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Originally Posted by dkveuro
The same company....tested end gaps of rings on blow-by and effeciency.
The supposition was that large end gaps would/did result in low compression and poor performance.
The test revealed that RADIAL pressure of the rings against the cylinder bore where the critical part that made or broke piston ring seal
I have a fixture to measure blow-by on the piston/block without a head.
So, end gaps seem most important on cranking speed, not dynamic speeds.....and on a diesel this IS important.
Both these results seem at first to be contradictary to popular engineering accepted results from doing this. However, my own tests prove this is very effective on diesels for cold start performance......once the engine is running , time/angle operating losses are conciderably reduced and even a low compression diesel will run reasonably well under load.......
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Please explain how radial pressure changes. Is it because of increasing end gap with worn bores? I am well aware of the fact that a diesel witl 100k on the clock that has been driven around town is in poorer shape than one with 300k of highway miles, because of the radial oressures exerted on the rings and cyl walls to get the sled moving. This would increase taper and effectively increase end gap. Correct me if I'm wrong.
Is the blow by tester you use the Sioux venturi vacuum gun with the disc on the end?
In conclusion I go agree with you that cranking compression can drop off to where you don't get the 900* or so needed to ignite the fuel, but I maintain that a valve job which is cheaper will give you more bang for the buck than a lower end overhaul. I can elaborate more on this later.
looking forward to hearing from you.