fractured apex seal(s) go un-noticed?
 

Has anyone pulled an engine apart to be totally surprised one or several apex seals were fractured? I was wondering if it's possible for my TII might have fractured OEM 3mm apex seals.

The TII was rebuilt about 20K miles ago and has OEM 3mm apex. With the exception of hot start challenges (that's aggreviated by my higher than stock static fuel psi) and vacuum that might be (??) viewed to be on the low side even for an aggresive street port (13.5 inHg @ 950 RPM), engine runs perfect otherwise and is supper strong under boost.

I'm quite sure my apex seals have been pounded by detonation on a few occasions.

i've seen 2mm engines where the seal is broken in the middle, and they still run, although not great.

3mm engines usually break in 3 pieces and come out of the seal groove and do lots of damage...

although on either seal the weak point is the triangular bit at the end, a little detonation can take the triangle off and it'll run, but be way down on power/rough idle.

i have seen OEM seals do just about everything under the sun. sometimes they fracture into 2,3 and 4 pieces that still hold in the seal slot and still build compression but allow the engine to run erratically but nearly normal still. all the way up to the seals literally turning to powder completely ejected from the slot that is spread across the rotor faces like little grains of sand in a pepper grinder.

I've found "grains" of apex seal in the other rotor by way of the ACV port. :D

well, will be tearing the block to see the amount of wear/damage.

decided to do a compression check and rear rotor had one weak pulse out of the 3. strange if you ask me. psi would hit 90, 90, fade, 90, 90, fade,.... front rotor @ 79 psi even. it's a s4 TII w/ an aggressive street port. didn't have the weak pulse on the rear when I did the last comp test 18 months ago. but shortly afterwards, while doing a hard pull my boost went thru the roof and the engine shuttered. I've been running since with no obvious performance degradation.

I'm leaning towards running Goopy apex/corner seals (if Karack likes them, then they should be OK). Hopefully my 88k rotor housing can be refurbished.

Interested to hear what you find out. I remember from talking to you before we have very similarly built engines from the same builder and ive had a few of those symptoms all along, lowish compression and vacuum, and very slight hot start issues but the car runs absolutely awesome.

I'll let you know the findings. Although might take 2-3 months before she's opened. If you haven't recently, do a comp test. If the #s are even w/every pulse and @ an acceptable level, my guess your seals are still 2 whole pieces. :)

is it possible that tiny parts of apex seal can break loose and be ejected out the exhaust and not see smoking out the pipe?

very easy, the sharp edge of the seal is usually the first to chip and break off, resulting in 30-60psi compression drop on 2 rotor faces. not enough to cause fuel to dump into the engine or smoking issues.

would that much debris cause damage to the turbos on its way out? im just asking cause my roomates car made a metallic noise in the exhaust(like something flew out through it) a few weeks ago and now it idles funny and sounds like shit.

Oh yeah, my compression is nice and even, just a little on the low side since it was first built. I know some people say ported 3mm engines just make less compression and vacuum while others say it shouldn't matter. Sorry about your motor, hope everything goes well when you open it up.

Here are my oem seals that suffered from catastrophic failure..I believe it ran with the fractured one that is split in half. No housing damage with the the fractured one, the other was a disaster.

http://i222.photobucket.com/albums/d...blownapex2.jpg

Yep when mine went it broke in three pieces jammed the rotor scored the housing and took out another apex seal and still ran well enough to get it into the shop 20 miles away.