Cylinder head temp

[John Ashcroft]

I am still getting used to our Maule which is an M5235c it has the std Maule Cht which is always indicating well on the hot side of normal. In climb if not careful it will go into the red. I have been used to the injected bonanza where the temp could be controlled quite easily with ff and speed.
Am I being over sensitive or should I investigate this further?

[aero101]

I would suggest first thing to do is throw the original indication sys away as far as you can... Then purchase something much more accurate, such as EI Instruments engine analyzer EGT/CHT for ALL the cylinders. Another option a little cheaper would be the multi-cyl CHT with a switch type indication system... It's been my experience on the older Maules that original system can be terribly inaccurate in either direction!!! If your oil temp is normal or low, the CHT is probably ok, but nice to have something reliable?

[John Ashcroft]

Thanks Aero
The oil temp is normal or low as you have said.
I will look into this
Thanks

[Mountain Doctor]

After using and gaining experiance with an engine analyzer (I have a JPI) I would never own a plane without one again.

You need to know what the temp of EACH cylinder REALLY is. Otherwise you are guessing at power, mixture, airspeed, and attitude settings and that's not the best way to operate a $40,000 engine you are trusting with your life, and the lives of your passengers.

[John Ashcroft]

Thanks
I had an analyser in my Bonanza, the main difference in that aircraft was that it was injected and fitted with Gami Injectors which were tuned to each cylinder. These allowed me to adjust the mixture quite accurately to achieve a very tight temperature range across the cylinders. I could accurately run the engine lean or rich of peak, and keep the cylinder pressures under control.
The Maule we have is a carby model and so the control of individual cylinder temperatures is not possible, other than by pushing large amounts of fuel through the system.
The main benefit I see from an engine analyser is in flight trouble shooting, through spotting a cool cylinder and possibly identifying a problem before it develops too far.
One of the benefits of the tuned injectors and the analyser was that the individual temps could be controlled so well, preserving the life of the engine. My Bonanza went well past TBO with no cylinder work at all.
One thing the Gami people did establish was that an engine run at less than 65% power was far less susceptible to increased wear due to cylinder head pressure.
In the Maule I am finding that 60% power works just fine, higher power settings seem to burn a lot more fuel for a small gain in speed.
I would love to hear other peoples theories on carby engine management.

[Mountain Doctor]

FWIW, depending on many variables, I can sometimes run my O-360 a little LOP. I can usually run at peak, and I keep my hottest cylinder less than 380 degrees. I could not do this without an analyzer.

The downdie is that 65% of 180 HP is a slow way to travel.

[John Ashcroft]

My view is that 380 is too high
I used to target 325 the Gami testing showed the max temp should be 380 not 460 or whatever the limitations in the manual
I ran either lop or peak or if over 65% 125 rop which gave me the desired operating temperature rop usually under 350

[maules.com]

Pretty close rule to follow re power settings and fuel burn.
Best power 75% and above
Best efficiency distance v fuel used 55%
Best fuel longevity time in air 45%

[Mountain Doctor]

My view is that 380 is too high
I used to target 325 the Gami testing showed the max temp should be 380 not 460 or whatever the limitations in the manual
I ran either lop or peak or if over 65% 125 rop which gave me the desired operating temperature rop usually under 350

According to much of the reading I have done, and it has been a lot, 380 is the target for max CHT. I have read all of John Deakin's material in print and on line, and have reviewed the data from GAMI and Lycoming.

I view 400 as a VNE, 380 as max allowable, and aim for 375 or lower.

OAT is a big factor in how I am able to run my motor.

On hot days sometimes I have to run 100 ROP, and/or less than 75% to acheive those temps. In the winter it is easier to run peak or sometimes, if circumstances permit, LOP.

[John Ashcroft]

John and George are a wealth of information, I would recommend the Advanced Pilot Seminars to anyone. The 380 was for CHT as you say.
It was a lot easier to manage the temps with an injected engine. I only have 25 hours or so in the Maule to date and I am still getting used to it. Not looking to go far in the Maule, more so use it as a paddock hopper and occasional trip into the outback with a swag.
I travelled a lot around Australia in the Bonanza and loved its capabilities. The Maule has its own strengths which I hope will suit this new phase in my flying.
Enjoyed the discussion

[aero101]

In my humble opinion, yes the engine analyzer can do more on the fuel injected - gami'd engine for fuel consumption, but I will never own another airplane without one, be it carburated or injected for all the same reasons... With carburated engines, especially, there can be, and usually is a fairly large difference in the EGT spread, and they all need monitoring when leaning, as you usually have one cylinder that's leaner and one on rich side, and also keeping eyes on CHT's... Single cylinder monitoring just don't get it if you want to preserve that investment up front... I've always been of old school in that 70% to 75% is best for normal cruz unless gas is issue... I usually make TBO, and babying engine is not good for it in respect to carbon and sludge build ups, etc, etc... What ever works for you, I guess, is what we'll use? You can probably talk to 10 pilots / mechanics and get at least 8 different opinions which just goes to show what our 1950's technology is getting us?

[John Ashcroft]

Thanks Jim
How rich do you run your carby engine to achieve the best CHT spread?

[Mountain Doctor]

There is some luck of the draw involved with the EGT spread of a carbureted engine.

In my communications with John Deakin it seems that the O-360 tends to give the best distribution. The Lycoming 6 cylinder engines less so, and the Continental engines give the widest spreads.

Frequently I get an even level across the graph on my JPI at peak or even a little LOP. Sometimes however the spread is too far and I have to run 100 degrees ROP, or at least monitor my CHT's carefully (which I do always anyways).

I don't know why some cirumstances give more even EGT's than others. OAT? Altitude? Attitude? Barometric pressure? Phase of the moon?

I would prefer a GAMI equipped fuel injected 6, but the fact is I couldn't even really afford my 180A!

[aero101]

I generally run about 50 degrees rich of peak which gives me between 9 to 9.5 GPH on fuel flow. Sometimes when stretching fuel, I'll bring that down to about 25 degrees ROP which gets me around 8.5 GPH at 2350 to 2400 RPM... I find EGT's in this range vary on average about 50 degrees, the number 2 cyl being the lowest and other 3 are pretty close for some reason. I suspect it's to do with the exhaust sys I have installed and maybe related to probe location at a slight bend on that cyl... CHT's at these settings are almost straight across and generally run from 310 to 340 depending upon airspeed, OAT, Weight, etc, etc...

These temps, etc will probably vary somewhat with a standard Maule 180 exhaust, as I've installed a 4 into 2 X-over style system, and swinging a longer, lower pitched prop...

[Nick]

1977 M5-235C with ~1300hrs
Just had the proper Maule cluster gauge installed after removing the Cessna gauges the previous owner thought looked better(???). The cyl temp gauge was inop due to the wrong sender for the gauge so I have been using an Alcor single cylinder temp and its been in the high 360- 375°F. Flown the last 100hrs like this without concern. With new maule gauge installed it reads red line. Sounds like I am not the only one with this issue, perhaps its time to change the baffling material to get better airflow to the #4 cyl.
Cheers