Squish & "Squish Land", a Closer Look at Optimizing Combustion

This is a fuller, better-illustrated explanation of what I meant in my reply to Iron Horse Re the nature of squish-velocity and "the interface" between 'Squish Land' & the chamber's charge. Simply put we all know that minimizing clearance is desirable, and I show in this video how to taper a squish band and, subsequently, account for the reduction in force that's seen at "the interface"(the meeting of squish charges, and combustion chamber charges, when piston is ATDC), by using a popup disc to create a "choke" to create last-second pressure of the squish ring around its central combustion-charge. IE, instead of doing 20thou flat, you do 19thou on the outer edge, 21thou on the inner...you increase speed of movement but are also inducing a "sawed off shotgun" type effect by increasing height(or clearance) around the inner perimeter of the band ATDC. The solution IMO is to utiliize an appropriate diameter popup disc to act as a "choke", for instance say your band is cut so that the outer perimeter has clearance of 19thou, and the inner perimeter is 21 thou clearance, you may want to start out trying to position (cut) your popup disc so that, ATDC, the disc // band interface creates a "channel" of approximately 18-20thou, just a lil 'punch'/boost in pressure "at the interface" where squish is doing most of its work, and remember while this is creating hot-spots, the hot-spots are so incredibly transient, maybe 1-1.5deg if I'm visualizing correctly, so am strongly suspecting you could "get away" with some very hot situations because, despite being very hot, they're even more remarkable for their speed, the disc - at 20thou max- is only exerting any influence for the shortest moment of time but it's that oh-so-critical moment of generation of peak-pressure at start of our powerstroke, a moment that influences the average-cylinder-pressure through the remainder of any particular revolution.

[@Ketis1985]

7-8 degree taper on a squish band is alot but it wont ruin a saw. We have to remember that many factory cylinders have cast band with alot of taper and they run great 😊 my Jonsered 525/535 hybrid has bunch of taper on a stock cylinder and 1,5mm squish and runs just fine 😊