High CHT... again. All help/experiences wanted!

[tawadc95]

Re: High CHT... again. All help/experiences wanted!

how long have you been using that engine Bill? is it new to you?

[VictorBravo]

Re: High CHT... again. All help/experiences wanted!

how long have you been using that engine Bill? is it new to you?

I have about 50-75 hours on it since I bought the airplane. I have not had the cylinders off, frankly it runs really well and there has been no reason. One guy here locally said that perhaps that cylinder is scuffing or too choked. But I would feel that when turning the prop by hand, would I not?

I dunno, I'm about to start building my 85 horse engine, if it is a cylinder problem then the newly topped 85 cylinders would not have this problem.

If the 85 has a similar problem with one cylinder then it's an airflow problem for sure. If it is a cylinder problem then it would at least partly vindicate the cowling design.

[flyguy]

Re: High CHT... again. All help/experiences wanted!

Connected up the CHT gauge this AM and selected the hot cylinder after runup. Just have 2 pair of wires below the dash, unmarked.
Made sure I had good contact on the connectors and took off.
On climb to 3000 the hot cylinder went to a hair over 500 F. The other cylinder (rear also) was about 400 when I checked it at 2700ft. OAT and cockpit temp were both at 70F. I was fooling around maintaining max rate at 800 ft/min which requires a lower airspeed.

Is that a record? A friend has a C-175 with the geared O-300 that shows right at 500 or a little over on the rear cylinders all the time.

I'm presently looking for my cover plate for the bowl inlet to see if it still lowers the temp on the hot cylinder, as it did before.

I did notice that the bare metal on backside fins of #1 does look a little on the brown side, guess I have to check that out. Will loosen the rear baffle and check in there to see how it looks. May just be a fine coat of dirt/sand. The compression test last month was good.

DC

[tawadc95]

Re: High CHT... again. All help/experiences wanted!

I was talking to my dad about your cylinder.
he said if you do not have baffle seals you might want to do so and that he has seen alot that run 450 over the years.
He has seen alot of radials over the years with 37,000 hrs of ag time and 1200 on each engine ,some less and each one is a different creature so he lets each one develope its habits and looks for trends outside of those habits.........providing of course it is within manufacturers parameters to begin with and all else feels and sounds ok

[flyguy]

Re: High CHT... again. All help/experiences wanted!

Reworked some stuff on the plane and went out this am and tested again. Beautiful clear, quiet. OAT 54 degrees.
Climb to 3500 ft got me an indicated of 400 F max this time. Putting in a correction factor for the 57 F reference junction temperature gave me 382 F at the end of the climb.
Cruised for 10 minutes, dropped to 332 F with correction subtracted.
I did one major thing with the baffle that I wasn't sure how it would work out, but it seems to have really helped.
DC

[Ragwing nut]

Re: High CHT... again. All help/experiences wanted!

I have seriously considered attempting to use Alon cylinder baffles and tank baffles to see what affect they would have. If it fixed the O-200 Ercoupes, should fix a Taylorcraft

[flyguy]

Re: High CHT... again. All help/experiences wanted!

Well, I changed several things so I'm going to see if I can determine which items give me the best cooling for the change. I have my suspicions already. I did forget to mention that BOTH rear cylinders were indicating 400F uncorrected at the end of the 3,500 climb.
DC

[VictorBravo]

Re: High CHT... again. All help/experiences wanted!

Mike, how are Alon baffles different... not familiar???

Darryl, just like THX movie sound... the audience is listening! What did you do to what part, and what did that do to the CHT???

[flyguy]

Re: High CHT... again. All help/experiences wanted!

There were some baffle edges next to the crankcase where the air could slip by so I used hardware store foil surfaced tape (the sticky goo type) to stop the air from leaking by the rear firewall type baffle.

There was a pretty good hole in the front baffle that would normally feed the cabin heat muff that wasn't being used. It had been uncovered for annual and I had forgotten to seal it off again. Took care of that, which keeeps high pressure air from leaking into the low pressure area under the engine. Pretty much sealed off anything that wasn't that would leak into the low pressure area.

Put on my winter cover plate that shuts off about 3/4's of the flow into the hole in nose bowl just above the filter. I use that to get the oil temp up in the winter time and it seems to also reduce the pressure under the engine and the cylinder head temperatures.

Finally, and I think most significant for the hot #1 cylinder, I increased the clearance between the rear baffle and the back side of the #1 cylinder to the same value as the opposite rear cylinder. That is about 1/4 inch now. It was resting against the cylinder fins before.

As I said I am going to reverse the process to see what is producing the greatest decrease in temperature and then decide if further tweaks are needed and make the seals more permanent.
DC

[Ragwing nut]

Re: High CHT... again. All help/experiences wanted!

Mike, how are Alon baffles different... not familiar???

Darryl, just like THX movie sound... the audience is listening! What did you do to what part, and what did that do to the CHT???

VERY DIFFERENT. Lots of tinfoil aluminum wrapped around every surface, noo, cranny. I would need a pic to describe, to difficult to try and explain.

Mike

[NY86]

Re: High CHT... again. All help/experiences wanted!

There's no real difference between the Ercoupe, Alon and Money M-10 baffling. They all tend to run hot. I'd look at the Cessna 120/140 setup. In good shape they'll run about 80* over ambient for oil temps.

'Course, most temp issues are due to poor seals on the baffles, not bad design...

[VictorBravo]

Re: High CHT... again. All help/experiences wanted!

FlyGuy... this is totally ironic, because I had an aero engineer type guy come and look at my setup, and he said to try something very similar.

His opinion was the the exit area (clearance between curved baffle and bottom cylinder fins) was too small, and that even though I was forcing all the flow thru the fins it was restricting the flow overall.

So yesterday my rear baffle had a romantic rendezvous with a ball peen hammer on a bed of steel shot The lower edge of the rear curve, in the stamped rear baffle on the #1 cylinder side... was bent back and away from the fins to provide larger exit area. The baffle still lies flat against the rear vertical portion of the cylinder fins, but there is a significantly higher exit area.

I also bent the inter-cylinder baffle a little to provide the same effect on the front side of #1.

This week there may be a test flight to see if this is at least heading in the right direction... tune in, same Bat-time, same Bat-station!