CHTs - What is acceptable?

"G.R. Patterson III" wrote in message ...

. The only way the airframe could make a
difference is if a) they have the probe in only one cylinder and b) the
temperatures on the other cylinders are known to be significantly different.

And both of the above are the case. Unless you have an engine analyzer
the CHT is only measuring one cylinder. They usually try to put it in the
hottest cylinder (one of the back ones), but that varies based on how the
engine cooling air is designed on the airframe.

The oil temperature temps have an even greater variation.

In a sense, you're probably right. There's a threaded hole in the
cylinder head. The probe goes there, no matter what the airframe. The
only way the airframe could make a difference is if a) they have the
probe in only one cylinder and b) the temperatures on the other
cylinders are known to be significantly different.

Actually, it can make a difference even beyond that. The fine folks at
GAMI (as part of their liquid air project) completely instrumented a few
cylinders (dozens of probes each) and went flying. They found 80
degree differences from one side of some cylinders to the other side.
So even a threaded CHT probe may or may not be telling you the true
temperature of even THAT cylinder.

FWIW, GAMI theorizes that this uneven cooling air around each cylinder
may be a significant cause of the cylinder operating "out of round" and
causing significant scuffing and wear.

I'm in a PA28 235 and I'm seeing 415ish on takeoff on this one cylinder.


Trip

In article , says...

I feel as long as I keep it under 400 degrees except on
take off it should be ok. I drop

Can a cylinder heat up that much on takeoff? I have never looked.

Wish I did. I have an old analog 6 cylinder anaylzer.


Trip


In article , says...


"TripFarmer" wrote in message
...
I just don't buy that "airframe" stuff. A cylinder head can only take
so much temperature for so long before it gives in. 400 degrees is
400 degrees no matter what airframe it's in. If I'm wrong please tell
me why.........

I've got about 15 hours on 6 new Superior Millinieums and just put in my
first quart of oil since 2TT. I have a range of temps at cruise from
320 - 380. They dropped a lot after about the first 30 - 60 minutes of
break in and seem to have stabilized since to these numbers. The hot one
will run 400-410 in a full power climb in my PA28 235.



I take it you have a good engine analyzer like the JPI 700?

"G.R. Patterson III" wrote in message ...
Steven Barnes wrote:

Our club's Skylane has one CHT gauge with a big 'ol green range & no temps
on it. Any recommendations on how to use this rather "useless" gauge?

That's what my Maule has. I just keep it in the green during climb and descent and
check it every once in a while during cruise.

George Patterson
If you want to know God's opinion of money, just look at the people
he gives it to.


All of the information most people need is available online at

http://www.airweb.faa.gov/Regulatory...e?OpenFrameSet

These are the Type Certificate Data Sheets (TCDS) for US made
airplanes, engines, propellers and appliances (equipment such as
Carbs, seat belts and so on).
Engine TCDS give CHTs and a lot of other stuff. The statement by
the engine guys that the airframe manufacturer sets CHTs is
misleading.

Dan

In article ,
(WARREN1157) wrote:

Can a cylinder heat up that much on takeoff? I have never looked.

yes. My 140 gets pretty close to 500 degrees during climbout
(500 is redline for my engine).

Are takeoff and climbout the same thing?

is the distinction important?

--
Bob Noel
Seen on Kerry's campaign airplane: "the real deal"
oh yeah baby.

"TripFarmer" wrote in message
...
Wish I did. I have an old analog 6 cylinder anaylzer.

If you want to protect your investment it would be HIGHLY recommended to get
a good engine analyzer.

I'm looking at $28K for a IO-550 Milleniunm exchange and I'm going to "baby"
those poppers. The previous owner of my bird had a JPI-700 and he got 1800
hours out of a IO-520 running LOP.


Trip


In article , says...

I take it you have a good engine analyzer like the JPI 700?

"Bob Noel" wrote in message
...
In article ,
(WARREN1157) wrote:

Can a cylinder heat up that much on takeoff? I have never looked.

yes. My 140 gets pretty close to 500 degrees during climbout
(500 is redline for my engine).

Are takeoff and climbout the same thing?

is the distinction important?

Well, yes. Beech recommends 105 for climb out, but better is 120 for better
visibility and MUCH BETTER COOLING. Rate of climb (after obstacle clearance)
is only marginally less (about 1025 fpm vs 1075 in my F33A).

In article , "Tom S."
wrote:

Can a cylinder heat up that much on takeoff? I have never looked.

yes. My 140 gets pretty close to 500 degrees during climbout
(500 is redline for my engine).

Are takeoff and climbout the same thing?

is the distinction important?

Well, yes. Beech recommends 105 for climb out, but better is 120 for
better
visibility and MUCH BETTER COOLING. Rate of climb (after obstacle
clearance)
is only marginally less (about 1025 fpm vs 1075 in my F33A).

Sure. I do the same type of thing in my 140 - only slower ;-).
WRT to CHT, I have to balance it with the RPM limit from the
160hp STC (yellow arc from 2650 to 2700 - five minute limit).
As a result I often do reduced-power climbs to keep the CHT closer
to 400 degrees and RPM comfortably below 2650.

I probably should look at the baffling, but it would run
pretty hot in climb before the engine overhaul and all new
baffling. Or I should check the CHT calibration again.

--
Bob Noel
Seen on Kerry's campaign airplane: "the real deal"
oh yeah baby.

In article , Steven
Barnes wrote:
Our club's Skylane has one CHT gauge with a big 'ol green range & no temps
on it. Any recommendations on how to use this rather "useless" gauge?



Keep it in the green.