Re-entrant vs. Entrant pistons?
- Thread starter Begle1
- Start date
Begle1
Active member
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- Nov 18, 2007
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Non Reentrant
Reentrant
Lip Reentrant (more like the cummins style)
Alright, so what are the pros and cons of each design?
dvst8r
Unobtainium
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- Feb 16, 2008
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Taken from some where on the internet (sorry I didn't copy the source when I was gathering information for myself at the time)
*** Not my words ***
"Large slow running DI engines (under 1500 rpm) have 'open chambers' where the piston has a very shallow dish shaped with a bump in the middle. Air movement is minimal and the multi hole injectors (often 8-12 hole) are set to inject a fine mist into the dish. Due to the size of the combustion chamber sufficient air is present to supply the fuel with oxygen and the fuel combusts before it contacts surfaces of the combustion chamber."
"With the quickest engines large air movement is required to give a fast mix. The fuel spray has to be more penetrating to overcome the increased air forces and the injection event rate is increased so that the fuel charge is swiftly delivered and has longer to mix and combust.
A trick used by several engine manufacturers is to give the bowl a lip to prevent the air squish motion pushing fuel above the piston crown, so that the majority of the fuel charge is mixed and burnt within the bowl. The lip also creates further micro turbulence within the bowl. The square chamber produces micro turbulence from its rounded corners which provide superior air-fuel mixing."
I have a vw/audi SAE paper on another computer, I will see if I can find them (I am a bit of an information pack rat)
*** Not my words ***
"Large slow running DI engines (under 1500 rpm) have 'open chambers' where the piston has a very shallow dish shaped with a bump in the middle. Air movement is minimal and the multi hole injectors (often 8-12 hole) are set to inject a fine mist into the dish. Due to the size of the combustion chamber sufficient air is present to supply the fuel with oxygen and the fuel combusts before it contacts surfaces of the combustion chamber."
"With the quickest engines large air movement is required to give a fast mix. The fuel spray has to be more penetrating to overcome the increased air forces and the injection event rate is increased so that the fuel charge is swiftly delivered and has longer to mix and combust.
A trick used by several engine manufacturers is to give the bowl a lip to prevent the air squish motion pushing fuel above the piston crown, so that the majority of the fuel charge is mixed and burnt within the bowl. The lip also creates further micro turbulence within the bowl. The square chamber produces micro turbulence from its rounded corners which provide superior air-fuel mixing."
I have a vw/audi SAE paper on another computer, I will see if I can find them (I am a bit of an information pack rat)