Today's Message Index:
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1. 02:56 PM - Re: Re: AG5B Jaguar (teamgrumman@aol.com)
2. 03:14 PM - Compression test (teamgrumman@aol.com)
3. 04:46 PM - Re: Compression test (Linn Walters)
4. 05:48 PM - Re: Re: AG5B Jaguar (teamgrumman@aol.com)
Message 1
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I have slowed the airflow down, Ned. And, thanks to a fellow named Bernou
lli, pressure goes up. I got 1.5 to 2.5 inches more pressure drop across
the cylinders than stock using half the inlet area. All those years in
fluid dynamics weren't wasted.
-----Original Message-----
From: 923te <923te@att.net>
Sent: Sun, May 2, 2010 9:23 pm
Subject: Re: TeamGrumman-List: Re: AG5B Jaguar
Gary,
In all your testing for the Jaguar Cowling did you happen to get before an
d after manifold pressure data? If so, for the same conditions, is the man
ifold pressure lower with the Jaguar cowl than with the factory cowl? See
ms apparent that you have slowed the airflow over the cylinders ie dropped
the pressure on top of the cylinders.....
Ned
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Message 2
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| Subject: | Compression test |
Cliff,
Remember when we talked about doing cranking pressure tests? I started do
ing cranking pressure tests as a side-by-side comparison test to the leak
down test.
Yesterday, I was doing the tests on a Tiger as
(1) leak-down/cranking
(3) cranking/leak-down
(2) leak-down/cranking
(4) cranking/leak-down.
I compared the previous years tests as I went. When I got to the #4, the
cranking pressure was about 6 psi lower. Not a big deal. I regularly se
e variations of plus or minus 4 or 5 lbs. This one, however, seemed like
it took 6 revolutions of the engine to build pressure. (it normally take
s about 4 passes to reach peak).
When I checked leak-down, it was 55/80. The odd thing was, no sound of le
aking air at the oil filler neck or exhaust pipe. That much would show up
somewhere. As I was looking for a leak, I noticed a lot of air coming ou
t of the #1 top plug hole. A leak at the #4 intake was the only explanati
on. I've never encountered a leak at the intake valve.
I removed the rocker cover and intake rocker arm thinking it might be a st
uck lifter. Same result. With pressure on it, I gave the intake valve a
quick 'pop' with a small rubber mallet. Compression went right to 77/80.
I took it apart and put it back together after cleaning the lifter and mea
suring the dry tappet clearance (0.048 inches). Ran the engine, checked
again, and 77/80.
Have you (or anyone else) seen such a thing?
Gary
Message 3
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| Subject: | Re: Compression test |
Well Gary ..... sort of. I've had engines over the years where the
pressures were normally close on all 4 cylinders, and all of a sudden
there's a big change in one ....... never for the better. However, I
could detect hissing in the exhaust. Pulling the prop through with air
pressure on the cylinder might change the reading when we got back to
firing position. Sometimes it would take rapping the valve stem with a
rubber mallet. I remove the rocker arm when I do that ...... just to
keep from an 'oops'. Usually one of the above works. I think some crap
gets on the valve seat causing it to leak. Don't know why it takes that
opportunity to get in the way, but it seems to. A last resort (to fix
it) was to go run the engine again, leaning the dickens out of it.
Borescoping the valve face was the final determinant.
Never had a fix for leaking rings though!!!
The rubber mallet thingy was told to me by an A&P/IA that mentored me
years ago. He was full of knowledge gained over the long years he was
involved in aviation ..... and he never led me astray. I miss him terribly.
Linn
teamgrumman@aol.com wrote:
> Cliff,
>
> Remember when we talked about doing cranking pressure tests? I started
> doing cranking pressure tests as a side-by-side comparison test to the
> leak down test.
>
> Yesterday, I was doing the tests on a Tiger as
> (1) leak-down/cranking
> (3) cranking/leak-down
> (2) leak-down/cranking
> (4) cranking/leak-down.
>
> I compared the previous years tests as I went. When I got to the #4,
> the cranking pressure was about 6 psi lower. Not a big deal. I
> regularly see variations of plus or minus 4 or 5 lbs. This one,
> however, seemed like it took 6 revolutions of the engine to build
> pressure. (it normally takes about 4 passes to reach peak).
>
> When I checked leak-down, it was 55/80. The odd thing was, no sound of
> leaking air at the oil filler neck or exhaust pipe. That much would
> show up somewhere. As I was looking for a leak, I noticed a lot of air
> coming out of the #1 top plug hole. A leak at the #4 intake was the
> only explanation. I've never encountered a leak at the intake valve.
>
> I removed the rocker cover and intake rocker arm thinking it might be a
> stuck lifter. Same result. With pressure on it, I gave the intake
> valve a quick 'pop' with a small rubber mallet. Compression went right
> to 77/80.
>
> I took it apart and put it back together after cleaning the lifter and
> measuring the dry tappet clearance (0.048 inches). Ran the engine,
> checked again, and 77/80.
>
> Have you (or anyone else) seen such a thing?
>
> Gary
>
> *
>
>
> *
Message 4
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I'd be using your money.
-----Original Message-----
From: 923te <923te@att.net>
Sent: Sun, May 2, 2010 9:16 pm
Subject: Re: TeamGrumman-List: Re: AG5B Jaguar
So why was it that you thought it was a great idea?
----- Original Message -----
From: teamgrumman@aol.com
Sent: Sunday, May 02, 2010 10:55 PM
Subject: Re: TeamGrumman-List: Re: AG5B Jaguar
The Mooney has a CS prop. There are a lot of things you can do with a
CS prop that you can't with a fixed pitch. Unless you are going to lim
it the 10:1 to planes that also purchase a $15,000 prop, the conversatio
n makes no sense. People out there just don't have that kind of money.
I can put a 10:1 engine together at top overhaul for $6,000. That mak
es a hell of a lot more sense than trying to sell an MT prop at the same
time.
Kevin opened the conversation when I talked about a derated 10:1 -A4K for
Tigers. How the conversation assumed a CS prop was included is beyond
me.
-----Original Message-----
From: Ned Thomas <923te@att.net>
Sent: Sun, May 2, 2010 6:59 pm
Subject: Re: TeamGrumman-List: Re: AG5B Jaguar
The idea is to show the FAA that you are not exceeding the HP certificat
ion of the engine. So put in 10:1 pistons and limit to manifold psi that
equals the previously FAA approved HP limit for the engine. This is the
route Firewall Forward took and were succesful with in achieving FAA
approval.
LAike you say Cliff if you limit by RPM you will get less Thrust. Limit
by MP pressure and you can still crank out the RPM up high.
This assumes a controllable pitch prop. AND most controllable pitch props
are most efficient at less than 2700 RPM more like 2400 - 2500 As I und
erstand it. So the idea is to get rated HP at the most efficient prop
RPM
Sent from my iPhone
On May 2, 2010, at 7:33 PM, "flyv35b" <flyv35b@minetfiber.com> wrote:
Why? Reducing either will decrease horsepower. A manifold pressure
limitation would be better since you would be able to have full power
at altitude after the MP drops to the limit. So at altitude it would
act as a larger more powerful engine. Limiting RPM would limit you
all the way from the ground up. But limiting RPM with the governor
setting is easier to control and less likely for the pilot to CHEAT
during takeoff and climb with a CS prop.
Bill Scott limited RPM to 26r0 since that was the rpm that resulted in
a 5% increase in HP. For the 180 hp that would amount to whatever re
sulted in 189 hp.
Cliff
----- Original Message -----
From: 923te
Sent: Sunday, May 02, 2010 4:46 PM
Subject: Re: TeamGrumman-List: Re: AG5B Jaguar
"Same as limiting manifold pressure" is true only for a fixed pitch
prop. We are talking about using a constant speed prop right?
----- Original Message -----
From: teamgrumman@aol.com
Sent: Sunday, May 02, 2010 4:03 PM
Subject: Re: TeamGrumman-List: Re: AG5B Jaguar
Bill Scott's STC limits rpm to 2650 rpm. Same as limiting manifol
d pressure at sea level.
Ned, I talked to Ken yesterday about making a 10:1 -A4K. A 10:1
-A4K would be limited to about 2550 rpm at sea level to make 180
hp. Limit with rpm or MAP, it's the same result. A none ported
and polished 10:1 -A4K will make about 210 hp at 2700 rpm.
Ken would be interested in doing the development work if you're in
terested. One of my customers is selling his plane, a 76 TIger wi
th a mid-time engine, for $58,000. If you buy the plane and get
the engine modded by LyCon, I can get Bob on board for the flight tests.
Since you know what needs to be done, you could work with Bob an
d Ken and perhaps duplicate the testing done by Firewall Forward.
I'll take care of the paperwork that I can do and do the flight
testing with Bob as the FAA rep. Sounds like a great idea.
Gary
-----Original Message-----
From: 923te <923te@att.net>
Sent: Sat, May 1, 2010 6:57 am
Subject: Re: TeamGrumman-List: Re: AG5B Jaguar
You just have to know the tricks of working with the FAA.
In this case the trick is in how to word the certification. That
is certify the 10:1 pistons in the Tiger by limiting the maximum
continuous horsepower to 180 by reducing manifold pressure and li
miting maximum continuous r.p.m. to 2700.
The 8.5:1 STC for the O-320 that Bill Scott has does it this way.
Then you would have to do similar proof tests just as Firewall For
ward did:
"The airframe and power plant certification testing involved engin
e dyno runs to verify and document both H.P. and torque increases;
engine detonation testing performed at sea level conditions by au
thorized FAA testing facilities; engine oil cooling tests performe
d by the FAA at gross weight, max rate of climb and an ambient tem
perature of 100F, engine propeller vibration and increase torque
compatibility testing performed by McCauley Engineers in Dayton,
Ohio; effects of torque increases on both spin entry and recovery
in all flight regimes, and engine out and airstart procedures eva
luated for P.O.H. compliance."
----- Original Message -----
From: teamgrumman@aol.com
Sent: Friday, April 30, 2010 11:14 PM
Subject: Re: TeamGrumman-List: Re: AG5B Jaguar
True. It can be done. You can put 10:1 pistons into an -A4K.
But. You would have to re-certify first, the engine, then the
airframe for the additional horsepower, change the POH, come up
with all new performance data, reliability data, cooling data,
. . . . . Is it worth it? You tell me. I'll use your money
to find out.
What I meant was, "the FAA would never approve putting 10:1 into
an A4K running at 2700 rpm without lots of money." Keeping the
-A4K at 180 hp makes all the difference in the world.
-----Original Message-----
From: 923te <923te@att.net>
Sent: Fri, Apr 30, 2010 8:04 pm
Subject: Re: TeamGrumman-List: Re: AG5B Jaguar
Two FAA certified examples of 10:1 pistons
1) The helicopter engine HIO-360-D1A which is rated at 190HP at
3200RPM on 100/100LL with compression ratio of 10.00:
1
2) Firewall Forward has STC'd 10:1 pistons in the Mooney and Ca
rdinal without RPM restrictions according to their representativ
e spoke with.
http://firewallforward.com/horsepowerplusstc.pdf
Admittedly, these are not paraleel valve but are angle valve eng
ines but they do show that the FAA has approved 10:1 pistons at
or above 2700rpm
----- Original Message ---
From: teamgrumman@aol.com
Sent: Friday, April 30, 2010 1:33 PM
Subject: Re: TeamGrumman-List: Re: AG5B Jaguar
Kevin,
The problem with running 2700 rpm, legally, with 10:1 compress
ion in a certified engine is that the FAA would never approve
it.
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