I was reading my web comics today when totally out of nowhere came the thought of reducing my NOx output on my hot rod without affecting my fuel economy, complete with graphs of NOx output over a range of fuel/air ratios and spark advances and NOx outputs compared to other pollutants (HC, CO, and CO2).
Basically NOx is the odd man out when it comes to reducing pollution. It is almost possible to get rid of everything except NOx with the same fuel economy tune and nothing else because what prevents making all the other pollutants is the ideal environment for creating NOx. What you need to prevent unburned HC and CO and to get best fuel economy is a high temperature combustion with excess O2. And guess what you need to make that nasty NOx that causes acid rain and smog? You guessed it, high temperatures and excess O2. And NOx is not just a progenitor for other forms of pollution but harmful in and of itself. That shit can burn the lungs, and irritate people who are already predisposed to breathing problems. I was exposed to high levels of NOx during industrial processes while I was in the electronics industry, I mean levels that were far beyond what you would see even on the worst days outside, and let me tell you that shit is NASTY!
So, what I can do is go ahead and tune for best fuel economy for part-throttle operation, best power for WOT situations, do an interpolation between the two with bias to fuel economy at lower power settings with a knee transition to WOT and a lot of transient enrichment to cover going between the two settings in a hurry. That covers the tuning. I would also need a reducing catalyst on the exhaust to take care of the NOx from the high temp modes the engine would operate in most of the time at cruise. Now the real fun part is getting a pair of those in the proper size for the engine. That will take more than a Google search, I’m afraid. Too big a catalyst would turn my CO2 back into CO and other pollutants, too small and it creates a restriction in the exhaust without cleaning up the NOx.
TBH I’m tempted to just tune for best economy and best power and just ignore the small amount of NOx I generate at best economy, because it’s just the one car, and I’m not required to meet any emission tests, but if I did that what kind of example would I be? After all transportation is the biggest contributor to the high NOx in the DFW airshed, but it doesn’t come from one vehicle, it’s the cumulative effect of millions of vehicles in the area. Even though my car would be exempt from pollution controls because it is a replica 1923 vehicle (kinda sorta) and I can almost eliminate my HC and CO emissions without a catalyst, I’m still going to install one to take care of my NOx.
So, how was your day?
Billed @€0.02, Opus the Unkillable