Head swap, Hemi for torroidal
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a blank bullet in a gun will take yur hand off if its in front of the barrel, a same sized explosion sitting on an open hand would only cause some minor burning. the charge would be allowed to go any direction like in a normal wide dome, instead of directly directly down at the piston.
That is pretty much what the stock shape is Zed (the one on the right):
And due to its long narrow flame travel it tends to be a slow burn, requiring a lot of advance, but insensitive to mixture and timing variation and fuel and oil splash. Its slow burn tends to limit rpm and early ignition away from the piston tends to keep the piston cool. As well, its deep nature does not let it get washed with fresh mixture very well, limiting its efficiency and power potential. All these would be reasons Yamaha decided to use it on a beginner bike.
The Hemispherical chamber: (photo credit to Joeak47)
Has very little surface area to volume (more efficient), promotes a fast burn needing very little timing advance, and is readily swept clean promoting power and efficiency. It is also very detonation resistant due to the functional squish band and effective chamber shape that supports vortex action.
The swirl cuts may or may not work depending if they work with or against the vortexes that are already in place. Since they are taking place in a vertical plane, I would not think you would want to start a horizontal movement in them. I could see straight cuts being beneficial. Could be tested out with cuts on a piston that was planned for replacement anyway...
should also think of how a gun blasts. a pin hits a charge that fires down the only barrel to travel. a head needs to take a charge redirect it and fire it at best potential. hmmm a bowl of some sort sounds to be more benifical
its no where as drastic as a barrel would be (length for velocity, etc). plus the ultra low compression stock makes it utterly useless in shape.
it would not be possible on a stock head but a gun designed with a spark plug instead of a firing pin could be designed.
to get velocity behind it it would need like a 2 inch rise, radically advanced timing, and no funnel shape until like the last half inch.
it would not be possible on a stock head but a gun designed with a spark plug instead of a firing pin could be designed.
to get velocity behind it it would need like a 2 inch rise, radically advanced timing, and no funnel shape until like the last half inch.
the charge it takes can be fed into the head design based on the port design. its a matter of making the porting work with the head, that should be in consideration already.
ive went over that before, good port timings are useless if the port shape is haggard and malformed.
ive went over that before, good port timings are useless if the port shape is haggard and malformed.
nah, my wifes current blaster looks VERY similar to this one actually.
that does not mean that a RADICALLY different design or way of thinking would not work. just that the COMMON designs are just that, common. and that we have pretty much reached max efficiency in thous designs so something DRASTICALLY different needs to be tried.
like an old school muzzle loader barrel shape. the problem would be reshaping the ports to stuff the charge up and pull the spent charge out.
that does not mean that a RADICALLY different design or way of thinking would not work. just that the COMMON designs are just that, common. and that we have pretty much reached max efficiency in thous designs so something DRASTICALLY different needs to be tried.
like an old school muzzle loader barrel shape. the problem would be reshaping the ports to stuff the charge up and pull the spent charge out.
Head on the left is our new KTM style toroidal 25cc head.
Head on the right is DT200 Hemi style 23.5cc, and includes a poor squish angle.
This head has been run for months on Triplecrown's stuffed intake and 1mm exhaust raised ported cylinder.
This cylinder was run with no basegasket to lower it 0.030" or about .75mm.
This is all part of ongoing, one step at a time testing.
Burn pattern on the hemi was toward the exhaust and off centered.
A sign of unbalanced transfer ports. Some power being lost here.
Both heads were cc'd to give the values above. Both show no signs of detonation with proper jetting.
So how did they work?
Well, adding the basegasket to the hemi head lowered its compression and made is noticeably softer on low rpm and mid range. Powerband came on in a burst now, and it is definitely stronger on top end, even with the lower compression. I spun it around a track for a quarter hour, hanging out the back end enjoying the new founf over-revs from the raised cylinder. Bottom end has lost its former strength and over all it is a better trak engine than trail engine.
So, off comes this head and on goes the 25cc KYM Toroidal style. Even LESS compression. What are we going to get? This head has the better 11 degree squish going for it. Started on first kick, heck for headgasket leaks (feel with your hand around the cylinder) and off we go. Bottom end still soft but better than the hemi, mid range noticeably stronger. Enough mid range that it doesn't have the big powerband burst. Top end is still strong but not as much overrev as the hemi. A hoot around the track, hanging tail a gear up from the increased mid range, and higher speeds overall. This head feels like a success but I'd suggest the volume is too large. Gotta build one about 20-22cc.
I only had about 15 minute runs of back to back track time on it, but Triplecrown has been out on it all day. Interesting to hear his views.
Please fix pixs....
Also no basegasket? What are you using to seal the cylinder to cases? Seems a little risky....
Risky? RISKY?
Hell, don't you know the difference between a "sport" and a game?
"Sport" involved a clear and present risk of death.
Everything else is just a game...
Now seriously;
Some Permatex gasket maker or ThreeBond or Yamabond case sealer will do the job.
I don't know what happened to the pictures but here are 22cc heads to compare:
Here are a couple 18cc toroidal and hemi heads made by JoeAK47:
Both pictures actually.
Perhaps it should be worded: <<<<<<<<<<<< TOROIDAL right, ...............HEMI left >>>>>>>>>
