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Need advice on an engine pipe combo - 7/16/2008 7:33:05 PM   
RTK


 

Posts: 3953
Joined: 4/20/2003
From: CENTRAL , CA, USA
Status: offline 		Hello, I am in need of some information on a G62 and a Mac's pipe. I will admit, I am lazy and do not want to pull my engine, put it on a test stand and do this the correct way.
Does any one know what a good starting point would be for length?? Oh, I am using a 25mm drop header.
       Post #: 1

RE: Need advice on an engine pipe combo - 7/16/2008 10:52:51 PM   
pe reivers



Posts: 2770
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline 		The '62 has sweet spot at a total length up to the reflector in the tuned pipe of about 730mm, give or take a little.
Prop should allow 8500RPM, Which is ripping!
Want to stay lower in rpm, lengthen the header accordingly to a tuned length of about 830mm @ 6500 rpm.

Tuned header length is the length from exhaust port window to mean reflector length in the muffler or tuned pipe. It is wise to start at cone beginning for length, and then work down to mean cone length.

_____________________________

Pe, Dealer for MVVS, MTW and Mejzlik; www.mvvs.nl
There is sanctuary in analisys.

(in reply to RTK)
       Post #: 2

RE: Need advice on an engine pipe combo - 7/16/2008 11:56:53 PM   
RTK


 

Posts: 3953
Joined: 4/20/2003
From: CENTRAL , CA, USA
Status: offline 		Thanks Pe!
I was told I could pick up 800rpm++ with good throttle-ability, I am now running a pretty open stock muffler and turning a Menz 23x8 at 7100 same for a Mejz 22x10.
On the exhaust port window, is that from front, middle, or back??

(in reply to pe reivers)
       Post #: 3

RE: Need advice on an engine pipe combo - 7/17/2008 1:39:47 AM   
Rcpilot


 

Posts: 6555
Joined: 3/20/2002
From: Arvada, CO, USA
Status: offline 		I did it once but I can't remember how long my header was. Seams like I ended up cutting off about 1.5" or 2"

It was HOWLING with a 22-10 prop. I ended up deciding on a 23-10 that was turning around 7100RPM. It's been a long time though, and I ain't getting any younger. Can't remember the brand of prop. It was a Macs header and pipe. I had the setup on a test stand. The intention was to mount it on an 85" Extra, but I didn't want to cut up the plane to put the pipe on the outside and properly support it. All I had was a 90* header. At the time, I had no idea a DA 50 header would bolt up. Had I known that, I'd have ordered K&S parts to make my own drop header and ran the pipe right down the bottom of the fuse, like everybody does nowadays.

I was extremely impressed with how the engine responded to the pipe. I had done a handful of glow engines on pipes over the years but never managed to get one that wasn't "peaky" It was no big deal to get a glow engine tuned to run nicely at WFO. The problem was they had very little throttlability at idle and mid range. It was like having an ON/OFF switch on my throttle.

The G62 was not like that at all. It had smooth power from idle to WFO. No mid range burbling or thumping idle. It was like a Swiss watch on steroids!!!!! I actually picked up between 800 - 1200 RPM, depending on which prop I tried. I'm anal and I had lots of time on my hands at the time. I'd put a prop on it and tach it. Then a different prop. Then another one. I'd record all the RPMs on the different props and then cut 1/4" off the header. Slap all the props on again and write it all down. Cut off 1/4" and do it again.

Unfortunately, the notebook was ruined in a flood when I lived in Pueblo, CO. We had a 500yr storm roll through and the basement window wells filled up with water until the windows actually exploded and filled the basement. I had knee-deep water in the basement. That notebook was never found.

I'm jealous. Wish I had the time and money to do it again right now. Other priorities.

_____________________________

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I''m not really an airplane pilot; but I did stay at a Holiday Inn Express last night.

(in reply to RTK)
       Post #: 4

RE: Need advice on an engine pipe combo - 7/17/2008 5:52:49 AM   
RTK


 

Posts: 3953
Joined: 4/20/2003
From: CENTRAL , CA, USA
Status: offline 		Thanks

(in reply to Rcpilot)
       Post #: 5

RE: Need advice on an engine pipe combo - 7/17/2008 11:29:13 AM   
Richard D Bahmann aka/Wrongway



Posts: 2046
Joined: 1/7/2004
From: Ormond Beach, FL, USA
Status: online
quote:

ORIGINAL: pe reivers

The '62 has sweet spot at a total length up to the reflector in the tuned pipe of about 730mm, give or take a little.
Prop should allow 8500RPM, Which is ripping!
Want to stay lower in rpm, lengthen the header accordingly to a tuned length of about 830mm @ 6500 rpm.

Tuned header length is the length from exhaust port window to mean reflector length in the muffler or tuned pipe. It is wise to start at cone beginning for length, and then work down to mean cone length.


Pe is right on. My G-62 on E-Composits pipe with real close to that 730 mm gives 8400 rpm on a Vess 22A or 7800 on Vess 23A. Curious that with the same setup the NX-23x8 would only give 7100. Vess props work good on this setup.

The midrange is smooth and you can do lots with the setup with my 17.75 lb EF-88 Yak without having to rip the prop (midrange is really quiet) but when I want that 44 pounds of thrust it is there.

I like the added torque of the 62 over a 50 when you are in the first half of the throttle.

I got my 50mm drop header from DA and modified the port flange to match the G-62 by widening the holes on the pipe about 1 mm out and the slots on the head in about 1 mm. RTK let me know if you are building a header, I have the 62 flange just sitting in the parts box.

Richard

_____________________________

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       Post #: 6

RE: Need advice on an engine pipe combo - 7/17/2008 2:38:16 PM   
pe reivers



Posts: 2770
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline
quote:

ORIGINAL: RTK

Thanks Pe!
I was told I could pick up 800rpm++ with good throttle-ability, I am now running a pretty open stock muffler and turning a Menz 23x8 at 7100 same for a Mejz 22x10.
On the exhaust port window, is that from front, middle, or back??


exhaust calculated length depnd on the duct track length, so you should take the piston face at port centerline as reference. That is where the duct starts.
For mean reflector distance value you should take the mean of start and end of reflector cone (in theory without the stinger diameter part cut off)
Practical values never adhere exactly to theory, so the mid of the reflector is good enough to start with.

_____________________________

Pe, Dealer for MVVS, MTW and Mejzlik; www.mvvs.nl
There is sanctuary in analisys.

(in reply to RTK)
       Post #: 7

RE: Need advice on an engine pipe combo - 7/17/2008 2:43:13 PM   
pe reivers



Posts: 2770
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline 		RCpilet,

With these notes at hand I could now have calculated the power curves with the different setups.
Lessons learnt: beware of the rising tide!

_____________________________

Pe, Dealer for MVVS, MTW and Mejzlik; www.mvvs.nl
There is sanctuary in analisys.

(in reply to Rcpilot)
       Post #: 8

RE: Need advice on an engine pipe combo - 7/17/2008 4:06:13 PM   
mrbigg



Posts: 2817
Joined: 10/30/2004
From: Streator, IL, USA
Status: online 		With the Macs pipe, a header length of less than 12" is required for an RPM gain. With my header at that length, I didn't gain any RPM over an Abell side dump muffler. I was going to fly the plane and then trim the header a little at a time, but have since sold the engine.

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PROVERBS 15:22 - Plans go wrong for lack of advice; many counselors bring success.

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       Post #: 9

RE: Need advice on an engine pipe combo - 7/17/2008 5:21:20 PM   
RTK


 

Posts: 3953
Joined: 4/20/2003
From: CENTRAL , CA, USA
Status: offline 		Thanks for all the information guy, like I said, I am too lazy to remove the engine and do it like I should. It's a real pain in the A$$ to keep removing the pipe and adjusting. The 12 hour work days are taking all the fun out of my hobbies Now I can get it close and if a gain a few hundred rpm I will be happy.

(in reply to mrbigg)
       Post #: 10

RE: Need advice on an engine pipe combo - 7/17/2008 8:08:21 PM   
Richard D Bahmann aka/Wrongway



Posts: 2046
Joined: 1/7/2004
From: Ormond Beach, FL, USA
Status: online
quote:

ORIGINAL: pe reivers

RCpilet,

With these notes at hand I could now have calculated the power curves with the different setups.
Lessons learnt: beware of the rising tide!



Pe, when are you going to update your prop calculator and add in a Vess prop value? Sure would be nice.



_____________________________

Gonna kick the tire and light up my
Torch...Gone Flying...WrongWay

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       Post #: 11

RE: Need advice on an engine pipe combo - 7/17/2008 10:17:59 PM   
karolh


 

Posts: 2305
Joined: 5/15/2002
From: Mandeville, JAMAICA
Status: online 		Xoar props have gotten quite popular as well and having them included too would be great. I have heard it said that they are almost identical in design to the BME and NX props.

Karol
       Post #: 12

RE: Need advice on an engine pipe combo - 7/17/2008 10:21:31 PM   
pe reivers



Posts: 2770
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline 		The calculator is based on pitch prop constant and diameter.
Vess only provides diameter, but has no fixed pitch like standard props. Any comparison would be wild guesswork, unless one could set up in flight equivalences.

_____________________________

Pe, Dealer for MVVS, MTW and Mejzlik; www.mvvs.nl
There is sanctuary in analisys.
       Post #: 13

RE: Need advice on an engine pipe combo - 7/17/2008 10:25:29 PM   
pe reivers



Posts: 2770
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline 		Xoar is very close to a lot of wood props. It will be in my next unnumbered update soon.

_____________________________

Pe, Dealer for MVVS, MTW and Mejzlik; www.mvvs.nl
There is sanctuary in analisys.

(in reply to karolh)
       Post #: 14

RE: Need advice on an engine pipe combo - 7/17/2008 11:21:08 PM   
karolh


 

Posts: 2305
Joined: 5/15/2002
From: Mandeville, JAMAICA
Status: online 		That's great news, will be on the lookout for your update.

Karol

(in reply to pe reivers)
       Post #: 15

RE: Need advice on an engine pipe combo - 7/18/2008 11:13:01 PM   
RTK


 

Posts: 3953
Joined: 4/20/2003
From: CENTRAL , CA, USA
Status: offline 		Some number for every one to look at.

Remember I said I didn't have much time to put in to this, so I mounted the cannister (Mac's products) a couple of weeks ago by centering it in the tunnel.
I am using a DA 25mm drop header which I had to move the exhaust holes out a mm or so to fit my 62's pattern.
In that configuration which was 7 or so inches past Pe's recommendation I pick up a couple hundred rpm to 7200 on a 23x8.
Next I moved the pipe forward and left about 1/4" gap between pipe and stock header. Now I am turning 7500-7600 rpm on the same 23x8. BUT,,,,,I am still 3 inches short of Pe's and others recommendations.
So,, I feel I might be able