piston rings

[gmjeric]

has anybody used different rings such as those from total seal that have antifriction coatings.....overlaping designs.....or thinner profiles

[gmjeric]

also has anybody used custom pistons with the ring pack and pin moved as high on the piston as possible

[Mike S]

Originally Posted by gmjeric

custom pistons with the ------- pin moved as high on the piston as possible

This will lower the compression....................

[Toobuilder]

I know the F-1 guys will use automotive gapless rings in the little O-200's, but they are also usually running plain steel barels, overbored to the limit of the rules. Once you start dealing with the big bore Lycoming cylinders, it is tough to even find "off the shelf" to fit. Add to that the requirements driven by chrome or nitrated cylinders, and it's even tougher to find compatable rings from the automotive world.

Not saying it cant be done, but I've not heard of such on a Lycoming. Perhaps someone else knows different?

[rocketbob]

I have a set of ECI 2nd rings I had TotalSeal modify to be gapless.

I have a friend running the same rings in an IO-360 on a Mustang 2 and last I talked to him his compressions were 80/80.

[jrs14855]

In the 70's and 80's the total seal rings were quite popular in 0 360. No sure about compatability withm nitride cylinders but I know they are still available for Lycoming steel cylinders.

[gmjeric]

Originally Posted by Mike S

This will lower the compression....................

no we make up for it in rod length....when building from scratch get the smallest combustion chamber to leave plenty of quench..design piston as compact and flat as possible....then determine stroke and get the rod last....


the deeper the rings are on the piston and the wider the gap from piston to wall the less efficient you become...this all becomes dead volume that must be filled burned exhausted but doesnt burn in time to add push.....im still looking to encapsulate the spark plug but leave electrode bare so that maybe we could get two pads for quench area......ill dig it up but if you look at harley heads they are in the same boat...then go look at a eldelbrock harley head and you see the quench areas...then go look at a nitro prostock billet harley head and youll see the refinement im after

[Mike S]

Originally Posted by gmjeric

also has anybody used custom pistons with the ring pack and pin moved as high on the piston as possible

Originally Posted by gmjeric

no we make up for it in rod length....when building from scratch get the smallest combustion chamber to leave plenty of quench..design piston as compact and flat as possible....then determine stroke and get the rod last....

My response was to your original post------nothing mentioned about rod length etc.

I stand by the comment that raising the pin height will lower compression, given the info in your original post. Your second post seems to be relating to a clean sheet design..........

What are you looking to accomplish with these design changes anyway???

Rod length is usually adjusted to accommodate stroke changes, or to lower piston skirt friction by lowering the rod angle----which is probably a negligible issue in our low RPM engines.

Your comment about needing to fill the volume above the rings is spot on, specially with our big bore engines.

A Dykes ring can actually be installed with virtually zero volume lost above the ring.

https://encrypted-tbn1.gstatic.com/i...TBNLlBxIu1PClQ

Dont forget cooling...................

[gmjeric]

Sorry i was making the assumption of gaining rod length to accommodate the piston pin change...

Im looking to maximize the efficiency of an o200...

as for the heat....add thermal coatings to ports, combustion chamber, valves and pistons.....keep the heat in the cylinder then keep it moving out the exhaust....also laying the valve seat from 45 to a 30 degree cut


with as low of a piston speed that we have im really concentrating on port velocities...we get about 3% increase from compression bump but when you match a cam profile to fit the compression increase your 3% can go to almost 10%

yes i could get all the power from an 320 or 360 but not fan of the extra weight....etc

[rocketbob]

Originally Posted by gmjeric

exhaust....also laying the valve seat from 45 to a 30 degree cut

Why would you do that on the exhaust valve. Most engines have a 45 cut on both valves but a Lycoming or any aircraft engine for the matter is slow turning so it was found that there were better port numbers at low lift on the intake with a 30 degree cut.