This thread post is prompted by the 'melting pistons and lean fuel mixture' thread as it has mentions of plasma plugs and hydrogen which are things I have been thinking of lately.  

As a long lurker and, more recently, occasional poster; My impression of this forum, especially the automotive areas, is that you get well informed, zero BS answers.

Some background first.  I have a late 60's Triumph with a 2 litre, in-line, 6 cylinder, ohv engine.  I have modified this over the years and now run multipoint EFI and 3D mapped ignition controlled by Megasquirt. It also has a (fairly poorly designed) 6-3-1 extractor manifold and some light cleaning-up of the valve(Gauge Valves) throat areas, but no heavy porting. The bottom end is stock and retains the OE 270? duration camshaft.

It goes well enough and fuel efficiency in particular is improved from 28mpg (IMP) to 34.5mpg in mixed driving.  As the car gets used in endurance events and fuel is expensive here, I'm always looking out for ways of improving mileage though.  Couple of thoughts/questions:

First:
Recently I tried some 'plasma plugs' sourced from somewhere in Eastern Europe (They were free!).  These have an inner, partly enclosed chamber with the electrode sat down inside it and angled drillings through into this chamber. Presumably the theory is that the charge in the inner chamber lights first and burning gas is ejected at speed through these drillings and the centre bore, forming plasma jets to rapidly and completely ignite the rest of the charge. The hope was that I would be able to run far leaner in most areas apart from max load and rpm.  Initially results seemed good and I was able to take alot of fuel out of the map and acheive part throttle cruise at 17 - 17.5:1 afr (according to the on board wideband O2 sensor) before going flat and another .5 before lean hitching set in.  On conventional plugs hitching set in around 16:1.  However, at very light or trailing throttle it misfired badly and to eliminate this actually required more fueling than before in the relevent areas of the map.  The net result of this is actually worse fuel consumption under normal mixed driving conditions.  On a 2000 mile run earlier in the year we ran the first 1000 on the plasma plugs and the second 1000 on conventional plugs (with relevent map tweaks) returning 34.3 mpg and 36.7mpg respectively. My take is that although these plugs may be partly effective at medium and higher loads, they are actually poor at lighting very low density charges, probably due to the recessed electrode.   I've now gone back to my usual triple electrode Bosch plugs.  Has anyone experimented with this kind of thing or have any thoughts on the subject?

Second:
I was talking to a guy a week or so back with an elderly turbo diesel 4wd, who had a very doubtful looking 'coffee jar' electrolysis set in his passenger footwell and a pipe running the hydrogen and oxygen produced into the intake upstream of the turbo.  He swore blind that his mileage had increased from 28 to 65 mpg with this rig.  The shoddy nature of the conversion and the fact that he proudly informed me he was now going to plumb it in downstream of the turbo (how are you going to keep the lid on your coffee jar pal?!) made me dismiss the whole thing, although I must say that I was concerned for his personal safety! However, I did google it.  There are, of course, many similar claims out there, even one linked from this very site just now.  So, my question:

Is there anything to this? Could the "HHO" even in quite small amounts, aid efficiency by making previously unlightable AFRs ignitable and giving more complete combustion?  Has there been any real detailed work done on this that doesn't require $50 for 'the secret plans'?

So called "HHO" systems are efficient at only one thing ... fleecing money out of people who don't know enough about thermodynamics to realize that they are being fleeced. The claim being made is so ridiculous that it's not even worthy of comment. Wouldn't you secretly like to see what that guy's face looks like when his mason jar connected post-turbo-compressor blows itself apart ... ! ! !

Your experience with the so-called "plasma" plugs is much more worthy of comment. I'm not surprised to hear that this design required more fuel under conditions when the mixture is weak because of trailing throttle. There's too much heat loss inside that mini-chamber. It's also quite interesting that you were able to extend the lean-misfire limit. But, probably what's happening is that although it extended the lean-misfire limit, the shape of the combustion chamber probably isn't matched to the direction that those jets were aimed, so the burning rate was probably not optimum.

A sequential-injection setup with the injector nozzles aimed and timed to get a stratified charge, and inlet ports arranged to give good swirl (not tumble) during light-load conditions, would be interesting when combined with plugs like that. If done right, under light-load conditions, you could get the little chamber filled with a near-stoichiometric charge and lean everywhere in the main chamber.

Application of prechamber spark plugs to a specific engine is typically done in conjunction with flow field modelling, thermodynamic analysis, and engine mapping with in-cylinder pressure measurement; all for the purpose of seeking optimum prechamber plug design parameters, which include prechamber volume, electrode location, geometry, & gap, and orifice size, number & orientation.
Therefore,it is unlikely that application of an off-the-shelf prechamber plug design to an existing engine would be successful.

MORE NEWS