Exhaust air intake scoop

[IdahoPilot]

Sorry for asking so dang many questions. Trying to figure out the exhaust intake for carb and cabin heat. I have seen a picture that shows scoops coming through the front baffle. But in the IPC it looks nothing like them. Just want to be sure we order the correct parts. Any help would be awesome. Thanks guys and gals

[n3833v]

Pass side goes to firewall for heat. Pilot side to carb heat. Don't have pics here

John

[Bruce Fenstermacher]

Well John might be correct depending on what mufflers you have on your '48.

The '48 IPC has the set up for the pancake mufflers. It is different if you have the correct Hanlon Wilson mufflers. By meaning correct you should have the Hanlon Wilsons for a '52 B model. Not a '53 or later.

First there should be no scoops sticking up above the baffles into the air intake. These where used later. If you have them someone added them in an attempt to get more hot air and I would leave them installed if there. As in the '48 IPC the 2" scat comes off the front baffles on each side and goes to the front exhaust air inlet on the heat shrouds on the mufflers. This is the same for pancakes as well as the correct Hanlon Wilson mufflers.

Now if you have the pancake mufflers you should also have a Y pipe which is attached to the carb heat box. This Y actually has 4 openings, two inlets and two outlets and a flapper inside. 2" scat should go from the rear of each muffler heat shroud exit to each side of this Y. Then 2" scat goes from the middle Y exit to your firewall heat manifold which is either in the lower middle or above the pilots feet.

If you don't have pancakes and you have the correct Hanlon Wilson setup 2" scat goes from the left rear muffler heat shroud directly to the firewall heat manifold. On the right 2" scat goes from the rear muffler heat shroud directly to the carb heat box. No Y is used.

All the above is correct and approved. But what if you don't have the correct right Hanlon Wilson muffler for the right side and you want to use what you have. Here is what I'd do and I'd talk my IA into it being a minor alteration.

IF you have the incorrect Hanlon Wilson muffler for the right side then the correct heat shroud will have a funnel like entry point for 3" scat. You can either adapt it to 2" coming of the from baffle or do as I would and change the 2" baffle inlet to 3". Then the exit of this heat shroud will be out of the back under a V shark mouth shaped shroud. This will also be 3" If you adapted the front down to 2" then I'd adapt this down to 2" and run it directly to the carb heat box.

Now if you adapted the scat to 3" on the right side then I would use the right side as my cabin heat by going the rear to the cabin heat manifold but you will have to do some more adapting because that manifold is made for 2" scat. I'd then run the 2" scat from the left side to the cabin heat. You will be getting the same amount of carb heat as the approved method, just from the other side. And you may actually get more heat from the lager 3" scat.

Hope you followed all of this.

[bagarre]

What year is the plane?
My '52 has the scoops in the front of the baffle that you mentioned. The 'scoop' attaches to the heat muff for that side directly.
Then, the heat muff connects directly to the heater valve (left muff) and carb heat (right muff) as mentioned prior.
I'm pretty sure the '52 is the same as the earlier 170's and very sure the 53 and up are quite different.

[Bruce Fenstermacher]

What year is the plane?
My '52 has the scoops in the front of the baffle that you mentioned. The 'scoop' attaches to the heat muff for that side directly.
Then, the heat muff connects directly to the heater valve (left muff) and carb heat (right muff) as mentioned prior.
I'm pretty sure the '52 is the same as the earlier 170's and very sure the 53 and up are quite different.

We were posting at the same time. Actually the '52 is similar depending on the mufflers. The scoops are a '52 thing and maybe even as far back as '50 but are not found on '49 and '48 aircraft. See my post above.

[HA]

just to help confuse things I'll add that my 172 doesn't have any scoops, just openings in the baffling. I've seen people add scoops to their planes of various types on the theory that they'd get some more airflow for heat, but I've never noticed any problem there. I did make a cutout on my homemade winter front that ramps air down to the heater opening and that all seems to work fine.

[bagarre]

Normally I get an alert when a post happens while Im posting.
But, yeah, what Bruce said

[IdahoPilot]

We were posting at the same time. Actually the '52 is similar depending on the mufflers. The scoops are a '52 thing and maybe even as far back as '50 but are not found on '49 and '48 aircraft. See my post above.

It is the 1948. It had the pancakes, but we had a Hanlon Wilson full system built by Knisely. I understand how the scat tubing is run, but the pancakes had a funny shroud that stuck out into holes in the font of the cowl. The horizontal baffle in front of the engine has the covers riveted in place. So on the 48 and 49, do the "intakes" just attach to the bottom of that horizontal opening up to it? (I hope that makes sense) Cause I think thats what you are all telling me, and thats what it looks like in the IPC? Cause that would make my job much easier!

[sfarringer]

....... I understand how the scat tubing is run, but the pancakes had a funny shroud that stuck out into holes in the font of the cowl. The horizontal baffle in front of the engine has the covers riveted in place......

It sounds like you had the cabin heater conversion kit (Item 87 on Fig 34 of the IPC), which I assume was an attempt to get some ram air into the heat muff.
This scheme had the intake to the heat muff poking straight out thru the front of the cowling, rather than off the bottom of the front baffle.

I do not know whether this modification was a practical success.

But I was amazed how much more carb heat and cabin heat I got by changing from pancake mufflers to Hanlon Wilson type.

[Bruce Fenstermacher]

Ken, yes the scat attaches just as if appears to the flange under the baffle.

It sounds like you had the cabin heater conversion kit (Item 87 on Fig 34 of the IPC)

I've learned another thing about our 170 models. I've seen this "conversion" before on aircraft and just thought it was someones ugly attempt at more cabin heat. Now I know it is an ugly rare Cessna "kit".

[IdahoPilot]

Ken, yes the scat attaches just as if appears to the flange under the baffle.

So next question. There is not flange to attach to on ours. And it looks like number 82 on figure 34 could be it. But can't be sure. Any thoughts?

[Bruce Fenstermacher]

Ken, there should be a flange in the underside of the front baffle. If not it's been removed. Scat goes from it to the heat shroud with shroud have two flanges.

Fig 50 B model IPC.png (40.48 KiB) Viewed 6284 times

Fig 49 B model IPC.png (32.36 KiB) Viewed 6284 times

This is from the B model pressure cowl but it shows the scat running to the underside of the front baffle.

Ken are you a TIC170A member? I only ask because we could (should) set you up to you can post pictures of what you have which could be a whole lot easier for both of us. If your not send pictures to my email address.

[3958v]

I had the cabin heat conversion on my plane when I bought it and I got rid of it with out noticing any difference. My advice if you dont have it dont do it and I would get rid of it if you do with the dollar dime patch system. Seems like no matter what you do heat is terrible in the early 170s. Cheap solution is a good pair of coveralls. Bill K

[bagarre]

Wow. You're the first person that I know of that has said that.
Most who do the conversion say its quite effective.
Did you have the new duct work across the firewall or just the newer valve?

[Bruce Fenstermacher]

David I think you are confusing the '48 conversion kit which places a heat intake on the front cowl, with upgrading the head distribution system inside the cabin with the '53 and later system. Bill had the former not the later.