Quote:
Originally Posted by mpg_numbers_guy
Best BSFC for acceleration and lowest RPM for cruising, right. The Fit auto has neither so that's probably why it performs worse.
Any wild ideas of lean burn tuning on the Fit after the Insight is done?
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I don't know if it has a narrow or wideband O2 sensor. You need a wideband for lean burn, and most will only go out to 18:1 or 19:1 reliably. You could, hypothetically, intercept the O2 sensor wire and change its resistance value to lean things out, but you'd need to make darn certain it only happens at low throttle and load or bad things can happen.
Just leaning out the motor is very suboptimal though. A lean mixture burns slower (slower flame front) so if ignition timing isn't advanced a lot, the piston would simply outrun the kaboom and your economy might get worse rather than better. To adjust ignition timing you need a programmable ECU, which means either custom (you'd probably lose gauge cluster operation) or something like Hondata's FlashPro:
https://www.hondata.com/flashpro/flashpro-fit
^ It's not as powerful as a hardware solution but you can edit a
lot of engine parameters anyway. Dunno if you could make a wideband work if the ECU doesn't naively support one.
Edit: confirmed Fit has a wideband.