Thread: Definition of Squish !
01-26-2006, 02:22 AM #1
Definition of Squish !
Here is some basic information on what the Squish Band is on an internal combustion engine.
There are experts out there such as Lowell Horning that can do this specialty work precisely.
The Squish Band or "Quench" is defined as that area between the flat of the piston and the flat of the cylinder head at top dead center (TDC). On the compression stroke, as the piston approaches TDC, the compressed mixture of fuel and air is "squished" to the remaining space of the combustion chamber where the spark plug and valves reside.
The "squeezing" of the mixture creates turbulence and is expected to promote a better and more complete combustion.
*Generally* anything you do to increase combustion chamber turbulence seems to increase bottom-end/midrange (with a corresponding tendency to heat more there). Remember: heat is power is heat .......... no way around it !!!
Things that increase turbulence:
- reduce squish
- reduce squish included angle
- reduce blending radius between squish and dome
- wider squish band / smaller dia-deeper dome
quotes from references:
Of the three things mentioned above, the most overlooked is probably the blending radius. When the squish gets "down" to under .030, this becomes fairly sensitive!
Gasoline motors tend to "like" a couple of degrees of squish angle. Running parallel squish on gasoline can be asking for trouble, especially on a highly-tuned engine. On a restricted-exhaust engine (can), it's much easier and more common to run parallel squish.
Road race motors tend to "like" a bit more open combustions chamber, ie: narrower squish band, bigger dome, decent size radius between the squish and the dome.
All these things go HAND in HAND with: pipe, fuel, timing, gear, impeller pitch, the driver positionin g(in the seat<g>), etc, etc.
How to Measure Squish
01-26-2006, 10:34 AM #2
Great info Billy
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