Equipment:
Engine: Cont TSIO 360 FB
Aircraft: Piper Turbo Arrow IV, 1982
Component: Cylinder # 2
Hrs on engine: 1500
Hrs on top: 900
Condition:
Cylinder # 2 is indicating a low EGT (yes I know its not a fixed number, its for reference) and low CHT when the RPM is low (below 1300), essentially at idle when compared to the other five cylinders. The lower the RPM the lower the EGT and CHT temps. It runs about 400 degrees lower than the others at low RPM. In cruise, it and they are right where they should be. GAMI spread is .3. EGT and CHT track together (both low) at low RPM. So, this unusual condition only exists at idle, not at cruise.
On start up, when cold, the EGT on #2 is comparative to the others. Only after about 4 minutes of operation does it start to go low. It will come up on the run up. It runs low at idle, comes up on take off and cruise and goes low again after landing and during taxi. EGT delta is about 400 degrees.
The concern is that I have not seen this abnormality in other Turbo Arrows and Bonanzas that I fly. The delta is triggering the engine monitor to flash a warning light that is distracting and annoying.
Historical data indicates this condition dates back to at least 2012. A top overhaul was completed in 2013. The condition existed before the top overhaul, remained after the top overhaul and continues to the present.
The engine is operated both ROP and LOP as required.
Manifold pressure at 1,000 RPM is 19”. Compared to two other Turbo Arrows; one high time is 16” at 1,000 RPM and another newly overhauled (100 hours) is 20”.
Plugs in # 1 and # 2 Look like they are running rich or cold (black soot).
Oil consumption is low.
I have not been able to definitively determine that the condition is in fact an issue within the cylinder or that it is an instrumentation issue. Since the EGT and the CHT are both low when the condition presents itself, I am assuming that because the temps on both are low together that the condition is probably a low power issue in the cylinder.
Things we have checked:
Induction leaks checked several times, none found. Have checked the induction system hot and cold.
A mag check at low RPM, high RPM, ROP or LOP all do not indicate a fault or drop out. High power LOP mag check is OK.
Mags overhauled 100 hours ago.
Calibrated fuel flow at all injector nozzles is equal and in spec.
Replaced GAMI injector nozzle on cyl # 2 (thanks GAMI) No change.
Replaced lifters on exhaust and intake on cyl # 2. No change. Cam and removed lifters in excellent condition.
Ignition wire checks OK.
New plugs 50 hours ago. No change.
Fuel flow plotted against EGT shows no abnormalities.
Cylinder compression 74/80.
Borescope of cyl # 2 normal. No sticking valves. No smilies on piston. No evidence of valve sticking.
Swap EGT probes between cylinders, did not migrate.
Replace EGT probe in cylinder # 2 with new. No change.
Fuel system reset per Continental spec. Metered FF 6.50. No change.
Visual inspection of induction system and seals, gaskets and cylinders all normal.
Considering:
Possible instrumentation issue. JPI instrument or wiring may have a temperature breakdown causing erroneous reading. Low EGT on # 2 at start of flight and end of flight make this unlikely. also CHT following EGT make low power in cylinder more likely. Plan to swap pins between # 1 and # 2 to see if condition migrates or remains to verify.
Have considered stuck or broken ring, but same condition (beginning and end of flight) make that unlikely.
