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Cheers automotivebreat(h)...lol. I thought you were angled slightly off point of igniton, now i'm begining to understanding why.
 

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Cheers automotivebreat(h)...lol. I thought you were angled slightly off point of igniton, now i'm begining to understanding why.
By now you may have guessed, I occasionally step "out side the box".

Here's a few of my own layouts, designed to balance combustion temperatures and
enhance combustion in "dead" areas of the chamber.








The administrator decided not to leave room for the (h)... Tull, showing my age!
 

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Whats heads are you showing us?

They have bloodly big squish band, I can see these heads will benefit loads with grooves.

As for pictures of a LET piston... I dont have any but im sure someone here does
 

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Whats heads are you showing us?

They have bloodly big squish band, I can see these heads will benefit loads with grooves.
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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Discussion Starter #66
C20LET pistons:










C20LET chambers:




This is a turbo engine with 0.6-0.8 bar (8.7-11.6 psi // 17.7-23.6 inHg) standard max boost pressure.
 

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Do you not have to worry about possible 'hot spots', which may lead to det in a turbo engine?
 

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looking at one of the last few pics, you have one where you have three grooves, going towards the valve....it looks aloost like your on the seat? couldnt that cause potential seat failure, after a certain time?

i may be wrong on this!!lmao
 

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Discussion Starter #70
Do you not have to worry about possible 'hot spots', which may lead to det in a turbo engine?
The opposite is true, detonation threshold is raised.

Volvo turbo after grooving with this pattern:

Morten VJ from Turbobricks said:
After 2 weeks of driving with the groves.
This is my results.
I'm able to use the same boost pressure on regular, as i had with premium petrol before.
220 kpa with the same timing.

Fuel consumption.
Before 28 Mpg Imp. Best.
After 32 Mpg Imp and i'm still tuning.

AFR before at cruise 16-1
After at cruise 17.5-1 and nothing strange drivability problems.
I'm going to try 18-1 next week if i can burn it.

So far i'm Happy.
http://forums.turbobricks.com/showthread.php?t=74370&page=3


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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C20LET chambers:
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.

Do you not have to worry about possible 'hot spots', which may lead to det in a turbo engine?
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.

looking at one of the last few pics, you have one where you have three grooves, going towards the valve....it looks aloost like your on the seat? couldnt that cause potential seat failure, after a certain time?

i may be wrong on this!!lmao

To an extent, I share the same concerns. I am a brave soul.
 

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Interesting!
But i suppose to find out the optimum, without trial and error you need to see where the current squish is happening, so you can 100% find the best angle for your grooves.
 

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Interesting!
But i suppose to find out the optimum, without trial and error you need to see where the current squish is happening, so you can 100% find the best angle for your grooves.
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”.

 

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Discussion Starter #74
Some possible groove patterns for the C20XE/C20LET head I'd suggest. From left to right, conservative to all-out.

 

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Yes I know this is a old thread but since there was never a conclusion....

Has anyone ever gone ahead with this modification?
 

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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.
 
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