Twelve of the Alanchi air chargers, is an effective decent maximum for my engine compartment. I could put more on, but not neatly, and I don't want spaghetti-tangle, right now it's as close to that as I want to get. So one way or another, we have to have air charger units which put out more than the ones in use.
For just a few days on AliExpress, I did see a unit advertised as producing 125M/cm3, costing approximately US$15. (The current ones are rated at 30M/cm3.) This big one ran on 110VAC only, and I found myself pondering a VAC-->VDC inverter under the hood, wondering about heat tolerance. But it vanished from the web site within a few days.
So at least for now, my thought have gone to building my own. Here's the test rig:
The little black box on the left (notice the warning!) is an EMCO F40, a component which takes 15VDC input and puts out 4000VDC output: DC to DC, quite the neat trick, not sure how it works, but possibly perfect for this, because I was able to obtain several independent reports (reportedly born of experience) stating that to minimize ozone and maximize ionization, 4000VDC is the desired. The output is clipped to an Amstat Industries eight-inch carbon fiber brush, of a sort designed to take static charges off or out of things; kind of exactly the reverse of this application, but it seemed a good place to start, and Amstat was great to work with, unlike the other companies I tried to work with concerning carbon fiber brushes. The white block is craft foam I bought from Michael's, which tests as having a very high electrical resistance, for safety.
The real challenge right now is measuring results. There are very cheap devices being called "ionization meters" out there, less than $50, but in the multiplicity of reviews of them, I have yet to find a reason to think I should try to rely on them for hard results. There is a large jump between those and industrial meters measuring ionization of air; the professional ones with the needed capacity, seem to start at about $800 and go up quite a lot, and I cannot justify this at this time. However, researching a lot and asking people in the field, I learned that these air chargers are doing what they do as a result of something called "corona discharge", which exists as a result of an artificial static electric field. So I bought an Electro-Static Discharge Meter, which is much less expensive, and I am using it. I am definitely producing a corona discharge, negative polarity, and am working on next steps!