Interesting you mentioned destroying the napier upon installation.
That coupled with the 'pride' total seal has on those things has given me a bad taste for them.... anyone have any help to offer so I don't scrap these things?
Barry_R wrote:Wow - - check out the guys answering on this post - pretty cool! Good to see you on the board Dave! Back when I was at Speed-Pro (way back - just over a year ago...) we went through the 2 ring dance about every other year. It goes something like this...
You can reduce drag by dropping the 2nd ring. But doing so lets oil into the chamber. To dry things back up you bump the oil tension a bit - which in turn brings the drag back up. Net gain ends up really close to nil in many cases. Now that the landscape has changed quite a bit with the advent of high vac in the sump, and the risks are thus lower. It might be a better deal now than it was back in the day...
Reducing the radial wall thickness of rings has proven a very effective means of keeping bore contact without requiring high tension or drag. Using a seriously back cut 2nd, with or without napier, will reduce drag to darn near nothing while still retaining the desired squeegee effect. You can keep taking tension out of the oil expander too when using a reduced radial wall package - - even OE engines are very, very light these days.
The only limitations on reducing ring cross sections - both radial wall thickness and height - are those imposed by temperature, material and manufacturing limitations. On top rings this is a limiting factor where the heat can kill many rings (unless they are in an engine subject to frequent replacement anyways). On 2nds there is really no reason not to go really small - they all rely on point contact. The same is likely true to some extent on oils - but since the real tension is controlled by the expander design I suspect the rewards are pretty small too....
In my eyes, the risk/reward ratio still favors a three ring combo in any application where you have adequate real estate on the piston.
cmw wrote:The problem of breaking rings on installation is easy to cure. Don't champers the top of the cylinder. As the piston comes out of the correct bore ring installer and if you have a champers on the top of the bore with a Napier ring or .8mm ring or smaller you will break it.
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