Quote:
Originally Posted by greasemonkee
According to Recardo's studies, peak thermal efficiencies generally occurred at about 15% lean which would put the AFR at roughly 16.9, that is to my knowledge, a typical number and is due solely to the fact that combustion temps are colder. Any leaner and flame speed drops off drastically.
According to Stone, highest flame temps occur just rich of stoichiometry, however, sufficient oxygen must be present for NOx to form so it occurs just lean of stoich.
Low ratios of EGR dilution significantly reduce NOx emissions. The catalyst is the booger, it must receive a burst of rich followed by oxygen; a continuous cycle.
 Credits to Toyota Motor Sales |
I've been wondering why an (older) EFI system switches between lean and rich fuel mixture instead of keeping very close to 14.7:1 ratio. (the 14.7:1 is said to be best for killing emissions) Is it because the control system is not capable doing it or is it for the catalytic converter that actually needs to have different poison after another poison to work properly? Not just steady mixture all the time?