KhanArtisT

iTrader: (2)

This engine randomly died on me one day when I went to start it. Had 0 compression on the rear rotor and 90-90-60 in the front cold. It was a 6 port turbo running:

Stock TII ECU/sensors/injectors/FD pump and 8psi. It hit fuel cut probably 8 times, 3 of which it detonated. Never had starting problems, always ran hard, it only had ~10 inches of vacuum at idle though and it NEVER idled right although it had wired open aux ports and no BAC. The leanest it ever got under WOT on the wideband was 10.5, it even went into the 9s in first and second gear. Stock timing.

The housings have grooves in them, the apex seals are intact but are badly worn (sorry no pics). All the bearings and other seals are good. The engine was a Kevin Landers rebuild with 60k on it, ~10k of which was boosted miles. I had unintentionally ran it low on oil (less than half) a couple times. They rotors are good too.

I'd like input from the pros on exactly what caused the faluire and how to prevent it. I'll probably run it off the wastegate spring now which is probably ~7psi. I actually won't even drive it hard anymore until I can graduate and go full T4.








I'd like to get away with just replacing everything (housings too) minus the side seals/springs and corner seals/springs. I'll be going with the basic RA kit.
Thanks in advance for the input.

rx-7 obsessed

as i seeing things or does that look like rotor chatter with excessive wear on the housing?

Aaron Cake

iTrader: (1)

Looks a lot like chatter to me.

10.5 and 9s is too rich. It could have been rich misfires that popped the engine. That, combined with "badly worn" apex seals (after only 60K?!) sounds like the explanation to me.

mazdaverx713b

iTrader: (91)

overrevving could also explain some chatter marks. i'd rebuiild using different housings.

KhanArtisT

iTrader: (2)

What does everyone think of how these seals wore? All of them look almost the same, with wear on the spring side. Was the wear increasing the seal to housing clearance slowly causing the engine to lose compression?

SonicRaT

iTrader: (6)

Do you know what apex springs and seals those are?

KhanArtisT

iTrader: (2)

Nope, no idea. The engine was the basic Kevin Lander's rebuild with ~60k.

SonicRaT

iTrader: (6)

Was there anything more definite as to the loss of compression than just that? I've personally never seen seals with the spring side worn down like that, no side seal issues/etc?

arghx

iTrader: (3)

Here's something to check. What is the free height of the sets of apex seal springs (FSM page 1-48) ? The measurements listed in the FC FSM are 4.6mm for the long spring and 3.0mm for the short spring. In the FD FSM (page C-57) they give a spec of 3.5mm for the long spring, which I guess would be the minimum height acceptable. I wonder if your springs were semi-flattened and that contributed to the chatter. Maybe they were never replaced the last time the motor was opened up.

If I were you I would measure your side seal to corner seal clearances before you decide whether to replace them or not. Mine were around 5.5 thousandths, which is just barely in spec (and it is WIDE spec of about 2 - 6 thou), so I elected to just replace all the seals and clearance them to 2 thou or so.

Not positive, but I think Kevin Landers uses atkins seals.

KhanArtisT

iTrader: (2)

Other than that there were groves in the rotor housings around the spark plug area, the Eshaft, bearings, rotors, corner/side seals and irons are all fine according to my builder. I can't measure anything, I don't have a dial caliper/feeler gauge and all the parts are at the shop.

This is pretty much what I think happened.

SonicRaT

iTrader: (6)

Do you have the springs that were taken out from this rotor? Were there properly two springs per seal? With the wear patterns it almost looks like either the small spring 'traveled' along the apex and wore those deep groves in multiple spots (The large spring should touch the step on the outer most edge and the edge of the corner peice not pictured). But there's 3 different wear spots on each seal along the inner part which means either the spring moved or there were more than just the two? At this point I'd either say it's an apex seal failure (bad batch/wore too easily?) or something wrong with the springs. Did the other rotors look anything like that?

KhanArtisT

iTrader: (2)

No but I'll probably pick them up from the shop on Monday and check the free height. The rotors looked fine, nothing unusual. I just wanted to be sure that I'm fixing the problem and not just what broke.

SonicRaT

iTrader: (6)

If everything else is still within spec and there's nothing wrong, and each of those 3 seals had only 2 springs i'd say it was either spring failure or an issue with the seals. I mean, the additional wear spot could be due to the spring being elongated (flattened). The severe ammount of wear certainly would've lead to severe compression loss, and is likely what contributed to the chatter. The chatter looks a lot like what I used to see with the old Rotary Aviation springs, however I didn't see the seal wear like that. Atkins uses mazda springs with their own seals, and I've never seen a mazda spring flatten except under severe abuse. Let us know what you find.

arghx

iTrader: (3)

The FSM recommends that the short apex seal springs be replaced if the apex seals have a height of 7.5mm or less. If they were never replaced on the last teardown, that surely would have been a contributing factor to the lost compression.