Today's Message Index:
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1. 10:23 AM - Re: JPI vs EI (teamgrumman@AOL.COM)
2. 02:33 PM - EI vs JPI (Richard Mutzman)
3. 09:21 PM - Re: EI vs JPI (teamgrumman@aol.com)
Message 1
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I got on line last night and did a Google search. =C2-The grounded thermal
couples are a totally different animal than the ungrounded ones. =C2-If E
I is using a spring loaded probe, is it a grounded type or not? =C2-If it
is not, my guess is you won't see any difference in temperatures because of
the floating ground. =C2-In a grounded circuit, it's grounded at the probe
. =C2-Don't ask me to explain how it works. =C2-
As for the newer style wires, did EI go to a grounded circuit? =C2-or do t
hey keep the floating ground?
I agree, Cliff. =C2-There is something else going on. =C2-Does it matter
?
-----Original Message-----
From: flyv35b <flyv35b@minetfiber.com>
Sent: Thu, 26 Mar 2009 3:35 pm
Subject: Re: TeamGrumman-List: JPI vs EI
=C2-
"If you turn on a soldering iron and touch the tip with a thermometer
(thermal couple) you'll get one reading. =C2-If you move it away from the
soldering iron 1/8 of an inch, you'll get another. =C2-The JPI probes touc
h
the cylinder head. =C2-The EI probes sit in the well, heated by the
surrounding aluminum. =C2-They are measuring different things." =C2-
=C2-
Gary, you have obviously done more comparative testing that anyone I know
of and I can't fault what you have done.=C2- Having said that, there still
are
a couple of things that have not been explained, to my satisfaction at
least.=C2- Everyone always brings up the different20types of CHT probes as
an
explanation as to why there is such a larger difference between the JPI and
EI
readings.=C2- As I mentioned in an email to the gang recently, EI sells th
e
exact same type of spring loaded bayonet CHT probe as JPI uses (it is an
option).=C2- And one test I know of with an EI instrument resulted in almo
st
no temperature variation between the standard P-100 CHT probe and the P-110
spring loaded probe.=C2- That would appear to refute the "theory" that the
temperature difference is due to the different probe styles.=C2- So what e
lse
is there?=C2- Different grounding?
=C2-
"The wires are a lot easier to route and you can cut them to length instead
of wrapping up and tying up large bundles of wiring. =C2-Quite often, on E
I
installations, the wire gets bundled up under the instrument panel in large
wads
of wiring. =C2-Looks l ike shit, but, I guess no one but me cares about wh
at
the backside of instrument panel looks like (based on what I see in everythi
ng I
work on)."
=C2-
I guess you haven't installed an EI system recently.=C2- I agree with you
about the older braided EI wires.=C2- I hated them as well.=C2- EI now u
ses
the same type of wires as JPI and you can cut them off or get them to not
install the terminals on the circular connector so you can cut them to the e
xact
length you want the them crimp on the terminals and plug them into the
connector.
=C2-
"I think s
omeone else needs to go out and duplicate the tests. =C2-Cliff?
=C2-The next time you get a plane in with a JPI, take one of the spare EIs
(you must have a spare) and temporarily=C2-install it and go fly."
=C2-
I guess you're right, I need to do so further testing as I think there are
still some things that need to be explained.=C2- And I=C2-don't think th
at
the two different style of probes account for 70 F temperature variation, or
at
least they shouldn't based on=C2-my conversations with EI.=C2-
=C2-
At one time you were going to test a spring loaded EI probe.=C2- I guess
you never got around to doing that?
=C2-
Cliff=C2-=C2-
----- Original Message -----
From:
teamgrumman@aol.com
Sent: Thursday, March 26, 2009 12:46
PM
Subject: Re: TeamGrumman-List: JPI vs
EI
If you turn on a soldering iron and touch the tip with a thermometer
(thermal couple) you'll get one reading. =C2-If you move it away from th
e
soldering iron 1/8 of an inch, you'll get another. =C2-The JPI probes to
uch
the cylinder head. =C2-The EI probes sit in the well, heated by the
surrounding aluminum. =C2-They are measuring different things. =C2-
It isn't a question of which one is accurate. =C2-I would bet
that both are within 1 degree of being accurate. =C2-Do a little researc
h
on
thermal couples and you'll find that thermal couples come in all
configurations. =C2-Some require grounding, some don't. =C2-Do I want
a
system that uses a floating ground (EI)? =C2-No.
I forget a lot from my engineering classes regarding thermal couples,
but, as I recall, some=C2-thermal couples are used as a source voltage
themselves in a circuit and other=C2-thermal couples are used is a power
ed
circuit requiring a common source ground. =C2-
As for which one is better, personally, the JPI makes for a much cleaner
installation. =C2-I think the JPI looks more professional and the operat
ing
logic is more what I would expect; i.e., less of a learning curve. =C2-T
he
wires are a lot easier to route and you can cut them to length instead of
wrapping up and tying up large bundles of wiring. =C2-Quite often, on EI
installations, the wire gets bundled up under the instrument panel in larg
e
wads of wiring. =C2-Looks l ike shit, but, I guess no one but me cares a
bout
what the backside of instrument panel looks like (based on what I see in
everything I work on). =C2-[Note: =C2-I wish you all could see behind
the
panel=C2-of 26392. =C2-You'd swear there were no wires at all.] =C2
-The
JPI has more features for the same money. =C2-As for customer service, t
here
have been big changes in the last 3 or 4 years regarding servi
ce. =C2-The
warranty is actually better than published. =C2-The JPI EDM 800 in my pl
ane,
since 2004, began displaying weird number flashing on occasion last year.
=C2-I sent it in and they fixed it at no cost. =C2-I did this with ano
ther
customers plane with a display that was dim (it was also 3 years out of
warrantee). =C2-No cost. =C2-Other than those two, I haven't had to se
nd a
JPI back for service in the 10 years I've been installing them.
The question was: =C2-What system did I use in the FAA portion of the
flight testing? =C2- EI of course. =C2-I wanted to get the lowest CHTs
possible. =C2-Besides, the DER already had a certified EI system.
=C2-Running all that shielded wiring, 14 of them, through the ADF hole i
n
the floor of the plane, was interesting. =C2-I could have run twice that
number of JPI wires through the same opening. =C2-
The question should be: =C2-What did I find with the JPI set-up in my
plane? =C2-and, what did I find with the JPI set up in the flight test
airplane. C2
BY-THE-WAY: =C2-It's trivial to remove a JPI CHT probe. =C2-The
wiring isn't fixed to the nut used to tighten the probe into the cylinder
head. =C2-The JPI uses a separate shell to tighten the probe in place.
=C2-THUS: =C2-a JPI CHT probe can be removed with the cowling in place
in
a
bout 1/10 the time it takes to remove an EI probe, WITHOUT REMOVING THE WIRE
FROM ITS CONNECTION. =C2-That being said, on the test plane, the JPI CHT
probes were left in place and tie-wrapped to the bundle in the neighborhoo
d of
the air leaving the cylinder. =C2-I was able to measure the temperature
drop, of the air (OAT) to the exit air, across cylinder #3 with the #3 pro
be
and across #2 with the #2 probe. =C2-The #1 CHT probe was placed in the
same
proximity to the EI probe used to measure the temperature of the air near
the
alternator. =C2-The #4 CHT probe was placed in the same proximity to the
EI
probe used to measure the temperature of the accessory case. =C2-Both JP
I
probes showed temps very close to the EI probes used to measure alternator
temps and accessory temps,=C2-respectively.=C2-=C2-
Prior to the FAA climb-cooling tests, I did the same tests with my
plane and the JPI 800. The 800 shows percent power so it's trivial to set
conditions for 75% power. =C2-During a Vy climb from 1000 feet to 17,800
feet on an 80 degree day, my CHTs peaked around 470 (roughly 400 on an EI
and
confirmed during testing with an EI installed on the test plane) at around
8000 feet. =C2-Oil temp was stable at 210 before it began to decrease by
about the same altitude. =C2-I ran this same test with the test airplane
,
climbing to 12,500 feet, and got abou
t the same results, 465 and 205 but it
was a cooler day. =C2-
About 6 months ago, I was flying at tree tops around Lake Berryessa
(spelling), a bit northeast of Napa. =C2-I was near full throttle most o
f
the time. =C2-OAT was in the high 80s. =C2- #3 cylinder began flashing
at
465 (that is where I set my limit). =C2-This surprised me. =C2-Lots of
fat, cool air over a lake and I was still pushing CHTs. =C2-Anyway, had
I
not flown for a year with an EI installed in my plane, I would have been
worried. =C2-I know that 465 was somewhere around 400 on an EI. =C2-
So, if you're using an EI, will you be wondering what the temperature of
the aluminum is near the combustion chamber really is when you see 400
degrees? =C2-If you're using a JPI, will you panic if you see 410 in cru
ise?
=C2-(my typical cruise temp) =C2-Maybe.
=9CFor those
who believe, no proof is necessary. For those who don't believe, no proof
is
possible.=9D=C2-=C2-- Stuart Chase
PS, I wonder why there is so much skepticism=C2-over my results with
the EI vs JPI.=2 0=C2-I think someone else needs to go out and duplica
te the
tests. =C2-Cliff? =C2-The next time you get a plane in with a JPI, tak
e
one of the spare EIs (you must have a spare) and temporarily=C2-install
it
and go fly. 0
-----Original Message-----
From: flyv35b
<flyv35b@minetfiber.com>
Sent:
Thu, 26 Mar 2009 6:12 am
Subject: Re: TeamGrumman-List: JPI vs EI
So if there is the large variation that you say
between EI and JPI, which one is accurate or the most accurate? And why?
=C2-
Apparently you don't feel that grounding problems are or can be an
issue.=C2- Which system did you use for your cowling cooling
tests?
=C2-
=C2-
Cliff
----- Original Message -----
From:
teamgrumman@aol.com
< div style="FONT: 10pt arial">Sent: Thursday, March 26,
2009 1:34 AM
Subject: Re: TeamGrumman-List: JPI vs
EI
I flew with both the EI and JPI installed in my plane for over
a year and over 25 flights. =C2-I had the EI in #3. =C2-Based on over
300
hours on previous flights over the previous 3 years, I know the #3 should
be
within 10 degrees of #4. =C2-
I tried to explain this the best I could in a write-up in the Star.
=C2-
=9CFor those
who believe, no proof is necessary. For those who don't believe, no proof
is
possible.=9D=C2-=C2-- Stuart Chase
-----Original
Message-----
From: teamgrumman@aol.com
Sent:
=2
0 Thu, 26 Mar 2009 1:13 am
Subject: Re: TeamGrumman-List: JPI vs EI
Dave doesn't know
what he's doing. =C2-I always add the ground and it's still a lot
higher.
-----Original Message-----
From: 923te <923te@att.net>
Sent:
Wed, 25 Mar202009 9:12 am
Subject: TeamGrumman-List: JPI vs EI
Gary,
I thought this an interesting thread on the
GG.
I understand that the JPI probes are
grounded while the EI are not.
Is it possible that this accounts for th
edifferences in your thorough comparison tests?
ned
=C2-
=C2-
----- Original Message -----
From: David Fletcher
Sent: Wednesday, March 25, 2009 10:41 AM
Subject: RE: Tiger outlet ramps - More Info Req.
> But, of course, I am sure we can all comment on the EI vs
JPI question
> accuracy. If the metallurgical properties of aluminum
degrade at temps
> higher than 450*, isn't the JPI more accurately
reflecting the true
> temperature of the aluminum cylinder
head?
Customer just had the same problem w ith a newly installed
JPI. cruise temps
were in the 425 range.=C2- Went back and added a new
ground directly to the
engine as the manual says in bold print, and his
temps dropped about 25
degrees. The EI doesn't seem to need it's own
special ground.
Davi
d Fletcher
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I have been following the discussion with interest.
One thing that I don't recall being addressed (maybe Gary addressed in his
article)=2C is=2C for the limits that Lycoming quotes=2C which probe did th
ey use for the testing. One that measures the actual metal temps via condu
ction=2C or one that measures the air in a well which is heated by radiatio
n from the hot metal? Hmmmm...conduction versus radiation?
Richard Mutzman
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Message 3
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I called Lycoming about 6 years ago and tried to find an engineer who could
answer that question. =C2-It took about 5 'engineers' saying, "Well, [fill
in the blank] would know, but, he died." before I realized all of the corpo
rate knowledge was gone. =C2-I researched it a bit and from what I recall,
probes similar to the EI probes were used.
I also spent a significant amount of time about 20 years ago trying to find
out which rocker when where. =C2-As you may know, the intake rocker and th
e exhaust rocker are different. =C2-IAs on my field (Lancaster) and the fo
lks at Lycoming were NO HELP AT ALL. =C2-I finally found an overhaul manua
l written in 1955 that described the differences.
-----Original Message-----
From: Richard Mutzman <rcmutz@msn.com>
Sent: Fri, 27 Mar 2009 2:28 pm
Subject: TeamGrumman-List: EI vs JPI
I have been following the discussion with interest.
=C2-
One thing that I don't recall being addressed (maybe Gary addressed in his a
rticle), is, for the limits that Lycoming quotes, which probe did they use f
or the testing.=C2- One that measures the actual metal temps via conductio
n, or one that measures the air in a well which is heated by radiation from
the hot metal?=C2- Hmmmm...conduction versus radiation?
Richard Mutzman
Windows Live=84=A2 SkyDrive: Get 25 GB of free online storage. Check it o
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