No more rings for me - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-06-2008, 08:32 PM   #1
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Default No more rings for me

Took the car from Chapel Hill to Myrtle Beach - long story short I've def killed a ring or two. Anything over 2psi = 8 - 10$ worth of Royal Purple out the tail pipe :-( Time for a compression/leakdown test and probably a motor (will post numbers) - still working on the house so poor miata has to wait a few months for it's transplant. It's perfectly drivable if I stay out of boost but that really sucks needless to say..
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Old 09-06-2008, 08:53 PM   #2
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What's the long story? How'd this happen? I'm curious since I haven't heard of any Xede mangaged engines dying..
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Old 09-06-2008, 09:47 PM   #3
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Dunno what caused it - just noticed a huge amount of smoke on acceleration (in boost) when I did a u turn and went down an exit ramp (I've basically driven it like I stole daily so it's no surprise the rings finally went - it's been @12psi for a while now). Car has 145K on it now too, I bought it with 18K on it and have driven the crap out of it. It's been boosted for ~30K miles now. Won't know more till I comp and leakdown test and pull the head but it really looks like rings given the massive blow by and no oil in the coolant and vice versa. Between one gas station and stopping at another with boosting in between (think 25 miles) it smoked a quart of oil. Now if I drive with no boost it's fine, no visible smoke and even up to 2psi it's good. So I'm thinking I'll set the wategate at 2psi till I can drop another motor in. I've had waaay too much fun in this car to give up on it :-) I don't care how many miles I rack up on it - I'm keeping forever unless it gets completely totaled etc.

The drive was ~4 hrs and I intermittently boosted slowing for hills etc where cops may hide out. Somewhere along the way one or more of the rings just bit the dust to a degree. Like I said it's derivable but not in >2psi unless you want to put oil in every time you stop. Lame. The good news - my buddy has a I-Beam in his garage with a rolling gantry and I'm gonna use the winch from my trailer (and buy a load leveler) to pull it along with tranny - since it's such a bitch to mate the tranny and motor under the car. Will be nice to get it all clean anyway.

I don't think exede is to blame in any way - Stephanie road tuned it and I found some small knock in 2nd when slowly going up hills etc and just added more fuel and that cured the prob. I did at one point run on retarded timing (think 6deg retard - my timing blet slipped!) which cooked a turbo and probably is to blame for the short life on the rings too since EGTs had to be well over 1500 (it was glowing bright red). Bell was awesome and replaced the turbo - no charge.

I will prob switch to MS PNP when I do the engine swap tho - I've been eying this for a long time now and want the granular control and better idle etc since exede cannot control pulswidth @ idle among many things a piggy back annot do (idle is rough but tollerable) and I have 550's among the many reasons to go to MS. But this will also let me take the old head and experiment on it :-) may port it etc while running the new motor and drop the old head on later. But it does mean the car is not really reliable and I commute ~90 miles a day which blows. The ring(s) could completely fail and I will be stranded - fun. I'm looking at buying another family/commuter car for doing the work drive so I don't put so much mileage on the miata but that's a hard decision too :-P
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Old 09-06-2008, 10:56 PM   #4
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Could be the seals in the turbo leaking. See if your charge pipes are really oily.
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Old 09-06-2008, 11:35 PM   #5
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I would hope not since this turbo has seen nothing but normal egt's etc on a good tune - no abuse on it per say but will check anyway when I do a comp test. A significant amount of blow by will oil up the piping too no ? I should add here that the valve cover vent is plumbed into the turbo inlet.
Thx,
-B
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Old 09-06-2008, 11:55 PM   #6
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It really sounds like turbo seals, it would be best to check that first seeing as thats the cheaper problem...
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Old 09-07-2008, 04:03 PM   #7
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GT 28!?! Ya, that sound's like a lot for stock rings (I hope this was a stock motor).

It's time like these that I wish someone would develop a pan for the miata you could get off without pulling the motor. That way you could pull a single piston without pulling whole motor. Last fall I snaped the crank in my truck; I just dropped the pan and got 'er done in one afternoon.

Of course a turbo model is more highly tuned than a old push-rod and will require a teidously machined, fine-tolerance rebuild. So where do you go from here? Gap-less or some other exotic internals for the next ring set?

Can't wait to see the carnage pics.
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Old 09-08-2008, 12:10 AM   #8
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Stock motor - still haven't had time to comp and leakdown test. If it's hosed I'm gonna buy a used motor and swap it then play with the old one.
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Old 09-09-2008, 01:58 AM   #9
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If the turbo oil seal is OK, you probably have cracked ring lands on a piston (or two). The stock pistons aren't all that strong and the top ring is placed relatively high on the piston to minimize emissions; one episode of detonation at 12psi can crack a ring land on a stock piston.
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Old 09-09-2008, 02:45 PM   #10
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It's also possible that your PCV shat it's guts into the head... pull your PCV and make sure it's still functional.

*edit * PVC != PCV
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