Some of you guys may be interested in about the findings of reading the hayabusa ECU program and bench testing of Busa K5/K6 ECU...
First of all the busa ecu is from factory a map select switch ready, even though there is no difference between the maps loaded in the ECU memory. You can start using the second set of maps by grounding the pin 21 on the harness connector - no magic, just a simple switch.
Inside the ECU there is an ignition map for 1st, 2nd 3&4 and 5&6 gears. This enables setting a different advance for 1st and second gear for better 60ft times ... the map is split between two banks, inner and outer cylinders. For neutral/clutch there is just a simple RPM based map for ignition advance. E.g. with TRE you just use the 5&6 ignition map which is very different to other maps particularly at part throttle areas. There seems to be much more advance on 5&6 map at very small throttle openings where as with other gears it looks like they had reduced the advance, maybe to avoid knock or just keep the front wheel down ? What ever the case, this looks like an area for optimization. With more than 10% throttle opening (30% total TPS voltage) there is not much difference, even though it looks like the top gears runs just a bit more advance even at full TPS/RPM.
For fuel, there is a separate map for each of the cylinders. (and a second set of maps in case you decide to install the map select swithc). Additionally there is a lot of other sensors affecting fuel delivery including injector opening time compensation based on the engine voltage or outside air temperature.
Then about the mystery of ramair compensation. There is actually two sets of ram air compensation maps. Normal load map for all gears 1...6 and a high load map for 3,4,5,and 6th gear. The total difference in injector pulse at around full throttle and 9krpm is about 0.2-0.3ms (have not had equipment to get exact figure). At 9krpm the injectors run around 10ms so its 0.2/10, i.e. compensation is 2-3%. For you guys who run TRE and dyno at 5th or 6th gear this means that your engine is about 2-3% too lean at LSR events (200+MPH). Suzuki seems to consider that anything above 56% TPS (voltage) or above 8000 rpm is high load.
Regarding RPM limiters, there ECU is limiting the 6th gear around 10050 rpm. Normal RPM limiter being at around 10800 and clutched being around 10500. The interesting thing is that there is three sets of limiters. The normal RPM limiters, Gear specific limiters (for top speed limiting) and third set for which I have not yet found a purpose. The maps maps run to about 13.000rpm and ingition maps even a bit higher. So it looks like the ecu is able to run up to appr 13k just by changing the limiters alone. Well done Suzuki for thinking in advance ... this is something I will certainly look to benefit for next season...
Then something more contraversary... Then there is an interesting issue of error codes to be looked more in detail if its just my mistake or something more. A misaligned IAP sensor produces an Ambient pressure FI code and Ambient pressure sensor fault produces an IAP sensor fault code. These two sensors work together. Anyhow it is certain that the ecu calculates the pressure by first measuring the ambient pressure and then reducing the intake pressure from that figure. Based on the result of that calculation the fuel delivered to the ECU is calculated. And then bad news for you guys running powercommanders and alikes. The fuel is always calculated based on the pressure, there is no TPS limit after which the pressure is not anymore taken into account. In practise this means that a TPS based fuel adjustment computer (a piggyback unit) will not be enough for compensating the fuel loads needed for various conditions. Its possible to dynotune something that works very well with fast acceleration on track, but that may not anymore work well under normal driving conditions - and vice versa. This may well explain why some persons are complaining a poor driveability on the street with bikes performing very well on the track.
The above applies only to 2004-2007 busas Euro and USA. I dont have a commercial interest in any of this so the above is just my personal opinion based on what I have learnt by looking inside the busa ecu. Something to be shared to make our bikes run stronger and faster on track...