Exhaust Stack: Which Way Does It Go?

sj · Post by sj » Mon Mar 03, 2003 1:09 am

When I bought my 170 my exhast stack pointed backwards like this. My AI turned it around and said the "cut" should face forward. Which is correct?

Thanks!

sj

doug8082a · Post by **doug8082a** » Mon Mar 03, 2003 1:25 am

From what I can see in my '52 owner's manual and the Illustrated Parts Catalog, facing the cut forward as your AI put it is correct. My '52 is also configured this way.

sj · Post by sj » Mon Mar 03, 2003 1:34 am

Thanks!

Koop · Post by **Koop** » Mon Mar 03, 2003 3:23 am

I think your AI put them on backwards.

sj · Post by sj » Mon Mar 03, 2003 12:33 pm

The picture above is the "wrong" (or original) way they were. I do not have a picture of how they are now. Are you referring to the picture?

sj

Koop · Post by **Koop** » Mon Mar 03, 2003 5:09 pm

sj wrote:The picture above is the "wrong" (or original) way they were. I do not have a picture of how they are now. Are you referring to the picture?

sj

What I'm saying is that I don't really know which is the correct way, but the picture looks right to me. The stacks on my 55' are the way yours are installed in the picture. Looks like a nice 170. koop

zero.one.victor · Post by **zero.one.victor** » Mon Mar 03, 2003 5:23 pm

With the slash facing aft,seems like the slipstream would help scavage the exhaust flow--with the slash facing forward,seems like the slipstream would increase back pressure,making it harder for the engine to "breathe".The difference might be pretty slight though. I think I'd face the slash aft.

Eric

Koop · Post by **Koop** » Mon Mar 03, 2003 5:34 pm

And a little more drag---koop

Watkinsnv · Post by **Watkinsnv** » Tue Mar 04, 2003 3:15 am

Continental ran all their tests and they want the back pressure. Lance

Koop · Post by **Koop** » Tue Mar 04, 2003 4:39 am

I would like to know more about Continental's test and why they want more back pressure. Do you have more information on this subject and or where we could find it? koop

mit · Post by **mit** » Tue Mar 04, 2003 7:07 am

sj wrote:When I bought my 170 my exhast stack pointed backwards like this. My AI turned it around and said the "cut" should face forward. Which is correct?

Thanks!

sj

Your picture does indeed have them backwards. However it is not the the only one that has been like that for years. So who knows if it makes a difference???

wa4jr · Post by **wa4jr** » Sat Mar 08, 2003 3:30 pm

I'd like to know more about this Continental engine test. Conventional wisdom says backpressure is the enemy of any effeciently breathing engine. The only reason I can see for having a substatial amount of backpressure is to reduce backfiring during engine decelleration or power off descents where the prop is driving the engine. I have the Bartone pipes so this is a non-issue for me...I'm just curios about the test and the logic behind it.

russfarris · Post by **russfarris** » Mon Mar 10, 2003 7:39 am

Boys! Some probably long dead engineer at Continental decided that the slash should angle toward the front. My IA wanted to turn them around the other way, until I showed him the IPC and numerous vintage photographs; then he relented.

Alright, so it doesn't make sense, but there is no doubt some reason.
I can't imagine it would make much difference, as illustrated by the many 170s that have them both ways.

What an interesting hobby this is! Russ Farris

zero.one.victor · Post by **zero.one.victor** » Mon Mar 10, 2003 6:13 pm

The one advantage would seem to be that the angle of the slash cut would pretty closely match the contour of the lower cowl,and be more pleasing to the eye.
I'll go you guys one better,my ragwing has the pancake mufflers,on which the tailpipes are welded one-piece. I have one with the slash facing aft,and one with the slash facing forward! The IPC indicates two different part numbers for LH/RH mufflers,I think the only difference is the tailpipe so I'm pretty sure I have two of the same p/n. The IPC doesn't show which way the slash is,so I don't know if they're both LH or RH.
Doesn't hurt the way it runs......

Eric

N170BP · Post by **N170BP** » Mon Mar 10, 2003 6:53 pm

What about the Swift guys? The stock O-300 powered ones
I mean.... I wonder if the mufflers / stacks are the same?

Have a look at these pictures:

http://www.napanet.net/~arbeau/swift/a0226.jpg

http://community.webshots.com/image2/1/ ... xwh_ph.jpg

I didn't do an exhaustive search, but a number of the photos
I did come across have the stacks oriented as in the above
photographs.

Bela P. Havasreti
'54 C-170B N170BP

The International Cessna^® 170 Association

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