This question is for whoever can field it:

Regarding engine operation; there are a lot of youtube videos (as well as other HHO site resources) that state that igniting HHO in the cylinder causes a suction (implosion) and therefore pulls or sucks on the piston and draws it towards the cylinder head. 

Its all about spark timing and wasted spark (for two strokes).
try this:
http://www.free-energy-info.co.uk/Chapter10.pdf
Page 50, amongst others.

I think this business about HHO suction is a bit ridiculous.

Obviously the density of water H^2O is greater then the
density of HHO per unit volume simply because HHO is a gas.

So you are going to get suction if you burn a stochiometric
amount of HHO. There no equivalent setup when you burn
hydrocarbon (unless you burn a CO carbon monoxide plus
hydrocarbon fuel mix - and then please, not around me).
There is no preliminary to CO^2 gas, it's all emitted.

Air, on the other hand, is 70% Nitrogen and except for very
small amount of nitrogen (forming the pollutant NOx) the
nitrogen gas is almost like a noble gas to the combustion
process. It simply passes through the combustion reaction,
but is does interact as a perfect gas volume to heat in
the Carnot cycle. But ICE engines have design
parameters to breath air!, so getting a small amount
of suction is to be expected if an ICE engine gets all of it's
energy from Hydrogen...and a larger amount if it's not
allowed to breath any extra air along with the the HHO.
If you don't like it, then design your own pure
hydrogen+oxygen stochiometric mix fuel powered internal
combustion engine...you will need to anyway, if you want
reliable long term operation.  As I've said previously I know
what I am saying is correct because you never hear of a
pure oxygen aspirated engine. Nitrogen must add something,
even if it just slows down the combustion process because
it forces the combustion to scrounge oxygen and I think that
something is the perfect gas volume from heat temperature
conversion.

So yes there is suction on the exhaust cycle which cools
the engine down...that's is why it makes some sense
to use hydrogen as an additive to hydrocarbon fuels.
And if mix is done via a computer to have it look at
engine temperature when determining the mix. Pure
hydrogen pulls the engine temperature down and
hydrocarbons could boost it back up. That's why during
WWII there was a "War Emergency water injection
switch on certain ICE fighter aircraft". One switched it
on to increase performance but it also tore the engine
up, so it was not used long term.

:S:MarkSCoffman