Apologies, I should have annotated the thing. There's a small port that's exposed when the outer pintle pushes forward. It'a in the sketch ,but easy to miss. I see no reason why, instead of having the chamber integrated with the injector, you can't branch it off into a hydraulic passage with a one way valve... so as soon as the injector opens a remote pre-chamber gets fed. There's another one I have that uses one driver that reverses direction to essentially do the same thing. (I have no idea if that's possible)