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article details
Author WongKN
Categories Performance Parts, All Honda/Acura, TOV World
Create Date August 01, 2000 00:00
Last Update April 30, 2002 01:04
Hondata ECU Analysis

Hondata ECU Analysis

Honda's PGM-Fi is world-famous. Created and perfected through years of top-level racing, including six years of total domination in Formula-1, PGM-Fi is crucial to the ultimate performance of Honda's super high-performance cars. Because PGM-Fi is an integral part of the entire engine package, enthusiasts who modifies their Honda should keep PGM-Fi and ensure that it is able to handle the new fuel and ignition needs. In stock form, PGM-Fi is able to handle the milder mods. But for heavier mods especially serious engine works like wild camshafts, stroke-up, and forced induction, fuel and ignition requirements become more than what PGM-Fi can handle in stock form. The solutions so far are complex and expensive. They range from add-on injectors and controllers, piggy-back fuel and ignition computer systems, and even straight replacement ECUs. But the best form of fuel and ignition control still remains PGM-Fi. Can anyone actually do better than Honda?

Cracking PGM-Fi

The idea has been floating around for a long time though its implementation is not as straightforward and simple as it seems. This is the idea that since the stock ECU is in actual fact a microprocessor based computer, and thus PGM-Fi is actually a program, it is possible to de-assemble this program, ie PGM-Fi, and once having gotten access to the assembler codes, one can then endeavor to understand the working logic and consequently attempt to modify or even to improve on it.

Things are of course easier said than done and I myself am aware of many people who have been trying to do this for many years. Earlier pre-1990 PGM-Fi's were written using a set of INTEL-compatible instruction set. Zdyne have reverse engineered these earlier Intel-based ECUs and there are in fact many development tools for it. But Honda changed to OKI microcontrollers since the late 1980s, starting with the VTEC models. So, the instruction set became proprietary. This made it difficult to derive the program logic. In addition, a program is actually made up of instruction codes and data. Now, there is no easy way to separate the data from instructions in the de-assembled codes. And even if they are successfully separated, it is still no mean task to decipher what the data means and how they are used. Most importantly though, thinking about actually 'improving' the logic of PGM-Fi will certainly be delusions of grandeur. Honda evolved PGM-Fi over many decades and fine-tuned it in their race-cars. This includes the winning Formula-1 McLaren-Honda cars in the late 1980-early 1990s, the TAKATA-DOME/CASTROL-MUGEN NSX'es that is currently dominating the all-Japan GT-Championship as well as the current F1 season's BAR/Honda and Jordan/MUGEN engines. Look at this list. The question begs : how can one actually think of doing better than Honda ?

HONDATA is a brand new product from New Zealand. When its founders Doug Macmillan and Derek Stevens first approached me some time ago, it was for the purpose of eventually announcing their achievement to the whole world and that is they have finally done what others couldn't do. They have 'cracked' the PGM-Fi code and now, their work is finally available to the world.


While cracking the PGM-Fi code is what I would rank as one of the most significant feats of recent times with regards to our ability to modify our Hondas, more importantly, it is after cracking the code that the real difficulties begins. Doug and Derek took what I would call the 'sensible' approach after they have cracked the PGM-Fi code. The source of their approach actually stems from their own requirements - Doug and Derek each races their own EF-CRX in New Zealand. So, what they did was to leave the actual logic of PGM-Fi alone and only to add new functions on top of it, functions which enhances the car -and tested- in their races. They also decided to make their work available to Honda enthusiasts by marketing it under the HONDATA brand-name.

HONDATA was initially available for the PR3/PW0 ECU used in the EF8/EF9 Civic/CRX SiR and DA6/DA8 Integra XSi/RSi but just recently also became available for the P30 ECU used in the EG2, EG6 and EG9 CRX DelSol/Civic/Civic Ferio (and the US domestic market's Del-Sol). Hondata will also be available for the P28 ECU used on the USDM Civic EX (1.6l SOHC VTEC). Hondata uses the base PGM-Fi codes and data at the minimum, and add varying degree of modifications and new functions on top of it. As explained, these functions are derived from actual racing requirements and experiences.

The HONDATA Approach

The PR3/PW0 ECU 1 - microprocessor, 2 - 256 ROM

Hondata is based on modified PGM-Fi, ie Hondata modifies both the codes and the data. But Hondata limits the code modifications to only the bare minimum necessary to implement its unique new functions. This is the most important and powerful feature of Hondata. PGM-Fi and the stock Honda ECU is an extremely powerful computer and is very flexible. The most important components of the stock Honda ECU are the main microprocessor chip (typically OKI or NEC) and a program chip, a 256Kb ROM. The 256 ROM contains the PGM-Fi codes and data. These data will be the fuel and ignition timing maps together with various operating parameters. The main ECU motherboard of course contains a lot of other circuitry, including a 'limp-home' mode back-up processor. The ECU also regulates accessories such as air conditioner and alternator to keep battery voltage constant and is programmed for tasks like " open idle speed control valve when air conditioning on". Replacement computers have very few of the wide range of functions, refinement and emissions the stock computer has. This is why Hondata have chosen to reprogram the stock computers when adding their new functions. As Doug explained to me in very clearly, the stock Honda ECU is extremely complex and is top-notch. Expecting to replace it is a fool-hardy endeavor.

Thus the HONDATA mod is based on (for the moment) a 256 EPROM (28pin DIP) which is an exact replacement for the stock PGM-Fi ROM. It contains exactly the same base PGM-Fi codes and data except for a minimum of codes modification for adding new functions. PGM-Fi stock size is below 256KBytes so it does not completely fill up the 256 chip. HONDATA utilized these empty slots to add codes that works in conjunction with PGM-Fi codes to implement their functions. Most of these functions makes use of an additional interface card. This card connects to the ECU via a 4-pin connector that will have to be soldered onto the ECU's motherboard. Interestingly the PCB for the PR3/PW0 ECU already has tracks for this connector, properly hooked up to the microprocessor and other circuitry. So installing the connector for the interface card merely entails soldering it onto 4 already available solder pads on the motherboard. It's almost as if the stock ECU were designed with the kit in mind...

The HONDATA Product Catalog

Doug and Derek currently markets Hondata in four stages, each with varying amount of functions added in.

Stage-1 is the simplest variation. A stage-1 HONDATA PGM-Fi chip contains the exact stock codes and data but with the logic to enforce the standard 180kph speed limiter bypassed. Thus a HONDATA equipped EF8 will work exactly like the stock car but will be able to accelerate beyond 180kph. An additional feature is that the check engine light will flash at 7600rpm and serves as a shift-light. Finally, the rev-cut which is around 8100rpm stock is moved slightly higher to 8500rpm. The Stage-1 package comes with a properly programmed PGM-Fi 256 EPROM and a high intensity red LED (with wires and connector clips). This LED is meant to be spliced into the check-engine light wire and a relay wire in the ECU wiring harness and will be able to function as a super-bright shift-light that can be located at any location convenient to the driver.

Stage-2 adds the capability to dynamically change three useful rpm points. The interface card is introduced in this stage and the 4-pin connector will need to be soldered to the ECU motherboard for hooking up the card. This interface card also has a connector for a push-button and this is used in conjunction with the foot-brake for the custom rpm changes. The rpm points that can be changed are the VTEC changeover, the shift-light, and the rev-cut. Each rpm point can be changed to any value, with a resolution of 100rpm, within a sensibly imposed range. Eg, the rev-cut rpm can be changed from 5000rpm to 9000rpm (the range higher than the stock limit will be changed at the owner's risk !). The changed data are stored in the interface card and the RPMs can be changed using either a dynamic method (with engine running) or static method (with engine off but ignition on). An additional feature in Stage 2 is the air-cond cut-off function. Codes are added to PGM-Fi that switches off the air-cond compressor clutch when the engine revs are above 5000rpm or the throttle is pushed beyond 50%. What this does is to automatically disengage the air-cond for high-throttle sprints and automatically re-engages it when the throttle is released - without intervention from the driver ! An extremely intelligent function.

Stage-3 is where the serious stuff comes in. Exploiting their racing experiences, Doug & Derek added two new important functions in this stage. The first is the 'full-throttle shift'. Full throttle shift is where one keeps the throttle pedal bottomed (ie WOT) when executing a gear-shift. For the uninitiated, this can be a rather unsettling experience since the engine will bounce wildly against the rev-cut once the clutch is disengaged at red-line for the gear shift. A shock always follows when the clutch is dumped back on after the gear shift since the engine rpm is now incompatible with the speed & gear the car is travelling at. Hondata's full-throttle shift introduces a new refinement to this process. Using a special switch that is attached to the clutch pedal, Hondata implements a lower rev-cut when the clutch pedal is depressed. This new rev-cut is usually set at around 6000rpm, ie the rpm point at the next higher gear which corresponds to the red-line rpm for the current gear. What happens at WOT and clutch disengagement is now the engine will bounce against a lower 6000rpm. This allows smoother shifting to the next gear since there is a better match of rpm against gear speed. More importantly when the clutch is dumped, what happens is a very smooth engagement since there is near perfect match of rpm and speed for the selected gear.

Building on this function, Hondata Stage-3 also implements a full-throttle launch control. For standing start drag races, experienced drivers will be well aware of the difficulty at having to modulate the throttle in order to maintain the correct launch rpm. Then when the clutch is engaged, one has to quickly dump the throttle so as to avoid bogging down. Launch control is a variation of the full-throttle shift. When the car is stationary, Hondata actually implements a second, separate rev-cut on the engine when the clutch pedal is depressed. This second rev-cut limit is set initially at 3000rpm, which is very optimal for launching B16As. So, with clutch disengaged, one can be at WOT and the engine will be bouncing against the 3000rpm point. Launching is now simply dumping the clutch. For stock B16As, minimal wheelspin will occur and the car will quickly hook up. There is no need to modulate the throttle, the right foot is fully against the floor all the while.

The interface card for stage-3 now allows modification of two additional rpm points. These two are for setting the rev-cuts for the full-throttle shift and the launch control respectively.

Hondata's ROMEditor (low cam ignition map in 3D editing mode)

Stage-4 is for the serious enthusiasts and is also what a Hondata dealer will be equipped with. Stage-4 Hondata adds a ROM editor and the HondaLogger. The ROM editor is a windows based editor that allows the fuel and ignition maps in PGM-Fi to be customized (attempt only with the help of a dyno and accurate wide-band air-fuel ratio sensor !). Various other important parameters are also modifiable using the editor including idle speed, VTEC changeover, air-cond cut-off rpm, etc. There is also an injector modifier value, something new introduced by Hondata. This modifier is used for injector sizing. The stock PGM-Fi fuel maps are calibrated for stock injectors. Any attempt to obtain greatly higher power (20% and higher) and the injectors will need to be changed to larger capacity models. When this is done, the fuel map values are no longer useable since they are opening durations for a lower flow rate injectors. Running in this condition will cause the car to over-fuel and lose power. The modifier value is used as a global multiplier to lower any values read from the maps by a fixed factor to account for the higher flow rate of the new injectors. A brilliant feature !

HondaLogger's digital dash

HondaLogger is a windows based software that communicates with the Hondata Stage-4 modified PGM-Fi program via the interface card. This interface is through the serial port. The Logger records and plays back practically all the engine sensors that the ECU reads, including the O2 sensors, air-temperature sensor, even the knock sensor (available on the 1st generation B16A). All data captured are recordable onto a file. But there is also a 'digital dash' which is a windows-based program that dynamically displays all recorded sensors on a specially designed 'dashboard'.

Stage-4 would be invaluable for the enthusiast who is forever modifying his engine. However, for those who does a one-time big project and then basically leaves the engine alone for long periods of time (typical of most of us), an alternative would be to purchase a Stage-2 or Stage-3 Hondata chip from a Hondata dealer who would be able to supply it as a complete package together with dyno-tuning. Thus the extra cost of Stage-4 which is due to the ROM editor and Logger can be used instead to partially pay for the dyno-tuning, to set the custom maps.

The Boost Option

However, what I would consider the most significant feature of Hondata would be the Boost Function. As most enthusiasts might know, when turbo-charging or super-charging a Honda engine, the ECU will throw a check engine condition and go into the back-up mode when boost is reached. The reason for this is because the fuel and ignition maps in PGM-Fi are calibrated only up to atmospheric pressure since Hondas are generally NA. Thus as a safety check PGM-Fi has codes to check that the MAP sensor signal is within operating parameters which is about -700mmHg to just slightly above 0-bar. If the MAP signal goes above 0-bar, Honda coded PGM-Fi to go into back-up mode since such a condition for the stock engine will mean a defective MAP sensor.

Pictorial representation of stock PGM-Fi Hondata PGM-Fi with boost option

Hondata deals with this condition in a very unique way. First Hondata added new fuel and ignition maps into PGM-Fi, utilizing the empty memory slots left in the 256 ROM. Next the upper limit for the MAP sensor signal is moved to a higher value at 0.9 bar of boost. The new maps are of sized to accommodate this amount of boost, with resolutions of approximately 0.1 bar. Along with moving this limit, Hondata changed the codes so that when the MAP sensor reads boost, PGM-Fi now refers to the new boost maps for the injector and ignition timing values.

The full-throttle shift function available in Stage-3 will be extremely beneficial for a turbo-charged or super-charged Honda since it functions as an anti-lag device. The ability to keep the throttle fully floored keeps the turbo or super charger spinning at speed and maintains boost to the engine even during gear shifts. This is an extremely powerful function.

Thus with a single code mod, Hondata has created a PGM-Fi program for forced-induction - Turbo-charged and Super-Charged Hondas ! Fuel and Ignition needs for turbo-charging our Honda are now met by simply adding a Hondata PGM-Fi ROM with the Boost Option. A Hondata equipped turbo-charged Honda will have absolutely no mods to the MAP sensor, wiring harness or the ECU. The only change, which will not be always visually obvious, would be a new 256 EPROM and the interface box.

Getting Hondata for your car

Readers who are interested to learn more about Hondata should visit the Hondata Web-Site . The site has more detailed information including descriptions of the 4 stages. An especially worthwhile section to go to on the site would be the Downloads where readers can download working demos of the HondaLogger and ROMEditor to play around with. There are also sample manuals and brochures in Acrobat format (PDF files) and even some videos, including the one where Doug launched his CRX to the New Zealand 1.6l class land speed record (240kph).

Readers with heavily modified Hondas must seriously consider using a Hondata chip for their fuel and ignition timing management needs. There are two ways to get a Hondata chip. One method would be direct ordering from the web-site. Detailed instructions are available on the site and payment can be made via credit card though Doug and Derek have not yet implemented the secure web store. A much better alternative in the near future would be to get a chip from a Hondata dealer. Hondata is currently evaluating and establishing a network of dealers to market their product. Note that Stages 1 to 3 contains only the stock fuel and ignition maps. Enthusiasts who are considering a modified PGM-Fi ROM will almost never have a completely stock engine. Thus modified fuel and ignition maps would be certain requirements from Hondata chips. These are available from Stage-4 but, especially with addition of the Boost function, it is an expensive option. Furthermore Stage-4 will require professional dyno-tuning in order to properly modify the maps.

The option of getting a Hondata chip from an approved dealer is the best way to get customized fuel and ignition maps together with the functions desired but without the expense of getting the full-blown Stage-4 chip. Furthermore Hondata dealers will be knowledgeable in modifying Hondas. They will of course be equipped with the ROM-Editor and the HondaLogger and will be able to arrange for proper dyno-tuning sessions to customize one of the 'lower' stages, either Stage-2 or Stage-3 (Stage-1 does not come with the interface card so will not be offered with customized maps).

Most enthusiasts with modified Hondas would go for one or two turn-key projects done individually over a period of time. The key requirements for us would be driveability and to enjoy the car. Getting a Hondata chip from an approved dealer would be hassle free with minimal mods to wiring and ECU, and will be the best option for such requirements. Enthusiasts on the other hand who regularly modifies their engine will want to get the full blown Stage-4 Hondata chip. Whichever way an enthusiast goes, the Hondata chip provides the ultimate in flexibility and power for modifying our Hondas.

August 2000
Temple of VTEC Asia.

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