Rotating Injectors Among Cylinders

My per-cyclinder avg EGTs are as follows:

#1: 1370
#2: 1390
#3: 1450
#4: 1450
#5: 1480
#6: 1430

The difference is 110 degrees between the coldest and hotest cylinder.
A colleague of mine says that is a bit high for a fuel-injected system.
Is that right?

He suggest rotating the injectors from the hotest cylinders to the
coldest ones to try to better balance them (so, for example, swapping #5
and #1). I am not sure why one would do that. Have others done that
with success?

-Sami
N2057M, Piper Turbo Arrow III

In article ,
"O. Sami Saydjari" wrote:

My per-cyclinder avg EGTs are as follows:

#1: 1370
#2: 1390
#3: 1450
#4: 1450
#5: 1480
#6: 1430

The difference is 110 degrees between the coldest and hotest cylinder.
A colleague of mine says that is a bit high for a fuel-injected system.
Is that right?

He suggest rotating the injectors from the hotest cylinders to the
coldest ones to try to better balance them (so, for example, swapping #5
and #1). I am not sure why one would do that. Have others done that
with success?

-Sami
N2057M, Piper Turbo Arrow III


Not all injectors have the same dimensions/tolerances -- especially (so
I have heard) in TCM Continental engines. That is the basis for GAMI
injectors. They are tailored to each engine.

Swapping injectors for #1 and #5 would be a first step in determining
what effects the injectors have on EGT.

--
Remove _'s from email address to talk to me.

O. Sami Saydjari wrote:
My per-cyclinder avg EGTs are as follows:

#1: 1370
#2: 1390
#3: 1450
#4: 1450
#5: 1480
#6: 1430

The difference is 110 degrees between the coldest and hotest cylinder. A
colleague of mine says that is a bit high for a fuel-injected system.
Is that right?

He suggest rotating the injectors from the hotest cylinders to the
coldest ones to try to better balance them (so, for example, swapping #5
and #1). I am not sure why one would do that. Have others done that
with success?

Why not perform a Coke-bottle test first to determine flows for each
injector?

I was taught and have read that you should not rotate injectors. Just my
..02. YMMV

Jon Kraus
'79 Mooney 201

O. Sami Saydjari wrote:
My per-cyclinder avg EGTs are as follows:

#1: 1370
#2: 1390
#3: 1450
#4: 1450
#5: 1480
#6: 1430

The difference is 110 degrees between the coldest and hotest cylinder. A
colleague of mine says that is a bit high for a fuel-injected system.
Is that right?

He suggest rotating the injectors from the hotest cylinders to the
coldest ones to try to better balance them (so, for example, swapping #5
and #1). I am not sure why one would do that. Have others done that
with success?

-Sami
N2057M, Piper Turbo Arrow III

Have you read the articles by John Deakin in Avweb? It's not the highest EGT
temp, but the cylinder that peaks first that's more important.

Also, CHT is really the more important parameter, not EGT.

This also leads up to lean of peak engine operations, which is kind of like
starting a discussion on the merits of specific religions.

"Jim N." wrote in message
...
Have you read the articles by John Deakin in Avweb? It's not the highest
EGT
temp, but the cylinder that peaks first that's more important.

Also, CHT is really the more important parameter, not EGT.

This also leads up to lean of peak engine operations, which is kind of
like
starting a discussion on the merits of specific religions.

Except that LOP has loads of supporting evidence, so you need not accept it
on blind faith. :~)

"O. Sami Saydjari" wrote in message
...
My per-cyclinder avg EGTs are as follows:

#1: 1370
#2: 1390
#3: 1450
#4: 1450
#5: 1480
#6: 1430

The difference is 110 degrees between the coldest and hotest cylinder.
A colleague of mine says that is a bit high for a fuel-injected system.
Is that right?

He suggest rotating the injectors from the hotest cylinders to the
coldest ones to try to better balance them (so, for example, swapping #5
and #1). I am not sure why one would do that. Have others done that
with success?


Not legal. That's the reason GAMI had to spend a lot of time and money
getting an STC.

http://www.avweb.com/news/reviews/182558-1.html


"Once Braly understood the reason for the mixture maldistribution, the
solution was obvious: vary the orifices in the injector nozzles to
compensate for the "borrowing" of fuel between cylinders. The lean-running
rear cylinders need larger-orifice injectors that deliver a bit more fuel,
while the rich-running front cylinders need smaller-orifice injectors that
deliver a bit less.
Of course, George wasn't the first to come up with this idea. Knowledgeable
A&Ps had been quietly playing "musical injectors" on their big-bore TCM
engines for years. I say "quietly" because the use of different-sized
injectors on a TCM engine wasn't exactly legal: the engine's type
certificate data sheet specifies that all injectors are to be the same size.
So this is the sort of thing that mechanics would usually do only on their
own airplanes, and it usually wouldn't show up in the logbooks or be spoken
of in public. Generally, this injector swapping was done on a hit-or-miss
basis without engineering discipline or instrumentation. Sometimes it
worked, sometimes not."

"Jon Kraus" wrote in message
.. .
I was taught and have read that you should not rotate injectors. Just my
.02. YMMV

Jon Kraus
'79 Mooney 201

Correct...that was an old "trick", but part of the reason GAMI had to get
and STC and PMA.

http://www.avweb.com/news/reviews/182558-1.html

I happen to agree with LOP ops completely, and do it as a matter of routine
in my Baron.

However, there are also people who believe that they need to follow the
"book" as the only way to operate an engine, despite convincing evidence to
the contrary.

O.,

The difference is 110 degrees between the coldest and hotest cylinder.
A colleague of mine says that is a bit high for a fuel-injected system.
Is that right?


Not really. Absolute temperatures are not that important (in the context
of leaning). Go to www.gami.com and run their lean-test to find the
spread between when your first and your last cylinder reach peak. THAT is
important - and you can change something by rotating the nozzles.

I would recommend you read the engine management columns by John Deakin
at www.avweb.com.

--
Thomas Borchert (EDDH)