OK. This thread has been very useful to me, because I have to know when I am in over my head on something and this is it. You have saved me a lot of time failing. (It is clear that it CAN be done, just not by me.) Thank you.
There are pleanty of ways to time ignition using Electronic Ignition modules and clever placement of the sensor (which is really all I was trying to avoid.)
So, I think I'm going to scrap this idea and approach it more mechanically (precise PLACEMENT) instead of with software. (It'll be easier for me to fabricate metal than to write this program.)

As for your questions on Hydrogen...there is no free lunch unless you make Hydrogen using Solar...and that isn't free either. BUT, we make up a lot in EFFICIENCY as a product of our efforts. And figuring gas engines are VERY wasteful, there is a lot to be gained even though we have to make it (Hydrogen.)

I'll try to keep in touch. I'm sure I will have plenty of other practical or hair-brained ideas for a PIC to do...I think they are so cool!
Thanks again,

Chris