Carbon Monoxide

[tonykasabasich]

Is there really that big of a performance loss with the longer exhaust tubes? I know it's catching some air but it'd be surprised if it was 1mph.

I didn't think Eric's looked that bad. And it seems like it's a safe idea.

Do you think the shape of the stack matters? Eric's come straight down. What about a slight backwards bend so they'd look cool even if hanging down 10" ?

Does bending them back allow the exhaust to get pulled from the tube easier? The loss of back pressure might help some and hurt others for engine performance.

Ideas ????

 

[EricM]

Tony,
My exhaust pipe extensions actually do have a 45 degree bend about 5" below the cowl and they do angle away from the cowl about 10 to 15 degrees. I think I my extensions may have been overkill but they do keep 100% of the CO out of the cockpit. If I cannot figure out a good way to install pipes inside the cowl which exit at the bottom, I will redesign the external ones to make them look more streamlined.

Eric

 

[Chuck in Indiana]

Is there really that big of a performance loss with the longer exhaust tubes? I know it's catching some air but it'd be surprised if it was 1mph.

I didn't think Eric's looked that bad. And it seems like it's a safe idea.

Do you think the shape of the stack matters? Eric's come straight down. What about a slight backwards bend so they'd look cool even if hanging down 10" ?

Does bending them back allow the exhaust to get pulled from the tube easier? The loss of back pressure might help some and hurt others for engine performance.

Ideas ????

I read an engineering thingy more than a few years ago that said the bolus of gas exiting a straight down exhaust like used in most Sonerais could be considered to have the equivalent drag of a round tube 18 inches long.
Really? Sounds like a lot. At any rate, I pointed them aft on Mouser..

 

[JuergenA]

Hi Chuck,
the engineering thingy you had read some times ago, give a good comparison.
In real, the exhaust gas, which comes out from the tube, have only the speed from exhaust and the speed of the plane, not the speed of the air, you fly through. You can imagine, that there is on each end of the four tubes a ball of exhaust gas and this will increase the drag of the plane. You don' see the exhaust ball, but it exists and must be (negative) accelerated to the speed of the air you fly through.
Build a exhaust with tube ends to the rear and your cruise speed will increase (5mph or so.. ) or the fuel consumption of your plane goes lower at the same speed.
with best regards
Juergen

 

[Gaston]

Very interesting...
I remember I read something similar to this, a very long time ago...
But at this time, I was more sport cars oriented ,and I didn't even fly...

many years ago ,I built an exhaust system for my 1834,which consisted of 4 long pipes exiting the cowling down under...
It performed very well even if they were not even in length,the main the goal at this time was to get rid of exhaust fumes in the cabin and it worked well for that...
as a side effect the exhaust sounded very melodious to my ears,with a lower cockpit noise level.

I got rid of this when I installed my 2276 for a few reasons including lower in cowling temp, less weight,and simplicity.
Now ,I miss them mainly for the great sound they made...

Y now use exhaust gap seal(see photo),on all 4 stacks and have very rarely light exhaust fumes inside...

Gaston

 

[Schmleff]

IMHO, I would be concerned with the long pipes breaking at the flange.

 

[Airskip.2010]

That you guys know of, has anyone tried curving the front stack to run along the line of the couling and dropping and joining the rear stack into that line, yielding a single outlet on each side, then maybe, directing the exhaust outward like some of the old fighter planes?
Just curious.
Skip

 

[Raceair]

Airskip.....I did a version of that originally on Blueberry...Welded the front stack into the rear, with the outlet facing aft and out, at about a 45 degree angle as much as possible....This was all up in the cowling, so was fairly tight. I also tried the four separate stacks for a while, and they faced almost totally aft at their exit. After I sold the airplane it got the 4 into 1 system.....Ed

 

[Airskip.2010]

Hey, Ed.
How did the two (left & right) single exit exausts work for you? Would it be wise to increase the diameter of the exiting exhaust stack for better flow?
Skip

 

[Raceair]

Worked well, 'sounded' a bit odd from the side....Yes, I forgot to mention,,,the front pipes were 1 1/2" or 1 3/8", I think, and the rear pipes were 1 1/2".....It's been so long, I can't remember all the details, but I put a stainless 'liner' around the exit area, riveted to the fiberglass cowl, which helped the cowl from burning....Ed