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Piped OS .25 FX: presssure fitting location?

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Old 03-15-2008, 10:23 AM
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betatester21
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Default Piped OS .25 FX: presssure fitting location?

Hi everyone...

I´m kinda new with pipes. Altough I understand the working principle, I can´t figure out where is the best place to put the pressure fitting. I want to make tests with my almost-new .25FX and a Macs pipe (see pic).
What do you reccomend?

Thank you!


Pipe:



Header:




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Old 03-15-2008, 10:29 AM
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soarrich
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Default RE: Piped OS .25 FX: presssure fitting location?

I've found that right on the flatbar of the header works well, I make the pressure fitting stick down into the stream, and cut it off at an angle so it acts as a scoop. If you put it right at the widest part of the pipe it work fine too , no need for any "scoop" on the pressure fitting there.
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Old 03-15-2008, 12:10 PM
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Default RE: Piped OS .25 FX: presssure fitting location?

Putting the fitting on the headpipe works well. I drilled and tapped the head pipe. You
only get one thread or so. Then I snugged a nut up to the pipe, and put a drop of thin
CA on the parts. It's held up now for 5-6 years. I remove the pressure line every time
I fuel the plane, so it is stronger than you would think.

FBD.
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Old 03-15-2008, 03:32 PM
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betatester21
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Default RE: Piped OS .25 FX: presssure fitting location?

OK, I like both ideas... I'm just thinking that putting the nipple on the flatbar can make pressure swirls and affect the returning waves, and it can be even worse if there's a scoop... it's also the easiest place to work on!
I think that maybe the right position will be the header tube itself, in order to keep the pipe as original as it can be. Maybe I do so.

Another one: I've read and re-read the Macs guide to tune the pipe, and I'm not quite sure about it. They say that you must tach your engine at "open face" (no muffler or nothing), and then install the header and pipe; then cut 1/4" of the hader pipe until the RPMs start to decrease, stop there and you're ready to go. Question is: is there any other "scientific" way to do it, or it's just trial and error? Is this the way you tune up pipes?

Thank you very much, your experience is invaluable for me!!

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Old 03-15-2008, 06:54 PM
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Default RE: Piped OS .25 FX: presssure fitting location?


ORIGINAL: betatester21

Question is: is there any other "scientific" way to do it, or it's just trial and error? Is this the way you tune up pipes?
It's trial and error. You just have to sneak up on it. Too many variances include the make of engine (day of the week it's made) fuel, plug, prop, temp, altitude, type of flying and on and on.

http://www.macspro.com/pressure.asp
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Old 03-15-2008, 08:24 PM
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Default RE: Piped OS .25 FX: presssure fitting location?

....you have to have the correct fuel, prop and plug before you work on the pipe.

It is important to know if the engines is actually going to come on the pipe (a radical
increase in RPM), or are you simply influncing what prop you are going to run. In other words
setting up the pipe for torque, or RPM.

FBD.
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Old 03-18-2008, 06:55 AM
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Default RE: Piped OS .25 FX: presssure fitting location?

Thanks!

I'll start my testings this weekend... I really apreciate your comments.


Thanks again!!
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