Hi guys,

so I did the most stupid thing known to mankind, I WOTed my FD with a newly installed Haltech Elite 2500 on its base map several times. Don't ask me why, I think the easiest answer would be I didn't know better. At 120mph on the last WOT run (I'm located in Germany, so no legal problems with that speed on the public autobahn) the inevitable happend, one apex seal broke on one side AND bent on the other side, accompanied with a big crack.

Here are the pictures (Sorry for the whitebalance, camera doesn't like the 50w LED):

Apex seal



Rotor
As you can see, on the side of the rotor where the corner of the apex seal chipped there is a tiny little notch that would easily be gone with a rasp.



On the other side, where the apex seal bent and cracked, the grove v'ed out a little bit, I couldn't meassure it yet but its barely visible th the eye, it became more obvious when I looked at the pictures at home.




Than there is a little dent, pressumably from the chipped apex seal or the detonation, that killed the seal:





On the rear iron there is this mark:

It is not too big, but pretty deep, I would say at least 1mm (0.03937 inch), I couldn't measure it because of improper equipment.

The housing doesn't have any damage on it.

The question I have now, is the engine repairable? I wouldn't of course anticipate the highest compression numbers or longevity from this engine, so to speak a budget build, but is it possible? The rotor is my biggest concern and if it is not reusable I wouldn't have the biggest problem buying another one but the iron would be a problem if not reusable, at least if both parts are not reusable. Of course I would try to source a similar apex seal with nearly the same wear on it as my other ones, they where in spec about 1200 miles ago, when I rebuild the engine the last time.

And one other big question remains: Where is the chipped corner of the apex seal gone? I didn't find it anywhere in the engine, the (Stock) turbine wheels look both fine. I would see big damage on the exhaust turbine wheels, if a chunk of the apex seal this size would go through them at WOT, right?

I thank you all for your answers in advance and wish you a happy new year.

 

Yeah I would replace that rotor. I have used rotors with a gouge in the face from an apex seal piece before, as long as it's flat and there's no hot spots it's OK, not the best thing on earth but OK. If the apex seal slot is boogered up that's game over, though, that would be a major problem in short order.

The iron could be re-used, not ideal but you can re-use that on a budget.

What shape is the rotor housing? They usually take a ton of damage from a broken apex seal.

The broken piece went through your turbo most likely. You need an endoscope or take the turbo apart, you have to see the edge of the turbine wheel. Just looking at it straight on you can't see it. Typically it chips up the edges of the turbine wheel then heads out the exhaust.

Read my recent thread on rebuilding your engine for some tips and advice -

https://www.rx7club.com/3rd-generati...rself-1154493/

Dale

 

interesting, i think the mark on the housing is where the apex seal hit it

 

Hi Dale,

thank you so much for your answer! As I said, the rotor housing has no damage whatsoever, I couldn't believe it either when I opened up the engine. I think I was pretty lucky in that respect.

Interesting point with the turbine wheel. I will have a look with the endoscope, because I actually only looked at them from above:





Or maybe I can film from this position and turn the wheel from the compressor side.

Thanks again!

 

I’m not seeing this; are those OE Mazda apex seals?

I’m having a hard time understanding how the broken piece escapes out from being trapped by the outer corner piece, unless it breaks up or disintegrates into much smaller pieces that can then get past it?
.

.

 

what is the max clearance between the apex seal and the groove?

FWIW i have never seen an apex seal with a longitudinal crack. wow.

what is the height of your corner seal springs?

you need to remove the hotside housing from the turbo to check your turbine wheel.

there is a good chance that your motor just needs a bit of massage and will be fine other than aesthetics.

going 120 on a starter map is...

 

The real question here is whether the OP will give it the beans again before a proper tune after this inevitable rebuild.
I figured enough people learned that lesson through the years for anyone not to do such a thing, but that's what I get for figuring...

 

I think they are not OE Mazda, IIRC they have a narrower corner piece. But I'm not sure, because they where already in there when I rebuild the last time. I reused them because they where in spec. The crack would also suggest they are not OE I think.

This question is in my head all the time.

I still have to meassure it. Will do shortly.
Yes, I know. Now. Some things you have to learn the hard way, right?

I think I stated in the beginning of my post, that I feel like an idiot because of this. I rushed things, I didn't do any research on the topic. So yeah, lesson learned.

 

Sorry, it took some time to get back to the car for messearing the clearances.

An intact apex seal groove on the same rotor has .005-.006
The groove where the apex seal broke and bent has the same on the side whre the piece broke off (and where I filed). But on the other side, where the apex seal was bent it's .0128 to .014, but only on the last 0.4 to 0.8 inch.

My feeling is, that if I want more than 1000 miles from the engine (on the track) I should at least change the rotor. One odd thing I saw: there is no weight letter stamp on both rotors. I searched for a letter from a to f, but the lowest letter I found on there was k. I would have searched for a rotor with an equal letter but this makes it kind of hard.

Than I searched for the broken off piece of the apex seal. I filmed into the exhaust turbine housings, no marks at all. I disassembled the rest of the engine, nothing. The only solution would be, that it popped out on the floor while disassembling without me noticing.

 

The weight code is stamped on the gear side of each rotor, just right if the bearing keyway.

 

You won't find it. The only time I've found the broken piece it was embedded in a rotor face.

Typically they disintegrate into nothing or just head out the exhaust and are on the side of the road somewhere.

It's nothing to worry about, though, it's not going to be somewhere that would cause future harm.

Dale

 

I have decided to repair the engine, I already bought a used C Rotor (Mine where both B, but the stamping tool made kind of a double stamp, so it was really hard to see).

The only problem I'm having right now is that I don't find anybody in Germany able to sell me a single used apex seal. I have the option to buy one new OEM Mazda seal, but than I have 5 unknown make, obviously not brittle used apex seals and one (kind of) brittle OEM Mazda seal. Do you guys see a problem here?

The aftermarket seals only come in sets, right?

 

Get a full set of new apex seals. If one took that much damage it's possible the others did as well - they may have damage that you can't see.

They aren't super expensive all things considered.

Dale

 

Replace the rotor. The iron will be fine providing the rest of it measure in Mazda's specs. Replace ALL the seals, and springs. IF you detonated enough to crack an apex seal like that, chances are the other seals are compromised and the springs are likely to be flattened.