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Edelweiss Edelweiss is offline
Registered User
Join Date: Feb 2013
Location: Essen, Germany
Posts: 174
Ring rotation

Dear Sirs,

doing min. one engine a week here is first hand information:

For sure it is so right as essential to be very correct and exact about the mounting position of the piston rings.

Why bother is a shocking statement to my ears.

And yes it is right - depending on the ring and cylinder material the rings are moving a little - some few degrees - during the break in process.

The physics behind this phenomena is simple - the rings are building sort of a labyrinth seal and the gases are traveling through it causing lateral forces to the rings ends in the gap zone.

This is without any effect as the rings are " broken in " to the cylinder surface, from that moment on the rings are not changing position any more and stay where they are for the engines lifespan.

We service our race engines on a yearly basis and when the cylinders come off I see the piston rings, more or less, exactly where they where positioned during the mounting process.

At some application we use gap less rings from total seal with good result - using this top rings is minimising the ring rotation against zero.

There is I a logic inside all this - the braking in means the rings found their position to the cylinder and the sealing effect against gas pressure from head side and oil from the crank side gets to its maximum. If they where not stop moving they would never break in, never seal and as an effect would wear out quick.

We produce our own nikasil plated cylinders in our own casting and we are using Mahle 124 to produce our pistons ( not even Mahle is using this high end material any more by the way ) so we deliver this parts to all top european engine builders and have to answer questions around this all day.

When braking in - use special break in oil or simple mineralic 10/40, never start a new engine using synth. oil with high viscosity.

If it is not a race engine and you have the time go for it approx 5000 km before you change for the premium synthetic juice.

We use nothing but Motul 20W60 then - this is by far the best for air cooled engines from our daily experience.

Best reg.

Old 07-27-2014, 03:40 AM
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