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Old May 23, 2012, 11:19 AM
CPA# 39
EscapeFlyer's Avatar
United States, MN, Brooklyn Center
Joined May 2009
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HB .61 PDP running a Vintage ST Tuned Pipe!

Starting to set up my HB with a tuned pipe. I own a vintage ST pipe and a Macs header.

Cool Power (Omega? The pink stuff...)15% nitro
OS F plug
11X7 APC prop
HB .61 PDP

Initial readings before I pipe it:

With Stock Muffler: 12,300rpm WOT

Open face (No muffler): 12,720rpm WOT
(The stock muffler really bogs down the engine!)

With Macs header (no pressure to tank): 12,900rpm WOT

13,000rpm goal is realistic. I might try to shoot for 13,500rpm. We'll see what it does as long as I keep a smooth transition from idle to WOT.)

Initial cut on header:

200,000 divided by 13,000= 15.38"

I can cut the header to 15.5 inches from center of the combustion chamber to the center of the converging cone on the pipe as the juices fly out of the combustion chamber.

I will choose to start on the safe, long side, and I will make my initial cut at 16.25 inches and slowly cut my way in. We'll see how it goes!

This engine is impressive!

(btw- my Super Kaos is loaded with Robart pneumatic trike retracts and weighs 6.2lbs before the pipe set-up with the stock muffler. This should be amazing!)

Brian
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Last edited by EscapeFlyer; May 23, 2012 at 08:53 PM.
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Old May 23, 2012, 02:12 PM
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It is looking really good. Do let us know how it goes and what you find out as you tune the pipe in.
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Old May 23, 2012, 02:17 PM
CPA# 39
EscapeFlyer's Avatar
United States, MN, Brooklyn Center
Joined May 2009
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OH YEAH!!!!

5/23/2012

Primary objective: 13,000 rpm

Stormy weather today. no flying. I decided to play with the tuned pipe a little more.

I was swinging roughly 12,500 RPM last post. I did the math for 12,500 and here is what Jim has shown me:

200,000 divided by 12,500= 16 inches.

Upon measuring, I was 12, 500 at 18 inches. Definitely too long.

My reasonable goal is at least 13,000.

200,000 divided by 13,000=15.38 inches (15.5")

I cut 1 1/4 inches off the header. There isn't much of the header left to cut!

I am now at 16 3/4 inches swinging 13,020 rpm at WOT consistantly settling. I am one happy camper. She is pulling out of my hands pointing straight up!

Problem is... She is still pretty rich and throttle sags rich at mid-range. She wants to give me some more! Not done yet.


Brian
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Old May 23, 2012, 02:33 PM
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As there is a lot of "header" on the pipe you might want to think about cutting the pipe lead in. Normally you don't want to cut the pipe. But this is only because the header is cheaper. You want to stay out of the header radius and the pipe's divergent cone with the part line.

You might want to think about going up in prop load (maybe an 11x8) and bringing down the rpm (this might fit the pipe and header a bit better). My mentor liked to measure the pipe length from the face of the piston as that is the opening and closing valve to the pipe.

Are you aware of this site and its applet?
http://www.mh-aerotools.de/airfoils/javapipe_en.htm

-Matt
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Old May 23, 2012, 03:51 PM
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If you go a bit too short, don't worry because it will unload in the air, especially with a higher pitched prop. In fact it may hold you back if it is too long. There is a point of no return though.
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Old May 23, 2012, 06:17 PM
CPA# 39
EscapeFlyer's Avatar
United States, MN, Brooklyn Center
Joined May 2009
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Quote:
Originally Posted by MDonnahoo View Post
As there is a lot of "header" on the pipe you might want to think about cutting the pipe lead in. Normally you don't want to cut the pipe. But this is only because the header is cheaper. You want to stay out of the header radius and the pipe's divergent cone with the part line.

You might want to think about going up in prop load (maybe an 11x8) and bringing down the rpm (this might fit the pipe and header a bit better). My mentor liked to measure the pipe length from the face of the piston as that is the opening and closing valve to the pipe.

Are you aware of this site and its applet?
http://www.mh-aerotools.de/airfoils/javapipe_en.htm

-Matt
Thinking about that one... It makes sence. I'll talk to my mentors on this.

I can probably cut another 1/4 to 1/2 inch off the header. I won't want to go any further than that. If needed, I will go after the pipe, but it is a vintage Super Tigre pipe and hard to find. If I don't have to and can fix it by going to a steeper pitch like an 11X8 I will.

I am enjoying this learning process very much!

Brian
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Old May 23, 2012, 08:00 PM
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United States, IA, Rockwell
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Brian, When you get "close" fly the plane as you want the engine to be responsive in the air. Flying is the true test. Easy to over do it on the test stand.

Now you must understand I got lucky on my one and only tuned pipe. I hit the nail the first time around. So with that said, take my words with a grain of salt

Ken

LOOOOOKING GOOOD
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Old May 24, 2012, 05:38 PM
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You may want to try a colder plug to clean up the midrange.
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Old May 24, 2012, 05:46 PM
CPA# 39
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United States, MN, Brooklyn Center
Joined May 2009
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Quote:
You may want to try a colder plug to clean up the midrange.
I had to stop rather abruptly yesterday because of the weather and never had the chance to adjust the High and low end. So I know I will pick up more rpms that way. (Weather was bad today too.. Maybe tomorrow will be kinder to me.) I doubt that will cure the problems with the mid-range as I think I need to adjust the system a little more yet.

I'll keep that in mind! Thanks!

Brian Lundberg
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Old May 24, 2012, 10:20 PM
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Current thinking on the colder plug is that if the plug is very hot (like a 4 stroke plug) you have to richen the high end too much to compensate thus creating a rich midrange. I have run into this situation several times. However if you have just begun to tune you may be fine.
Great looking plane by the way.
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Old May 25, 2012, 01:38 PM
CPA# 39
EscapeFlyer's Avatar
United States, MN, Brooklyn Center
Joined May 2009
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Thank you for that compliment. I really appreciate it. I am proud of the way it turned out.

I adjusted the carbonmaker today to allow for a 200 rpm increase using the pinch test on the fuel line.

This system is still too long and has plenty more power to give me. But, with this being my 1st tuned pipe experience, I think I will fly it here for now and see how I like it.

I can always cut more header, but I can't add to it!

I have a nice transition between idle and WOT.

Top end is 12,900rpm.

I'll probably be swinging 13,400-13,500 in the air as it unloads.

I will try it here for now...

Hope to fly tomorrow!

Brian
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Old May 27, 2012, 08:01 PM
CPA# 39
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United States, MN, Brooklyn Center
Joined May 2009
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I think I will try a cooler plug... like say an OS 8 maybe.

Brian
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Old May 27, 2012, 08:38 PM
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If you can get Merlin plugs you may try a 2002HD or 2003, I just love Merlin plugs.
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