Mr. Eccentric

Everybody is familiar with the way the combustion recesses look now. I whipped up a few crude drawings. Anybody have any input on what would happen if they were changed to any of my proposals? Increase in detonation? Decrease? etc...

Mr. Eccentric

Sorry the attachment didn't work out with the start thread, so here it is now.

diabolical1

iTrader: (3)

very interesting question. i thought i was the only one that thought about this sort of thing. anyway, my guess is very, very POOR gas mileage, less power and terrible vibrations.

i think that whether engine rotated clockwise or counter-clockwise (with respect to the recess, not the ports ) the pocket that you've created would not promote complete burning, localized hotspots and it would also make it hard to set decent timing ...

keep in mind that this is just a poor, old man's guess, the last time i sat in a physics class was about 11 years ago.

peejay

The bottom pic is what '76-up 12A rotors have. Yes, they are front and rear specific.

RETed

If the "pocket" is on the leading edge, this will actually increase torque output - think about it.&nbsp Downsides?&nbsp It increases the chances of detonation, especially on a turbo'd engine...


-Ted

rotarygod

iTrader: (1)

The top picture (and the way our 13B's are done) is referred to by Mazda as MDR which stands for Middle Deep Recess. The bottom picture (assuming the rotor turns clockwise) is referred to as LDR (leading deep recess). Mazda used the LDR in 12A engines from 1979-1985. The LDR recess was not only deeper at one end than the MDR but it was also a longer recess. The leading spark plug position was also moved ahead 5mm from previous versions to account for this. The new combustion chamber helped speed up flame propagation by virtue of increased squish effect. In this engine, ignition altered between single and two plug operation (1979-1980). When the leading plug alone was used under part load conditions, the LDR chamber resulted in better fuel economy as well as being advantageous for emission control (hotter thermal reactor running). In 1981 when Mazda changed distributers all plugs remained firing at all times but the rest of the engine design wasn't changed. The engine also gained about 15 hp. this year. It worked better for one plug since a majority of the fuel was concentrated in the leading recess. When 2 plugs are used the advantage is gone.

peejay

Well, the main reason for having the pocket offset like that is the pocket is placed more advantageously to the leading plug.