It's Inevitable Part: Double Quadrahelix - Miata Turbo Forum - Boost cars, acquire cats.

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Old 07-12-2008, 07:44 PM   #1
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Default It's Inevitable Part: Double Quadrahelix

Prologue: A few months back I PM paul and ask him if he ever had issues shaving down the screws on his butterfly valve when he ported it. Said all was well for years, so i decided to go at it as well.

Inevitability:
Car runs great for 5 months driving over 100 miles a week to work, averaging something like 25mpg.

A few days before I have a scheduled dyno tuning hour, I stop at a stoplight and notice my idle is smooth at 1500RPM. hmm. try to blip the throttle, turn the a/c on/off...nothing, steady at 1500RPM. Light turns green. Sounds of death and lack of power. shut it off.

pull over, try the ignition again and get out...sounds like something is bouncing through my motor....run to shut it off, then nothing. blip the throttle, sounds great. decide to continue to drive to work.

put two and two together and discover this:




BLAH:


Decided to ignore it and pretend I was very lucky. However it seems that's not the case.



Here's the comparison of what I ran last year with no headwork and a restrictive exhaust and a shitty tune:




So something is fubared :( there's no way my resonator did that....so I have to blame a fubared turbo. I absolutely cant make more than 12.5psi. I fear chewed up turbine blades, I all my logs from last week show me at 13.5-14psi and I was hitting it closer to 3700. Compression check resulted in 185 - 177 - 180 - 187.

Here's how the motor ran on the exact same setup. Only difference physically is an added resonator and larger FMIC:




I fail.
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Old 07-12-2008, 07:48 PM   #2
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Ouch! Thanks for the heads-up Scott, hope you get up-n-running again soon!
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Old 07-12-2008, 07:56 PM   #3
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Scott, could you post a pic of the TB like it should be so we have an idea of what you think the motor ate?

Is it a screw or bolt or what? How much room is there between the valve and the seat? Could it have gotten through? Do you think you bent a valve a little or what? Take the head off? Pop the turbo off at the least... what?
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Old 07-12-2008, 08:15 PM   #4
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https://www.miataturbo.net/forum/showthread.php?t=22438


Post two has the original pictures before he messed with it.
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Old 07-12-2008, 08:43 PM   #5
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Why not remove the screw, loctite it, then return prior to shaving?
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Old 07-12-2008, 08:50 PM   #6
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I'm just trying to figure out the purpose of the screw, it's no onger there and the butterfly valve didnt fly in the mootr or anything, so why couldn't you just remove the screw and fill the hole with JB weld or something along those lines?
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Old 07-12-2008, 08:51 PM   #7
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Quote:
Originally Posted by Ben View Post
Why not remove the screw, loctite it, then return prior to shaving?
Or better yet, leave the stock TB alone since that probably netted him about 0.5 hp.
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Old 07-12-2008, 08:52 PM   #8
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Quote:
Originally Posted by brgracer View Post
Or better yet, leave the stock TB alone since that probably netted him about 0.5 hp.
Actually it netted him negative 23 and the privelege of buying a new turbo
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Old 07-12-2008, 08:53 PM   #9
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Quote:
Originally Posted by KPLAFIN View Post
ctually it netted him negative 23 and the privelege of buying a new turbo
Dayum, burn on a burn.
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Old 07-12-2008, 09:00 PM   #10
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I was just reading bout this the other day thinking...."hmmm, that seems easy/safe enough"....

Hope not as bad as ur thinking man...
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Old 07-12-2008, 09:01 PM   #11
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scott when's the teardown?
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Old 07-12-2008, 09:24 PM   #12
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Sorry to see that Scott.

BTW, what turbo did you have?
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Old 07-12-2008, 09:25 PM   #13
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yikes. theres one mod I was considering, that I wont be doing.
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Old 07-12-2008, 10:37 PM   #14
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Quote:
Originally Posted by Ben View Post
Why not remove the screw, loctite it, then return prior to shaving?
I actually tried this as a safety measure. I literally couldn't remove them.

Furthermore, I figured I'd take a screw from my stock TB and simply plug the hole...but again, even after an hour in PB, I couldn't remove the screw... stripped.


The motor seems to be fine, compression is good, no issues relating so a bad valve. The turbo is what seems to be Fubared. Chad has a spare turbine that he can send me, what a nice lad. Probably be back at 100% next weekend. Got my Begi heatshields I can mount too
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Old 07-12-2008, 10:45 PM   #15
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Quote:
Originally Posted by samnavy View Post
Scott, could you post a pic of the TB like it should be so we have an idea of what you think the motor ate?
should be two screws....



Quote:
Is it a screw or bolt or what? How much room is there between the valve and the seat? Could it have gotten through? Do you think you bent a valve a little or what? Take the head off? Pop the turbo off at the least... what?
yeah a screw. not sure, enough to pass it through...obviously. i thought i might have, but i think the HLAs might have saved me form that. I have no symptoms of a bad valve. no, i dont want it. i will, next weekend, maybe tomorrow evening.

but like i said, if i completely close my wastegate (100% DC), i still make 10psi at 4k and builds to 12.5psi at redline. when last week, the ebc was flat at 13.5psi at 22% DC.





sidenote: i was lucky to find a modded TB at the shop we were at that had a Wells TPS120 on a miata TB. so I took it, and now i can have tps on my stock TB.

anyone want a ported auto TB with a missing screw?
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Old 07-12-2008, 11:17 PM   #16
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I'll take it!
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Old 07-14-2008, 01:30 PM   #17
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soo.. dibs on broken turbo for my desk fan project?
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Old 07-14-2008, 01:46 PM   #18
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If the only thing that's fubar'd after going through the motor is the turbine I'd be pretty happy.
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Old 07-14-2008, 02:06 PM   #19
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Quote:
Originally Posted by johndoe View Post
If the only thing that's fubar'd after going through the motor is the turbine I'd be pretty happy.

i know right! but it seems to be that way. ill know for sure this weekend. but the compression check says the motor is healthy and the symptoms of slow spool and low peak boost is identical to Rob's issues....where he had a chewed up turbine.
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Old 07-14-2008, 03:09 PM   #20
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I remember a couple of months ago, you were talking about how you have so much build time and so little seat time. This seems to be holding true... That really sucks!
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