Piston Ring Pressurisation

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Page created by T Jan 20th 2008:

 

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==Piston Ring Pressurisation:==

Gas pressurisation of the Piston Rings in Holden engines improves the Engine's ability to draw in charge,

to compress charge and to harness the combustion gases.


===How it Works:===

A higher pressure on the top or bottom of the Piston Rings makes its way behind each Compression Ring until it encounters

a chamfer on the inside of the Ring.

 

A Piston from a 160 cu in Pro Stock Harley Davidson Engine. Small holes drilled around the outside of the Piston allow combustion gases to pressurise the upper Piston Ring and increase performance . Click to Enlargen. Image by HPEngines


The chamfer reacts to the pressure and forces the Piston Ring hard against the Cylinder Wall increasing the Piston Ring's

ability to seal against the wall.

 

===This is How the Ring Pack Operates When the Ring Grooves are Clear:===

Clear Piston Ring Grooves. Click to Enlargen. Image by T


===The Top Compression Piston Ring:===

The Top Piston Ring  is installed with the chamfer facing upwards. This gives the top Piston Ring the job of performing most

of the sealing during the Compression Stroke, during the Power Stroke and during the Exhaust Stroke because the chamfer is
most effective when the gas force is downward and the pressure is greatest on the Cylinder Head side of the Piston.

 

===The Bottom Compression Piston Ring:===

The Bottom Piston Ring  is installed with the chamfer downwards.

This gives the bottom Piston Ring the job of performing most of the sealing during the Intake Stroke when the pressure
is greatest on the Crankcase side of the Piston.

===The Ring Pack:=== 

Sometimes the group of Piston Rings is called called the Ring Pack.

 

===Piston Ring Grooves:===

The Piston Ring Grooves have a part to play in allowing the gases to get behind the rings.

 

If the Piston Ring Grooves become blocked up the gases will simply bypass the Piston and the spring tension in the Rings

will not be enough to make a proper seal.

 

Dirty Oil and improper use of the Car can cause the Piston Ring Grooves to become congested. Keeping the Oil clean

and giving the Car proper running will keep the problem away, see Engine Life.

===This is How the Ring Pack Operates When the Ring Grooves are Blocked:===

 

Blocked Piston Ring Grooves. Click to Enlargen. Image by T

===Loss of Compression:===

Gummed up Piston Ring Grooves prevents Gas Pressurisation of the Piston Rings.

A Compression Test will fail if performed on an Engine with this condition because the charge will "blow by" the Rings as the Piston tries to compress.

 

===Excessive Blow By Gas:===
Excessive Blow By Gas will result because the Ring Pack cannot hold the charge during the Power Stroke.


===Oil Burning:===
Blocked Piston Ring Grooves cause Oil Burning by allowing Crankcase Air to be drawn up around the Piston
during the Intake Stroke. The Air carries Oil from below the Piston with it. Note that the Oil Rings are scrapers which are designed to pull Oil from the Bore Face. They are not so effective at sealing pressure. 

 

PistonRings.gif

 

====Clearing Piston Ring Grooves:==== To clear the Piston Ring Grooves, steam is dirt cheap and very effective.

Clearing Piston Ring Grooves

 

Blow-By covered Pistons from an HR Red Six. Note that the Upper Compression Ring is not Gas Pressurising whereas the Lower one is. Photo by TomKelly. Click to Enlargen.

 

Piston from a mis-used Grey Motor. Dirty Oil and not reaching operating Temperature are only 2 of the problems. Photo by 1962_EJ. Click to Enlargen.

The Piston is Cam Ground meaning that it is oval shaped cold and becomes round as reaches operating Temperature. Photo by 1962_EJ. Click to Enlargen.

Note that the Ring Lands show minimal wear yet the outside of the Piston Rings are  burned. The Piston Ring Grooves are filled with watery/Oil sludge preventing the Ring Pack from Gas Pressurising properly. Photo by 1962_EJ. Click to Enlargen.

 

==Links:==

Tom Kelly's Shed

 ===Terms:===

Terms

 

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