Today's Message Index:
----------------------
1. 12:25 AM - Re: Details on Gary's new cylinders (TeamGrumman@aol.com)
2. 12:26 AM - High CHTs (TeamGrumman@aol.com)
3. 12:38 AM - Re: High CHTs (TeamGrumman@aol.com)
4. 06:34 AM - Re: High CHTs (Steven Jackson)
5. 06:36 AM - Re: Details on Gary's new cylinders (Steven Jackson)
6. 08:45 AM - Re: High CHTs (TeamGrumman@aol.com)
7. 11:21 PM - Re: High CHTs (Steven Jackson)
Message 1
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| Subject: | Re: Details on Gary's new cylinders |
--> TeamGrumman-List message posted by: TeamGrumman@aol.com
In a message dated 7/18/04 10:37:41 PM, steven.jackson14@adelphia.net writes:
> My crank was case-in-point.=A0 Manufactured in 1956, and when it was measured
> dimensionally, the journals came out within Lycomings "factory new"
> tolerances.
>
I took an O320 apart that had a bad crank (for how long I don't know, at
least for the 20 hours that I flew it before finding metal in the filter) and the
crank measured as new. Even the oil pump looked new with no measurable wear.
Message 2
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--> TeamGrumman-List message posted by: TeamGrumman@aol.com
A lot has been said about the high CHTs in Grummans. If you read GG, you'll
read
--------------------------------
In a message dated 7/17/04 4:24:00 PM, rblevy@mindspring.com writes:
> If you have to do this trick to keep your CHT's under 450F in a climb, you
> have significant
> cooling problems (see Bob S's remarks about baffling, etc.) that should
> be repaired before further flight.
>
> [Levy] Cool EGT's are generally associated with inefficient combustion.
> That means higher fuel consumption and lead fouling.=A0 I recommend
> against the use of carb heat as a temperature control except as an
> emergency measure to get the plane back on the ground where it can be
> repaired.
>
No where did I propose to fly continuously with the carb heat on.
Even with perfect baffles, climbing under full power with high ambient temps
(over 80 F) will cause the CHTs to go too high (i.e., over 450F). You can
reduce power, go full rich (if not already), and wait for the temps to come
down. And wait. However, they will take a while to cool off. Adding carb
heat will bring the temps down pretty quickly. Also, adding carb heat will
leave the throttle wide open and keep the enrichment system operating. Then,
just as quickly, you can reduce the amount of carb heat needed to keep the temps
from going down below, say 400 F, during the climb out. You'll notice you
can reduce the amount of carb heat needed to keep the temps in check once you
level off and accelerate.
Yes, if you ran with the carb heat on for extended periods, you will foul the
plugs. Plugs are easy to clean. A lot easier than replacing the
cylinders.
Somewhere on the net, and I don't recall where, I read an article about using
a small amount of carb heat to even out the CHT's and EGTs. I have noticed
that the EGTs respond quickly to various amounts of carb heat. Fortunately,
my EGTs rarely differ by more than 50 degrees F between the cylinders.
I've investigated a lot of approaches to reducing high CHTs (particulary in
Tigers). Personally, I think every plane should have digital CHT/EGT.
You'd be surprised by what you see.
On my plane, #2 and #4 are within a few degrees of each other on CHT and
within 20 degrees on EGT. #1 was running 15 degrees cooler CHT than either 2
or 4 under almost any condition and #3 was running 15 degrees hotter than
either 2 or 4. A piece of aluminum about 2 inches high, placed in front of #1
raised #1 by 15 degrees and lowered #3 by a few degrees. The next step is=20to
investigate the effects of removing the very small amounts of slag between the
fins.
Message 3
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--> TeamGrumman-List message posted by: TeamGrumman@aol.com
--> TeamGrumman-List message posted by: TeamGrumman@aol.com
A lot has been said about the high CHTs in Grummans.=A0=A0 If you read GG, you'll
read
--------------------------------
In a message dated 7/17/04 4:24:00 PM, rblevy@mindspring.com writes:
> [Levy] If you have to do this trick to keep your CHT's under 450F in a
climb, you
> have significant cooling problems (see Bob S's remarks about baffling,
etc.) that should
> be repaired before further flight.
>
> [Levy] Cool EGT's are generally associated with inefficient combustion.
> That means higher fuel consumption and lead fouling.A0 I recommend
> against the use of carb heat as a temperature control except as an
> emergency measure to get the plane back on the ground where it can be
> repaired.
No where did I propose to fly continuously with the carb heat on.=A0
Even with perfect baffles, climbing under full power with high ambient temps
(over 80 F) will cause the CHTs to go too high (i.e., over 450F).=A0=A0 You=20can
reduce power, go full rich (if not already), and wait for the temps to come
down.=A0=A0 And wait.=A0=A0 However, they will take a while to cool off.=A0=A0
Adding
carb
heat will bring the temps down pretty quickly.=A0=A0 Also, adding carb heat=20will
leave the throttle wide open and keep the enrichment system operating.=A0=20=A0
Then,
just as quickly, you can reduce the amount of carb heat needed to keep the
temps
from going down below, say 400 F, during the climb out.=A0=A0 You'll notice=20you
can reduce the amount of carb heat needed to keep the temps in check once you
level off and accelerate.=A0
Yes, if you ran with the carb heat on for extended periods, you will foul the
plugs.=A0=A0 Plugs are easy to clean.=A0=A0 A lot easier than replacing the
cylinders.=A0
Somewhere on the net, and I don't recall where, I read an article about using
a small amount of carb heat to even out the CHT's and EGTs.=A0=A0 I have noticed
that the EGTs respond quickly to various amounts of carb heat.=A0=A0 Fortunately,
my EGTs rarely differ by more than 50 degrees F between the cylinders.=A0
I've investigated a lot of approaches to reducing high CHTs (particulary in
Tigers).=A0 Personally, I think every plane should have digital CHT/EGT.=A0
You'd be surprised by what you see.
On my plane,=A0=A0 #2 and #4 are within a few degrees of each other on CHT and
within 20 degrees on EGT.=A0=A0 #1 was running 15 degrees cooler CHT than either
2
or 4 under almost any condition and #3 was running 15 degrees hotter than
either 2 or 4.=A0=A0 A piece of aluminum about 2 inches high, placed in front of
#1
raised #1 by 15 degrees and lowered #3 by a few degrees.=A0=A0 The next step
is20to
investigate the effects of removing the very small amounts of slag between
the
fins.
---------------------------------
I have been able to reduce the CHTs by messaging the baffle (strap) that
wraps around the heads on #1 and #3 and by increasing the size of the exit ramps.
A hangar neighbor had a LOT of problems with slag between the fins on his new
ECI Titan cylinders. The local engine shop has had problems with slag in
Superior cylinders. There is no clear leader. What I have found, however, is
NO slag in older Lycoming cylinders. (I have a dozen or so really trashed
cylinders sitting around. No one wants them.)
I'll keep you all posted on what I find in my new Lycoming cylinders.
Gary
By-the-way, the new cowling is being stiffened up a bit. We made a
completely new cowling and vacuum bagged it. Most of it was 4 layers with=20up
to 7
layers around the edges. Total weight without hardware was 14 pounds.
Message 4
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--> TeamGrumman-List message posted by: "Steven Jackson" <steven.jackson14@adelphia.net>
Gary wrote,
"Somewhere on the net, and I don't recall where, I read an article about
using
a small amount of carb heat to even out the CHT's and EGTs. I have noticed
that the EGTs respond quickly to various amounts of carb heat.
Fortunately,
my EGTs rarely differ by more than 50 degrees F between the cylinders."
Wasn't there an article either in Flying or AOPA magazine a couple of months
ago written about the guys at GAMI and their research into lean of peak
operations? They said something about how LOP is hard to do in a carb
aircraft because of the fuel distribution, but that engaging carb heat would
allow you to go relatively LOP during cruise, since it will enrichen the
mixture in whichever cylinder leans first, and allow you to lean more.
Now, I have a question. Carb heat in my plane knocks off about 100 rpm.
Why not back off a 100 rpm during the climb instead of engaging the carb
heat? Wouldn't the lower rpm setting keep you from developing max CHT in
the climb?
Steven Jackson
N1434R
L22
Yucca Valley, CA
Message 5
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| Subject: | Details on Gary's new cylinders |
--> TeamGrumman-List message posted by: "Steven Jackson" <steven.jackson14@adelphia.net>
Oh, I guess my reasoning fails then. I guess that's why they NDI the things
then. So how is the bottom end "bullet proof" then--and I'm asking, not
being a smarty pants...
Steven Jackson
N1434R
L22
Yucca Valley, CA
-----Original Message-----
From: owner-teamgrumman-list-server@matronics.com
[mailto:owner-teamgrumman-list-server@matronics.com]On Behalf Of
TeamGrumman@aol.com
Subject: Re: TeamGrumman-List: Details on Gary's new cylinders
--> TeamGrumman-List message posted by: TeamGrumman@aol.com
In a message dated 7/18/04 10:37:41 PM, steven.jackson14@adelphia.net
writes:
> My crank was case-in-point.=A0 Manufactured in 1956, and when it was
measured
> dimensionally, the journals came out within Lycomings "factory new"
> tolerances.
>
I took an O320 apart that had a bad crank (for how long I don't know, at
least for the 20 hours that I flew it before finding metal in the filter)
and the
crank measured as new. Even the oil pump looked new with no measurable
wear.
Message 6
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--> TeamGrumman-List message posted by: TeamGrumman@aol.com
In a message dated 7/19/04 6:34:58 AM, steven.jackson14@adelphia.net writes:
> Now, I have a question.=A0 Carb heat in my plane knocks off about 100 rpm.
> Why not back off a 100 rpm during the climb instead of engaging the carb
> heat?=A0 Wouldn't the lower rpm setting keep you from developing max CHT in
> the climb?
>
well, the enrichment system in the carb would also disengage and it takes a
long time to lower the temps just by reducing power. If you have 4 cyl
CHT/EGT, go try it.
Gary
Message 7
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--> TeamGrumman-List message posted by: "Steven Jackson" <steven.jackson14@adelphia.net>
I'll take your word for it, but once my JPI is installed, I'll do a test...
Steve
-----Original Message-----
From: owner-teamgrumman-list-server@matronics.com
[mailto:owner-teamgrumman-list-server@matronics.com]On Behalf Of
TeamGrumman@aol.com
Subject: Re: TeamGrumman-List: High CHTs
--> TeamGrumman-List message posted by: TeamGrumman@aol.com
In a message dated 7/19/04 6:34:58 AM, steven.jackson14@adelphia.net writes:
> Now, I have a question.=A0 Carb heat in my plane knocks off about 100 rpm.
> Why not back off a 100 rpm during the climb instead of engaging the carb
> heat?=A0 Wouldn't the lower rpm setting keep you from developing max CHT
in
> the climb?
>
well, the enrichment system in the carb would also disengage and it takes a
long time to lower the temps just by reducing power. If you have 4 cyl
CHT/EGT, go try it.
Gary
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