Section cut C20XE-C20LET head pictures?
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Yes, benifits can be found with piston modifications, got pictures?
Need pictures of piston and head.
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Yes more grooves provide more of the same benefit.
Most of my work is on after market wedge heads for American made V8 engines, primarily
small block Chevrolet. Those seeking high performance utilize every bit of the available
squish area to their benefit.
The OEM would reduce the squish area and lower the compression ratio with a dished
piston. These pictures are from the production engine in my tow truck.
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Enjoying this thread!
The opposite is true, detonation threshold is raised.
Volvo turbo after grooving with this pattern:
http://forums.turbobricks.com/showthread.php?t=74370&page=3Morten VJ from Turbobricks said:
Please notice that Volvo 2V open bathtub chamber with parallel valves is far more detonation sensitive than the C20LET 4V pentroofs.
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If I were modifying this engine, I would groove the cylinder heads to direct squish flow
high into the roof of the chamber. The valve angles of this design creates a tall chamber,
this is undesirable for optimal flame travel. Benefits can be found by encouraging
additional mixture motion in the vicinity of the spark plug.
Additional mixture motion in the dish of the piston of this engine design will generate
improved combustion, to what extent I don’t know.
The spark plug ground electrode glows red at sustained peak torque, next comes a
poorly seated exhaust valve. Most other surfaces provide sufficient heat sink to avoid
pre-ignition.
To an extent, I share the same concerns. I am a brave soul.
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Unfortunately we don’t have the resources needed to “see” what’s happening inside the active
cylinder. This forces us to use the work of others and fill in the void with our “imagination”.
.. :beer: to you
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duplicate
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Always interesting to read something new.
I would summise that the way it works is two fold.
Under compression stroke, as the piston approaches the head, combustable gases are tapped in the squish/quench area and are forced out, causing turbulence. However, this also increases the temperature, especially near the edge of the chamber where the gases can't escape - in extreme cases this will cause either detonation as the combustion gases raise the temperature in the unburned fuel enough to cause localised ignition, or actual pre-ignition, when the gases are heated enough to initiate the combustion process.
I would expect these slots allow inproved gas flow from the quench area, so reducing the peak pressures and thus temperatures and so reducing or eliminating the gas ignition problem. this would also mean a lower octane fuel may be used as less anti-detonation additives are required.
Under combustion, when the spark ignites the mixture, the expanding gases can cover a greater area of the piston and so increase the pressure on the piston more rapidly.
Seems to be a win-win situation, a similar advance to the fire slots on high dome pistons.
I expect this improved combustion means reduced ignition advance is required - the advance is to maximise the average pressure on the piston - which will increase torque as there's less pressure BTDC to be overcome.
I would summise that the way it works is two fold.
Under compression stroke, as the piston approaches the head, combustable gases are tapped in the squish/quench area and are forced out, causing turbulence. However, this also increases the temperature, especially near the edge of the chamber where the gases can't escape - in extreme cases this will cause either detonation as the combustion gases raise the temperature in the unburned fuel enough to cause localised ignition, or actual pre-ignition, when the gases are heated enough to initiate the combustion process.
I would expect these slots allow inproved gas flow from the quench area, so reducing the peak pressures and thus temperatures and so reducing or eliminating the gas ignition problem. this would also mean a lower octane fuel may be used as less anti-detonation additives are required.
Under combustion, when the spark ignites the mixture, the expanding gases can cover a greater area of the piston and so increase the pressure on the piston more rapidly.
Seems to be a win-win situation, a similar advance to the fire slots on high dome pistons.
I expect this improved combustion means reduced ignition advance is required - the advance is to maximise the average pressure on the piston - which will increase torque as there's less pressure BTDC to be overcome.
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