marc wiese wrote:

I found this interesting since we all are discussing seals recently....

<< t's a trade off. The stock 3-piece seals give better combustion
sealing
over the 1- and 2-piece seals.

How so? I am just wondering..

Multi-piece seals have always had better sealing properties by being able
to "slide" into place to seal along it's width (more a function of it's
apex seal springs, but the diagonal face along most of it's width
contributes slightly) and along both ends (due to the "triangle" assist
piece on a 2- and 3-piece apex seal). Mazda engineers document this in
both their Mazda Technical Journals which are referenced in the Formula
SAE papers.

The 1-piece seal is stronger (versus detonation) due to the fact that the
seal transmits force along the entire "height" of the apex seal versus
~3mm of height for a 3-piece seal. To "crack" a 3-piece apex seal,
detonation only has to break the top "height" piece of the 3-piece apex
seal to kill that apex seal; for a 1-piece apex seal, detonation has to
"crack" the entire "height" of the 1-piece apex seal to cause failure.

Most motors (I've seen) that fail (due to detonation) chip the sharp
triangle assist piece or the apex seal section right next to it. 3- and
2-piece apex seals both have this "weak point" due to the triangle assist
piece at one end - the 1-piece apex seal (obviously) don't. New
(multi-piece) apex seals are more resistant to this type of failure,
probably due to the fact that the seals haven't been heat-cycled and are
more brittle to the heat-cycling. High mileage motors (apex seals)
definitely do tend to chip the triangle assist piece or the apex seal
section right next to it.

- -Ted

Ted Koseki
K2RD Technical Advisor
K2 Racing Development
http://k2rd.freeservers.com/

 
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