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tuned pipe

Old 04-29-2012, 03:41 PM
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hydronut
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Default tuned pipe

I have bought a tuned pipe for a .21 os max.. I have cut and rewelded the manifold so the exhaust goes out the cowling on my Pay n Pak hydro, so now I cannot change the length of it. need to shorten the pipe up for high speed performance. Can I cut some length off the front of the pipe? Seems to be plenty there. Can someboly explain to me why not? Thanks for any help.
Old 04-29-2012, 03:46 PM
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Jerry Dunlap
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Default RE: tuned pipe

You can remove material from the front of the pipe.

JD
Old 04-29-2012, 04:54 PM
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HendricX
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Default RE: tuned pipe

Make your pipe adjustible .. after finding the right tuned-length with a decent prop . you can weld it again.

But I'm not a fan of that ... a different prop may need another tuned-length.

Here in Europe the proper tuned-length for a .21 is between 8.2 and 9.4".

Measured over the center-line from glowplug to exhaust belly-seam.
Old 04-29-2012, 05:53 PM
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hydronut
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Default RE: tuned pipe

If I measured right I have about 10.75".  Do I understand correctly?  I measured from the glow plug to the widest part of the pipe, and that's after I cut off 3/8" of the pipe.  I'm not going to get too carried away though.  I will be able to adjust it.
Old 04-30-2012, 03:07 AM
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Blackout
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Default RE: tuned pipe

ORIGINAL: hydronut

If I measured right I have about 10.75''. Do I understand correctly? I measured from the glow plug to the widest part of the pipe, and that's after I cut off 3/8'' of the pipe. I'm not going to get too carried away though. I will be able to adjust it.
Correct.

10.75" is too long to maximize rpm's. Any way to get it shorter?

Old 04-30-2012, 02:51 PM
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hydronut
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Default RE: tuned pipe

I shortened it up so I can adjust it from about 9.5" to 8.5".  I would like to thank you guys for the GOOD advice, I just ran it on the hose in my yard and it sounds like it is ready to scream , a big difference.  Seems to run good at all rpms.  Again THANK YOU VERY MUCH.  
Old 05-01-2012, 04:28 PM
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HendricX
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Default RE: tuned pipe

And if you have found the right prop/tuned-length , cut-off the manifold-length that is INSIDE the exhaust.
Old 05-01-2012, 05:10 PM
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hydronut
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Default RE: tuned pipe

HendricX,   I don't understand what you mean.  Could you please explain further.
Old 05-01-2012, 09:10 PM
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c.k.y.
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Default RE: tuned pipe

Hi hydronut

Direct
drive is to use 240-260m.m Scope....Important that you use propellers large and small.....Percentage of nitro (Need each other, cooperate with)
Propeller UseOctura 1445 or the ABC the H5 or H7 is O.K.
Exhaust joint position not to be longer than tunepipe Diffusion part of .
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Old 05-01-2012, 09:33 PM
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Default RE: tuned pipe

What they are telling you is that if the header extends inside the pipe, it changes the way the pipe works. You need to cut the header so that it's exit end is approximately in the same location as the inlet end of your tuned pipe. I would recommend moving the pipe back out to the end of the header and run it on the water and then start cutting it off a little at a time, running the boat so that you can monitor how the engine reacts to the changes under load

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