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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 02-22-2013, 12:21 PM   #81
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not sure how this will affect vibration significantly.

assumptions I'm making:

1. the manifold stiffness is >> the crane stiffness (thick tubing with large section vs. lil pipey)
2. vibration amplitude can only be decreased by:
a) reducing the excitor (engine vibration, chassis vibration)
b) isolation of the excitor from the target
c) moving the resonance frequency of the target far away from the excitor frequency(ies)

The cranes don't really do any of those. They DO provide a little bit of load bearing capability against the weight of the turbo / mani, but that's pretty much it.

If you want reduce vibes, you can really only increase stiffness (reinforcements, cranes) of the system or increase mass of the system. I'd argue that increasing stiffness will only raise the resonant frequency of the vibration to a higher rev range, and not above the working conditions.

adding mass will probalby help but might make the weight load much worse than it already is. But if you're building a crane, might as well build a bigger crane!
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Old 02-22-2013, 12:26 PM   #82
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The crane by itself might not be very stiff, but Look at what it does to the geometry of the whole package and how that changes sitffness. I can go out the the fase car and cut one or two 1/2" thin wall tubes and turn that chassis from a raging hard on to a flaccid piece of ****.
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Old 02-22-2013, 12:47 PM   #83
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Wrap the manifold with dynamat. A few boxes worth.
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Old 02-23-2013, 11:22 AM   #84
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So is a crane worth it for preventative reasons on a car that will see a lot of street time but will also have 8-10 race weekends on it a year?
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Old 02-23-2013, 11:34 AM   #85
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Unless you've characterized the problem with an engineering analysis and know exactly what you're trying to address . . . no.

If you look at those F1 cranes from the '80s Renault engines, you'll notice:
1. The turbo components are large and at extended moment arms away from the engine (not a compact log manifold);
2. There were no structural elements available for bracing (in our case, downpipes run along the engine and transmission offering a lot of good places for effective braces/supports);
3. They did finite element analyses and vibration analyses. They knew exactly what they were trying to address and designed the lightest possible effective supports. None of that preliminary engineering work has been done here.

The effective solution for Miatas is a downpipe brace secured by the transmission bolts. Especially when running a log manifold and Inconel studs. I think what Curly is trying to do here is relieve some of the tension on his top turbo studs, but I doubt it's needed. In comparison to the strength of the log manifold, those braces are low-strength.

Simpler = Better.
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Old 02-23-2013, 11:41 AM   #86
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Alrighty then, thank you for the detailed answer.
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Old 02-23-2013, 12:17 PM   #87
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Yup, Just looking for a little stud support. An exercise in fabrication as well.
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Old 02-23-2013, 12:41 PM   #88
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using the center bolt is going to be REALLY hard for him.
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Old 02-23-2013, 01:54 PM   #89
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Quote:
Originally Posted by curly View Post
Yup, Just looking for a little stud support.
Attached Thumbnails
Pictures of my rod for Hustler-542707_341135009330986_1250718343_n.jpg  
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Old 03-07-2013, 01:24 AM   #90
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^wow, way to gay it up
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Old 03-07-2013, 01:49 AM   #91
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Quote:
Originally Posted by greddygalant View Post
^wow, way to gay it up
Did you climax without the funnel mask for the first time in your pathetic life?
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