[rebel-builders] High EGT

[Del Schmucker]

Mike:


What EGT are you aiming for?? Why?? My Subaru easily can run at 1400 or
higher maybe Ken can pipe with he has found on his Subaru. I know our Sub.s
are not the same as your V8 but the information might be useful.


Thank You,

Del Schmucker
Information Systems Manager
Keewatin-Patricia District School Board
807-223-1254
807-221-8769 Cell
del.schmucker@kpdsb.on.ca
www.kpdsb.on.ca
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Mike
Kimball
Sent: Wednesday, July 25, 2007 11:39 PM
To: Rebel Builder's List
Subject: [rebel-builders] High EGT

I have solved all of my engine problems except one. High EGT. 1200 F at
2000 RPM rising steadily to a bit over 1600 F at 5000 RPM. About 1500 F at
3500 RPM. My initial timing is 14 degrees with a maximum of 18 degrees of
advance from the distributor which is reached at 3500 RPM. Max total timing
is 32 degrees advanced. The engine starts and runs beautifully throughout
the RPM range from idle to max power. The spark plugs look perfect, not
showing too rich or lean. No fouling. Oil and coolant temps right where
you would want them. I changed out my regular unleaded fuel for 100LL.
(EGT problem the same before and after.) My EGT probe is about 3 inches
from the exhaust port on cylinder #2 which is nearest the firewall on the
pilot's side.

I am now convinced that the reason I burned a hole in piston #5 is that I
was paying too much attention to EGT readings before when setting my timing
and I was way too far advanced in an attempt to reduce EGT. I won't be led
down that path again so I am leaving the timing right where it is. There
has got to be another reason for the high EGT.

It is incredibly frustrating to watch day after day of precious summer
trickle away without flying. But I really don't want another short flight,
emergency landing, and a winter rebuilding the engine again. Any
suggestions would be GREATLY appreciated.

Mike





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[Ken]

I climb and ecnomy cruise at 800 C. or 1470 F
Fast cruise gives 820 C or about 1500 F.
I would expect lower with a carb as the oem fuel injection runs peak EGT
unless firewalled but Mike's engine is sure not a soob. If course most
EGT's are not very accurate and they don't have to be for leaning
purposes. I suspect there are guys that could estimate whether the 1600
F is accurate just be watching the color of the exhaust manifold. 1500
glows pretty good.

Ken

Del Schmucker wrote:

Mike:


What EGT are you aiming for?? Why?? My Subaru easily can run at 1400 or
higher maybe Ken can pipe with he has found on his Subaru. I know our Sub.s
are not the same as your V8 but the information might be useful.


Thank You,

Del Schmucker

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[Mike Kimball]

I would like to see no more than 1450F at max power. I suppose I could live
with 1500F with a limit on max power run time which is so common with
airplane engines. I would also like to see less than 1400F at cruise power.
The reason I am seeking lower temps is that I have no computer to adjust
timing and air/fuel ratios. I have to err on a more conservative profile.
With the timing set in the proper place, 100LL in the tanks, and colder
spark plugs I am already better protected against preignition/detonation
than I was before.

I think I may be on to something after more test runs today. I decided to
really check out max power. I selected max power and the engine started to
die like it was running out of fuel. I glanced down and noticed that I
wasn't quite full rich. I pushed in the last bit of mixture and the engine
ran at max power just fine. I have my prop currently set for 4500RPM static
at max power. (I can easily go way past 5000RPM with finer pitch but I know
that is too fine for flight.) I decided to check EGT at various RPMS.

1500RPM - 1150F
2000RPM - 1300F
2500RPM - 1350F
3000RPM - 1400F
3500RPM - 1500F
4000RPM - 1550F
4500RPM - 1350F

I'm sure you'll notice the max power anomaly. Apparently, the Holly somehow
enrichens the mixture more at full throttle. The fact that the engine
wouldn't even stay running at max power with a setting just slightly lean of
full rich leads me to believe that although I was able to get it to stay
running at max power, it is probably still too lean through the rest of the
power range and EGT supports that theory. Since the EGT is acceptable all
the way to 3000RPM I am thinking that I will try larger jets in the
secondaries. If necessary, I may alter the primary mixture plate to allow
more fuel through as well. My timing stop prevents more timing advance past
3500RPM. I may change to a stop that allows continuous advance to 4500RPM.
That should help EGT at higher power settings as well.

Mike

P.S. It's always something. My vacuum pump stopped giving me any vacuum
today. It was pretty hot after the engine runs. I think I may have fried
it. I gotta look at ways to get more cooling air to it.

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ken
Sent: Thursday, July 26, 2007 6:01 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] High EGT

I climb and ecnomy cruise at 800 C. or 1470 F
Fast cruise gives 820 C or about 1500 F.
I would expect lower with a carb as the oem fuel injection runs peak EGT
unless firewalled but Mike's engine is sure not a soob. If course most
EGT's are not very accurate and they don't have to be for leaning
purposes. I suspect there are guys that could estimate whether the 1600
F is accurate just be watching the color of the exhaust manifold. 1500
glows pretty good.

Ken

Del Schmucker wrote:

Mike:


What EGT are you aiming for?? Why?? My Subaru easily can run at 1400 or
higher maybe Ken can pipe with he has found on his Subaru. I know our

Sub.s

are not the same as your V8 but the information might be useful.


Thank You,

Del Schmucker

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[Rick Muller]

Mike,

You have had some interesting and unusual problems along the way. It
strikes me that someone that "REALLY" understands engines may be of help. I
learned of such a person from Contact magazine. In this months issue there
is a wonderful write-up on a guy named Bud Warren. He makes PSRU's or
transmissions as he calls them, and the article indicates he is a very
aviation supportive kind of guy. His PSRU's are far beyond anything else I
have seen to date. They utilize a clutch mechanism to eliminate harmonics.
His web site is www.GearedDrivers.com . You might give him a call, phone
etc. on the web site.

Rick Muller
(303) 664 9219 Home
(303) 641 6623 Cell
rickhm@comcast.net

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Mike
Kimball
Sent: Wednesday, July 25, 2007 10:39 PM
To: Rebel Builder's List
Subject: [rebel-builders] High EGT

I have solved all of my engine problems except one. High EGT. 1200 F at
2000 RPM rising steadily to a bit over 1600 F at 5000 RPM. About 1500 F at
3500 RPM. My initial timing is 14 degrees with a maximum of 18 degrees of
advance from the distributor which is reached at 3500 RPM. Max total timing
is 32 degrees advanced. The engine starts and runs beautifully throughout
the RPM range from idle to max power. The spark plugs look perfect, not
showing too rich or lean. No fouling. Oil and coolant temps right where
you would want them. I changed out my regular unleaded fuel for 100LL.
(EGT problem the same before and after.) My EGT probe is about 3 inches
from the exhaust port on cylinder #2 which is nearest the firewall on the
pilot's side.

I am now convinced that the reason I burned a hole in piston #5 is that I
was paying too much attention to EGT readings before when setting my timing
and I was way too far advanced in an attempt to reduce EGT. I won't be led
down that path again so I am leaving the timing right where it is. There
has got to be another reason for the high EGT.

It is incredibly frustrating to watch day after day of precious summer
trickle away without flying. But I really don't want another short flight,
emergency landing, and a winter rebuilding the engine again. Any
suggestions would be GREATLY appreciated.

Mike





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[Mike Kimball]

Thanks Rick!

Mike

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Rick
Muller
Sent: Thursday, July 26, 2007 8:45 PM
To: rebel-builders@dcsol.com
Subject: RE: [rebel-builders] High EGT

Mike,

You have had some interesting and unusual problems along the way. It
strikes me that someone that "REALLY" understands engines may be of help. I
learned of such a person from Contact magazine. In this months issue there
is a wonderful write-up on a guy named Bud Warren. He makes PSRU's or
transmissions as he calls them, and the article indicates he is a very
aviation supportive kind of guy. His PSRU's are far beyond anything else I
have seen to date. They utilize a clutch mechanism to eliminate harmonics.
His web site is www.GearedDrivers.com . You might give him a call, phone
etc. on the web site.

Rick Muller
(303) 664 9219 Home
(303) 641 6623 Cell
rickhm@comcast.net

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Mike
Kimball
Sent: Wednesday, July 25, 2007 10:39 PM
To: Rebel Builder's List
Subject: [rebel-builders] High EGT

I have solved all of my engine problems except one. High EGT. 1200 F at
2000 RPM rising steadily to a bit over 1600 F at 5000 RPM. About 1500 F at
3500 RPM. My initial timing is 14 degrees with a maximum of 18 degrees of
advance from the distributor which is reached at 3500 RPM. Max total timing
is 32 degrees advanced. The engine starts and runs beautifully throughout
the RPM range from idle to max power. The spark plugs look perfect, not
showing too rich or lean. No fouling. Oil and coolant temps right where
you would want them. I changed out my regular unleaded fuel for 100LL.
(EGT problem the same before and after.) My EGT probe is about 3 inches
from the exhaust port on cylinder #2 which is nearest the firewall on the
pilot's side.

I am now convinced that the reason I burned a hole in piston #5 is that I
was paying too much attention to EGT readings before when setting my timing
and I was way too far advanced in an attempt to reduce EGT. I won't be led
down that path again so I am leaving the timing right where it is. There
has got to be another reason for the high EGT.

It is incredibly frustrating to watch day after day of precious summer
trickle away without flying. But I really don't want another short flight,
emergency landing, and a winter rebuilding the engine again. Any
suggestions would be GREATLY appreciated.

Mike





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[Mike Davis]

I think that web site should be www.geareddrives.com.

Mike

----- Original Message -----
From: "Rick Muller" <rickhm@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Thursday, July 26, 2007 8:44 PM
Subject: RE: [rebel-builders] High EGT

Mike,

You have had some interesting and unusual problems along the way. It
strikes me that someone that "REALLY" understands engines may be of help.
I
learned of such a person from Contact magazine. In this months issue
there
is a wonderful write-up on a guy named Bud Warren. He makes PSRU's or
transmissions as he calls them, and the article indicates he is a very
aviation supportive kind of guy. His PSRU's are far beyond anything else
I
have seen to date. They utilize a clutch mechanism to eliminate
harmonics.
His web site is www.GearedDrivers.com . You might give him a call, phone
etc. on the web site.

Rick Muller
(303) 664 9219 Home
(303) 641 6623 Cell
rickhm@comcast.net

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Mike
Kimball
Sent: Wednesday, July 25, 2007 10:39 PM
To: Rebel Builder's List
Subject: [rebel-builders] High EGT

I have solved all of my engine problems except one. High EGT. 1200 F at
2000 RPM rising steadily to a bit over 1600 F at 5000 RPM. About 1500 F
at
3500 RPM. My initial timing is 14 degrees with a maximum of 18 degrees of
advance from the distributor which is reached at 3500 RPM. Max total
timing
is 32 degrees advanced. The engine starts and runs beautifully throughout
the RPM range from idle to max power. The spark plugs look perfect, not
showing too rich or lean. No fouling. Oil and coolant temps right where
you would want them. I changed out my regular unleaded fuel for 100LL.
(EGT problem the same before and after.) My EGT probe is about 3 inches
from the exhaust port on cylinder #2 which is nearest the firewall on the
pilot's side.

I am now convinced that the reason I burned a hole in piston #5 is that I
was paying too much attention to EGT readings before when setting my
timing
and I was way too far advanced in an attempt to reduce EGT. I won't be
led
down that path again so I am leaving the timing right where it is. There
has got to be another reason for the high EGT.

It is incredibly frustrating to watch day after day of precious summer
trickle away without flying. But I really don't want another short
flight,
emergency landing, and a winter rebuilding the engine again. Any
suggestions would be GREATLY appreciated.

Mike





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[Rick Muller]

Sorry about that! Correct!

Rick Muller
(303) 664 9219 Home
(303) 641 6623 Cell
rickhm@comcast.net

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]
Sent: Thursday, July 26, 2007 11:49 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] High EGT

I think that web site should be www.geareddrives.com.

Mike

----- Original Message -----
From: "Rick Muller" <rickhm@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Thursday, July 26, 2007 8:44 PM
Subject: RE: [rebel-builders] High EGT

Mike,

You have had some interesting and unusual problems along the way. It
strikes me that someone that "REALLY" understands engines may be of help.
I
learned of such a person from Contact magazine. In this months issue
there
is a wonderful write-up on a guy named Bud Warren. He makes PSRU's or
transmissions as he calls them, and the article indicates he is a very
aviation supportive kind of guy. His PSRU's are far beyond anything else
I
have seen to date. They utilize a clutch mechanism to eliminate
harmonics.
His web site is www.GearedDrivers.com . You might give him a call, phone
etc. on the web site.

Rick Muller
(303) 664 9219 Home
(303) 641 6623 Cell
rickhm@comcast.net

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Mike
Kimball
Sent: Wednesday, July 25, 2007 10:39 PM
To: Rebel Builder's List
Subject: [rebel-builders] High EGT

I have solved all of my engine problems except one. High EGT. 1200 F at
2000 RPM rising steadily to a bit over 1600 F at 5000 RPM. About 1500 F
at
3500 RPM. My initial timing is 14 degrees with a maximum of 18 degrees of
advance from the distributor which is reached at 3500 RPM. Max total
timing
is 32 degrees advanced. The engine starts and runs beautifully throughout
the RPM range from idle to max power. The spark plugs look perfect, not
showing too rich or lean. No fouling. Oil and coolant temps right where
you would want them. I changed out my regular unleaded fuel for 100LL.
(EGT problem the same before and after.) My EGT probe is about 3 inches
from the exhaust port on cylinder #2 which is nearest the firewall on the
pilot's side.

I am now convinced that the reason I burned a hole in piston #5 is that I
was paying too much attention to EGT readings before when setting my
timing
and I was way too far advanced in an attempt to reduce EGT. I won't be
led
down that path again so I am leaving the timing right where it is. There
has got to be another reason for the high EGT.

It is incredibly frustrating to watch day after day of precious summer
trickle away without flying. But I really don't want another short
flight,
emergency landing, and a winter rebuilding the engine again. Any
suggestions would be GREATLY appreciated.

Mike





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[Brad Hewlett]

This is just a test.

Brad.

Brad Hewlett
Saskatoon, SK
bhewlett@sasktel.net

----- Original Message -----
From: "Rick Muller" <rickhm@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Friday, July 27, 2007 7:40 AM
Subject: RE: [rebel-builders] High EGT

Sorry about that! Correct!

Rick Muller
(303) 664 9219 Home
(303) 641 6623 Cell
rickhm@comcast.net

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]
Sent: Thursday, July 26, 2007 11:49 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] High EGT

I think that web site should be www.geareddrives.com.

Mike

----- Original Message -----
From: "Rick Muller" <rickhm@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Thursday, July 26, 2007 8:44 PM
Subject: RE: [rebel-builders] High EGT

Mike,

You have had some interesting and unusual problems along the way. It
strikes me that someone that "REALLY" understands engines may be of help.
I
learned of such a person from Contact magazine. In this months issue
there
is a wonderful write-up on a guy named Bud Warren. He makes PSRU's or
transmissions as he calls them, and the article indicates he is a very
aviation supportive kind of guy. His PSRU's are far beyond anything else
I
have seen to date. They utilize a clutch mechanism to eliminate
harmonics.
His web site is www.GearedDrivers.com . You might give him a call, phone
etc. on the web site.

Rick Muller
(303) 664 9219 Home
(303) 641 6623 Cell
rickhm@comcast.net

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Mike
Kimball
Sent: Wednesday, July 25, 2007 10:39 PM
To: Rebel Builder's List
Subject: [rebel-builders] High EGT

I have solved all of my engine problems except one. High EGT. 1200 F at
2000 RPM rising steadily to a bit over 1600 F at 5000 RPM. About 1500 F
at
3500 RPM. My initial timing is 14 degrees with a maximum of 18 degrees
of
advance from the distributor which is reached at 3500 RPM. Max total
timing
is 32 degrees advanced. The engine starts and runs beautifully
throughout
the RPM range from idle to max power. The spark plugs look perfect, not
showing too rich or lean. No fouling. Oil and coolant temps right where
you would want them. I changed out my regular unleaded fuel for 100LL.
(EGT problem the same before and after.) My EGT probe is about 3 inches
from the exhaust port on cylinder #2 which is nearest the firewall on the
pilot's side.

I am now convinced that the reason I burned a hole in piston #5 is that I
was paying too much attention to EGT readings before when setting my
timing
and I was way too far advanced in an attempt to reduce EGT. I won't be
led
down that path again so I am leaving the timing right where it is. There
has got to be another reason for the high EGT.

It is incredibly frustrating to watch day after day of precious summer
trickle away without flying. But I really don't want another short
flight,
emergency landing, and a winter rebuilding the engine again. Any
suggestions would be GREATLY appreciated.

Mike





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[Ken]

Mike

Most automotive carbs that I've had did have some kind of enrichment
circuit to richen up the mixture at high power settings which does
indeed drop EGT while allowing more power to be developed. Sometimes
called the "power valve". I'd consider the lower egt at max power to be
normal. Perhaps you are a bit lean prior to the enrichment operating. I
don't know whether the enrichment starts when the secondaries open or
before that on your carb. Adventures like yours are part of the reason
that I kept my engine internally stock and deferred decisions about
whether to do mods for the next engine.

My vacuum pump is OK but my horizon has become unreliable. Kind of wish
it was just my pump...

Ken

Mike Kimball wrote:

I would like to see no more than 1450F at max power. I suppose I could live
with 1500F with a limit on max power run time which is so common with
airplane engines. I would also like to see less than 1400F at cruise power.
The reason I am seeking lower temps is that I have no computer to adjust
timing and air/fuel ratios. I have to err on a more conservative profile.
With the timing set in the proper place, 100LL in the tanks, and colder
spark plugs I am already better protected against preignition/detonation
than I was before.

I think I may be on to something after more test runs today. I decided to
really check out max power. I selected max power and the engine started to
die like it was running out of fuel. I glanced down and noticed that I
wasn't quite full rich. I pushed in the last bit of mixture and the engine
ran at max power just fine. I have my prop currently set for 4500RPM static
at max power. (I can easily go way past 5000RPM with finer pitch but I know
that is too fine for flight.) I decided to check EGT at various RPMS.

1500RPM - 1150F
2000RPM - 1300F
2500RPM - 1350F
3000RPM - 1400F
3500RPM - 1500F
4000RPM - 1550F
4500RPM - 1350F

I'm sure you'll notice the max power anomaly. Apparently, the Holly somehow
enrichens the mixture more at full throttle. The fact that the engine
wouldn't even stay running at max power with a setting just slightly lean of
full rich leads me to believe that although I was able to get it to stay
running at max power, it is probably still too lean through the rest of the
power range and EGT supports that theory. Since the EGT is acceptable all
the way to 3000RPM I am thinking that I will try larger jets in the
secondaries. If necessary, I may alter the primary mixture plate to allow
more fuel through as well. My timing stop prevents more timing advance past
3500RPM. I may change to a stop that allows continuous advance to 4500RPM.
That should help EGT at higher power settings as well.

Mike

P.S. It's always something. My vacuum pump stopped giving me any vacuum
today. It was pretty hot after the engine runs. I think I may have fried
it. I gotta look at ways to get more cooling air to it.

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[Mike Kimball]

Yeah, I know about the power valve for enrichment. Only problem is, I don't
have one. One of the mods that the manufacturer of the cockpit mixture
control specifies is to remove the power valve and block off the hole with a
supplied plug. I'm thinking the enrichment I am getting at max power must
have something to do with the secondaries. Just guessing though. I have no
real idea what causes enrichment between 4000 RPM and full throttle. I may
experiment with removing my mixture control and try a bunch of jets in the
stock config for the carb to see what happens. I may even see what happens
if I put the power valve back in. Oh, the life of the experimenter.

Mike

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ken
Sent: Friday, July 27, 2007 3:24 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] High EGT

Mike

Most automotive carbs that I've had did have some kind of enrichment
circuit to richen up the mixture at high power settings which does
indeed drop EGT while allowing more power to be developed. Sometimes
called the "power valve". I'd consider the lower egt at max power to be
normal. Perhaps you are a bit lean prior to the enrichment operating. I
don't know whether the enrichment starts when the secondaries open or
before that on your carb. Adventures like yours are part of the reason
that I kept my engine internally stock and deferred decisions about
whether to do mods for the next engine.

My vacuum pump is OK but my horizon has become unreliable. Kind of wish
it was just my pump...

Ken

Mike Kimball wrote:

I would like to see no more than 1450F at max power. I suppose I could

live

with 1500F with a limit on max power run time which is so common with
airplane engines. I would also like to see less than 1400F at cruise

power.

The reason I am seeking lower temps is that I have no computer to adjust
timing and air/fuel ratios. I have to err on a more conservative profile.
With the timing set in the proper place, 100LL in the tanks, and colder
spark plugs I am already better protected against preignition/detonation
than I was before.

I think I may be on to something after more test runs today. I decided to
really check out max power. I selected max power and the engine started to
die like it was running out of fuel. I glanced down and noticed that I
wasn't quite full rich. I pushed in the last bit of mixture and the engine
ran at max power just fine. I have my prop currently set for 4500RPM

static

at max power. (I can easily go way past 5000RPM with finer pitch but I

know

that is too fine for flight.) I decided to check EGT at various RPMS.

1500RPM - 1150F
2000RPM - 1300F
2500RPM - 1350F
3000RPM - 1400F
3500RPM - 1500F
4000RPM - 1550F
4500RPM - 1350F

I'm sure you'll notice the max power anomaly. Apparently, the Holly

somehow

enrichens the mixture more at full throttle. The fact that the engine
wouldn't even stay running at max power with a setting just slightly lean

of

full rich leads me to believe that although I was able to get it to stay
running at max power, it is probably still too lean through the rest of the
power range and EGT supports that theory. Since the EGT is acceptable all
the way to 3000RPM I am thinking that I will try larger jets in the
secondaries. If necessary, I may alter the primary mixture plate to allow
more fuel through as well. My timing stop prevents more timing advance

past

3500RPM. I may change to a stop that allows continuous advance to 4500RPM.
That should help EGT at higher power settings as well.

Mike

P.S. It's always something. My vacuum pump stopped giving me any vacuum
today. It was pretty hot after the engine runs. I think I may have fried
it. I gotta look at ways to get more cooling air to it.

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[Ken]

Mike
FWIW I'd be tempted to try larger main jet(s) first and if that doesn't
do it, then larger secondary jets before changing anything else in the carb.
Ken

Mike Kimball wrote:

Yeah, I know about the power valve for enrichment. Only problem is, I don't
have one. One of the mods that the manufacturer of the cockpit mixture
control specifies is to remove the power valve and block off the hole with a
supplied plug. I'm thinking the enrichment I am getting at max power must
have something to do with the secondaries. Just guessing though. I have no
real idea what causes enrichment between 4000 RPM and full throttle. I may
experiment with removing my mixture control and try a bunch of jets in the
stock config for the carb to see what happens. I may even see what happens
if I put the power valve back in. Oh, the life of the experimenter.

Mike

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ken
Sent: Friday, July 27, 2007 3:24 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] High EGT

Mike

Most automotive carbs that I've had did have some kind of enrichment
circuit to richen up the mixture at high power settings which does
indeed drop EGT while allowing more power to be developed. Sometimes
called the "power valve". I'd consider the lower egt at max power to be
normal. Perhaps you are a bit lean prior to the enrichment operating. I
don't know whether the enrichment starts when the secondaries open or
before that on your carb. Adventures like yours are part of the reason
that I kept my engine internally stock and deferred decisions about
whether to do mods for the next engine.

My vacuum pump is OK but my horizon has become unreliable. Kind of wish
it was just my pump...

Ken

Mike Kimball wrote:

I would like to see no more than 1450F at max power. I suppose I could

live

with 1500F with a limit on max power run time which is so common with
airplane engines. I would also like to see less than 1400F at cruise

power.

The reason I am seeking lower temps is that I have no computer to adjust
timing and air/fuel ratios. I have to err on a more conservative profile.
With the timing set in the proper place, 100LL in the tanks, and colder
spark plugs I am already better protected against preignition/detonation
than I was before.

I think I may be on to something after more test runs today. I decided to
really check out max power. I selected max power and the engine started to
die like it was running out of fuel. I glanced down and noticed that I
wasn't quite full rich. I pushed in the last bit of mixture and the engine
ran at max power just fine. I have my prop currently set for 4500RPM

static

at max power. (I can easily go way past 5000RPM with finer pitch but I

know

that is too fine for flight.) I decided to check EGT at various RPMS.

1500RPM - 1150F
2000RPM - 1300F
2500RPM - 1350F
3000RPM - 1400F
3500RPM - 1500F
4000RPM - 1550F
4500RPM - 1350F

I'm sure you'll notice the max power anomaly. Apparently, the Holly

somehow

enrichens the mixture more at full throttle. The fact that the engine
wouldn't even stay running at max power with a setting just slightly lean

of

full rich leads me to believe that although I was able to get it to stay
running at max power, it is probably still too lean through the rest of the
power range and EGT supports that theory. Since the EGT is acceptable all
the way to 3000RPM I am thinking that I will try larger jets in the
secondaries. If necessary, I may alter the primary mixture plate to allow
more fuel through as well. My timing stop prevents more timing advance

past

3500RPM. I may change to a stop that allows continuous advance to 4500RPM.
That should help EGT at higher power settings as well.

Mike

P.S. It's always something. My vacuum pump stopped giving me any vacuum
today. It was pretty hot after the engine runs. I think I may have fried
it. I gotta look at ways to get more cooling air to it.

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[Dave Ricker]

Mike

I don't know if I'm out in left field here but would a wide band O2 sensor
(exhaust sniffer) be useful here to tell you what mixture you're getting at
various points on the power curve? I know the car guys use them to get their
ECU maps right when adding a turbo, basically the issue there is to make the
most power but not go lean at any point to keep from burning pistons.

They usually go with stand-alone fuel injection/engine management systems like
the 034 but air/fuel ratio is the same whether it's a carb or EFI.

Google "wide band oxygen sensor". Just had a thought, I don't think these
things like lead so you'd have to be running MOGAS but you have done some work
with it haven't you?

I think a wide band is under $200.

Dave



Mike Kimball wrote:

Yeah, I know about the power valve for enrichment. Only problem is, I don't
have one. One of the mods that the manufacturer of the cockpit mixture
control specifies is to remove the power valve and block off the hole with a
supplied plug. I'm thinking the enrichment I am getting at max power must
have something to do with the secondaries. Just guessing though. I have no
real idea what causes enrichment between 4000 RPM and full throttle. I may
experiment with removing my mixture control and try a bunch of jets in the
stock config for the carb to see what happens. I may even see what happens
if I put the power valve back in. Oh, the life of the experimenter.

Mike

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ken
Sent: Friday, July 27, 2007 3:24 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] High EGT

Mike

Most automotive carbs that I've had did have some kind of enrichment
circuit to richen up the mixture at high power settings which does
indeed drop EGT while allowing more power to be developed. Sometimes
called the "power valve". I'd consider the lower egt at max power to be
normal. Perhaps you are a bit lean prior to the enrichment operating. I
don't know whether the enrichment starts when the secondaries open or
before that on your carb. Adventures like yours are part of the reason
that I kept my engine internally stock and deferred decisions about
whether to do mods for the next engine.

My vacuum pump is OK but my horizon has become unreliable. Kind of wish
it was just my pump...

Ken

Mike Kimball wrote:

I would like to see no more than 1450F at max power. I suppose I could

live

with 1500F with a limit on max power run time which is so common with
airplane engines. I would also like to see less than 1400F at cruise

power.

The reason I am seeking lower temps is that I have no computer to adjust
timing and air/fuel ratios. I have to err on a more conservative profile.
With the timing set in the proper place, 100LL in the tanks, and colder
spark plugs I am already better protected against preignition/detonation
than I was before.

I think I may be on to something after more test runs today. I decided to
really check out max power. I selected max power and the engine started to
die like it was running out of fuel. I glanced down and noticed that I
wasn't quite full rich. I pushed in the last bit of mixture and the engine
ran at max power just fine. I have my prop currently set for 4500RPM

static

at max power. (I can easily go way past 5000RPM with finer pitch but I

know

that is too fine for flight.) I decided to check EGT at various RPMS.

1500RPM - 1150F
2000RPM - 1300F
2500RPM - 1350F
3000RPM - 1400F
3500RPM - 1500F
4000RPM - 1550F
4500RPM - 1350F

I'm sure you'll notice the max power anomaly. Apparently, the Holly

somehow

enrichens the mixture more at full throttle. The fact that the engine
wouldn't even stay running at max power with a setting just slightly lean

of

full rich leads me to believe that although I was able to get it to stay
running at max power, it is probably still too lean through the rest of the
power range and EGT supports that theory. Since the EGT is acceptable all
the way to 3000RPM I am thinking that I will try larger jets in the
secondaries. If necessary, I may alter the primary mixture plate to allow
more fuel through as well. My timing stop prevents more timing advance

past

3500RPM. I may change to a stop that allows continuous advance to 4500RPM.
That should help EGT at higher power settings as well.

Mike

P.S. It's always something. My vacuum pump stopped giving me any vacuum
today. It was pretty hot after the engine runs. I think I may have fried
it. I gotta look at ways to get more cooling air to it.

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--
David A. Ricker
Fall River, Nova Scotia
Canada






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[Dale Fultz]

Mike ,, Not being a smart ass but ,, a person needs more information to help
you out.. Like are the high egt's on climb out ? level flight? more
information would be helpful... Dale SR-033 N269DF
----- Original Message -----




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[Ken]

Guys report 20+ to 100+ hours from O2 sensors that are fed with avgas.
TCP or Decalin fuel additive should increase that. However I would not
trust the reading when used on short individual exhaust stacks as puffs
of air will travel back up the pipes between exhaust pulses. Even a
$30. narrow band sensor with a multimeter will give a lot of info but
you'd need decent length exhaust pipes.

With the leaning block one should be able to estimate rich or lean of
peak though. Full rich should be rich of peak at all throttle positions.
If leaning does not increas EGT then the main jets are definately too small.

Ken

Dave Ricker wrote:

Mike

I don't know if I'm out in left field here but would a wide band O2 sensor
(exhaust sniffer) be useful here to tell you what mixture you're getting at
various points on the power curve? I know the car guys use them to get their
ECU maps right when adding a turbo, basically the issue there is to make the
most power but not go lean at any point to keep from burning pistons.

They usually go with stand-alone fuel injection/engine management systems like
the 034 but air/fuel ratio is the same whether it's a carb or EFI.

Google "wide band oxygen sensor". Just had a thought, I don't think these
things like lead so you'd have to be running MOGAS but you have done some work
with it haven't you?

I think a wide band is under $200.

Dave



Mike Kimball wrote:

Yeah, I know about the power valve for enrichment. Only problem is, I don't
have one. One of the mods that the manufacturer of the cockpit mixture
control specifies is to remove the power valve and block off the hole with a
supplied plug. I'm thinking the enrichment I am getting at max power must
have something to do with the secondaries. Just guessing though. I have no
real idea what causes enrichment between 4000 RPM and full throttle. I may
experiment with removing my mixture control and try a bunch of jets in the
stock config for the carb to see what happens. I may even see what happens
if I put the power valve back in. Oh, the life of the experimenter.

Mike

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ken
Sent: Friday, July 27, 2007 3:24 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] High EGT

Mike

Most automotive carbs that I've had did have some kind of enrichment
circuit to richen up the mixture at high power settings which does
indeed drop EGT while allowing more power to be developed. Sometimes
called the "power valve". I'd consider the lower egt at max power to be
normal. Perhaps you are a bit lean prior to the enrichment operating. I
don't know whether the enrichment starts when the secondaries open or
before that on your carb. Adventures like yours are part of the reason
that I kept my engine internally stock and deferred decisions about
whether to do mods for the next engine.

My vacuum pump is OK but my horizon has become unreliable. Kind of wish
it was just my pump...

Ken

Mike Kimball wrote:

I would like to see no more than 1450F at max power. I suppose I could

live

with 1500F with a limit on max power run time which is so common with
airplane engines. I would also like to see less than 1400F at cruise

power.

The reason I am seeking lower temps is that I have no computer to adjust
timing and air/fuel ratios. I have to err on a more conservative profile.
With the timing set in the proper place, 100LL in the tanks, and colder
spark plugs I am already better protected against preignition/detonation
than I was before.

I think I may be on to something after more test runs today. I decided to
really check out max power. I selected max power and the engine started to
die like it was running out of fuel. I glanced down and noticed that I
wasn't quite full rich. I pushed in the last bit of mixture and the engine
ran at max power just fine. I have my prop currently set for 4500RPM

static

at max power. (I can easily go way past 5000RPM with finer pitch but I

know

that is too fine for flight.) I decided to check EGT at various RPMS.

1500RPM - 1150F
2000RPM - 1300F
2500RPM - 1350F
3000RPM - 1400F
3500RPM - 1500F
4000RPM - 1550F
4500RPM - 1350F

I'm sure you'll notice the max power anomaly. Apparently, the Holly

somehow

enrichens the mixture more at full throttle. The fact that the engine
wouldn't even stay running at max power with a setting just slightly lean

of

full rich leads me to believe that although I was able to get it to stay
running at max power, it is probably still too lean through the rest of the
power range and EGT supports that theory. Since the EGT is acceptable all
the way to 3000RPM I am thinking that I will try larger jets in the
secondaries. If necessary, I may alter the primary mixture plate to allow
more fuel through as well. My timing stop prevents more timing advance

past

3500RPM. I may change to a stop that allows continuous advance to 4500RPM.
That should help EGT at higher power settings as well.

Mike

P.S. It's always something. My vacuum pump stopped giving me any vacuum
today. It was pretty hot after the engine runs. I think I may have fried
it. I gotta look at ways to get more cooling air to it.

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--
David A. Ricker
Fall River, Nova Scotia
Canada






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[Kim Kimball]

Not flying yet Dale. Finding this stuff on the ground. Don't want to fly until I get it straightened out. Definitely not being a smart ass for asking for more info. Any info I can provide that helps knowledgeable people help me is gladly given.

Mike

----- Original Message -----
From: Dale Fultz <dfultz17086@earthlink.net>
Date: Saturday, July 28, 2007 10:31 am
Subject: Re: [rebel-builders] High EGT
To: rebel-builders@dcsol.com

Mike ,, Not being a smart ass but ,, a person needs more
information to help
you out.. Like are the high egt's on climb out ? level flight?
more
information would be helpful... Dale SR-033 N269DF
----- Original Message -----




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