[brucepick]

I'm pretty sure that if you use custom ECU programming like MegaSquirt you can map your own rich/lean ratios. But you have to be pretty smart about it - too lean and you'll burn valves etc. I bet it can be done though.

The Honda Civic VX and the later Civic HX ('96 - '05) both had lean burn capabilities coded into their ECUs. I think some of the later Hondas also had/have lean burn but I can't say which ones for certain. I think Insight Gen 1 and Civic Hybrid?? Maybe others??

My own thinking is that lean burn lets you get max power out of a given qty of fuel because you're not sending a percentage out the exhaust unburned. Standard stoich ratio leaves some unburned fuel in the exhaust deliberately to keep the cat converter temp up - it combusts in the converter. The lean burn Civics keep the cat temp up by having the cat in the exhaust manifold (at least that's what my HX has) so it tends to stay pretty hot.