Exhaust Stack: Which Way Does It Go?

[zero.one.victor]

The C-125 powered Swifts I've seen,as well as several of the 145's,use the stock "3 into 3" straight pipes. They really sound good too,smooth yet sorta growly! I can only hope my 170 sounds as good!
BTW,in case you didn't know,the GC1-A model Swifts were powered by a C-85,the GC1-B used a C-125. Anything else is a mod. The upgrade to a C-145 is an easy and common improvement,from what I've seen and heard.

Eric

[sj]

Can't access the second picture.

I do notice the bird is louder with them turned around the "right" way.

sj

[Koop]

The C-125 powered Swifts I've seen,as well as several of the 145's,use the stock "3 into 3" straight pipes. They really sound good too,smooth yet sorta growly! I can only hope my 170 sounds as good!
BTW,in case you didn't know,the GC1-A model Swifts were powered by a C-85,the GC1-B used a C-125. Anything else is a mod. The upgrade to a C-145 is an easy and common improvement,from what I've seen and heard.

Eric

I was wondering how the Swift obtained cabin heat with straight pipes and I assume no mufflers? I have been thinking about straight pipes ever since I payed over $900 for two new mufflers for my 1955 170 B. I know this model comes with an optional heater but I suppose you would have to go through the FAA even if you could do away with the cost of the mufflers. I have seen a modification on an RV6A with straight pipes for cabin heat. I bet the FAA would like to see that set up! Not sure how it works or how safe it is. koop7435

[zero.one.victor]

Koop,there's a kinda triangular-shaped heat muff on each side around the exhaust pipes right where the three of them come together side by side,above where they exit the lower cowl. Ya don't need a muffler to have a heat muff. I've seen Luscombes with a heat muff just around a straight piece of pipe.

Eric

[Koop]

Koop,there's a kinda triangular-shaped heat muff on each side around the exhaust pipes right where the three of them come together side by side,above where they exit the lower cowl. Ya don't need a muffler to have a heat muff. I've seen Luscombes with a heat muff just around a straight piece of pipe.

Eric

So what is the reason for having mufflers except to quiet things down? Are Cessna 170s required to have mufflers? I don't remember reading about them in the Type Certificate. Guess I should get up and go look. There is a Cessna 120 in our shop and it just has the metal shield around the exhaust pipes. I was told by the mechanic that he didn't think they put out that much heat. I quess my real question is, if some of the Swifts have the 0300 in them and are running them without mufflers shouldn't 170 owners have the same option? koop7435

[zero.one.victor]

Items 103 (pancake mufflers) & 110 (Hanlon-Wilson mufflers) on the type certificate data sheet identify the approved exhaust systems for the 170 models. Straight pipes would have to be installed by field approval. the only exhaust mod I've ever seen on a C-145 powered 170 is the swept tailpipes for the H-W system,as sold by Bartone and Benham.
I suppose a person could fabricate straight pipes,or pirate a set off a Swift. Lighter and better sounding,I'm all for it. Let me know when ya get your approval.......

Eric

[wa4jr]

NOW we are talking! I've been thinking about this as well. There are a bunch of planes flying with no mufflers and I think the 170 would do well without them. Keeping CO out of the cockpit would be much easier with no mufflers as there would be less surface area inside the heat muff in which to develop a crack...of course I suspect that would mean less heat for carb and cabin heat as well. What does George have to say about us throwing away our mufflers when they crack and just going to straight pipes with fabricated heat muffs and of course a nice new FAA field approval??? George?????

[Koop]

George is gone! Most likely on some beach in South America. koop7435

[funseventy]

I'm waiting for george to chime in. I know I have seen it in print talking about this and I'm sure georg has it on the shelf. With it facing forward it is actually cut parrallel to the slipstream. If it is facing aft it creates a burble that causes back pressure that they thought was excessive. Does it make any difference? I don't know, but forward is correct. Come on George I need some Back up!!

Kelly

[GAHorn]

I don't believe "back pressure" was ever an issue. Straight pipes would have done the trick, but would not have looked streamlined. The cut is faced forward and outward to parallel the lower cowl in order to reduce soot deposits.