The Murphy Builders Site

I wonder how effective you folks find your carb heat on installations using
the Murphy (Forsling) exhaust system? I am using it with a Vans carb air
box, and it is almost totally ineffective. At runup RPM (~2200) there is
no
drop in RPM, and no movement in carb temp. At cruise (~2500), I get maybe
a
50 RPM drop.

The muff is like an octagonal can with one side removed. I think things
would work better if I close in most of the opening, forcing the air to
transit the length of the muff, rather than just going around the
circumference and straight in to the scat hose. Any comments?

Al





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Hi Al. That was the system I was using on my Rebel with an O320 H2AD. I also
did not get much of a mag drop on run up, but those mornings I was getting
carb ice roughness during taxi, would sure clear up in a hurry when I pulled
the carb heat. I also got about the same drop in cruise as your indicating.
I think the system works quite well. Bob J
----- Original Message -----
From: "Alan Hepburn" <ahepburn@renc.igs.net>
To: <rebel-builders@dcsol.com>
Sent: Friday, July 15, 2005 7:45 AM
Subject: Carb Heat Effectiveness

I wonder how effective you folks find your carb heat on installations using
the Murphy (Forsling) exhaust system? I am using it with a Vans carb air
box, and it is almost totally ineffective. At runup RPM (~2200) there is
no
drop in RPM, and no movement in carb temp. At cruise (~2500), I get maybe
a
50 RPM drop.

The muff is like an octagonal can with one side removed. I think things
would work better if I close in most of the opening, forcing the air to
transit the length of the muff, rather than just going around the
circumference and straight in to the scat hose. Any comments?

Al





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Hi Al !

I'll second that ! You don't usually see a very big drop with the
Lyc's - not like the 100+ rpm on Continentals, with their cooler
intake air !

Some days it's almost impossible to see the drop at lower rpms,
but never had a problem with clearing ice ...

Have fun flying again ! :-)

.....bobp

-------------------------------orig.-------------------------
On Friday 15 July 2005 10:19 am, Robert and Olga Johnson wrote:

Hi Al. That was the system I was using on my Rebel with an O320 H2AD. I
also
did not get much of a mag drop on run up, but those mornings I was
getting
carb ice roughness during taxi, would sure clear up in a hurry when I
pulled
the carb heat. I also got about the same drop in cruise as your
indicating.
I think the system works quite well. Bob J
----- Original Message -----
From: "Alan Hepburn" <ahepburn@renc.igs.net>
To: <rebel-builders@dcsol.com>
Sent: Friday, July 15, 2005 7:45 AM
Subject: Carb Heat Effectiveness

I wonder how effective you folks find your carb heat on installations
using
the Murphy (Forsling) exhaust system? I am using it with a Vans carb
air
box, and it is almost totally ineffective. At runup RPM (~2200) there
is
no
drop in RPM, and no movement in carb temp. At cruise (~2500), I get
maybe
a
50 RPM drop.

The muff is like an octagonal can with one side removed. I think
things
would work better if I close in most of the opening, forcing the air to
transit the length of the muff, rather than just going around the
circumference and straight in to the scat hose. Any comments?

Al





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I wonder how effective you folks find your carb heat on installations using
the Murphy (Forsling) exhaust system? I am using it with a Vans carb air
box, and it is almost totally ineffective. At runup RPM (~2200) there is no
drop in RPM, and no movement in carb temp. At cruise (~2500), I get maybe a
50 RPM drop.

The muff is like an octagonal can with one side removed. I think things
would work better if I close in most of the opening, forcing the air to
transit the length of the muff, rather than just going around the
circumference and straight in to the scat hose. Any comments?

Al





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Hello!

I fly a PA-22 Colt (until my Rebel be ready to fly!) with a 0-235 C1B
without oil cooler. My carb heat drop my rpm between 75-100 rpm and also
it is easy too see a temp getting higher on the carb temperature gauge.
No opinion, but just want let you know!

Jean
Rebel 747R
----- Original Message -----
From: "Bob Patterson" <beep@sympatico.ca>
To: <rebel-builders@dcsol.com>
Sent: Friday, July 15, 2005 12:20 PM
Subject: Re: Carb Heat Effectiveness

Hi Al !

I'll second that ! You don't usually see a very big drop with the
Lyc's - not like the 100+ rpm on Continentals, with their cooler
intake air !

Some days it's almost impossible to see the drop at lower rpms,
but never had a problem with clearing ice ...

Have fun flying again ! :-)

.....bobp

-------------------------------orig.-------------------------
On Friday 15 July 2005 10:19 am, Robert and Olga Johnson wrote:

Hi Al. That was the system I was using on my Rebel with an O320 H2AD. I
also
did not get much of a mag drop on run up, but those mornings I was
getting
carb ice roughness during taxi, would sure clear up in a hurry when I
pulled
the carb heat. I also got about the same drop in cruise as your
indicating.
I think the system works quite well. Bob J
----- Original Message -----
From: "Alan Hepburn" <ahepburn@renc.igs.net>
To: <rebel-builders@dcsol.com>
Sent: Friday, July 15, 2005 7:45 AM
Subject: Carb Heat Effectiveness

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You receive that engine yet Jean?? Wayne

----- Original Message -----
From: "Jean Poirier" <oxyport@globetrotter.net>
To: <rebel-builders@dcsol.com>
Sent: Friday, July 15, 2005 1:21 PM
Subject: Re: Carb Heat Effectiveness

Hello!

I fly a PA-22 Colt (until my Rebel be ready to fly!) with a 0-235 C1B
without oil cooler. My carb heat drop my rpm between 75-100 rpm and
also
it is easy too see a temp getting higher on the carb temperature gauge.
No opinion, but just want let you know!

Jean
Rebel 747R
----- Original Message -----
From: "Bob Patterson" <beep@sympatico.ca>
To: <rebel-builders@dcsol.com>
Sent: Friday, July 15, 2005 12:20 PM
Subject: Re: Carb Heat Effectiveness

Hi Al !

I'll second that ! You don't usually see a very big drop with
the
Lyc's - not like the 100+ rpm on Continentals, with their cooler
intake air !

Some days it's almost impossible to see the drop at lower rpms,
but never had a problem with clearing ice ...

Have fun flying again ! :-)

.....bobp

-------------------------------orig.-------------------------
On Friday 15 July 2005 10:19 am, Robert and Olga Johnson wrote:

there

to

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I find the carb heat on my O-360 almost totally ineffective. With the
cooler weather coming on, I'd like to do something about that. I am
using the standard Murphy (Forsling) exhaust and muffs, with the Vans
airbox. I have a carb heat probe, and if I see 1*C difference, and a
few 10s of RPM change, that's about it. Talked to Forsling at OSH and
he said to orient the slot in the muff so it was facing the other
exhaust pipe. That would require reworking the outlet position on my
muff, which would be OK if I was satisfied it would work.

I wonder what others are getting?

Al




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-----Original Message-----
From: mike.davis@dcsol.com
[mailto:mike.davis@dcsol.com]On Behalf Of
Wayne G. O'Shea
Sent: Tuesday, September 13, 2005 8:26 PM
To: rebel-builders@dcsol.com
Subject: Re: Carb Heat Effectiveness


I get a 150 to 200 RPM drop on my O-320-C2A at 1800
RPM's. I'm using nothing
but an old small shroud from some certified aircraft
that covers no more
than about 3 inches of a single pipe.

Does your engine need to be leaned agressively to get
a higher RPM. Maybe
you are already running so rich the heated air from
carb heat doesn't have
the same effect....but of course that doesn't explain
the temp difference.
Sure you don't have a blocked/collapsed SCAT tube from
the shroud to the
carb box....or a flapper valve that isn't cycling all
the way to draw air
strictly from the shroud.

Wayne

----- Original Message -----
From: "Alan Hepburn" <ahepburn@renc.igs.net>
To: <rebel-builders@dcsol.com>
Sent: Tuesday, September 13, 2005 11:20 PM
Subject: Carb Heat Effectiveness

I find the carb heat on my O-360 almost totally

ineffective. With the

cooler weather coming on, I'd like to do something

about that. I am

using the standard Murphy (Forsling) exhaust and

muffs, with the Vans

airbox. I have a carb heat probe, and if I see 1*C

difference, and a

few 10s of RPM change, that's about it. Talked to

Forsling at OSH and

he said to orient the slot in the muff so it was

facing the other

exhaust pipe. That would require reworking the

outlet position on my

muff, which would be OK if I was satisfied it would work.

I wonder what others are getting?

Al

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-------------------------------------------------------
----------





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----------

I find the carb heat on my O-360 almost totally ineffective. With the
cooler weather coming on, I'd like to do something about that. I am
using the standard Murphy (Forsling) exhaust and muffs, with the Vans
airbox. I have a carb heat probe, and if I see 1*C difference, and a
few 10s of RPM change, that's about it. Talked to Forsling at OSH and
he said to orient the slot in the muff so it was facing the other
exhaust pipe. That would require reworking the outlet position on my
muff, which would be OK if I was satisfied it would work.

I wonder what others are getting?

Al




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