Quote:
Originally Posted by Ecky
I'll probably try running 18:1 in a few days. However, there's something to consider with leaner mixtures: ignition timing needs to change quite a bit.
When the mix is leaner, flame spreads more slowly. When timing is adjusted such that peak pressure is where it needs to be, a larger percent of burn will be before TDC or where piston angle is poor. The more I've read about it, the more it surprises me Honda was able to improve economy with ultra-lean burn. Maybe it was the lack of infinitely variable gearing, and lean AFRs were a way to virtually reduce displacement on demand.
In order to get ignition timing right without a dyno, I'll likely need to buy an exhaust gas temperature sensor.
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How important are such timing changes under light load? You are at like 20% load at 60 mph, right? Seems slight risk of problems under such conditions, no?