by How much is the stock ECU capable of adjusting its map for different amounts of airflow and fuel requirements? If I have IXIL no-cat Race header pipes, Yoshi muffler, PAIR system removed, and airbox modified with K&N air filter installed - Do you think the stock ECU could cope with these mods, or will I be running dangerously lean fuel mixture? I currently have the O2 sensor removed and bypassed by way of a resistor plug on the loom, but I get the feeling I should install the stock O2 sensor into the IXIL headers to let the ECU read whats going on down there.... Your thoughts and advise please. thank you, Grant.E (NZ)
Based on what I have seen on the very dynojet graphs which show AFR, and what I've read from tothezenith's dyno feedback the stock ecu runs nicely rich @WOT. However you currently have disabled its auto adjusting capability by cutting/faking feedback to it. An ecu allways looks for a fluctuating signal from the O2 sensor - so a simple resistor ladder will not result in ideal running conditions on the long run.
Before going further it is important to understand how the ecu operates.
In closed loop mode there's no other way, but the O2 feedback have to altered. For this the best method is a WideBand O2 sensor with a controller what has an adjustable simulated NB output. This can properly give real time feedback to the ECU and can be set for your general AFR target.
Open loop can be adjusted by piggyback controllers - as unfortunately the Honda ECUs are well protected - so apart from a few HRC models and earlier ECUs I'm not aware they could be flashed unlike KTM or some Yamaha ones.
Now. The fact is, that if it is a race only bike it will operate in closed loop mode only very briefly anyway so that part is less interesting.
Depending on your budget there are a few options.
Best results can be reached for a competition only bike by buying a piggyback controller and getting a base program during a dyno session. And have a logging capability with an WB O2 sensor to be able to adapt to local conditions if needed (eg. grat elevation changes, humidity, temperature).
Budget option is a stock NB O2 sensor with an acfive EFIE what can offset the 02 signal line towards the ecu to cheat it to a bit richer operation. It does not directly alter open loop operation, but you have use the bike every now and then in a "civilised" mode around the track so the fuel trim tables get populated and adding a bit of an extra fuel to Open loop operations also.
For piggyback units there are three major options;
The Bazzaz ZZ-Fi & Power Commander V are majorly the same, both have logging and self mapping (extra cost) functions, both handle ignition tweakingband allow gear based trimming also. Very advanced stuff but costs an arm and a leg.
EJK from Dobeck unfortunately no self mapping feature (their AFR+ which is a fuel controller linked to a Wideband controller is not available for the 500 series as far as I know), and completely different setup and logic. More like an Electronic Jet Kit (as the name implies) so one can adjust three major areas idle, cruise and WOT and transitions (like float level, main and accel jet in a carb) to alter fueling. No logging, no ignition, but half the price.
I've bought my PCV second hand - it is rare and one needs to wait quite long time for one to drop, but it can be had for significantly less than new. Also Im using a wideband controller what I've built (I'm a recovering electrical engineer, but even I would not build the next one, but buy a second hand WB2 or similar) with a heated bosch 4.9 WB O2 sensor.
I'd recommend the PCV simply because more tuners know it and it has a higher chance to be available used - and as Tothezenith has done some pioneering work - you could use his flash as a baseline.