By Conrad H. Blickenstorfer

Most Honda enthusiasts agree that the K-Series engine introduced in 2001 for use in the Acura RSX and then in a number of other vehicles is among Honda’s finest ever, and some think it is the best, better even than the vaunted B-Series. However, it is also quite different from any earlier Honda engine (for starters, it turns the other way around) and that means performance parts were initially hard to find, and it will likely be a few more years until the full potential of the K-Series is realized. So while the RSX Type-S was certainly a lively car, drivers soon complained about a lack of punch below the rather high VTEC crossover from the low to the high cam (5800 rpm) and the engine’s tendency to easily hit the rev limiter even though that was set at a seemingly astronomical 8100 rpm. With B-Series and other Honda-powered cars this was not a problem—simply get the proper parts or reprogram the ECU, and that’s usually where a company called Hondata came into play. They specialize in cracking the computer code of Honda engines and offer products to tweak it. For the B, D, F, and H series engines that was an elaborate system of ECU programming via Hondata’s Stage 1/2/3/4 and then s100 and s200 systems. Those were computer programmable interface boxes that would then burn code into a suitable Honda ECU. Why not simply get a third party replacement ECU? Simple: those are very expensive, and Hondata believes that no one knows how to make a Honda engine run as smooth and economical as Honda itself, so let’s keep the ECU. It just needs a little tweaking.

The ballgame changed when the K-Series arrived. Not only was the engine very different, it also had a new and much more powerful computer. It took Hondata, a company founded by two New Zealanders who migrated from their idyllic island nation to hectic Torrance, California specifically to cater to the large Honda community here in the United States, two years to "crack" the code of the K-Series ECU at least to the extent where they could offer reflashes for the K-Series. A reflash, in this case, meant you sent in your ECU (plus key and immobilizer as those are needed to get access to the ECU) to Hondata. The wizards at Hondata then reprogrammed the ECU with a more performance oriented configuration, one that also lowered the VTEC point from 5800 to 5200 rpm and raised the fuel-cutoff from 8100 to 8600 rpm. Since almost no performance parts were initially available for the K-Series, Hondata optimized those reflashes for whatever they could get their hands on, and that was mostly cold air intakes. So the by now legendary Hondata #4 reflash performs best with a cold air intake. The program works wonders and totally transforms a RSX. A stock 2002-2004 Type-S can gain as much as 20 ft-lb of torque and 20 horsepower around 5800 rpm, about 10-15 peak horsepower, and end up with much better overall drivability. How did Hondata do that? Well, once they had deciphered the ECU code they found that the stock RSX Type-S runs very rich at high rpm, has very conservative ignition timing and was very sensitive to knock sensor input. Once tuned, the engine had more power, the same or better emission results, and better fuel economy. The Hondata reflashes quickly became very popular, and Hondata began creating custom reflashes for more extreme applications, such as the Jackson Racing supercharger, GReddy turbos, and Toda cams.

Problem was that a reflash, by nature, is still a compromise. It must provide additional power, yet still work reliably in engines that as time went on had an ever wider variety of modifications. You can imagine that a stock engine has different timing and fuel requirements than one with a cold air intake, a race header, and a very low restriction exhaust. Since a reflash is not tunable once it is installed (it can be replaced, of course), the Hondata #4 reflash had to be conservative enough to run in many engines without endangering them with lean conditions or engine knock.

The answer would be a user programmable ECU management system, and that came in March of 2004 with the Hondata K-Pro. Contrary to common belief, the Hondata K-Pro is not a replacement ECU. It is a stock Honda ECU onto which Hondata solders a daughterboard with a USB port. This way Hondata gains direct access to the ECU via the high speed of a USB interface as opposed to using the much slower OBD-II port that’s mandatory in every car sold in the US since 1996. In order to have their ECU upgraded to K-Pro status, a K-Series driver would send the ECU to Hondata and receive it back within two or three days, together with a USB cable and a CD containing the USB drivers necessary for a PC to recognize the Honda ECU and the Hondata K-Manager software for Microsoft Windows. The list price of the ECU upgrade is about a thousand US dollars. Existing Hondata reflash customers get a substantial break.

What can you do with a K-Pro ECU and how will it affect a K-Series engine?

In order to fully appreciate that, let’s first do a refresher on some of the basics that you’ve heard a million times: The engine is really just an air pump. The more air you get into it, the more power it makes, as long as you add the proper amount of fuel and ignite the mixture at the exact right time. And you have to make sure there aren’t too many restrictions so that the air quickly moves through the whole system. It’s as simple as that.

The laws of physics can be helped along a bit, and Honda has been doing that with its ingenious VTEC (Variable valve Timing Electronic lift Control) technology for years. VTEC basically means there are two camshaft profiles, a "mild" one for good low end drivability, torque, and fuel economy, and a second "wild" one for high end power. The "VTEC point" is where the engine switches, via a hydraulic mechanism that uses engine oil pressure, from the low cam to the high cam.

A second cool Honda innovation is VTC or Variable Timing Control. This is a system that continually changes the intake camshaft timing because different cam angles provide best power and/or economy at different rpms. By using different cam angles you can make sure you get the best possible power at any rpm—smooth, economical running with very little overlap around town, and a much more aggressive setting at high rpm for that extra punch. The VTC system is also completely controlled by the ECU and uses hydraulics for operation. The intake cam of a K-Series engine can rotate by no less than 50 degrees (25 degrees in some K-Series variations such as the engine used in the Acura TSX).

iVTEC is what Honda calls a combination of VTEC and VTC. The computer in an iVTEC-equipped car therefore has control over the switch from the low to the high cam, and also over the cam angle at every running condition. Hondata calls VTC "Honda’s gift to Honda tuners" because of the great flexibility it offers when tuning a car, but that gift comes at the price of some very considerable programming if one is to take control of it.

To illustrate the predicament, let’s see how the Honda ECU handles VTEC and VTC. First of all, all automotive computers use lookup tables with ignition and fuel values. The values in those tables may be modified based on other conditions (such as startup, acceleration, engine knocking, etc.), but they are the basis of all operation. Since Honda uses VTEC, the Honda ECU needs two cam angle maps, one for the mild "low speed" cam, and one for the wild "high speed" cam. The maps themselves—be they for cam angles, fuel, or ignition—all have rpm on the vertical axis and engine intake vacuum on the horizontal axis. So the "low speed" cam angle map shows what cam angle the ECU will set for each rpm-engine vacuum point in the map. Likewise, the "high-speed" map shows the cam angles for after the engine "goes into VTEC" as Honda enthusiasts like to say. Problem is that the ignition and fuel requirements are very different for the low and the high cam, and also very different for different cam angles. So what Honda did was include no less than 26 total maps! That’s the low and high speed cam angle maps, and then fuel and ignition maps for each cam.

Why so many? Because for each cam, there are ignition and fuel tables for a cam angle of 0 degrees, 10 degrees, 20, 30, 40 and 50 degrees. That’s a lot of maps, and Hondata had to find a way to make them all accessible.

But that’s not all. Anyone who wants to boost their engine either via a supercharger or a turbocharger needs extended tables that contain cam angle, ignition and fuel values for the boost ranges. Boosted engines, of course, can run quite well via piggy backs that add fuel and intercept ECU signals, but it stands to reason that they run a lot better if fuel, ignition and cam angles are tailored exactly for boost. Hondata did that by adding six "boost columns" to each of the 26 tables. Three of them are for the boost range supported by the stock K-Series MAP sensor (up to about 12 psi boost) and three require a replacement MAP sensor and support boost levels up to 28 psi.

So what you get when you have Hondata upgrade a stock K-Series ECU to K-Pro status is a system where you have complete and total control over cam angles, ignition, and fuel via an easy-to-learn software application, the Hondata K-Series ECU Editor that runs on Windows computers. The Windows software lets you view, edit and then upload "calibrations," which is the name for a complete file that contains all the cam angle, ignition, and fuel data for your engine. The software is frequently upgraded and you can download it free from Hondata’s website (hondata.com) so you can check it out for yourself. You won’t, of course, be able to program your ECU with it because that requires the daughterboard and USB interface.

Isn’t it very difficult to create such a "calibration"? If you had to start from scratch, yes. Fortunately, the K-Pro comes with a growing library of pre-tuned calibrations that can be used as starting points for your car. When I wrote this article, the K-Pro was available for the US Acura RSX base and Type-S, the US Civic Si, and the Euro Civic Type-R, and it had calibrations for stock engines, mildly modified engines, as well as supercharged and turbocharged engines. In most cases, someone with just a cold air intake will be able to load a calibration and the car will run fine with it. Calibrations for super or turbocharged cars, on the other hand, are more like starting points for tuning.

However, adjusting fuel, ignition, and cam angles is not all you can do with the Hondata K-Pro system. You can also adjust the VTEC point or even set a "VTEC window" so that the engine switches to the aggressive high cam at a low rpm when you floor the accelerator, but at a much higher rpm when you just tool around town. You can set the rev limiter anywhere you want (though it’s not a good idea to go too high unless you know your valve train can handle it). You can set the point where the engine should go from closed to open loop operation, you can edit air temperature compensation tables, set overheat and overboost protection values, disable OBDII sensors for race engines, adjust the fuel trim for individual cylinders, set a launch limiter and much more.

But programming the ECU is not all the K-Pro lets you do. It is also an absolutely first rate datalogging system. While run-of-the-mill OBDII loggers usually let you record a few engine variables at a fairly low speed, the K-Pro logs the output from over 40 engine sensors at up to 60 frames a second! A notebook computer must be hooked up to the K-Pro ECU to do that, and you can record data for hours, literally until you run out of disk space. Later, you can analyze the data on the PC. Here, another feature of the K-Pro software comes in very handy: you can create as many custom graph templates as you want. For example, if you want to view how engine rpm, air-fuel ratio, injector opening and duty cycle relate to one another, you simply create a graph for that. Then you can see what those four parameters do, up to 60 times a second. This kind of diagnostics capability can often help you determine the source of a problem within minutes. Datalogging also shows you, at a glance, how well your engine is running. No more guessing about the air-fuel ratio and such!

Over the year or so that I have used the K-Pro and helped others using it and tuning with it, I noticed that a lot of people shy away from computer engine management systems such as the Hondata K-Pro because they think it is too complicated for them to handle, and that includes some seasoned Honda specialists who replace camshafts during a lunch break and such. The "I am not good with computers" fear keeps a lot of those people from getting the most out of their engines and also from hitching a ride into the future of engine tuning. Is electronic engine tuning really that difficult? Yes and no. Anyone who has a basic understanding of computers and engines can learn the Hondata software in a couple of hours. That said, it IS possible to make serious mistakes and end up with a car that runs worse instead of better. So setting aside a weekend to really understand the software is a good idea.

What can a K-Series owner expect from the Hondata K-Pro? That depends. If the K-Pro is installed in a stock engine, the difference will be even more dramatic than a Hondata reflash. That’s because K-Pro calibrations tend to be more aggressive than reflashes. Why? Because you can always tune them down if you encounter engine knock or if the air-fuel ratio is not quite right. As a result, using the K-Pro’s calibration for stock engines with a cold air intake is a revelation. The VTEC point is lowered to 4300 rpm, the redline is 8600 rpm, and all tables have been carefully dyno-tuned by Hondata. This means that an additional 25 horsepower in the often used midrange and 15 at the high end are quite common.

What if you encounter engine knock? No problem. A datalog will show exactly at which engine rpm, intake vacuum and cam angle the knock occurs. You then simply use the software to reduce spark advance in that area by a degree or two, then save the calibration and upload it into the ECU.

What if you find in a datalog that your air-fuel ratio under full throttle acceleration is okay up to, say, 7000 rpm, but rises to a rather lean 14.5 above that? Then you select the cells where you are running lean and add some fuel to them. As a rule of thumb, 10% fuel will raise or lower the air-fuel ratio by a full point.

So now that the car is running right, doesn’t knock, and has a nice flat air-fuel curve, how can you make sure you have the most power? For that you still need a dyno. Once on there, you’d do a base run to establish baseline power and torque, then start experimenting. For example, you could use the K-Manager software to increase spark advance under full throttle by two degrees and then do another dyno run to see if power increased without engine knock. Or you could test your theories on cam angles by increasing or decreasing the cam angle at full throttle between 5000 and 8500 rpm and then check the result. Numerous K-Pro users have done just that and found a bunch of "free" power.

How would a professional tuner use the K-Pro for an engine where no preconfigured calibration exists? He’d likely start with a calibration that comes relatively close. For example, a calibration for a GReddy turbo installation with 7 pounds of boost and 550 cc injectors could likely serve as a starting point for another manufacturer’s turbo with 11 pounds of boost and 650 cc injectors. For a really comprehensive tune, the tuner would then use the K-Pro software to first set all cam angles to zero degrees and dyno tune fuel and ignition for best power. He’d then do the same for cam angles of 10, 20, 30, 40, and 50 degrees. Then he’d overlay those six power curves and construct a composite curve that consisted of the cam angles that make the best power in each rpm range. And don’t forget, he needs to do that for both the low and the high speed cam. Using this very technique, Hondata has managed to find plenty of extra horsepower in a variety of normally aspirated and forced induction cars (see the Hondata website for examples).

Does the K-Pro system work with nitrous or even alcohol? Affirmative. There’s a special control panel for nitrous applications. You can use it for arming nitrous, you can set minimum and maximum rpm engine load, throttle, and vehicle speed for nitrous to engage, and you can determine ignition retarding and fuel enrichment during nitrous runs. Nitrous has never been safer.

So what’s the bottom-line of Hondata approach of adding programmability to a stock ECU?

There are many advantages: since it is a stock ECU, around-town drivability remains first rate, the ECU is proven and reliable, and it can always be "detuned" back to pretty much the stock configuration. The Hondata K-Pro upgrade is also a lot less expensive than replacement third party ECUs. Its datalogging is sensational as is the ease with which you can reprogram your ECU to get every last bit of power from your engine, no matter how many additional modifications you add.

Are there disadvantages? None that matter to most Honda enthusiasts. The K-Pro is not a real-time system like the much more expensive third party ECUs from the likes of MoTeC or Autronic. Instead, you make changes, then upload them into the ECU. And since it is still a Honda ECU with most of its Honda programming intact, there are areas that cannot be controlled with the Hondata software (yet).

All in all, the K-Pro is a terrific engine management tool that has quickly acquired an enthusiastic following among K-Series owners. It’s truly tuning 21^st century style.

Conrad H. Blickenstorfer is a writer, car nut, enthusiastic K-Pro user, and moderator of the ECU Tuning and Supercharger forums at ClubRSX.com.