[dcb]

1. I don't hardly ever idle, so it isn't a question I'm terribly interested in. You get zero mpg at a stop with the engine running, and it is on the least efficient end of throttle positions.

2. re: deep cycle, just for experiments sake, sure. if you are just trying to see what hydrogen by itself does then get a tank from airgas or something, not sure how you are going to log/measure the hydrogen though, but you must account for it. You also must account for fuel used somehow, and I would suggest monitoring the injector over monitoring the obd port for accuracy. But of course that means you have more stuff to calibrate/double check/validate.

But if you are leaving the car alone, including o2 sensor, except for adding hydrogen, the injectors should show a lower duty cycle as the hydrogen displaces some fuel in combustion. It is very easy to say something works, it is a lot harder to prove it. But in the end, if the energy content of the added hydrogen was less than the energy content of the fuel no longer being added, then you are at least closer to something reproducable.

If you can dial in a repeated ABA testing at idle on a warmed up car under reasonably identical atmospheric conditions (and reasonable cost), then you will have some reference point as to the potential gains at idle. The next test would be to figure out how to test it under load.