The Bucket Foundry

[Grumph]

Wouldn't be HCCI then, would it?

Be a sort of glow plug.

Yes, but I'd argue it would still occur later than the "normal" spark ignition. And as i read it, it's the later ignition which is releasing more usable work.

Have i got that correct ?

[Ocean1]

Yes, but I'd argue it would still occur later than the "normal" spark ignition. And as i read it, it's the later ignition which is releasing more usable work.

Have i got that correct ?

Certainly less of an issue with det, but yes, supposedly more efficient combustion process, producing more energy per fuel unit.

[Flettner]

If exhaust gas recirculation causes HCCI in twostrokes ie hot exhaust gas can't get out in time so stays in to re ignite the next charge, then with turbo fourstrokes this could easily be achived by ECU turbo control of turbo back pressure and special valve timing, let the exhaust valve open just a bit on inlet cycle. So no need for fancy combustion chambers under the exhaust valves.
I don't think the piston on the piston is a viable/workable idea.

[Ocean1]

If exhaust gas recirculation causes HCCI in twostrokes ie hot exhaust gas can't get out in time so stays in to re ignite the next charge, then with turbo fourstrokes this could easily be achived by ECU turbo control of turbo back pressure and special valve timing, let the exhaust valve open just a bit on inlet cycle. So no need for fancy combustion chambers under the exhaust valves.
I don't think the piston on the piston is a viable/workable idea.

I thought the definition of HCCI inferred a compression high enough to auto-ignite the mixture throughout? In which case anything pre-igniting it locally isn't HCCI?

I was suggesting a small blind cavity in the main piston. Possibly hemispherical. And a corresponding piston in the head, moved vertically so as to control compression, and therefore ignition.

Fewer mechanical issues with both alignment and room to actuate the small piston. Might look a bit too much like a 4T for this crowd, though.

[TZ350]

Could the smaller HCCI piston be operated with a cam and spring like a poppet valve, that way the movement of the piston does not have to be linear. The rate of acceleration and compression could be very rapid and the timing of the event altered on the fly like the valve timing in a Vtec engine.

[Ocean1]

Could the smaller HCCI piston be operated with a cam and spring like a poppet valve, that way the movement of the piston does not have to be linear. The rate of acceleration and compression could be very rapid and the timing of the event altered on the fly like the valve timing in a Vtec engine.

Yes. Or with a solenoid, or pneumatics, which will do whatever the ECU tells it to.

Is there a way around the need to have the engine run non- HCCI speeds/load? Seems like that's where most of the tuning issues may come from.

Maybe we could have an "electric transmission". Engine runs at 17K rpm, (or whatever's needed for HCCI) and drives a generator which feeds a motor which drives the rear wheel. Add a battery/capacitor just big enough to dampen down the all or nothing engine output. In fact you might have to shut the main engine down on the start line, use the battery to drive it off the line until 1st gear gets the engine up to minimum HCCI speeds, turn on the fuel and away...

[Flettner]

The cam idea would be possible (if one didn't hate cams so much) but yes strict sense HCCI is compression based but I guess that covers anything not spark plug or direct injected. I just like to use timed high compression as it does not rely on hot previous gases so will start cold and run at any rpm without a spark plug, under control, although you wouldn't think so by the video
Right, lets start putting some of these ideas into practice, anyone / everyone.
I'll have the AG fitted up to the dyno next week (thanks to Drew and the clutch).

[Ocean1]

Right, lets start putting some of these ideas into practice, anyone / everyone.

Too busy with work.

I'm only here now because I'm boring something in the lathe that takes 8min per cut.

...And I'm outa here.

[Ocean1]

I was suggesting a small blind cavity in the main piston. Possibly hemispherical. And a corresponding piston in the head, moved vertically so as to control compression, and therefore ignition.

And thinking a little more clearly: there doesn't have to be any cavity in the main piston, does there?

The "compression-enhancing" piston can simply move out to flush with the rest of the combustion chamber, rapidly, a degree or so past tdc

[Grumph]

Like Ocean, thinking while working...this whole HCCI thing in the applications it's reputed to be appearing on would seem to be rpm related.
The Ryger (sorry for mentioning it) would seem to have an upper rpm boost of some kind - which does not seem to be included in customer engines,LOL..
And the F1 engines may actually be using it to beat the mandated RPM limits of the common software they have to use now.
If some time this F1 season there is a shitfight about the leaders using too many revs, we may find out.

Edit - if it's being used in F1, no reason it can't be used in MotoGP - except they make too much power now, so we probably won't see it.

[eldog]

Too busy with work.

I'm only here now because I'm boring something in the lathe that takes 8min per cut.

...And I'm outa here.

Need a bigger lathe? Almost a tip edge per cut?

[eldog]

Since it's a racing engine why not a flexible end to the piston, much like a pressure Flexi disc.
a separate internal piston may have a problem with guidance length vs diameter.

recess the exhaust valves to create a space to not all is exhausted

race engine only has to last a race not a life time

[Ocean1]

Need a bigger lathe? Almost a tip edge per cut?

Lathe's big enough, what's taking the time is using a 25mm boring bar 300mm long in 420 stainless.

Bloody noise is still in my head...

[Drew]

Since it's a racing engine why not a flexible end to the piston, much like a pressure Flexi disc.
a separate internal piston may have a problem with guidance length vs diameter.

recess the exhaust valves to create a space to not all is exhausted

race engine only has to last a race not a life time

Haven't they got some gay single motor per round rule?

[Frits Overmars]

if the plug was in the centre of the head, it’d be in the middle of the supposed HCCI chamber.

Top view of a Formula 1 piston. The head looks the same, only mirrored: all cluttered up with valves. There's barely room for a spark plug, so forget a second piston in the head.

as i read it, it's the later ignition which is releasing more usable work. Have i got that correct ?

More or less, Grump. The later ignition has the advantage that there is less pressure on the piston before TDC, so that yields some power. This later ignition is made possible by the much faster burn in a HCCI process. But the main advantage of HCCI is that there is spontaneous combustion all over the place, without the need for a flame spreading outward, starting at the spark plug.
HCCI will tolerate mixtures that are too lean or too rich for a flame to spread, and it will consume all the fuel (if lean) or all the oxygen (if rich) present.

supposedly more efficient combustion process, producing more energy per fuel unit.

Not more energy per burned fuel unit, but all units really do get burned; spark ignition leaves something to be desired in this respect.