×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Moly filled vs plain ductile iron top piston ring
2

Moly filled vs plain ductile iron top piston ring

Moly filled vs plain ductile iron top piston ring

(OP)
I've done some searching, and nothing I found specifically addresses my question.  I am rebuilding a factory turbocharged engine that originally came with a chrome faced top piston ring.  These rings are no longer available, so my choices are a typical moly-filled top ring, or a traditional non-filled iron top ring.  What are the pro's and con's of each, considering that I intend to make use of a great deal of the engine's inherent power capability?

RE: Moly filled vs plain ductile iron top piston ring

Moly has better scuff resistance than chrome.  The only time it may not be the best choice is in very dusty conditions were the dirt may get trapped in the pores of the moly and act as an abrasive.  If you have good air filtration or do not operate in dusty off road environments, opt for moly.

Rule of thumb: If the engine makes more than one horsepower per cubic inch,  (60 hp/liter), then a nodular (ductile) iron or steel is the best choice as a base ring material - for strength.

The plain iron ring is strictly a low cost option.

RE: Moly filled vs plain ductile iron top piston ring

(OP)
Doing a little more searching on the net, I found out that ductile iron rings are relatively new and not to be confused with old-fangled cast iron.  My question is, for my application, am I better off with a new style ductile iron ring with no fill, or one with that is moly-faced?

RE: Moly filled vs plain ductile iron top piston ring

Ductile, also call nodular or spherical graphite iron has been used in piston rings for at least 40 years.  Moly has been used as a wear surface on rings for about the same length of time.  There is nothing new about either

Get a moly-filled, ductile iron ring.

The ductile iron is stronger and will stand up to pressure better than grey cast iron.  The moly is wear resistant and scuff resistant.

RE: Moly filled vs plain ductile iron top piston ring

(OP)
Thanks for the info.  The latest findings in my web search lead me to the same conclusion.  Thanks again!

RE: Moly filled vs plain ductile iron top piston ring

basic moly filled rings can lose their moly whjen subjected to detonation.  Detonation is pretty much a given in a turbo engine.
Plasma moly has a stronger bond, but it is still weaker than chrome's bond.

RE: Moly filled vs plain ductile iron top piston ring

(OP)
Great info!  I will be sure to get the plasma sprayed variety of moly rings.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources