Doing a bit more testing and some of those 6 engines exploded so...yea :X Looks like it can keep 3 combustions topped off, but struggles with the 4th, gonna see how that compares with than autarchic gate sending out pulse + signal to 4 redstone engines.
Edit: After a bit of running the gate and four engines are struggling to supply the 4th combustion engine as well, so we can say that one Accumulater is pretty darn effective to say the least. Also, just built an incredibly silly water tank made of about 84 accumulaters. Now to find a way to pipe all that water out and use it :X
Second Edit: And now that same setup is feeding 6 engines easily...I hate these kinda things sometimes -_-