Why Apex Seals Fail

[j9fd3s]

Originally Posted by Barry Bordes

A couple of observations.

Detonation can be a cause of breaking apex seals but it is not a root cause.

Leaning out at high boost and too much advance can be a root causes, but how many of us run conservative maps and still have problems? There is something else going on.

Also, no one has brought up the warping of apex seals. Using OEM I haven't seen this. Can anyone share their experiences with this problem?

Barry

i can see detonation breaking things, however on an iron seal NA engine, you can let it knock and ping all day and it'll take that abuse for a while. it will come apart, but not right away. with carbon seals detonation is a problem. i built a carbon seal PP engine, and everybody was warning me about detonation. which seems weird, its non turbo. although i actually have gotten it to detonate/ping a little. it makes the same bird chirpy detonation that the Rx8 does, similar conditions too, 1800-2200rpm, mid 14's afr, 18BTDC timing. throttle is around 40-60%

the SAE papers are on NA engines, and they point to the root cause being temperature related. when you add the turbo this doesn't change, except that you can have "conservative" maps and still be too hot.

so the question is what is too hot? and when is it too hot? note this is going to vary with the apex seal. we know the stock seals want about 900-950c EGT at peak power with a max of 1100c.

warping is a symptom i think. i don't think i've seen it, but i really don't have a good way to tell.

mike