel but the wet system keeps supplying it. 2) As a result you will run very lean. Likely result will be: “where did my piston go!” Ignition retard is essential as with nitrous the mixture burns faster. Not retarding the ignition will put huge stress on the rods.

I have a boosted car. What specific advantages does the K-Pro offer me?

Hondata says:

1) Factory boost mapping with ignition retard and fuel increase on boost
2) Switching to open loop on boost eliminating hesitation and part throttle lean spots.
3) Correct calibration for larger injectors. (Meaning easy starts and good emissions)
4) Correct altitude compensation. The stock ECU leans out and advances ignition the higher in altitude you climb. You do not want this in a boosted car.
5) The cam angles can be dialed in for your specific exhaust setup. The better your exhaust, the more cam advance is needed.

The “Maintenance Required” light is on in my car. Can K-Pro turn it off?

You don’t even need a K-Pro to turn it off. Simply turn off the engine, press and hold the odometer button, switch the ignition to position II, and then keep holding the button in and the maintenance light should go out within about five seconds.

I have a (fill in brand of fuel management piggyback). Can I still use the K-Pro?

Hondata advises: Remove it. Anything that modifies signals to the ECU will not allow you to tune the car properly.

Is the K-20 supposed to have high or low impedance injectors?

Hondata advises: Any injector driven directly by the Honda ECU should be a 12 ohm injector.

What ECUs will work in my car, can I upgrade them to K-Pro, and are there any differences?

The ECUs for all US market RSX base (manual shift only), RSX Type-S and Civic Si are interchangeable as long as they have been modified to K-Pro status and loaded with the proper calibrations. According to Hondata, there are some minor differences: “The PRB (RSX -S) has reverse lockout for the 6 speed. The others do not. The PND (RSX Base Manual) has intake runner control. The PPA (CRV Manual) has intake runner control. The PNF has neither intake runner control nor reverse lockout. There may be other differences, but it would seem a program runs the same in all these ECUs.”

I heard the US RSX has a wideband oxygen sensor. True?

Yes it has (although it only reads down to 11.48 AF). This is terrific if you ant to use datalogging to adjust your air-fuel ratios. However, note that not all K20 -Series engines have the wideband sensor. Those that have one are the US RSX Type-S, the US RSX base, the JDM ITR, the JDM Civic Type R. Sadly, those that don’t include the Euro Civic Type R.

Can I retrofit a wideband sensor into my CTR?

I think you can. All you’d need is a ECU that supports wideband (in the US you can get a used RSX ECU for around US$250), have it upgraded to K-Pro by Hondata, and replace the narrowband with a 4-wire wideband sensor (either from Honda or via a place like oxygensensors.com).

Hondata sounds wonderful. Are there any drawbacks?

That depends. The Hondata reflash and K-Pro are officially intended for off-road and racing use only. In California, especially, aftermarket changes must be CARB (California Air Resources Board) approved and come with a CARB sticker to prove it. Changing ECU settings is never CARB approved. A reflash could theoretically be CARB-approved (if Hondata went through the expense of having it tested and certified) because the customer cannot further change it. You can always have Hondata reflash a flashed ECU back to factory standard, or you could use two ECUs, one factory for road driving and one with the K-Pro modifications for racing.

Another issue is that the K-Pro DOES requires both the ability and the willingness to learn and fiddle with software. If you want to stay away from that, a simple reflash may be the way to go for you.

Finally, and this really has nothing to do with a Hondata reflash or K-Pro upgrade, make sure grounding is okay in your car! Hondata says, “It is very important that the ground from the wiring harness to the engine (G101) makes good electrical contact with the cylinder head. Otherwise the return path for the sensors, ignition and VTEC may be through the ECU case to the vehicle body, which may damage the ECU and/or programmable board inside the ECU.”

I am really confused. Should I get the reflash or the K-Pro?

Here are the pros and cons for each:

Hondata #4: A tried-and-true reflash that works with most cars. It brings a bunch of extra power in the midrange by moving the VTEC point from 5800 to 5200, and it adds some on top. It is a relatively mild tune. It has to because once it’s in, you can’t go and fine-tune in case you have knocking. You can also have it reverted to stock by Hondata should the need arise. One problem: it may not work optimally with your particular setup. I had a distinct power dip with Hondata 4 and my Icebox. That’s because each I/H/E combo has different air-fuel characteristics and Hondata 4 is one-size-fit-all.

K-Pro: This gives you complete and total control over your ECU via a daughterboard and a USB connection to your laptop. You can monitor 42 datapoints at frames rates up to 60 frames per second. You can change fueling, ignition advance, cam angles, fuel cut-off, VTEC, and tons more. The calibrations that come with it are quite aggressive and you’ll likely have to play with the settings to get rid of initial knock, and Hondata suggests you have it professionally tuned. You’ll need to learn a lot about not only the software, but about ignition, fueling, can cam timing concepts. If you’re game, the K-Pro is endlessly fascinating, you’ll never outgrow it as you modify your car, and you’ll learn how it all fits together. However, in order to revert to factory stock, you’ll have to undo the whole thing.

Those who have a CAI and don’t want to mess with the car or learn new stuff should go with the reflash. All others will be much happier with the K-Pro.

Cool FAQ, but I have a more questions, some quite technical

Check my website at http://www.pencomputing.com/rsx/ for a lot of additional information on Hondata and engine tuning. Also check the tech section on the Hondata website at http://www.hondata.com. And always post questions or send them to me at [email protected].