Discussion and questions related to the course EFI Tuning Fundamentals
Hi got a haltech elite 2000 with a wideband CAN controller all set up downloaded base maps for an rb25det which is slightly modified with 850cc flow tested injectors with dead times, splitfire coil packs, high mount turbo and a front facing intake manifold. Iv got the car to start and idle fine when cold but then the car will start hunting for idle once at temps over 70 degrees C. When I pulled a bit of timing idle came fine and correct but then AFRs were reading very low about 11 I had to turn the STFT off or it would start hunting again but soon as I'd add fuel to bring my AFR close to 14 it would start hunting again. Also my o2 STFT % would read -20 so it wants to pull lots out which im scared will make it very lean. Do I need to recalibrate something? Any help would be great thank you :)
If your Air to Fuel Ratio is 11:1, then to get to 14:1 you want to remove fuel, not add fuel. That is what your Short Term Fuel Trims were doing as well. Sounds like your fuel table is too rich, or your airflow at idle is too low (is there an idle air control that might be too closed because it trying to hit a low RPM with too much ignition advance?)
David is on point with that one.
I would add that running lean without load isn’t detrimental to the engine. It’s highly application specific but idling at 15:1-15.5:1 should be fine - the OEM would likely run leaner than that.
It’s good practice to limit the variables with idle tuning meaning using a flat value for ignition and fuel maps across the zero load sites. Try an ignition value of 0 to -10 and fuelling wise make use of the idle functions within the SW, there’s usually an offset or multiplier based on temperature or time since engine start etc.