Ottoman

i've come up with a theory.. hear me out and tell me what u think


First of all lemme say... I've heard detonation in piston engines before.. the dreaded metallic popcorn sound... but the car will still keep pulling

but mine was a diff kind... everything would seem to run ok.. then suddenly the car would fall totally flat on it's face... and the note of the exhaust would totally change and become a monotone steady brrrr sound momentarily and i'd let off the gas...



on my T2 FC.. i had "detonation" a few times... at least 4... or at least i thought it was..
eventually the car stopped wanting to stay running... and had trouble hot starting..

compression on ALL faces of the engine had gone way down... but still had 6 weak puffs...

when i tore the engine down to a short block.. i could still see and feel all 6 apex seals in their respective places... and the turbo was ok... no damage on the turbine side


fast forward to dec 31st (what a day to go) while doing a long distance wangan like run with some friends... i think the SMIC soaked and caused the "detonation"... same kind as the FC only not as lucky...

I lost compression on 2 faces of the rear rotor...

i thought the engine broke a seal and shot it out before chewing up the others...

i didn't touch it for a long time.. while i saved up for a rebuild.. (new housings and new oem everything..)

anyways last night i stripped it down to a short block(turned out it was a reman I had no idea) ... all six apex seals are still in their grooves.. and there's no signs of damage on any rotor face... and the turbo was ok... no damage on the turbine side


so did i have "minor" detonation that flattend a Seal Spring? or was it something else?


thoughts? opinions? similar experiences?

Erdin

I may be wrong but this is what I think is happening. The springs can flatted out when they are subjected to heat over a long period of time you say you ware doing a long distance wagon like run with some friends’’ when you have your car at WOT for a short time the seals have time to cool dawn but if you stay WOT for a long time the heat will build up in and around the Apex seals which could cause the apex springs to collapse also I think clearances are important if the seals are not clearanced correctly then the spring could be subjected to work harder . But I think its got more to do with the heat building up on the seals I don’t know what the fix would be for this maybe someone can fill in. what mods have you done to the car?

Ottoman

Thanks Erdin,

that's an interesting theory..

but that doesn't really explain the sound and sudden loss of power... i figured a heat related failure would be a progressive thing... not a sudden jolt..

water temps were normal.. (it was like 15* C outside)

RETed

First of all, you need to tear the engine down to really inspect the apex seals.
Looking into the exhaust ports will not always tell you the story.

Detonation likes to chip the end with the triangle assist piece.
Either the top / long piece chips (more obvious looking into the exhaust port) or the triangle assist piece corner chips (not so obvious looking into the exhaust port).

Also, it's a combination of heat and pressure that flattens the apex seals.
You need to understand what detonation is...
Typical combustion pressures are around 1,000psi.
Detonation can peak combustion pressures up to 10,000psi or 10x normal!
On top of that, EGT's go through the roof.
So it's the combination of pressure and heat that kills the apex seal spring.

Tear down the engine - I bet the triangle assist piece side has a chipped corner.


-Ted