N4655R
Senior Member
So, I am just trying to think outside the box here...
My #3 Cylinder runs hotter in both EGT and CHT than my other three cylinders. This makes it not so easy to lean out the engine while at altitude as #3 Cylinder will reach peak before the other three. Both I and my A&P that rebuilt my engine believe that it is nothing more than an air flow issue. All my baffling appears to be in good condition with no obvious gaps or tears.
I fly a PA28-140 rated at 150HP. The temperatures at a random spot in the flight are typically as follow:
EGT CHT
1) 1270 306
2) 1252 310
3) 1391 373
4) 1297 330
The Scat tubing to the muffler that creates heat in the cabin comes off the baffling right behind the #3 Cylinder. The opening to that Scat Tubing is larger than the opening behind the #4 Cylinder that cools the fuel pump and left Mag.
So, my thoughts questions to the collective are: Could the airflow be too much opposed to not enough as it's flowing over the top of the #3 cylinder and entering the opening to the Scat Tubing and not cooling the lower part of the #3 Cylinder? Or... The airflow is not enough and somehow the heat from the muffler is back flowing up the scat tubing to the #3 Cylinder? I suppose, I could open the heat vent while in flight and see if it effects cylinder temperatures. In addition, all 4 cylinders' exhaust stacks merge together before going through the muffler and the last convergence is right below the #3 exhaust stack, could this all just be normal?
I did have the exact same readings prior to the rebuild and we did not change the cylinders.
My #3 Cylinder runs hotter in both EGT and CHT than my other three cylinders. This makes it not so easy to lean out the engine while at altitude as #3 Cylinder will reach peak before the other three. Both I and my A&P that rebuilt my engine believe that it is nothing more than an air flow issue. All my baffling appears to be in good condition with no obvious gaps or tears.
I fly a PA28-140 rated at 150HP. The temperatures at a random spot in the flight are typically as follow:
EGT CHT
1) 1270 306
2) 1252 310
3) 1391 373
4) 1297 330
The Scat tubing to the muffler that creates heat in the cabin comes off the baffling right behind the #3 Cylinder. The opening to that Scat Tubing is larger than the opening behind the #4 Cylinder that cools the fuel pump and left Mag.
So, my thoughts questions to the collective are: Could the airflow be too much opposed to not enough as it's flowing over the top of the #3 cylinder and entering the opening to the Scat Tubing and not cooling the lower part of the #3 Cylinder? Or... The airflow is not enough and somehow the heat from the muffler is back flowing up the scat tubing to the #3 Cylinder? I suppose, I could open the heat vent while in flight and see if it effects cylinder temperatures. In addition, all 4 cylinders' exhaust stacks merge together before going through the muffler and the last convergence is right below the #3 exhaust stack, could this all just be normal?
I did have the exact same readings prior to the rebuild and we did not change the cylinders.
